foundationdb/fdbserver/storageserver.actor.cpp

/*
 * storageserver.actor.cpp
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2013-2022 Apple Inc. and the FoundationDB project authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <cinttypes>
#include <functional>
#include <type_traits>
#include <unordered_map>

#include "fmt/format.h"
#include "fdbclient/CommitTransaction.h"
#include "fdbclient/FDBTypes.h"
#include "fdbrpc/fdbrpc.h"
#include "fdbrpc/LoadBalance.h"
#include "fdbserver/OTELSpanContextMessage.h"
#include "flow/ActorCollection.h"
#include "flow/Arena.h"
#include "flow/Error.h"
#include "flow/Hash3.h"
#include "flow/Histogram.h"
#include "flow/IRandom.h"
#include "flow/IndexedSet.h"
#include "flow/SystemMonitor.h"
#include "flow/Trace.h"
#include "fdbclient/Tracing.h"
#include "flow/Util.h"
#include "fdbclient/Atomic.h"
#include "fdbclient/CommitProxyInterface.h"
#include "fdbclient/DatabaseContext.h"
#include "fdbclient/FDBTypes.h"
#include "fdbclient/KeyBackedTypes.h"
#include "fdbclient/KeyRangeMap.h"
#include "fdbclient/NativeAPI.actor.h"
#include "fdbclient/Notified.h"
#include "fdbclient/StatusClient.h"
#include "fdbclient/StorageServerShard.h"
#include "fdbclient/SystemData.h"
#include "fdbclient/Tenant.h"
#include "fdbclient/TransactionLineage.h"
#include "fdbclient/Tuple.h"
#include "fdbclient/VersionedMap.h"
#include "fdbrpc/sim_validation.h"
#include "fdbrpc/Smoother.h"
#include "fdbrpc/Stats.h"
#include "fdbserver/EncryptedMutationMessage.h"
#include "fdbserver/FDBExecHelper.actor.h"
#include "fdbserver/GetEncryptCipherKeys.h"
#include "fdbserver/IKeyValueStore.h"
#include "fdbserver/Knobs.h"
#include "fdbserver/LatencyBandConfig.h"
#include "fdbserver/LogProtocolMessage.h"
#include "fdbserver/LogSystem.h"
#include "fdbserver/MoveKeys.actor.h"
#include "fdbserver/MutationTracking.h"
#include "fdbserver/OTELSpanContextMessage.h"
#include "fdbserver/RecoveryState.h"
#include "fdbserver/RocksDBCheckpointUtils.actor.h"
#include "fdbserver/ServerCheckpoint.actor.h"
#include "fdbserver/ServerDBInfo.h"
#include "fdbserver/SpanContextMessage.h"
#include "fdbserver/StorageMetrics.h"
#include "fdbserver/TLogInterface.h"
#include "fdbserver/TransactionTagCounter.h"
#include "fdbserver/WaitFailure.h"
#include "fdbserver/WorkerInterface.actor.h"
#include "flow/ActorCollection.h"
#include "flow/Arena.h"
#include "flow/Error.h"
#include "flow/Hash3.h"
#include "flow/Histogram.h"
#include "flow/IRandom.h"
#include "flow/IndexedSet.h"
#include "flow/SystemMonitor.h"
#include "flow/TDMetric.actor.h"
#include "flow/Trace.h"
#include "flow/Util.h"
#include "flow/genericactors.actor.h"

#include "flow/actorcompiler.h" // This must be the last #include.

#ifndef __INTEL_COMPILER
#pragma region Data Structures
#endif

#define SHORT_CIRCUT_ACTUAL_STORAGE 0

namespace {
bool canReplyWith(Error e) {
	switch (e.code()) {
	case error_code_transaction_too_old:
	case error_code_future_version:
	case error_code_wrong_shard_server:
	case error_code_process_behind:
	case error_code_watch_cancelled:
	case error_code_unknown_change_feed:
	case error_code_server_overloaded:
	case error_code_change_feed_popped:
	case error_code_tenant_name_required:
	case error_code_unknown_tenant:
	// getMappedRange related exceptions that are not retriable:
	case error_code_mapper_bad_index:
	case error_code_mapper_no_such_key:
	case error_code_mapper_bad_range_decriptor:
	case error_code_quick_get_key_values_has_more:
	case error_code_quick_get_value_miss:
	case error_code_quick_get_key_values_miss:
	case error_code_get_mapped_key_values_has_more:
	case error_code_key_not_tuple:
	case error_code_value_not_tuple:
	case error_code_mapper_not_tuple:
		// case error_code_all_alternatives_failed:
		return true;
	default:
		return false;
	}
}
} // namespace

#define PERSIST_PREFIX "\xff\xff"

FDB_DECLARE_BOOLEAN_PARAM(UnlimitedCommitBytes);
FDB_DEFINE_BOOLEAN_PARAM(UnlimitedCommitBytes);

// Immutable
static const KeyValueRef persistFormat(LiteralStringRef(PERSIST_PREFIX "Format"),
                                       LiteralStringRef("FoundationDB/StorageServer/1/4"));
static const KeyValueRef persistShardAwareFormat(LiteralStringRef(PERSIST_PREFIX "Format"),
                                                 LiteralStringRef("FoundationDB/StorageServer/1/5"));
static const KeyRangeRef persistFormatReadableRange(LiteralStringRef("FoundationDB/StorageServer/1/2"),
                                                    LiteralStringRef("FoundationDB/StorageServer/1/6"));
static const KeyRef persistID = LiteralStringRef(PERSIST_PREFIX "ID");
static const KeyRef persistTssPairID = LiteralStringRef(PERSIST_PREFIX "tssPairID");
static const KeyRef persistSSPairID = LiteralStringRef(PERSIST_PREFIX "ssWithTSSPairID");
static const KeyRef persistTssQuarantine = LiteralStringRef(PERSIST_PREFIX "tssQ");
static const KeyRef persistClusterIdKey = LiteralStringRef(PERSIST_PREFIX "clusterId");

// (Potentially) change with the durable version or when fetchKeys completes
static const KeyRef persistVersion = LiteralStringRef(PERSIST_PREFIX "Version");
static const KeyRangeRef persistShardAssignedKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "ShardAssigned/"), LiteralStringRef(PERSIST_PREFIX "ShardAssigned0"));
static const KeyRangeRef persistShardAvailableKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "ShardAvailable/"), LiteralStringRef(PERSIST_PREFIX "ShardAvailable0"));
static const KeyRangeRef persistByteSampleKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "BS/"), LiteralStringRef(PERSIST_PREFIX "BS0"));
static const KeyRangeRef persistByteSampleSampleKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "BS/" PERSIST_PREFIX "BS/"),
                LiteralStringRef(PERSIST_PREFIX "BS/" PERSIST_PREFIX "BS0"));
static const KeyRef persistLogProtocol = LiteralStringRef(PERSIST_PREFIX "LogProtocol");
static const KeyRef persistPrimaryLocality = LiteralStringRef(PERSIST_PREFIX "PrimaryLocality");
static const KeyRangeRef persistChangeFeedKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "CF/"), LiteralStringRef(PERSIST_PREFIX "CF0"));
static const KeyRangeRef persistTenantMapKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "TM/"), LiteralStringRef(PERSIST_PREFIX "TM0"));
// data keys are unmangled (but never start with PERSIST_PREFIX because they are always in allKeys)

static const KeyRangeRef persistStorageServerShardKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "StorageServerShard/"),
                LiteralStringRef(PERSIST_PREFIX "StorageServerShard0"));

// Checkpoint related prefixes.
static const KeyRangeRef persistCheckpointKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "Checkpoint/"), LiteralStringRef(PERSIST_PREFIX "Checkpoint0"));
static const KeyRangeRef persistPendingCheckpointKeys =
    KeyRangeRef(LiteralStringRef(PERSIST_PREFIX "PendingCheckpoint/"),
                LiteralStringRef(PERSIST_PREFIX "PendingCheckpoint0"));
static const std::string rocksdbCheckpointDirPrefix = "/rockscheckpoints_";

struct AddingShard : NonCopyable {
	KeyRange keys;
	Future<Void> fetchClient; // holds FetchKeys() actor
	Promise<Void> fetchComplete;
	Promise<Void> readWrite;

	// During the Fetching phase, it saves newer mutations whose version is greater or equal to fetchClient's
	// fetchVersion, while the shard is still busy catching up with fetchClient. It applies these updates after fetching
	// completes.
	std::deque<Standalone<VerUpdateRef>> updates;

	struct StorageServer* server;
	Version transferredVersion;
	Version fetchVersion;

	// To learn more details of the phase transitions, see function fetchKeys(). The phases below are sorted in
	// chronological order and do not go back.
	enum Phase {
		WaitPrevious,
		// During Fetching phase, it fetches data before fetchVersion and write it to storage, then let updater know it
		// is ready to update the deferred updates` (see the comment of member variable `updates` above).
		Fetching,
		// During the FetchingCF phase, the shard data is transferred but the remaining change feed data is still being
		// transferred. This is equivalent to the waiting phase for non-changefeed data.
		FetchingCF,
		// During Waiting phase, it sends updater the deferred updates, and wait until they are durable.
		Waiting
		// The shard's state is changed from adding to readWrite then.
	};

	Phase phase;

	AddingShard(StorageServer* server, KeyRangeRef const& keys);

	// When fetchKeys "partially completes" (splits an adding shard in two), this is used to construct the left half
	AddingShard(AddingShard* prev, KeyRange const& keys)
	  : keys(keys), fetchClient(prev->fetchClient), server(prev->server), transferredVersion(prev->transferredVersion),
	    fetchVersion(prev->fetchVersion), phase(prev->phase) {}
	~AddingShard() {
		if (!fetchComplete.isSet())
			fetchComplete.send(Void());
		if (!readWrite.isSet())
			readWrite.send(Void());
	}

	void addMutation(Version version, bool fromFetch, MutationRef const& mutation);

	bool isDataTransferred() const { return phase >= FetchingCF; }
	bool isDataAndCFTransferred() const { return phase >= Waiting; }
};

class ShardInfo : public ReferenceCounted<ShardInfo>, NonCopyable {
	ShardInfo(KeyRange keys, std::unique_ptr<AddingShard>&& adding, StorageServer* readWrite)
	  : adding(std::move(adding)), readWrite(readWrite), keys(keys), version(0) {}

public:
	// A shard has 3 mutual exclusive states: adding, readWrite and notAssigned.
	std::unique_ptr<AddingShard> adding;
	struct StorageServer* readWrite;
	KeyRange keys;
	uint64_t changeCounter;
	uint64_t shardId;
	uint64_t desiredShardId;
	Version version;

	static ShardInfo* newNotAssigned(KeyRange keys) { return new ShardInfo(keys, nullptr, nullptr); }
	static ShardInfo* newReadWrite(KeyRange keys, StorageServer* data) { return new ShardInfo(keys, nullptr, data); }
	static ShardInfo* newAdding(StorageServer* data, KeyRange keys) {
		return new ShardInfo(keys, std::make_unique<AddingShard>(data, keys), nullptr);
	}
	static ShardInfo* addingSplitLeft(KeyRange keys, AddingShard* oldShard) {
		return new ShardInfo(keys, std::make_unique<AddingShard>(oldShard, keys), nullptr);
	}

	static ShardInfo* newShard(StorageServer* data, const StorageServerShard& shard) {
		ShardInfo* res = nullptr;
		switch (shard.getShardState()) {
		case StorageServerShard::NotAssigned:
			res = newNotAssigned(shard.range);
			break;
		case StorageServerShard::MovingIn:
		case StorageServerShard::ReadWritePending:
			res = newAdding(data, shard.range);
			break;
		case StorageServerShard::ReadWrite:
			res = newReadWrite(shard.range, data);
			break;
		default:
			TraceEvent(SevError, "UnknownShardState").detail("State", shard.shardState);
		}
		res->populateShard(shard);
		return res;
	}

	static bool canMerge(const ShardInfo* l, const ShardInfo* r) {
		if (l == nullptr || r == nullptr || l->keys.end != r->keys.begin || l->version == invalidVersion ||
		    r->version == invalidVersion) {
			return false;
		}
		if (l->shardId != r->shardId || l->desiredShardId != r->desiredShardId) {
			return false;
		}
		return (l->isReadable() && r->isReadable()) || (!l->assigned() && !r->assigned());
	}

	StorageServerShard toStorageServerShard() const {
		StorageServerShard::ShardState st;
		if (this->isReadable()) {
			st = StorageServerShard::ReadWrite;
		} else if (!this->assigned()) {
			st = StorageServerShard::NotAssigned;
		} else {
			ASSERT(this->adding);
			if (this->adding)
				st = this->adding->phase == AddingShard::Waiting ? StorageServerShard::ReadWritePending
				                                                 : StorageServerShard::MovingIn;
		}
		return StorageServerShard(this->keys, this->version, this->shardId, this->desiredShardId, st);
	}

	// Copies necessary information from `shard`.
	void populateShard(const StorageServerShard& shard) {
		this->version = shard.version;
		this->shardId = shard.id;
		this->desiredShardId = shard.desiredId;
	}

	// Returns true if the current shard is merged with `other`.
	bool mergeWith(const ShardInfo* other) {
		if (!canMerge(this, other)) {
			return false;
		}
		this->keys = KeyRangeRef(this->keys.begin, other->keys.end);
		this->version = std::max(this->version, other->version);
		return true;
	}

	void validate() const {
		// TODO: Complete this.
	}

	bool isReadable() const { return readWrite != nullptr; }
	bool notAssigned() const { return !readWrite && !adding; }
	bool assigned() const { return readWrite || adding; }
	bool isInVersionedData() const { return readWrite || (adding && adding->isDataTransferred()); }
	bool isCFInVersionedData() const { return readWrite || (adding && adding->isDataAndCFTransferred()); }
	void addMutation(Version version, bool fromFetch, MutationRef const& mutation);
	bool isFetched() const { return readWrite || (adding && adding->fetchComplete.isSet()); }

	const char* debugDescribeState() const {
		if (notAssigned())
			return "NotAssigned";
		else if (adding && !adding->isDataAndCFTransferred())
			return "AddingFetchingCF";
		else if (adding && !adding->isDataTransferred())
			return "AddingFetching";
		else if (adding)
			return "AddingTransferred";
		else
			return "ReadWrite";
	}
};

struct StorageServerDisk {
	explicit StorageServerDisk(struct StorageServer* data, IKeyValueStore* storage) : data(data), storage(storage) {}

	void makeNewStorageServerDurable(const bool shardAware);
	bool makeVersionMutationsDurable(Version& prevStorageVersion,
	                                 Version newStorageVersion,
	                                 int64_t& bytesLeft,
	                                 UnlimitedCommitBytes unlimitedCommitBytes);
	void makeVersionDurable(Version version);
	void makeTssQuarantineDurable();
	Future<bool> restoreDurableState();

	void changeLogProtocol(Version version, ProtocolVersion protocol);

	void writeMutation(MutationRef mutation);
	void writeKeyValue(KeyValueRef kv);
	void clearRange(KeyRangeRef keys);

	Future<Void> addRange(KeyRangeRef range, std::string id) { return storage->addRange(range, id); }

	std::vector<std::string> removeRange(KeyRangeRef range) { return storage->removeRange(range); }

	void persistRangeMapping(KeyRangeRef range, bool isAdd) { storage->persistRangeMapping(range, isAdd); }

	Future<Void> cleanUpShardsIfNeeded(const std::vector<std::string>& shardIds) {
		return storage->cleanUpShardsIfNeeded(shardIds);
	};

	Future<Void> getError() { return storage->getError(); }
	Future<Void> init() { return storage->init(); }
	Future<Void> canCommit() { return storage->canCommit(); }
	Future<Void> commit() { return storage->commit(); }

	// SOMEDAY: Put readNextKeyInclusive in IKeyValueStore
	// Read the key that is equal or greater then 'key' from the storage engine.
	// For example, readNextKeyInclusive("a") should return:
	//  - "a", if key "a" exist
	//  - "b", if key "a" doesn't exist, and "b" is the next existing key in total order
	//  - allKeys.end, if keyrange [a, allKeys.end) is empty
	Future<Key> readNextKeyInclusive(KeyRef key, IKeyValueStore::ReadType type = IKeyValueStore::ReadType::NORMAL) {
		++(*kvScans);
		return readFirstKey(storage, KeyRangeRef(key, allKeys.end), type);
	}
	Future<Optional<Value>> readValue(KeyRef key,
	                                  IKeyValueStore::ReadType type = IKeyValueStore::ReadType::NORMAL,
	                                  Optional<UID> debugID = Optional<UID>()) {
		++(*kvGets);
		return storage->readValue(key, type, debugID);
	}
	Future<Optional<Value>> readValuePrefix(KeyRef key,
	                                        int maxLength,
	                                        IKeyValueStore::ReadType type = IKeyValueStore::ReadType::NORMAL,
	                                        Optional<UID> debugID = Optional<UID>()) {
		++(*kvGets);
		return storage->readValuePrefix(key, maxLength, type, debugID);
	}
	Future<RangeResult> readRange(KeyRangeRef keys,
	                              int rowLimit = 1 << 30,
	                              int byteLimit = 1 << 30,
	                              IKeyValueStore::ReadType type = IKeyValueStore::ReadType::NORMAL) {
		++(*kvScans);
		return storage->readRange(keys, rowLimit, byteLimit, type);
	}

	Future<CheckpointMetaData> checkpoint(const CheckpointRequest& request) { return storage->checkpoint(request); }

	Future<Void> restore(const std::vector<CheckpointMetaData>& checkpoints) { return storage->restore(checkpoints); }

	Future<Void> deleteCheckpoint(const CheckpointMetaData& checkpoint) {
		return storage->deleteCheckpoint(checkpoint);
	}

	KeyValueStoreType getKeyValueStoreType() const { return storage->getType(); }
	StorageBytes getStorageBytes() const { return storage->getStorageBytes(); }
	std::tuple<size_t, size_t, size_t> getSize() const { return storage->getSize(); }

	// The following are pointers to the Counters in StorageServer::counters of the same names.
	Counter* kvCommitLogicalBytes;
	Counter* kvClearRanges;
	Counter* kvGets;
	Counter* kvScans;
	Counter* kvCommits;

private:
	struct StorageServer* data;
	IKeyValueStore* storage;
	void writeMutations(const VectorRef<MutationRef>& mutations, Version debugVersion, const char* debugContext);

	ACTOR static Future<Key> readFirstKey(IKeyValueStore* storage, KeyRangeRef range, IKeyValueStore::ReadType type) {
		RangeResult r = wait(storage->readRange(range, 1, 1 << 30, type));
		if (r.size())
			return r[0].key;
		else
			return range.end;
	}
};

struct UpdateEagerReadInfo {
	std::vector<KeyRef> keyBegin;
	std::vector<Key> keyEnd; // these are for ClearRange

	std::vector<std::pair<KeyRef, int>> keys;
	std::vector<Optional<Value>> value;

	Arena arena;

	void addMutations(VectorRef<MutationRef> const& mutations) {
		for (auto& m : mutations)
			addMutation(m);
	}

	void addMutation(MutationRef const& m) {
		// SOMEDAY: Theoretically we can avoid a read if there is an earlier overlapping ClearRange
		if (m.type == MutationRef::ClearRange && !m.param2.startsWith(systemKeys.end) &&
		    SERVER_KNOBS->ENABLE_CLEAR_RANGE_EAGER_READS)
			keyBegin.push_back(m.param2);
		else if (m.type == MutationRef::CompareAndClear) {
			if (SERVER_KNOBS->ENABLE_CLEAR_RANGE_EAGER_READS)
				keyBegin.push_back(keyAfter(m.param1, arena));
			if (keys.size() > 0 && keys.back().first == m.param1) {
				// Don't issue a second read, if the last read was equal to the current key.
				// CompareAndClear is likely to be used after another atomic operation on same key.
				keys.back().second = std::max(keys.back().second, m.param2.size() + 1);
			} else {
				keys.emplace_back(m.param1, m.param2.size() + 1);
			}
		} else if ((m.type == MutationRef::AppendIfFits) || (m.type == MutationRef::ByteMin) ||
		           (m.type == MutationRef::ByteMax))
			keys.emplace_back(m.param1, CLIENT_KNOBS->VALUE_SIZE_LIMIT);
		else if (isAtomicOp((MutationRef::Type)m.type))
			keys.emplace_back(m.param1, m.param2.size());
	}

	void finishKeyBegin() {
		if (SERVER_KNOBS->ENABLE_CLEAR_RANGE_EAGER_READS) {
			std::sort(keyBegin.begin(), keyBegin.end());
			keyBegin.resize(std::unique(keyBegin.begin(), keyBegin.end()) - keyBegin.begin());
		}
		std::sort(keys.begin(), keys.end(), [](const std::pair<KeyRef, int>& lhs, const std::pair<KeyRef, int>& rhs) {
			return (lhs.first < rhs.first) || (lhs.first == rhs.first && lhs.second > rhs.second);
		});
		keys.resize(std::unique(keys.begin(),
		                        keys.end(),
		                        [](const std::pair<KeyRef, int>& lhs, const std::pair<KeyRef, int>& rhs) {
			                        return lhs.first == rhs.first;
		                        }) -
		            keys.begin());
		// value gets populated in doEagerReads
	}

	Optional<Value>& getValue(KeyRef key) {
		int i = std::lower_bound(keys.begin(),
		                         keys.end(),
		                         std::pair<KeyRef, int>(key, 0),
		                         [](const std::pair<KeyRef, int>& lhs, const std::pair<KeyRef, int>& rhs) {
			                         return lhs.first < rhs.first;
		                         }) -
		        keys.begin();
		ASSERT(i < keys.size() && keys[i].first == key);
		return value[i];
	}

	KeyRef getKeyEnd(KeyRef key) {
		int i = std::lower_bound(keyBegin.begin(), keyBegin.end(), key) - keyBegin.begin();
		ASSERT(i < keyBegin.size() && keyBegin[i] == key);
		return keyEnd[i];
	}
};

const int VERSION_OVERHEAD =
    64 + sizeof(Version) + sizeof(Standalone<VerUpdateRef>) + // mutationLog, 64b overhead for map
    2 * (64 + sizeof(Version) +
         sizeof(Reference<VersionedMap<KeyRef, ValueOrClearToRef>::PTreeT>)); // versioned map [ x2 for
                                                                              // createNewVersion(version+1) ], 64b
                                                                              // overhead for map
// For both the mutation log and the versioned map.
static int mvccStorageBytes(MutationRef const& m) {
	return VersionedMap<KeyRef, ValueOrClearToRef>::overheadPerItem * 2 +
	       (MutationRef::OVERHEAD_BYTES + m.param1.size() + m.param2.size()) * 2;
}

struct FetchInjectionInfo {
	Arena arena;
	std::vector<VerUpdateRef> changes;
};

struct ChangeFeedInfo : ReferenceCounted<ChangeFeedInfo> {
	std::deque<Standalone<MutationsAndVersionRef>> mutations;
	Version fetchVersion = invalidVersion; // The version that commits from a fetch have been written to storage, but
	                                       // have not yet been committed as part of updateStorage.
	Version storageVersion = invalidVersion; // The version between the storage version and the durable version are
	                                         // being written to disk as part of the current commit in updateStorage.
	Version durableVersion = invalidVersion; // All versions before the durable version are durable on disk
	Version emptyVersion = 0; // The change feed does not have any mutations before emptyVersion
	KeyRange range;
	Key id;
	AsyncTrigger newMutations;
	NotifiedVersion durableFetchVersion;
	// A stopped change feed no longer adds new mutations, but is still queriable.
	// stopVersion = MAX_VERSION means the feed has not been stopped
	Version stopVersion = MAX_VERSION;

	// We need to track the version the change feed metadata was created by private mutation, so that if it is rolled
	// back, we can avoid notifying other SS of change feeds that don't durably exist
	Version metadataCreateVersion = invalidVersion;

	bool removing = false;
	bool destroyed = false;
	bool possiblyDestroyed = false;
	bool refreshInProgress = false;

	KeyRangeMap<std::unordered_map<UID, Promise<Void>>> moveTriggers;

	void triggerOnMove(KeyRange range, UID streamUID, Promise<Void> p) {
		auto toInsert = moveTriggers.modify(range);
		for (auto triggerRange = toInsert.begin(); triggerRange != toInsert.end(); ++triggerRange) {
			triggerRange->value().insert({ streamUID, p });
		}
	}

	void moved(KeyRange range) {
		auto toTrigger = moveTriggers.intersectingRanges(range);
		for (auto& triggerRange : toTrigger) {
			for (auto& triggerStream : triggerRange.cvalue()) {
				if (triggerStream.second.canBeSet()) {
					triggerStream.second.send(Void());
				}
			}
		}
		// coalesce doesn't work with promises
		moveTriggers.insert(range, std::unordered_map<UID, Promise<Void>>());
	}

	void removeOnMoveTrigger(KeyRange range, UID streamUID) {
		auto toRemove = moveTriggers.modify(range);
		for (auto triggerRange = toRemove.begin(); triggerRange != toRemove.end(); ++triggerRange) {
			auto streamToRemove = triggerRange->value().find(streamUID);
			ASSERT(streamToRemove != triggerRange->cvalue().end());
			triggerRange->value().erase(streamToRemove);
		}
		// TODO: may be more cleanup possible here
	}

	void destroy(Version destroyVersion) {
		removing = true;
		destroyed = true;
		refreshInProgress = false;
		moved(range);
		newMutations.trigger();
	}
};

class ServerWatchMetadata : public ReferenceCounted<ServerWatchMetadata> {
public:
	Key key;
	Optional<Value> value;
	Version version;
	Future<Version> watch_impl;
	Promise<Version> versionPromise;
	Optional<TagSet> tags;
	Optional<UID> debugID;

	ServerWatchMetadata(Key key, Optional<Value> value, Version version, Optional<TagSet> tags, Optional<UID> debugID)
	  : key(key), value(value), version(version), tags(tags), debugID(debugID) {}
};

struct StorageServer {
	typedef VersionedMap<KeyRef, ValueOrClearToRef> VersionedData;

private:
	// versionedData contains sets and clears.

	// * Nonoverlapping: No clear overlaps a set or another clear, or adjoins another clear.
	// ~ Clears are maximal: If versionedData.at(v) contains a clear [b,e) then
	//      there is a key data[e]@v, or e==allKeys.end, or a shard boundary or former boundary at e

	// * Reads are possible: When k is in a readable shard, for any v in [storageVersion, version.get()],
	//      storage[k] + versionedData.at(v)[k] = database[k] @ v    (storage[k] might be @ any version in
	//      [durableVersion, storageVersion])

	// * Transferred shards are partially readable: When k is in an adding, transferred shard, for any v in
	// [transferredVersion, version.get()],
	//      storage[k] + versionedData.at(v)[k] = database[k] @ v

	// * versionedData contains versions [storageVersion(), version.get()].  It might also contain version
	// (version.get()+1), in which changeDurableVersion may be deleting ghosts, and/or it might
	//      contain later versions if applyUpdate is on the stack.

	// * Old shards are erased: versionedData.atLatest() has entries (sets or intersecting clears) only for keys in
	// readable or adding,transferred shards.
	//   Earlier versions may have extra entries for shards that *were* readable or adding,transferred when those
	//   versions were the latest, but they eventually are forgotten.

	// * Old mutations are erased: All items in versionedData.atLatest() have insertVersion() > durableVersion(), but
	// views
	//   at older versions may contain older items which are also in storage (this is OK because of idempotency)

	VersionedData versionedData;
	std::map<Version, Standalone<VerUpdateRef>> mutationLog; // versions (durableVersion, version]
	std::unordered_map<KeyRef, Reference<ServerWatchMetadata>> watchMap; // keep track of server watches

public:
	struct PendingNewShard {
		PendingNewShard(uint64_t shardId, KeyRangeRef range) : shardId(format("%016llx", shardId)), range(range) {}

		std::string toString() const {
			return fmt::format("PendingNewShard: [ShardID]: {} [Range]: {}",
			                   this->shardId,
			                   Traceable<KeyRangeRef>::toString(this->range));
		}

		std::string shardId;
		KeyRange range;
	};

	std::map<Version, std::vector<CheckpointMetaData>> pendingCheckpoints; // Pending checkpoint requests
	std::unordered_map<UID, CheckpointMetaData> checkpoints; // Existing and deleting checkpoints
	TenantMap tenantMap;
	TenantPrefixIndex tenantPrefixIndex;
	std::map<Version, std::vector<PendingNewShard>>
	    pendingAddRanges; // Pending requests to add ranges to physical shards
	std::map<Version, std::vector<KeyRange>>
	    pendingRemoveRanges; // Pending requests to remove ranges from physical shards

	bool shardAware; // True if the storage server is aware of the physical shards.

	// Histograms
	struct FetchKeysHistograms {
		const Reference<Histogram> latency;
		const Reference<Histogram> bytes;
		const Reference<Histogram> bandwidth;

		FetchKeysHistograms()
		  : latency(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
		                                    FETCH_KEYS_LATENCY_HISTOGRAM,
		                                    Histogram::Unit::microseconds)),
		    bytes(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
		                                  FETCH_KEYS_BYTES_HISTOGRAM,
		                                  Histogram::Unit::bytes)),
		    bandwidth(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
		                                      FETCH_KEYS_BYTES_PER_SECOND_HISTOGRAM,
		                                      Histogram::Unit::bytes_per_second)) {}
	} fetchKeysHistograms;

	Reference<Histogram> tlogCursorReadsLatencyHistogram;
	Reference<Histogram> ssVersionLockLatencyHistogram;
	Reference<Histogram> eagerReadsLatencyHistogram;
	Reference<Histogram> fetchKeysPTreeUpdatesLatencyHistogram;
	Reference<Histogram> tLogMsgsPTreeUpdatesLatencyHistogram;
	Reference<Histogram> storageUpdatesDurableLatencyHistogram;
	Reference<Histogram> storageCommitLatencyHistogram;
	Reference<Histogram> ssDurableVersionUpdateLatencyHistogram;

	// watch map operations
	Reference<ServerWatchMetadata> getWatchMetadata(KeyRef key) const;
	KeyRef setWatchMetadata(Reference<ServerWatchMetadata> metadata);
	void deleteWatchMetadata(KeyRef key);
	void clearWatchMetadata();

	// tenant map operations
	bool insertTenant(TenantNameRef tenantName, TenantMapEntry tenantEntry, Version version);
	void insertTenant(TenantNameRef tenantName, ValueRef value, Version version);
	void clearTenants(TenantNameRef startTenant, TenantNameRef endTenant, Version version);

	Optional<TenantMapEntry> getTenantEntry(Version version, TenantInfo tenant);
	KeyRangeRef clampRangeToTenant(KeyRangeRef range, Optional<TenantMapEntry> tenantEntry, Arena& arena);

	std::vector<StorageServerShard> getStorageServerShards(KeyRangeRef range);

	class CurrentRunningFetchKeys {
		std::unordered_map<UID, double> startTimeMap;
		std::unordered_map<UID, KeyRange> keyRangeMap;

		static const StringRef emptyString;
		static const KeyRangeRef emptyKeyRange;

	public:
		void recordStart(const UID id, const KeyRange& keyRange) {
			startTimeMap[id] = now();
			keyRangeMap[id] = keyRange;
		}

		void recordFinish(const UID id) {
			startTimeMap.erase(id);
			keyRangeMap.erase(id);
		}

		std::pair<double, KeyRange> longestTime() const {
			if (numRunning() == 0) {
				return { -1, emptyKeyRange };
			}

			const double currentTime = now();
			double longest = 0;
			UID UIDofLongest;
			for (const auto& kv : startTimeMap) {
				const double currentRunningTime = currentTime - kv.second;
				if (longest <= currentRunningTime) {
					longest = currentRunningTime;
					UIDofLongest = kv.first;
				}
			}
			if (BUGGIFY) {
				UIDofLongest = deterministicRandom()->randomUniqueID();
			}
			auto it = keyRangeMap.find(UIDofLongest);
			if (it != keyRangeMap.end()) {
				return { longest, it->second };
			}
			return { -1, emptyKeyRange };
		}

		int numRunning() const { return startTimeMap.size(); }
	} currentRunningFetchKeys;

	Tag tag;
	std::vector<std::pair<Version, Tag>> history;
	std::vector<std::pair<Version, Tag>> allHistory;
	Version poppedAllAfter;
	std::map<Version, Arena>
	    freeable; // for each version, an Arena that must be held until that version is < oldestVersion
	Arena lastArena;
	double cpuUsage;
	double diskUsage;

	std::map<Version, Standalone<VerUpdateRef>> const& getMutationLog() const { return mutationLog; }
	std::map<Version, Standalone<VerUpdateRef>>& getMutableMutationLog() { return mutationLog; }
	VersionedData const& data() const { return versionedData; }
	VersionedData& mutableData() { return versionedData; }

	double old_rate = 1.0;
	double currentRate() {
		auto versionLag = version.get() - durableVersion.get();
		double res;
		if (versionLag >= SERVER_KNOBS->STORAGE_DURABILITY_LAG_HARD_MAX) {
			res = 0.0;
		} else if (versionLag > SERVER_KNOBS->STORAGE_DURABILITY_LAG_SOFT_MAX) {
			res =
			    1.0 -
			    (double(versionLag - SERVER_KNOBS->STORAGE_DURABILITY_LAG_SOFT_MAX) /
			     double(SERVER_KNOBS->STORAGE_DURABILITY_LAG_HARD_MAX - SERVER_KNOBS->STORAGE_DURABILITY_LAG_SOFT_MAX));
		} else {
			res = 1.0;
		}
		if (res != old_rate) {
			TraceEvent(SevDebug, "LocalRatekeeperChange", thisServerID)
			    .detail("Old", old_rate)
			    .detail("New", res)
			    .detail("NonDurableVersions", versionLag);
			old_rate = res;
		}
		return res;
	}

	void addMutationToMutationLogOrStorage(
	    Version ver,
	    MutationRef m); // Appends m to mutationLog@ver, or to storage if ver==invalidVersion

	// Update the byteSample, and write the updates to the mutation log@ver, or to storage if ver==invalidVersion
	void byteSampleApplyMutation(MutationRef const& m, Version ver);
	void byteSampleApplySet(KeyValueRef kv, Version ver);
	void byteSampleApplyClear(KeyRangeRef range, Version ver);

	void popVersion(Version v, bool popAllTags = false) {
		if (logSystem && !isTss()) {
			if (v > poppedAllAfter) {
				popAllTags = true;
				poppedAllAfter = std::numeric_limits<Version>::max();
			}

			std::vector<std::pair<Version, Tag>>* hist = &history;
			std::vector<std::pair<Version, Tag>> allHistoryCopy;
			if (popAllTags) {
				allHistoryCopy = allHistory;
				hist = &allHistoryCopy;
			}

			while (hist->size() && v > hist->back().first) {
				logSystem->pop(v, hist->back().second);
				hist->pop_back();
			}
			if (hist->size()) {
				logSystem->pop(v, hist->back().second);
			} else {
				logSystem->pop(v, tag);
			}
		}
	}

	Standalone<VerUpdateRef>& addVersionToMutationLog(Version v) {
		// return existing version...
		auto m = mutationLog.find(v);
		if (m != mutationLog.end())
			return m->second;

		// ...or create a new one
		auto& u = mutationLog[v];
		u.version = v;
		if (lastArena.getSize() >= 65536)
			lastArena = Arena(4096);
		u.arena() = lastArena;
		counters.bytesInput += VERSION_OVERHEAD;
		return u;
	}

	MutationRef addMutationToMutationLog(Standalone<VerUpdateRef>& mLV, MutationRef const& m) {
		byteSampleApplyMutation(m, mLV.version);
		counters.bytesInput += mvccStorageBytes(m);
		return mLV.push_back_deep(mLV.arena(), m);
	}

	void setTssPair(UID pairId) {
		tssPairID = Optional<UID>(pairId);

		// Set up tss fault injection here, only if we are in simulated mode and with fault injection.
		// With fault injection enabled, the tss will start acting normal for a bit, then after the specified delay
		// start behaving incorrectly.
		if (g_network->isSimulated() && !g_simulator.speedUpSimulation &&
		    g_simulator.tssMode >= ISimulator::TSSMode::EnabledAddDelay) {
			tssFaultInjectTime = now() + deterministicRandom()->randomInt(60, 300);
			TraceEvent(SevWarnAlways, "TSSInjectFaultEnabled", thisServerID)
			    .detail("Mode", g_simulator.tssMode)
			    .detail("At", tssFaultInjectTime.get());
		}
	}

	// If a TSS is "in quarantine", it means it has incorrect data. It is effectively in a "zombie" state where it
	// rejects all read requests and ignores all non-private mutations and data movements, but otherwise is still part
	// of the cluster. The purpose of this state is to "freeze" the TSS state after a mismatch so a human operator can
	// investigate, but preventing a new storage process from replacing the TSS on the worker. It will still get removed
	// from the cluster if it falls behind on the mutation stream, or if its tss pair gets removed and its tag is no
	// longer valid.
	bool isTSSInQuarantine() { return tssPairID.present() && tssInQuarantine; }

	void startTssQuarantine() {
		if (!tssInQuarantine) {
			// persist quarantine so it's still quarantined if rebooted
			storage.makeTssQuarantineDurable();
		}
		tssInQuarantine = true;
	}

	StorageServerDisk storage;

	KeyRangeMap<Reference<ShardInfo>> shards;
	uint64_t shardChangeCounter; // max( shards->changecounter )

	KeyRangeMap<bool> cachedRangeMap; // indicates if a key-range is being cached

	KeyRangeMap<std::vector<Reference<ChangeFeedInfo>>> keyChangeFeed;
	std::map<Key, Reference<ChangeFeedInfo>> uidChangeFeed;
	Deque<std::pair<std::vector<Key>, Version>> changeFeedVersions;
	std::map<UID, PromiseStream<Key>> changeFeedRemovals;
	std::set<Key> currentChangeFeeds;
	std::set<Key> fetchingChangeFeeds;
	std::unordered_map<NetworkAddress, std::map<UID, Version>> changeFeedClientVersions;
	std::unordered_map<Key, Version> changeFeedCleanupDurable;
	int64_t activeFeedQueries = 0;

	// newestAvailableVersion[k]
	//   == invalidVersion -> k is unavailable at all versions
	//   <= storageVersion -> k is unavailable at all versions (but might be read anyway from storage if we are in the
	//   process of committing makeShardDurable)
	//   == v              -> k is readable (from storage+versionedData) @ [storageVersion,v], and not being updated
	//   when version increases
	//   == latestVersion  -> k is readable (from storage+versionedData) @ [storageVersion,version.get()], and thus
	//   stays available when version increases
	CoalescedKeyRangeMap<Version> newestAvailableVersion;

	CoalescedKeyRangeMap<Version> newestDirtyVersion; // Similar to newestAvailableVersion, but includes (only) keys
	                                                  // that were only partly available (due to cancelled fetchKeys)

	// The following are in rough order from newest to oldest
	Version lastTLogVersion, lastVersionWithData, restoredVersion, prevVersion;
	NotifiedVersion version;
	NotifiedVersion desiredOldestVersion; // We can increase oldestVersion (and then durableVersion) to this version
	                                      // when the disk permits
	NotifiedVersion oldestVersion; // See also storageVersion()
	NotifiedVersion durableVersion; // At least this version will be readable from storage after a power failure
	Version rebootAfterDurableVersion;
	int8_t primaryLocality;
	NotifiedVersion knownCommittedVersion;

	Deque<std::pair<Version, Version>> recoveryVersionSkips;
	int64_t versionLag; // An estimate for how many versions it takes for the data to move from the logs to this storage
	                    // server

	Optional<UID> sourceTLogID; // the tLog from which the latest batch of versions were fetched

	ProtocolVersion logProtocol;

	Reference<ILogSystem> logSystem;
	Reference<ILogSystem::IPeekCursor> logCursor;

	Promise<UID> clusterId;
	// The version the cluster starts on. This value is not persisted and may
	// not be valid after a recovery.
	Version initialClusterVersion = 1;
	UID thisServerID;
	Optional<UID> tssPairID; // if this server is a tss, this is the id of its (ss) pair
	Optional<UID> ssPairID; // if this server is an ss, this is the id of its (tss) pair
	Optional<double> tssFaultInjectTime;
	bool tssInQuarantine;

	Key sk;
	Reference<AsyncVar<ServerDBInfo> const> db;
	Database cx;
	ActorCollection actors;

	StorageServerMetrics metrics;
	CoalescedKeyRangeMap<bool, int64_t, KeyBytesMetric<int64_t>> byteSampleClears;
	AsyncVar<bool> byteSampleClearsTooLarge;
	Future<Void> byteSampleRecovery;
	Future<Void> durableInProgress;

	AsyncMap<Key, bool> watches;
	int64_t watchBytes;
	int64_t numWatches;
	AsyncVar<bool> noRecentUpdates;
	double lastUpdate;

	std::string folder;

	// defined only during splitMutations()/addMutation()
	UpdateEagerReadInfo* updateEagerReads;

	FlowLock durableVersionLock;
	FlowLock fetchKeysParallelismLock;
	FlowLock fetchChangeFeedParallelismLock;
	int64_t fetchKeysBytesBudget;
	AsyncVar<bool> fetchKeysBudgetUsed;
	std::vector<Promise<FetchInjectionInfo*>> readyFetchKeys;

	FlowLock serveFetchCheckpointParallelismLock;

	int64_t instanceID;

	Promise<Void> otherError;
	Promise<Void> coreStarted;
	bool shuttingDown;

	Promise<Void> registerInterfaceAcceptingRequests;
	Future<Void> interfaceRegistered;

	bool behind;
	bool versionBehind;

	bool debug_inApplyUpdate;
	double debug_lastValidateTime;

	int64_t lastBytesInputEBrake;
	Version lastDurableVersionEBrake;

	int maxQueryQueue;
	int getAndResetMaxQueryQueueSize() {
		int val = maxQueryQueue;
		maxQueryQueue = 0;
		return val;
	}

	TransactionTagCounter transactionTagCounter;

	Optional<LatencyBandConfig> latencyBandConfig;

	struct Counters {
		CounterCollection cc;
		Counter allQueries, getKeyQueries, getValueQueries, getRangeQueries, getMappedRangeQueries,
		    getRangeStreamQueries, finishedQueries, lowPriorityQueries, rowsQueried, bytesQueried, watchQueries,
		    emptyQueries, feedRowsQueried, feedBytesQueried, feedStreamQueries, feedVersionQueries;

		// Bytes of the mutations that have been added to the memory of the storage server. When the data is durable
		// and cleared from the memory, we do not subtract it but add it to bytesDurable.
		Counter bytesInput;
		// Bytes pulled from TLogs, it counts the size of the key value pairs, e.g., key-value pair ("a", "b") is
		// counted as 2 Bytes.
		Counter logicalBytesInput;
		// Bytes pulled from TLogs for moving-in shards, it counts the mutations sent to the moving-in shard during
		// Fetching and Waiting phases.
		Counter logicalBytesMoveInOverhead;
		// Bytes committed to the underlying storage engine by SS, it counts the size of key value pairs.
		Counter kvCommitLogicalBytes;
		// Count of all clearRange operatons to the storage engine.
		Counter kvClearRanges;
		// ClearRange operations issued by FDB, instead of from users, e.g., ClearRange operations to remove a shard
		// from a storage server, as in removeDataRange().
		Counter kvSystemClearRanges;
		// Bytes of the mutations that have been removed from memory because they durable. The counting is same as
		// bytesInput, instead of the actual bytes taken in the storages, so that (bytesInput - bytesDurable) can
		// reflect the current memory footprint of MVCC.
		Counter bytesDurable;
		// Bytes fetched by fetchKeys() for data movements. The size is counted as a collection of KeyValueRef.
		Counter bytesFetched;
		// Like bytesInput but without MVCC accounting. The size is counted as how much it takes when serialized. It
		// is basically the size of both parameters of the mutation and a 12 bytes overhead that keeps mutation type
		// and the lengths of both parameters.
		Counter mutationBytes;

		// Bytes fetched by fetchChangeFeed for data movements.
		Counter feedBytesFetched;

		Counter sampledBytesCleared;
		// The number of key-value pairs fetched by fetchKeys()
		Counter kvFetched;
		Counter mutations, setMutations, clearRangeMutations, atomicMutations;
		Counter updateBatches, updateVersions;
		Counter loops;
		Counter fetchWaitingMS, fetchWaitingCount, fetchExecutingMS, fetchExecutingCount;
		Counter readsRejected;
		Counter wrongShardServer;
		Counter fetchedVersions;
		Counter fetchesFromLogs;
		// The following counters measure how many of lookups in the getMappedRangeQueries are effective. "Miss"
		// means fallback if fallback is enabled, otherwise means failure (so that another layer could implement
		// fallback).
		Counter quickGetValueHit, quickGetValueMiss, quickGetKeyValuesHit, quickGetKeyValuesMiss;

		// The number of logical bytes returned from storage engine, in response to readRange operations.
		Counter kvScanBytes;
		// The number of logical bytes returned from storage engine, in response to readValue operations.
		Counter kvGetBytes;
		// The number of keys read from storage engine by eagerReads.
		Counter eagerReadsKeys;
		// The count of readValue operation to the storage engine.
		Counter kvGets;
		// The count of readValue operation to the storage engine.
		Counter kvScans;
		// The count of commit operation to the storage engine.
		Counter kvCommits;

		LatencySample readLatencySample;
		LatencyBands readLatencyBands;
		LatencySample mappedRangeSample; // Samples getMappedRange latency
		LatencySample mappedRangeRemoteSample; // Samples getMappedRange remote subquery latency
		LatencySample mappedRangeLocalSample; // Samples getMappedRange local subquery latency

		Counters(StorageServer* self)
		  : cc("StorageServer", self->thisServerID.toString()), allQueries("QueryQueue", cc),
		    getKeyQueries("GetKeyQueries", cc), getValueQueries("GetValueQueries", cc),
		    getRangeQueries("GetRangeQueries", cc), getMappedRangeQueries("GetMappedRangeQueries", cc),
		    getRangeStreamQueries("GetRangeStreamQueries", cc), finishedQueries("FinishedQueries", cc),
		    lowPriorityQueries("LowPriorityQueries", cc), rowsQueried("RowsQueried", cc),
		    bytesQueried("BytesQueried", cc), watchQueries("WatchQueries", cc), emptyQueries("EmptyQueries", cc),
		    feedRowsQueried("FeedRowsQueried", cc), feedBytesQueried("FeedBytesQueried", cc),
		    feedStreamQueries("FeedStreamQueries", cc), feedVersionQueries("FeedVersionQueries", cc),
		    bytesInput("BytesInput", cc), logicalBytesInput("LogicalBytesInput", cc),
		    logicalBytesMoveInOverhead("LogicalBytesMoveInOverhead", cc),
		    kvCommitLogicalBytes("KVCommitLogicalBytes", cc), kvClearRanges("KVClearRanges", cc),
		    kvSystemClearRanges("KVSystemClearRanges", cc), bytesDurable("BytesDurable", cc),
		    bytesFetched("BytesFetched", cc), mutationBytes("MutationBytes", cc),
		    feedBytesFetched("FeedBytesFetched", cc), sampledBytesCleared("SampledBytesCleared", cc),
		    kvFetched("KVFetched", cc), mutations("Mutations", cc), setMutations("SetMutations", cc),
		    clearRangeMutations("ClearRangeMutations", cc), atomicMutations("AtomicMutations", cc),
		    updateBatches("UpdateBatches", cc), updateVersions("UpdateVersions", cc), loops("Loops", cc),
		    fetchWaitingMS("FetchWaitingMS", cc), fetchWaitingCount("FetchWaitingCount", cc),
		    fetchExecutingMS("FetchExecutingMS", cc), fetchExecutingCount("FetchExecutingCount", cc),
		    readsRejected("ReadsRejected", cc), wrongShardServer("WrongShardServer", cc),
		    fetchedVersions("FetchedVersions", cc), fetchesFromLogs("FetchesFromLogs", cc),
		    quickGetValueHit("QuickGetValueHit", cc), quickGetValueMiss("QuickGetValueMiss", cc),
		    quickGetKeyValuesHit("QuickGetKeyValuesHit", cc), quickGetKeyValuesMiss("QuickGetKeyValuesMiss", cc),
		    kvScanBytes("KVScanBytes", cc), kvGetBytes("KVGetBytes", cc), eagerReadsKeys("EagerReadsKeys", cc),
		    kvGets("KVGets", cc), kvScans("KVScans", cc), kvCommits("KVCommits", cc),
		    readLatencySample("ReadLatencyMetrics",
		                      self->thisServerID,
		                      SERVER_KNOBS->LATENCY_METRICS_LOGGING_INTERVAL,
		                      SERVER_KNOBS->LATENCY_SAMPLE_SIZE),
		    readLatencyBands("ReadLatencyBands", self->thisServerID, SERVER_KNOBS->STORAGE_LOGGING_DELAY),
		    mappedRangeSample("GetMappedRangeMetrics",
		                      self->thisServerID,
		                      SERVER_KNOBS->LATENCY_METRICS_LOGGING_INTERVAL,
		                      SERVER_KNOBS->LATENCY_SAMPLE_SIZE),
		    mappedRangeRemoteSample("GetMappedRangeRemoteMetrics",
		                            self->thisServerID,
		                            SERVER_KNOBS->LATENCY_METRICS_LOGGING_INTERVAL,
		                            SERVER_KNOBS->LATENCY_SAMPLE_SIZE),
		    mappedRangeLocalSample("GetMappedRangeLocalMetrics",
		                           self->thisServerID,
		                           SERVER_KNOBS->LATENCY_METRICS_LOGGING_INTERVAL,
		                           SERVER_KNOBS->LATENCY_SAMPLE_SIZE) {
			specialCounter(cc, "LastTLogVersion", [self]() { return self->lastTLogVersion; });
			specialCounter(cc, "Version", [self]() { return self->version.get(); });
			specialCounter(cc, "StorageVersion", [self]() { return self->storageVersion(); });
			specialCounter(cc, "DurableVersion", [self]() { return self->durableVersion.get(); });
			specialCounter(cc, "DesiredOldestVersion", [self]() { return self->desiredOldestVersion.get(); });
			specialCounter(cc, "VersionLag", [self]() { return self->versionLag; });
			specialCounter(cc, "LocalRate", [self] { return int64_t(self->currentRate() * 100); });

			specialCounter(cc, "BytesReadSampleCount", [self]() { return self->metrics.bytesReadSample.queue.size(); });
			specialCounter(
			    cc, "FetchKeysFetchActive", [self]() { return self->fetchKeysParallelismLock.activePermits(); });
			specialCounter(cc, "FetchKeysWaiting", [self]() { return self->fetchKeysParallelismLock.waiters(); });
			specialCounter(cc, "FetchChangeFeedFetchActive", [self]() {
				return self->fetchChangeFeedParallelismLock.activePermits();
			});
			specialCounter(
			    cc, "FetchChangeFeedWaiting", [self]() { return self->fetchChangeFeedParallelismLock.waiters(); });
			specialCounter(cc, "ServeFetchCheckpointActive", [self]() {
				return self->serveFetchCheckpointParallelismLock.activePermits();
			});
			specialCounter(cc, "ServeFetchCheckpointWaiting", [self]() {
				return self->serveFetchCheckpointParallelismLock.waiters();
			});
			specialCounter(cc, "QueryQueueMax", [self]() { return self->getAndResetMaxQueryQueueSize(); });
			specialCounter(cc, "BytesStored", [self]() { return self->metrics.byteSample.getEstimate(allKeys); });
			specialCounter(cc, "ActiveWatches", [self]() { return self->numWatches; });
			specialCounter(cc, "WatchBytes", [self]() { return self->watchBytes; });
			specialCounter(cc, "KvstoreSizeTotal", [self]() { return std::get<0>(self->storage.getSize()); });
			specialCounter(cc, "KvstoreNodeTotal", [self]() { return std::get<1>(self->storage.getSize()); });
			specialCounter(cc, "KvstoreInlineKey", [self]() { return std::get<2>(self->storage.getSize()); });
			specialCounter(cc, "ActiveChangeFeeds", [self]() { return self->uidChangeFeed.size(); });
			specialCounter(cc, "ActiveChangeFeedQueries", [self]() { return self->activeFeedQueries; });
		}
	} counters;

	// Bytes read from storage engine when a storage server starts.
	int64_t bytesRestored = 0;

	Reference<EventCacheHolder> storageServerSourceTLogIDEventHolder;

	StorageServer(IKeyValueStore* storage,
	              Reference<AsyncVar<ServerDBInfo> const> const& db,
	              StorageServerInterface const& ssi)
	  : shardAware(false), tlogCursorReadsLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                                               TLOG_CURSOR_READS_LATENCY_HISTOGRAM,
	                                                                               Histogram::Unit::microseconds)),
	    ssVersionLockLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                          SS_VERSION_LOCK_LATENCY_HISTOGRAM,
	                                                          Histogram::Unit::microseconds)),
	    eagerReadsLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                       EAGER_READS_LATENCY_HISTOGRAM,
	                                                       Histogram::Unit::microseconds)),
	    fetchKeysPTreeUpdatesLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                                  FETCH_KEYS_PTREE_UPDATES_LATENCY_HISTOGRAM,
	                                                                  Histogram::Unit::microseconds)),
	    tLogMsgsPTreeUpdatesLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                                 TLOG_MSGS_PTREE_UPDATES_LATENCY_HISTOGRAM,
	                                                                 Histogram::Unit::microseconds)),
	    storageUpdatesDurableLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                                  STORAGE_UPDATES_DURABLE_LATENCY_HISTOGRAM,
	                                                                  Histogram::Unit::microseconds)),
	    storageCommitLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                          STORAGE_COMMIT_LATENCY_HISTOGRAM,
	                                                          Histogram::Unit::microseconds)),
	    ssDurableVersionUpdateLatencyHistogram(Histogram::getHistogram(STORAGESERVER_HISTOGRAM_GROUP,
	                                                                   SS_DURABLE_VERSION_UPDATE_LATENCY_HISTOGRAM,
	                                                                   Histogram::Unit::microseconds)),
	    tag(invalidTag), poppedAllAfter(std::numeric_limits<Version>::max()), cpuUsage(0.0), diskUsage(0.0),
	    storage(this, storage), shardChangeCounter(0), lastTLogVersion(0), lastVersionWithData(0), restoredVersion(0),
	    prevVersion(0), rebootAfterDurableVersion(std::numeric_limits<Version>::max()),
	    primaryLocality(tagLocalityInvalid), knownCommittedVersion(0), versionLag(0), logProtocol(0),
	    thisServerID(ssi.id()), tssInQuarantine(false), db(db), actors(false),
	    byteSampleClears(false, LiteralStringRef("\xff\xff\xff")), durableInProgress(Void()), watchBytes(0),
	    numWatches(0), noRecentUpdates(false), lastUpdate(now()), updateEagerReads(nullptr),
	    fetchKeysParallelismLock(SERVER_KNOBS->FETCH_KEYS_PARALLELISM),
	    fetchChangeFeedParallelismLock(SERVER_KNOBS->FETCH_KEYS_PARALLELISM),
	    fetchKeysBytesBudget(SERVER_KNOBS->STORAGE_FETCH_BYTES), fetchKeysBudgetUsed(false),
	    serveFetchCheckpointParallelismLock(SERVER_KNOBS->SERVE_FETCH_CHECKPOINT_PARALLELISM),
	    instanceID(deterministicRandom()->randomUniqueID().first()), shuttingDown(false), behind(false),
	    versionBehind(false), debug_inApplyUpdate(false), debug_lastValidateTime(0), lastBytesInputEBrake(0),
	    lastDurableVersionEBrake(0), maxQueryQueue(0), transactionTagCounter(ssi.id()), counters(this),
	    storageServerSourceTLogIDEventHolder(
	        makeReference<EventCacheHolder>(ssi.id().toString() + "/StorageServerSourceTLogID")) {
		version.initMetric(LiteralStringRef("StorageServer.Version"), counters.cc.id);
		oldestVersion.initMetric(LiteralStringRef("StorageServer.OldestVersion"), counters.cc.id);
		durableVersion.initMetric(LiteralStringRef("StorageServer.DurableVersion"), counters.cc.id);
		desiredOldestVersion.initMetric(LiteralStringRef("StorageServer.DesiredOldestVersion"), counters.cc.id);

		newestAvailableVersion.insert(allKeys, invalidVersion);
		newestDirtyVersion.insert(allKeys, invalidVersion);
		if (CLIENT_KNOBS->SHARD_ENCODE_LOCATION_METADATA &&
		    (SERVER_KNOBS->STORAGE_SERVER_SHARD_AWARE || storage->shardAware())) {
			addShard(ShardInfo::newShard(this, StorageServerShard::notAssigned(allKeys)));
		} else {
			addShard(ShardInfo::newNotAssigned(allKeys));
		}

		cx = openDBOnServer(db, TaskPriority::DefaultEndpoint, LockAware::True);

		this->storage.kvCommitLogicalBytes = &counters.kvCommitLogicalBytes;
		this->storage.kvClearRanges = &counters.kvClearRanges;
		this->storage.kvGets = &counters.kvGets;
		this->storage.kvScans = &counters.kvScans;
		this->storage.kvCommits = &counters.kvCommits;
	}

	//~StorageServer() { fclose(log); }

	// Puts the given shard into shards.  The caller is responsible for adding shards
	//   for all ranges in shards.getAffectedRangesAfterInsertion(newShard->keys)), because these
	//   shards are invalidated by the call.
	void addShard(ShardInfo* newShard) {
		ASSERT(!newShard->keys.empty());
		newShard->changeCounter = ++shardChangeCounter;
		//TraceEvent("AddShard", this->thisServerID).detail("KeyBegin", newShard->keys.begin).detail("KeyEnd", newShard->keys.end).detail("State", newShard->isReadable() ? "Readable" : newShard->notAssigned() ? "NotAssigned" : "Adding").detail("Version", this->version.get());
		/*auto affected = shards.getAffectedRangesAfterInsertion( newShard->keys, Reference<ShardInfo>() );
		for(auto i = affected.begin(); i != affected.end(); ++i)
		    shards.insert( *i, Reference<ShardInfo>() );*/
		shards.insert(newShard->keys, Reference<ShardInfo>(newShard));
	}
	void addMutation(Version version,
	                 bool fromFetch,
	                 MutationRef const& mutation,
	                 KeyRangeRef const& shard,
	                 UpdateEagerReadInfo* eagerReads);
	void setInitialVersion(Version ver) {
		version = ver;
		desiredOldestVersion = ver;
		oldestVersion = ver;
		durableVersion = ver;
		lastVersionWithData = ver;
		restoredVersion = ver;

		mutableData().createNewVersion(ver);
		mutableData().forgetVersionsBefore(ver);
	}

	bool isTss() const { return tssPairID.present(); }

	bool isSSWithTSSPair() const { return ssPairID.present(); }

	void setSSWithTssPair(UID idOfTSS) { ssPairID = Optional<UID>(idOfTSS); }

	void clearSSWithTssPair() { ssPairID = Optional<UID>(); }

	// This is the maximum version that might be read from storage (the minimum version is durableVersion)
	Version storageVersion() const { return oldestVersion.get(); }

	bool isReadable(KeyRangeRef const& keys) {
		auto sh = shards.intersectingRanges(keys);
		for (auto i = sh.begin(); i != sh.end(); ++i)
			if (!i->value()->isReadable())
				return false;
		return true;
	}

	void checkChangeCounter(uint64_t oldShardChangeCounter, KeyRef const& key) {
		if (oldShardChangeCounter != shardChangeCounter && shards[key]->changeCounter > oldShardChangeCounter) {
			CODE_PROBE(true, "shard change during getValueQ");
			throw wrong_shard_server();
		}
	}

	void checkChangeCounter(uint64_t oldShardChangeCounter, KeyRangeRef const& keys) {
		if (oldShardChangeCounter != shardChangeCounter) {
			auto sh = shards.intersectingRanges(keys);
			for (auto i = sh.begin(); i != sh.end(); ++i)
				if (i->value()->changeCounter > oldShardChangeCounter) {
					CODE_PROBE(true, "shard change during range operation");
					throw wrong_shard_server();
				}
		}
	}

	Counter::Value queueSize() { return counters.bytesInput.getValue() - counters.bytesDurable.getValue(); }

	// penalty used by loadBalance() to balance requests among SSes. We prefer SS with less write queue size.
	double getPenalty() {
		return std::max(std::max(1.0,
		                         (queueSize() - (SERVER_KNOBS->TARGET_BYTES_PER_STORAGE_SERVER -
		                                         2.0 * SERVER_KNOBS->SPRING_BYTES_STORAGE_SERVER)) /
		                             SERVER_KNOBS->SPRING_BYTES_STORAGE_SERVER),
		                (currentRate() < 1e-6 ? 1e6 : 1.0 / currentRate()));
	}

	// Normally the storage server prefers to serve read requests over making mutations
	// durable to disk. However, when the storage server falls to far behind on
	// making mutations durable, this function will change the priority to prefer writes.
	Future<Void> getQueryDelay() {
		if ((version.get() - durableVersion.get() > SERVER_KNOBS->LOW_PRIORITY_DURABILITY_LAG) ||
		    (queueSize() > SERVER_KNOBS->LOW_PRIORITY_STORAGE_QUEUE_BYTES)) {
			++counters.lowPriorityQueries;
			return delay(0, TaskPriority::LowPriorityRead);
		}
		return delay(0, TaskPriority::DefaultEndpoint);
	}

	template <class Reply>
	using isLoadBalancedReply = std::is_base_of<LoadBalancedReply, Reply>;

	template <class Reply>
	typename std::enable_if<isLoadBalancedReply<Reply>::value, void>::type
	sendErrorWithPenalty(const ReplyPromise<Reply>& promise, const Error& err, double penalty) {
		if (err.code() == error_code_wrong_shard_server) {
			++counters.wrongShardServer;
		}
		Reply reply;
		reply.error = err;
		reply.penalty = penalty;
		promise.send(reply);
	}

	template <class Reply>
	typename std::enable_if<!isLoadBalancedReply<Reply>::value, void>::type
	sendErrorWithPenalty(const ReplyPromise<Reply>& promise, const Error& err, double) {
		if (err.code() == error_code_wrong_shard_server) {
			++counters.wrongShardServer;
		}
		promise.sendError(err);
	}

	template <class Request>
	bool shouldRead(const Request& request) {
		auto rate = currentRate();
		if (isTSSInQuarantine() || (rate < SERVER_KNOBS->STORAGE_DURABILITY_LAG_REJECT_THRESHOLD &&
		                            deterministicRandom()->random01() >
		                                std::max(SERVER_KNOBS->STORAGE_DURABILITY_LAG_MIN_RATE,
		                                         rate / SERVER_KNOBS->STORAGE_DURABILITY_LAG_REJECT_THRESHOLD))) {
			sendErrorWithPenalty(request.reply, server_overloaded(), getPenalty());
			++counters.readsRejected;
			return false;
		}
		return true;
	}

	template <class Request, class HandleFunction>
	Future<Void> readGuard(const Request& request, const HandleFunction& fun) {
		bool read = shouldRead(request);
		if (!read) {
			return Void();
		}
		return fun(this, request);
	}

	Version minFeedVersionForAddress(const NetworkAddress& addr) {
		auto& clientVersions = changeFeedClientVersions[addr];
		Version minVersion = version.get();
		for (auto& it : clientVersions) {
			/*fmt::print("SS {0} Blocked client {1} @ {2}\n",
			           thisServerID.toString().substr(0, 4),
			           it.first.toString().substr(0, 8),
			           it.second);*/
			minVersion = std::min(minVersion, it.second);
		}
		return minVersion;
	}

	void getSplitPoints(SplitRangeRequest const& req) {
		try {
			Optional<TenantMapEntry> entry = getTenantEntry(version.get(), req.tenantInfo);
			metrics.getSplitPoints(req, entry.map<Key>([](TenantMapEntry e) { return e.prefix; }));
		} catch (Error& e) {
			req.reply.sendError(e);
		}
	}
};

const StringRef StorageServer::CurrentRunningFetchKeys::emptyString = LiteralStringRef("");
const KeyRangeRef StorageServer::CurrentRunningFetchKeys::emptyKeyRange =
    KeyRangeRef(StorageServer::CurrentRunningFetchKeys::emptyString,
                StorageServer::CurrentRunningFetchKeys::emptyString);

// If and only if key:=value is in (storage+versionedData),    // NOT ACTUALLY: and key < allKeys.end,
//   and H(key) < |key+value|/bytesPerSample,
//     let sampledSize = max(|key+value|,bytesPerSample)
//     persistByteSampleKeys.begin()+key := sampledSize is in storage
//     (key,sampledSize) is in byteSample

// So P(key is sampled) * sampledSize == |key+value|

void StorageServer::byteSampleApplyMutation(MutationRef const& m, Version ver) {
	if (m.type == MutationRef::ClearRange)
		byteSampleApplyClear(KeyRangeRef(m.param1, m.param2), ver);
	else if (m.type == MutationRef::SetValue)
		byteSampleApplySet(KeyValueRef(m.param1, m.param2), ver);
	else
		ASSERT(false); // Mutation of unknown type modfying byte sample
}

// watchMap Operations
Reference<ServerWatchMetadata> StorageServer::getWatchMetadata(KeyRef key) const {
	const auto it = watchMap.find(key);
	if (it == watchMap.end())
		return Reference<ServerWatchMetadata>();
	return it->second;
}

KeyRef StorageServer::setWatchMetadata(Reference<ServerWatchMetadata> metadata) {
	KeyRef keyRef = metadata->key.contents();

	watchMap[keyRef] = metadata;
	return keyRef;
}

void StorageServer::deleteWatchMetadata(KeyRef key) {
	watchMap.erase(key);
}

void StorageServer::clearWatchMetadata() {
	watchMap.clear();
}

#ifndef __INTEL_COMPILER
#pragma endregion
#endif

/////////////////////////////////// Validation ///////////////////////////////////////
#ifndef __INTEL_COMPILER
#pragma region Validation
#endif
bool validateRange(StorageServer::VersionedData::ViewAtVersion const& view,
                   KeyRangeRef range,
                   Version version,
                   UID id,
                   Version minInsertVersion) {
	// * Nonoverlapping: No clear overlaps a set or another clear, or adjoins another clear.
	// * Old mutations are erased: All items in versionedData.atLatest() have insertVersion() > durableVersion()

	//TraceEvent("ValidateRange", id).detail("KeyBegin", range.begin).detail("KeyEnd", range.end).detail("Version", version);
	KeyRef k;
	bool ok = true;
	bool kIsClear = false;
	auto i = view.lower_bound(range.begin);
	if (i != view.begin())
		--i;
	for (; i != view.end() && i.key() < range.end; ++i) {
		ASSERT(i.insertVersion() > minInsertVersion);
		if (kIsClear && i->isClearTo() ? i.key() <= k : i.key() < k) {
			TraceEvent(SevError, "InvalidRange", id)
			    .detail("Key1", k)
			    .detail("Key2", i.key())
			    .detail("Version", version);
			ok = false;
		}
		// ASSERT( i.key() >= k );
		kIsClear = i->isClearTo();
		k = kIsClear ? i->getEndKey() : i.key();
	}
	return ok;
}

void validate(StorageServer* data, bool force = false) {
	try {
		if (force || (EXPENSIVE_VALIDATION)) {
			data->newestAvailableVersion.validateCoalesced();
			data->newestDirtyVersion.validateCoalesced();

			for (auto s = data->shards.ranges().begin(); s != data->shards.ranges().end(); ++s) {
				TraceEvent(SevVerbose, "ValidateShard", data->thisServerID)
				    .detail("Range", s->range())
				    .detail("ShardRange", s->value()->keys)
				    .detail("ShardState", s->value()->debugDescribeState())
				    .log();
				ASSERT(s->value()->keys == s->range());
				ASSERT(!s->value()->keys.empty());
				if (data->shardAware) {
					s->value()->validate();
				}
			}

			for (auto s = data->shards.ranges().begin(); s != data->shards.ranges().end(); ++s) {
				if (s->value()->isReadable()) {
					auto ar = data->newestAvailableVersion.intersectingRanges(s->range());
					for (auto a = ar.begin(); a != ar.end(); ++a) {
						TraceEvent(SevVerbose, "ValidateShardReadable", data->thisServerID)
						    .detail("Range", s->range())
						    .detail("ShardRange", s->value()->keys)
						    .detail("ShardState", s->value()->debugDescribeState())
						    .detail("AvailableRange", a->range())
						    .detail("AvailableVersion", a->value())
						    .log();
						ASSERT(a->value() == latestVersion);
					}
				}
			}

			// * versionedData contains versions [storageVersion(), version.get()].  It might also contain version
			// (version.get()+1), in which changeDurableVersion may be deleting ghosts, and/or it might
			//      contain later versions if applyUpdate is on the stack.
			ASSERT(data->data().getOldestVersion() == data->storageVersion());
			ASSERT(data->data().getLatestVersion() == data->version.get() ||
			       data->data().getLatestVersion() == data->version.get() + 1 ||
			       (data->debug_inApplyUpdate && data->data().getLatestVersion() > data->version.get()));

			auto latest = data->data().atLatest();

			// * Old shards are erased: versionedData.atLatest() has entries (sets or clear *begins*) only for keys in
			// readable or adding,transferred shards.
			for (auto s = data->shards.ranges().begin(); s != data->shards.ranges().end(); ++s) {
				ShardInfo* shard = s->value().getPtr();
				if (!shard->isInVersionedData()) {
					if (latest.lower_bound(s->begin()) != latest.lower_bound(s->end())) {
						TraceEvent(SevError, "VF", data->thisServerID)
						    .detail("LastValidTime", data->debug_lastValidateTime)
						    .detail("KeyBegin", s->begin())
						    .detail("KeyEnd", s->end())
						    .detail("FirstKey", latest.lower_bound(s->begin()).key())
						    .detail("FirstInsertV", latest.lower_bound(s->begin()).insertVersion());
					}
					ASSERT(latest.lower_bound(s->begin()) == latest.lower_bound(s->end()));
				}
			}

			// FIXME: do some change feed validation?

			latest.validate();
			validateRange(latest, allKeys, data->version.get(), data->thisServerID, data->durableVersion.get());

			data->debug_lastValidateTime = now();
		}
	} catch (...) {
		TraceEvent(SevError, "ValidationFailure", data->thisServerID)
		    .detail("LastValidTime", data->debug_lastValidateTime);
		throw;
	}
}
#ifndef __INTEL_COMPILER
#pragma endregion
#endif

void updateProcessStats(StorageServer* self) {
	if (g_network->isSimulated()) {
		// diskUsage and cpuUsage are not relevant in the simulator,
		// and relying on the actual values could break seed determinism
		self->cpuUsage = 100.0;
		self->diskUsage = 100.0;
		return;
	}

	SystemStatistics sysStats = getSystemStatistics();
	if (sysStats.initialized) {
		self->cpuUsage = 100 * sysStats.processCPUSeconds / sysStats.elapsed;
		self->diskUsage = 100 * std::max(0.0, (sysStats.elapsed - sysStats.processDiskIdleSeconds) / sysStats.elapsed);
	}
}

///////////////////////////////////// Queries /////////////////////////////////
#ifndef __INTEL_COMPILER
#pragma region Queries
#endif

ACTOR Future<Version> waitForVersionActor(StorageServer* data, Version version, SpanContext spanContext) {
	state Span span("SS:WaitForVersion"_loc, spanContext);
	choose {
		when(wait(data->version.whenAtLeast(version))) {
			// FIXME: A bunch of these can block with or without the following delay 0.
			// wait( delay(0) );  // don't do a whole bunch of these at once
			if (version < data->oldestVersion.get())
				throw transaction_too_old(); // just in case
			return version;
		}
		when(wait(delay(SERVER_KNOBS->FUTURE_VERSION_DELAY))) {
			if (deterministicRandom()->random01() < 0.001)
				TraceEvent(SevWarn, "ShardServerFutureVersion1000x", data->thisServerID)
				    .detail("Version", version)
				    .detail("MyVersion", data->version.get())
				    .detail("ServerID", data->thisServerID);
			throw future_version();
		}
	}
}

// If the latest commit version that mutated the shard(s) being served by the specified storage
// server is below the client specified read version then do a read at the latest commit version
// of the storage server.
Version getRealReadVersion(VersionVector& ssLatestCommitVersions, Tag& tag, Version specifiedReadVersion) {
	Version realReadVersion =
	    ssLatestCommitVersions.hasVersion(tag) ? ssLatestCommitVersions.getVersion(tag) : specifiedReadVersion;
	ASSERT(realReadVersion <= specifiedReadVersion);
	return realReadVersion;
}

// Find the latest commit version of the given tag.
Version getLatestCommitVersion(VersionVector& ssLatestCommitVersions, Tag& tag) {
	Version commitVersion =
	    ssLatestCommitVersions.hasVersion(tag) ? ssLatestCommitVersions.getVersion(tag) : invalidVersion;
	return commitVersion;
}

Future<Version> waitForVersion(StorageServer* data, Version version, SpanContext spanContext) {
	if (version == latestVersion) {
		version = std::max(Version(1), data->version.get());
	}

	if (version < data->oldestVersion.get() || version <= 0) {
		// TraceEvent(SevDebug, "WFVThrow", data->thisServerID).detail("Version", version).detail("OldestVersion", data->oldestVersion.get());
		return transaction_too_old();
	} else if (version <= data->version.get()) {
		return version;
	}

	if ((data->behind || data->versionBehind) && version > data->version.get()) {
		return process_behind();
	}

	if (deterministicRandom()->random01() < 0.001) {
		TraceEvent("WaitForVersion1000x").log();
	}
	return waitForVersionActor(data, version, spanContext);
}

Future<Version> waitForVersion(StorageServer* data,
                               Version commitVersion,
                               Version readVersion,
                               SpanContext spanContext) {
	ASSERT(commitVersion == invalidVersion || commitVersion < readVersion);

	if (commitVersion == invalidVersion) {
		return waitForVersion(data, readVersion, spanContext);
	}

	if (readVersion == latestVersion) {
		readVersion = std::max(Version(1), data->version.get());
	}

	if (readVersion < data->oldestVersion.get() || readVersion <= 0) {
		return transaction_too_old();
	} else {
		if (commitVersion < data->oldestVersion.get()) {
			return data->oldestVersion.get();
		} else if (commitVersion <= data->version.get()) {
			return commitVersion;
		}
	}

	if ((data->behind || data->versionBehind) && commitVersion > data->version.get()) {
		return process_behind();
	}

	if (deterministicRandom()->random01() < 0.001) {
		TraceEvent("WaitForVersion1000x");
	}
	return waitForVersionActor(data, std::max(commitVersion, data->oldestVersion.get()), spanContext);
}

ACTOR Future<Version> waitForVersionNoTooOld(StorageServer* data, Version version) {
	// This could become an Actor transparently, but for now it just does the lookup
	if (version == latestVersion)
		version = std::max(Version(1), data->version.get());
	if (version <= data->version.get())
		return version;
	choose {
		when(wait(data->version.whenAtLeast(version))) { return version; }
		when(wait(delay(SERVER_KNOBS->FUTURE_VERSION_DELAY))) {
			if (deterministicRandom()->random01() < 0.001)
				TraceEvent(SevWarn, "ShardServerFutureVersion1000x", data->thisServerID)
				    .detail("Version", version)
				    .detail("MyVersion", data->version.get())
				    .detail("ServerID", data->thisServerID);
			throw future_version();
		}
	}
}

Optional<TenantMapEntry> StorageServer::getTenantEntry(Version version, TenantInfo tenantInfo) {
	if (tenantInfo.name.present()) {
		auto view = tenantMap.at(version);
		auto itr = view.find(tenantInfo.name.get());
		if (itr == view.end()) {
			TraceEvent(SevWarn, "StorageUnknownTenant", thisServerID).detail("Tenant", tenantInfo.name).backtrace();
			throw unknown_tenant();
		} else if (itr->id != tenantInfo.tenantId) {
			TraceEvent(SevWarn, "StorageTenantIdMismatch", thisServerID)
			    .detail("Tenant", tenantInfo.name)
			    .detail("TenantId", tenantInfo.tenantId)
			    .detail("ExistingId", itr->id)
			    .backtrace();
			throw unknown_tenant();
		}

		return *itr;
	}

	return Optional<TenantMapEntry>();
}

std::vector<StorageServerShard> StorageServer::getStorageServerShards(KeyRangeRef range) {
	std::vector<StorageServerShard> res;
	for (auto t : this->shards.intersectingRanges(range)) {
		res.push_back(t.value()->toStorageServerShard());
	}
	return res;
}

ACTOR Future<Void> getValueQ(StorageServer* data, GetValueRequest req) {
	state int64_t resultSize = 0;
	Span span("SS:getValue"_loc, req.spanContext);
	if (req.tenantInfo.name.present()) {
		span.addAttribute("tenant"_sr, req.tenantInfo.name.get());
	}
	span.addAttribute("key"_sr, req.key);
	// Temporarily disabled -- this path is hit a lot
	// getCurrentLineage()->modify(&TransactionLineage::txID) = req.spanContext.first();

	try {
		++data->counters.getValueQueries;
		++data->counters.allQueries;
		data->maxQueryQueue = std::max<int>(
		    data->maxQueryQueue, data->counters.allQueries.getValue() - data->counters.finishedQueries.getValue());

		// Active load balancing runs at a very high priority (to obtain accurate queue lengths)
		// so we need to downgrade here
		wait(data->getQueryDelay());

		if (req.debugID.present())
			g_traceBatch.addEvent("GetValueDebug",
			                      req.debugID.get().first(),
			                      "getValueQ.DoRead"); //.detail("TaskID", g_network->getCurrentTask());

		state Optional<Value> v;
		Version commitVersion = getLatestCommitVersion(req.ssLatestCommitVersions, data->tag);
		state Version version = wait(waitForVersion(data, commitVersion, req.version, req.spanContext));
		if (req.debugID.present())
			g_traceBatch.addEvent("GetValueDebug",
			                      req.debugID.get().first(),
			                      "getValueQ.AfterVersion"); //.detail("TaskID", g_network->getCurrentTask());

		Optional<TenantMapEntry> entry = data->getTenantEntry(version, req.tenantInfo);
		if (entry.present()) {
			req.key = req.key.withPrefix(entry.get().prefix);
		}
		state uint64_t changeCounter = data->shardChangeCounter;

		if (!data->shards[req.key]->isReadable()) {
			//TraceEvent("WrongShardServer", data->thisServerID).detail("Key", req.key).detail("Version", version).detail("In", "getValueQ");
			throw wrong_shard_server();
		}

		state int path = 0;
		auto i = data->data().at(version).lastLessOrEqual(req.key);
		if (i && i->isValue() && i.key() == req.key) {
			v = (Value)i->getValue();
			path = 1;
		} else if (!i || !i->isClearTo() || i->getEndKey() <= req.key) {
			path = 2;
			Optional<Value> vv = wait(data->storage.readValue(req.key, IKeyValueStore::ReadType::NORMAL, req.debugID));
			data->counters.kvGetBytes += vv.expectedSize();
			// Validate that while we were reading the data we didn't lose the version or shard
			if (version < data->storageVersion()) {
				CODE_PROBE(true, "transaction_too_old after readValue");
				throw transaction_too_old();
			}
			data->checkChangeCounter(changeCounter, req.key);
			v = vv;
		}

		DEBUG_MUTATION("ShardGetValue",
		               version,
		               MutationRef(MutationRef::DebugKey, req.key, v.present() ? v.get() : LiteralStringRef("<null>")),
		               data->thisServerID);
		DEBUG_MUTATION("ShardGetPath",
		               version,
		               MutationRef(MutationRef::DebugKey,
		                           req.key,
		                           path == 0   ? LiteralStringRef("0")
		                           : path == 1 ? LiteralStringRef("1")
		                                       : LiteralStringRef("2")),
		               data->thisServerID);

		/*
		StorageMetrics m;
		m.bytesPerKSecond = req.key.size() + (v.present() ? v.get().size() : 0);
		m.iosPerKSecond = 1;
		data->metrics.notify(req.key, m);
		*/

		if (v.present()) {
			++data->counters.rowsQueried;
			resultSize = v.get().size();
			data->counters.bytesQueried += resultSize;
		} else {
			++data->counters.emptyQueries;
		}

		if (SERVER_KNOBS->READ_SAMPLING_ENABLED) {
			// If the read yields no value, randomly sample the empty read.
			int64_t bytesReadPerKSecond =
			    v.present() ? std::max((int64_t)(req.key.size() + v.get().size()), SERVER_KNOBS->EMPTY_READ_PENALTY)
			                : SERVER_KNOBS->EMPTY_READ_PENALTY;
			data->metrics.notifyBytesReadPerKSecond(req.key, bytesReadPerKSecond);
		}

		if (req.debugID.present())
			g_traceBatch.addEvent("GetValueDebug",
			                      req.debugID.get().first(),
			                      "getValueQ.AfterRead"); //.detail("TaskID", g_network->getCurrentTask());

		// Check if the desired key might be cached
		auto cached = data->cachedRangeMap[req.key];
		// if (cached)
		//	TraceEvent(SevDebug, "SSGetValueCached").detail("Key", req.key);

		GetValueReply reply(v, cached);
		reply.penalty = data->getPenalty();
		req.reply.send(reply);
	} catch (Error& e) {
		if (!canReplyWith(e))
			throw;
		data->sendErrorWithPenalty(req.reply, e, data->getPenalty());
	}

	data->transactionTagCounter.addRequest(req.tags, resultSize);

	++data->counters.finishedQueries;

	double duration = g_network->timer() - req.requestTime();
	data->counters.readLatencySample.addMeasurement(duration);
	if (data->latencyBandConfig.present()) {
		int maxReadBytes =
		    data->latencyBandConfig.get().readConfig.maxReadBytes.orDefault(std::numeric_limits<int>::max());
		data->counters.readLatencyBands.addMeasurement(duration, resultSize > maxReadBytes);
	}

	return Void();
}

// Pessimistic estimate the number of overhead bytes used by each
// watch. Watch key references are stored in an AsyncMap<Key,bool>, and actors
// must be kept alive until the watch is finished.
extern size_t WATCH_OVERHEAD_WATCHQ, WATCH_OVERHEAD_WATCHIMPL;

ACTOR Future<Version> watchWaitForValueChange(StorageServer* data, SpanContext parent, KeyRef key) {
	state Location spanLocation = "SS:watchWaitForValueChange"_loc;
	state Span span(spanLocation, parent);
	state Reference<ServerWatchMetadata> metadata = data->getWatchMetadata(key);

	if (metadata->debugID.present())
		g_traceBatch.addEvent("WatchValueDebug",
		                      metadata->debugID.get().first(),
		                      "watchValueSendReply.Before"); //.detail("TaskID", g_network->getCurrentTask());

	wait(success(waitForVersionNoTooOld(data, metadata->version)));
	if (metadata->debugID.present())
		g_traceBatch.addEvent("WatchValueDebug",
		                      metadata->debugID.get().first(),
		                      "watchValueSendReply.AfterVersion"); //.detail("TaskID", g_network->getCurrentTask());

	state Version minVersion = data->data().latestVersion;
	state Future<Void> watchFuture = data->watches.onChange(metadata->key);
	loop {
		try {
			metadata = data->getWatchMetadata(key);
			state Version latest = data->version.get();
			CODE_PROBE(latest >= minVersion && latest < data->data().latestVersion,
			           "Starting watch loop with latestVersion > data->version");
			GetValueRequest getReq(
			    span.context, TenantInfo(), metadata->key, latest, metadata->tags, metadata->debugID, VersionVector());
			state Future<Void> getValue = getValueQ(
			    data, getReq); // we are relying on the delay zero at the top of getValueQ, if removed we need one here
			GetValueReply reply = wait(getReq.reply.getFuture());
			span = Span(spanLocation, parent);

			if (reply.error.present()) {
				ASSERT(reply.error.get().code() != error_code_future_version);
				throw reply.error.get();
			}
			if (BUGGIFY) {
				throw transaction_too_old();
			}

			DEBUG_MUTATION(
			    "ShardWatchValue",
			    latest,
			    MutationRef(MutationRef::DebugKey,
			                metadata->key,
			                reply.value.present() ? StringRef(reply.value.get()) : LiteralStringRef("<null>")),
			    data->thisServerID);

			if (metadata->debugID.present())
				g_traceBatch.addEvent(
				    "WatchValueDebug",
				    metadata->debugID.get().first(),
				    "watchValueSendReply.AfterRead"); //.detail("TaskID", g_network->getCurrentTask());

			if (reply.value != metadata->value && latest >= metadata->version) {
				return latest; // fire watch
			}

			if (data->watchBytes > SERVER_KNOBS->MAX_STORAGE_SERVER_WATCH_BYTES) {
				CODE_PROBE(true, "Too many watches, reverting to polling");
				throw watch_cancelled();
			}

			state int64_t watchBytes =
			    (metadata->key.expectedSize() + metadata->value.expectedSize() + key.expectedSize() +
			     sizeof(Reference<ServerWatchMetadata>) + sizeof(ServerWatchMetadata) + WATCH_OVERHEAD_WATCHIMPL);

			data->watchBytes += watchBytes;
			try {
				if (latest < minVersion) {
					// If the version we read is less than minVersion, then we may fail to be notified of any changes
					// that occur up to or including minVersion To prevent that, we'll check the key again once the
					// version reaches our minVersion
					watchFuture = watchFuture || data->version.whenAtLeast(minVersion);
				}
				if (BUGGIFY) {
					// Simulate a trigger on the watch that results in the loop going around without the value changing
					watchFuture = watchFuture || delay(deterministicRandom()->random01());
				}
				wait(watchFuture);
				data->watchBytes -= watchBytes;
			} catch (Error& e) {
				data->watchBytes -= watchBytes;
				throw;
			}
		} catch (Error& e) {
			if (e.code() != error_code_transaction_too_old) {
				throw e;
			}

			CODE_PROBE(true, "Reading a watched key failed with transaction_too_old");
		}

		watchFuture = data->watches.onChange(metadata->key);
		wait(data->version.whenAtLeast(data->data().latestVersion));
	}
}

void checkCancelWatchImpl(StorageServer* data, WatchValueRequest req) {
	Reference<ServerWatchMetadata> metadata = data->getWatchMetadata(req.key.contents());
	if (metadata.isValid() && metadata->versionPromise.getFutureReferenceCount() == 1) {
		// last watch timed out so cancel watch_impl and delete key from the map
		data->deleteWatchMetadata(req.key.contents());
		metadata->watch_impl.cancel();
	}
}

ACTOR Future<Void> watchValueSendReply(StorageServer* data,
                                       WatchValueRequest req,
                                       Future<Version> resp,
                                       SpanContext spanContext) {
	state Span span("SS:watchValue"_loc, spanContext);
	state double startTime = now();
	++data->counters.watchQueries;
	++data->numWatches;
	data->watchBytes += WATCH_OVERHEAD_WATCHQ;

	loop {
		double timeoutDelay = -1;
		if (data->noRecentUpdates.get()) {
			timeoutDelay = std::max(CLIENT_KNOBS->FAST_WATCH_TIMEOUT - (now() - startTime), 0.0);
		} else if (!BUGGIFY) {
			timeoutDelay = std::max(CLIENT_KNOBS->WATCH_TIMEOUT - (now() - startTime), 0.0);
		}

		try {
			choose {
				when(Version ver = wait(resp)) {
					// fire watch
					req.reply.send(WatchValueReply{ ver });
					checkCancelWatchImpl(data, req);
					--data->numWatches;
					data->watchBytes -= WATCH_OVERHEAD_WATCHQ;
					return Void();
				}
				when(wait(timeoutDelay < 0 ? Never() : delay(timeoutDelay))) {
					// watch timed out
					data->sendErrorWithPenalty(req.reply, timed_out(), data->getPenalty());
					checkCancelWatchImpl(data, req);
					--data->numWatches;
					data->watchBytes -= WATCH_OVERHEAD_WATCHQ;
					return Void();
				}
				when(wait(data->noRecentUpdates.onChange())) {}
			}
		} catch (Error& e) {
			data->watchBytes -= WATCH_OVERHEAD_WATCHQ;
			checkCancelWatchImpl(data, req);
			--data->numWatches;

			if (!canReplyWith(e))
				throw e;
			data->sendErrorWithPenalty(req.reply, e, data->getPenalty());
			return Void();
		}
	}
}

// Finds a checkpoint.
ACTOR Future<Void> getCheckpointQ(StorageServer* self, GetCheckpointRequest req) {
	// Wait until the desired version is durable.
	wait(self->durableVersion.whenAtLeast(req.version + 1));

	TraceEvent(SevDebug, "ServeGetCheckpointVersionSatisfied", self->thisServerID)
	    .detail("Version", req.version)
	    .detail("Range", req.range.toString())
	    .detail("Format", static_cast<int>(req.format));

	try {
		std::unordered_map<UID, CheckpointMetaData>::iterator it = self->checkpoints.begin();
		for (; it != self->checkpoints.end(); ++it) {
			const CheckpointMetaData& md = it->second;
			if (md.version == req.version && md.format == req.format && md.range.contains(req.range) &&
			    md.getState() == CheckpointMetaData::Complete) {
				req.reply.send(md);
				TraceEvent(SevDebug, "ServeGetCheckpointEnd", self->thisServerID).detail("Checkpoint", md.toString());
				break;
			}
		}

		if (it == self->checkpoints.end()) {
			req.reply.sendError(checkpoint_not_found());
		}
	} catch (Error& e) {
		if (!canReplyWith(e)) {
			throw;
		}
		req.reply.sendError(e);
	}
	return Void();
}

// Delete the checkpoint from disk, as well as all related presisted meta data.
ACTOR Future<Void> deleteCheckpointQ(StorageServer* self, Version version, CheckpointMetaData checkpoint) {
	wait(delay(0, TaskPriority::Low));

	wait(self->durableVersion.whenAtLeast(version));

	TraceEvent("DeleteCheckpointBegin", self->thisServerID).detail("Checkpoint", checkpoint.toString());

	self->checkpoints.erase(checkpoint.checkpointID);

	try {
		wait(deleteCheckpoint(checkpoint));
	} catch (Error& e) {
		// TODO: Handle errors more gracefully.
		throw;
	}

	state Key persistCheckpointKey(persistCheckpointKeys.begin.toString() + checkpoint.checkpointID.toString());
	state Key pendingCheckpointKey(persistPendingCheckpointKeys.begin.toString() + checkpoint.checkpointID.toString());
	auto& mLV = self->addVersionToMutationLog(self->data().getLatestVersion());
	self->addMutationToMutationLog(
	    mLV, MutationRef(MutationRef::ClearRange, pendingCheckpointKey, keyAfter(pendingCheckpointKey)));
	self->addMutationToMutationLog(
	    mLV, MutationRef(MutationRef::ClearRange, persistCheckpointKey, keyAfter(persistCheckpointKey)));

	return Void();
}

// Serves FetchCheckpointRequests.
ACTOR Future<Void> fetchCheckpointQ(StorageServer* self, FetchCheckpointRequest req) {
	state ICheckpointReader* reader = nullptr;
	TraceEvent("ServeFetchCheckpointBegin", self->thisServerID)
	    .detail("CheckpointID", req.checkpointID)
	    .detail("Token", req.token);

	req.reply.setByteLimit(SERVER_KNOBS->CHECKPOINT_TRANSFER_BLOCK_BYTES);

	// Returns error is the checkpoint cannot be found.
	const auto it = self->checkpoints.find(req.checkpointID);
	if (it == self->checkpoints.end()) {
		req.reply.sendError(checkpoint_not_found());
		TraceEvent("ServeFetchCheckpointNotFound", self->thisServerID).detail("CheckpointID", req.checkpointID);
		return Void();
	}

	try {
		reader = newCheckpointReader(it->second, deterministicRandom()->randomUniqueID());
		wait(reader->init(req.token));

		loop {
			state Standalone<StringRef> data = wait(reader->nextChunk(CLIENT_KNOBS->REPLY_BYTE_LIMIT));
			wait(req.reply.onReady());
			FetchCheckpointReply reply(req.token);
			reply.data = data;
			req.reply.send(reply);
		}
	} catch (Error& e) {
		if (e.code() == error_code_end_of_stream) {
			req.reply.sendError(end_of_stream());
			TraceEvent("ServeFetchCheckpointEnd", self->thisServerID)
			    .detail("CheckpointID", req.checkpointID)
			    .detail("Token", req.token);
		} else {
			TraceEvent(SevWarnAlways, "ServerFetchCheckpointFailure")
			    .errorUnsuppressed(e)
			    .detail("CheckpointID", req.checkpointID)
			    .detail("Token", req.token);
			if (!canReplyWith(e)) {
				throw e;
			}
			req.reply.sendError(e);
		}
	}

	wait(reader->close());
	return Void();
}

// Serves FetchCheckpointKeyValuesRequest, reads local checkpoint and sends it to the client over wire.
ACTOR Future<Void> fetchCheckpointKeyValuesQ(StorageServer* self, FetchCheckpointKeyValuesRequest req) {
	wait(self->serveFetchCheckpointParallelismLock.take(TaskPriority::DefaultYield));
	state FlowLock::Releaser holder(self->serveFetchCheckpointParallelismLock);

	TraceEvent("ServeFetchCheckpointKeyValuesBegin", self->thisServerID)
	    .detail("CheckpointID", req.checkpointID)
	    .detail("Range", req.range);

	req.reply.setByteLimit(SERVER_KNOBS->CHECKPOINT_TRANSFER_BLOCK_BYTES);

	// Returns error if the checkpoint cannot be found.
	const auto it = self->checkpoints.find(req.checkpointID);
	if (it == self->checkpoints.end()) {
		req.reply.sendError(checkpoint_not_found());
		TraceEvent("ServeFetchCheckpointNotFound", self->thisServerID).detail("CheckpointID", req.checkpointID);
		return Void();
	}

	try {
		state ICheckpointReader* reader = newCheckpointReader(it->second, self->thisServerID);
		wait(reader->init(BinaryWriter::toValue(req.range, IncludeVersion())));

		loop {
			state RangeResult res =
			    wait(reader->nextKeyValues(CLIENT_KNOBS->REPLY_BYTE_LIMIT, CLIENT_KNOBS->REPLY_BYTE_LIMIT));
			if (!res.empty()) {
				TraceEvent(SevDebug, "FetchCheckpontKeyValuesReadRange", self->thisServerID)
				    .detail("CheckpointID", req.checkpointID)
				    .detail("FirstReturnedKey", res.front().key)
				    .detail("LastReturnedKey", res.back().key)
				    .detail("Size", res.size());
			} else {
				TraceEvent(SevInfo, "FetchCheckpontKeyValuesEmptyRange", self->thisServerID)
				    .detail("CheckpointID", req.checkpointID);
			}

			wait(req.reply.onReady());
			FetchCheckpointKeyValuesStreamReply reply;
			reply.arena.dependsOn(res.arena());
			for (int i = 0; i < res.size(); ++i) {
				reply.data.push_back(reply.arena, res[i]);
			}

			req.reply.send(reply);
		}
	} catch (Error& e) {
		if (e.code() == error_code_end_of_stream) {
			req.reply.sendError(end_of_stream());
			TraceEvent("ServeFetchCheckpointKeyValuesEnd", self->thisServerID)
			    .detail("CheckpointID", req.checkpointID)
			    .detail("Range", req.range);
		} else {
			TraceEvent(SevWarnAlways, "ServerFetchCheckpointKeyValuesFailure")
			    .errorUnsuppressed(e)
			    .detail("CheckpointID", req.checkpointID)
			    .detail("Range", req.range);
			if (!canReplyWith(e)) {
				throw e;
			}
			req.reply.sendError(e);
		}
	}

	wait(reader->close());
	return Void();
}

ACTOR Future<Void> overlappingChangeFeedsQ(StorageServer* data, OverlappingChangeFeedsRequest req) {
	wait(delay(0));
	wait(data->version.whenAtLeast(req.minVersion));

	if (!data->isReadable(req.range)) {
		req.reply.sendError(wrong_shard_server());
		return Void();
	}

	Version metadataVersion = invalidVersion;

	auto ranges = data->keyChangeFeed.intersectingRanges(req.range);
	std::map<Key, std::tuple<KeyRange, Version, Version>> rangeIds;
	for (auto r : ranges) {
		for (auto& it : r.value()) {
			if (!it->removing) {
				// Can't tell other SS about a change feed create or stopVersion that may get rolled back, and we only
				// need to tell it about the metadata if req.minVersion > metadataVersion, since it will get the
				// information from its own private mutations if it hasn't processed up that version yet
				metadataVersion = std::max(metadataVersion, it->metadataCreateVersion);

				Version stopVersion;
				if (it->stopVersion != MAX_VERSION && req.minVersion > it->stopVersion) {
					stopVersion = it->stopVersion;
					metadataVersion = std::max(metadataVersion, stopVersion);
				} else {
					stopVersion = MAX_VERSION;
				}

				rangeIds[it->id] = std::tuple(it->range, it->emptyVersion, stopVersion);
			}
		}
	}
	state OverlappingChangeFeedsReply reply;
	for (auto& it : rangeIds) {
		reply.rangeIds.push_back(OverlappingChangeFeedEntry(
		    it.first, std::get<0>(it.second), std::get<1>(it.second), std::get<2>(it.second)));
		TraceEvent(SevDebug, "OverlappingChangeFeedEntry", data->thisServerID)
		    .detail("MinVersion", req.minVersion)
		    .detail("FeedID", it.first)
		    .detail("Range", std::get<0>(it.second))
		    .detail("EmptyVersion", std::get<1>(it.second))
		    .detail("StopVersion", std::get<2>(it.second));
	}

	// Make sure all of the metadata we are sending won't get rolled back
	if (metadataVersion != invalidVersion && metadataVersion > data->knownCommittedVersion.get()) {
		CODE_PROBE(true, "overlapping change feeds waiting for metadata version to be committed");
		wait(data->desiredOldestVersion.whenAtLeast(metadataVersion));
	}
	req.reply.send(reply);
	return Void();
}

MutationsAndVersionRef filterMutationsInverted(Arena& arena, MutationsAndVersionRef const& m, KeyRange const& range) {
	Optional<VectorRef<MutationRef>> modifiedMutations;
	for (int i = 0; i < m.mutations.size(); i++) {
		if (m.mutations[i].type == MutationRef::SetValue) {
			if (modifiedMutations.present() && !range.contains(m.mutations[i].param1)) {
				modifiedMutations.get().push_back(arena, m.mutations[i]);
			}
			if (!modifiedMutations.present() && range.contains(m.mutations[i].param1)) {
				modifiedMutations = m.mutations.slice(0, i);
				arena.dependsOn(range.arena());
			}
		} else {
			ASSERT(m.mutations[i].type == MutationRef::ClearRange);
			if (!modifiedMutations.present() &&
			    (m.mutations[i].param2 > range.begin && m.mutations[i].param1 < range.end)) {
				modifiedMutations = m.mutations.slice(0, i);
				arena.dependsOn(range.arena());
			}
			if (modifiedMutations.present()) {
				if (m.mutations[i].param1 < range.begin) {
					modifiedMutations.get().push_back(arena,
					                                  MutationRef(MutationRef::ClearRange,
					                                              m.mutations[i].param1,
					                                              std::min(range.begin, m.mutations[i].param2)));
				}
				if (m.mutations[i].param2 > range.end) {
					modifiedMutations.get().push_back(arena,
					                                  MutationRef(MutationRef::ClearRange,
					                                              std::max(range.end, m.mutations[i].param1),
					                                              m.mutations[i].param2));
				}
			}
		}
	}
	if (modifiedMutations.present()) {
		return MutationsAndVersionRef(modifiedMutations.get(), m.version, m.knownCommittedVersion);
	}
	return m;
}

MutationsAndVersionRef filterMutations(Arena& arena,
                                       MutationsAndVersionRef const& m,
                                       KeyRange const& range,
                                       bool inverted) {
	if (m.mutations.size() == 1 && m.mutations.back().param1 == lastEpochEndPrivateKey) {
		return m;
	}

	if (inverted) {
		return filterMutationsInverted(arena, m, range);
	}

	Optional<VectorRef<MutationRef>> modifiedMutations;
	for (int i = 0; i < m.mutations.size(); i++) {
		if (m.mutations[i].type == MutationRef::SetValue) {
			if (modifiedMutations.present() && range.contains(m.mutations[i].param1)) {
				modifiedMutations.get().push_back(arena, m.mutations[i]);
			}
			if (!modifiedMutations.present() && !range.contains(m.mutations[i].param1)) {
				modifiedMutations = m.mutations.slice(0, i);
				arena.dependsOn(range.arena());
			}
		} else {
			ASSERT(m.mutations[i].type == MutationRef::ClearRange);
			if (!modifiedMutations.present() &&
			    (m.mutations[i].param1 < range.begin || m.mutations[i].param2 > range.end)) {
				modifiedMutations = m.mutations.slice(0, i);
				arena.dependsOn(range.arena());
			}
			if (modifiedMutations.present()) {
				if (m.mutations[i].param1 < range.end && range.begin < m.mutations[i].param2) {
					modifiedMutations.get().push_back(arena,
					                                  MutationRef(MutationRef::ClearRange,
					                                              std::max(range.begin, m.mutations[i].param1),
					                                              std::min(range.end, m.mutations[i].param2)));
				}
			}
		}
	}
	if (modifiedMutations.present()) {
		return MutationsAndVersionRef(modifiedMutations.get(), m.version, m.knownCommittedVersion);
	}
	return m;
}

// set this for VERY verbose logs on change feed SS reads
#define DEBUG_CF_TRACE false

// To easily find if a change feed read missed data. Set the CF to the feedId, the key to the missing key, and the
// version to the version the mutation is missing at.
#define DO_DEBUG_CF_MISSING false
#define DEBUG_CF_MISSING_CF ""_sr
#define DEBUG_CF_MISSING_KEY ""_sr
#define DEBUG_CF_MISSING_VERSION invalidVersion
#define DEBUG_CF_MISSING(cfId, keyRange, beginVersion, lastVersion)                                                    \
	DO_DEBUG_CF_MISSING&& cfId.printable().substr(0, 6) ==                                                             \
	        DEBUG_CF_MISSING_CF&& keyRange.contains(DEBUG_CF_MISSING_KEY) &&                                           \
	    beginVersion <= DEBUG_CF_MISSING_VERSION&& lastVersion >= DEBUG_CF_MISSING_VERSION

// efficiently searches for the change feed mutation start point at begin version
static std::deque<Standalone<MutationsAndVersionRef>>::const_iterator searchChangeFeedStart(
    std::deque<Standalone<MutationsAndVersionRef>> const& mutations,
    Version beginVersion,
    bool atLatest) {

	if (mutations.empty() || beginVersion > mutations.back().version) {
		return mutations.end();
	} else if (beginVersion <= mutations.front().version) {
		return mutations.begin();
	}

	MutationsAndVersionRef searchKey;
	searchKey.version = beginVersion;
	if (atLatest) {
		int jump = 1;
		// exponential search backwards, because atLatest means the new mutations are likely only at the very end
		auto lastEnd = mutations.end();
		auto currentEnd = mutations.end() - 1;
		while (currentEnd > mutations.begin()) {
			if (beginVersion >= currentEnd->version) {
				break;
			}
			lastEnd = currentEnd + 1;
			currentEnd -= jump;
			jump <<= 1;
		}
		if (currentEnd < mutations.begin()) {
			currentEnd = mutations.begin();
		}
		auto ret = std::lower_bound(currentEnd, lastEnd, searchKey, MutationsAndVersionRef::OrderByVersion());
		// TODO REMOVE: for validation
		if (ret != mutations.end()) {
			if (ret->version < beginVersion) {
				fmt::print("ERROR: {0}) {1} < {2}\n", ret - mutations.begin(), ret->version, beginVersion);
			}
			ASSERT(ret->version >= beginVersion);
		}
		if (ret != mutations.begin()) {
			if ((ret - 1)->version >= beginVersion) {
				fmt::print("ERROR: {0}) {1} >= {2}\n", (ret - mutations.begin()) - 1, (ret - 1)->version, beginVersion);
			}
			ASSERT((ret - 1)->version < beginVersion);
		}
		return ret;
	} else {
		// binary search
		return std::lower_bound(
		    mutations.begin(), mutations.end(), searchKey, MutationsAndVersionRef::OrderByVersion());
	}
}

ACTOR Future<std::pair<ChangeFeedStreamReply, bool>> getChangeFeedMutations(StorageServer* data,
                                                                            ChangeFeedStreamRequest req,
                                                                            bool inverted,
                                                                            bool atLatest,
                                                                            UID streamUID /* for debugging */) {
	state ChangeFeedStreamReply reply;
	state ChangeFeedStreamReply memoryReply;
	state int remainingLimitBytes = CLIENT_KNOBS->REPLY_BYTE_LIMIT;
	state int remainingDurableBytes = CLIENT_KNOBS->REPLY_BYTE_LIMIT;
	state Version startVersion = data->version.get();

	if (DEBUG_CF_TRACE) {
		TraceEvent(SevDebug, "TraceChangeFeedMutationsBegin", data->thisServerID)
		    .detail("FeedID", req.rangeID)
		    .detail("StreamUID", streamUID)
		    .detail("Range", req.range)
		    .detail("Begin", req.begin)
		    .detail("End", req.end);
	}

	if (data->version.get() < req.begin) {
		wait(data->version.whenAtLeast(req.begin));
		// we must delay here to ensure that any up-to-date change feeds that are waiting on the
		// mutation trigger run BEFORE any blocked change feeds run, in order to preserve the
		// correct minStreamVersion ordering
		wait(delay(0));
	}

	state uint64_t changeCounter = data->shardChangeCounter;
	if (!inverted && !data->isReadable(req.range)) {
		throw wrong_shard_server();
	}

	auto feed = data->uidChangeFeed.find(req.rangeID);
	if (feed == data->uidChangeFeed.end()) {
		throw unknown_change_feed();
	}

	state Reference<ChangeFeedInfo> feedInfo = feed->second;

	// We must copy the mutationDeque when fetching the durable bytes in case mutations are popped from memory while
	// waiting for the results
	state Version dequeVersion = data->version.get();
	state Version dequeKnownCommit = data->knownCommittedVersion.get();
	state Version emptyVersion = feedInfo->emptyVersion;
	Version fetchStorageVersion = std::max(feedInfo->fetchVersion, feedInfo->durableFetchVersion.get());

	if (DEBUG_CF_TRACE) {
		TraceEvent(SevDebug, "TraceChangeFeedMutationsDetails", data->thisServerID)
		    .detail("FeedID", req.rangeID)
		    .detail("StreamUID", streamUID)
		    .detail("Range", req.range)
		    .detail("Begin", req.begin)
		    .detail("End", req.end)
		    .detail("AtLatest", atLatest)
		    .detail("DequeVersion", dequeVersion)
		    .detail("EmptyVersion", feedInfo->emptyVersion)
		    .detail("StorageVersion", feedInfo->storageVersion)
		    .detail("DurableVersion", feedInfo->durableVersion)
		    .detail("FetchStorageVersion", fetchStorageVersion)
		    .detail("FetchVersion", feedInfo->fetchVersion)
		    .detail("DurableFetchVersion", feedInfo->durableFetchVersion.get());
	}

	if (req.end > emptyVersion + 1) {
		auto it = searchChangeFeedStart(feedInfo->mutations, req.begin, atLatest);
		while (it != feedInfo->mutations.end()) {
			if (it->version >= req.end || it->version > dequeVersion || remainingLimitBytes <= 0) {
				break;
			}
			auto m = filterMutations(memoryReply.arena, *it, req.range, inverted);
			if (m.mutations.size()) {
				memoryReply.arena.dependsOn(it->arena());
				memoryReply.mutations.push_back(memoryReply.arena, m);
				remainingLimitBytes -= sizeof(MutationsAndVersionRef) + m.expectedSize();
			}
			it++;
		}
	}

	state bool readDurable = feedInfo->durableVersion != invalidVersion && req.begin <= feedInfo->durableVersion;
	state bool readFetched = req.begin <= fetchStorageVersion && !atLatest;
	state bool waitFetched = false;
	if (req.end > emptyVersion + 1 && (readDurable || readFetched)) {
		if (readFetched && req.begin <= feedInfo->fetchVersion) {
			waitFetched = true;
			// Request needs data that has been written to storage by a change feed fetch, but not committed yet
			// To not block fetchKeys making normal SS data readable on making change feed data written to storage, we
			// wait in here instead for all fetched data to become readable from the storage engine.
			ASSERT(req.begin <= feedInfo->fetchVersion);
			CODE_PROBE(true, "getChangeFeedMutations before fetched data durable");

			// Wait for next commit to write pending feed data to storage
			wait(feedInfo->durableFetchVersion.whenAtLeast(feedInfo->fetchVersion));
			// To let update storage finish
			wait(delay(0));
		}
		RangeResult res = wait(
		    data->storage.readRange(KeyRangeRef(changeFeedDurableKey(req.rangeID, std::max(req.begin, emptyVersion)),
		                                        changeFeedDurableKey(req.rangeID, req.end)),
		                            1 << 30,
		                            remainingDurableBytes));

		data->counters.kvScanBytes += res.logicalSize();

		if (!inverted && !req.range.empty()) {
			data->checkChangeCounter(changeCounter, req.range);
		}

		// TODO eventually: only do verify in simulation?
		int memoryVerifyIdx = 0;

		Version lastVersion = req.begin - 1;
		Version lastKnownCommitted = invalidVersion;
		for (auto& kv : res) {
			Key id;
			Version version, knownCommittedVersion;
			Standalone<VectorRef<MutationRef>> mutations;
			std::tie(id, version) = decodeChangeFeedDurableKey(kv.key);
			std::tie(mutations, knownCommittedVersion) = decodeChangeFeedDurableValue(kv.value);

			// gap validation
			while (memoryVerifyIdx < memoryReply.mutations.size() &&
			       version > memoryReply.mutations[memoryVerifyIdx].version) {
				if (req.canReadPopped) {
					// There are weird cases where SS fetching mixed with SS durability and popping can mean there are
					// gaps before the popped version temporarily
					memoryVerifyIdx++;
					continue;
				}

				// There is a case where this can happen - if we wait on a fetching change feed, and the feed is
				// popped while we wait, we could have copied the memory mutations into memoryReply before the
				// pop, but they may or may not have been skipped writing to disk
				if (waitFetched && feedInfo->emptyVersion > emptyVersion &&
				    memoryReply.mutations[memoryVerifyIdx].version <= feedInfo->emptyVersion) {
					memoryVerifyIdx++;
					continue;
				} else {
					fmt::print("ERROR: SS {0} CF {1} SQ {2} has mutation at {3} in memory but not on disk (next disk "
					           "is {4}) (emptyVersion={5}, emptyBefore={6})!\n",
					           data->thisServerID.toString().substr(0, 4),
					           req.rangeID.printable().substr(0, 6),
					           streamUID.toString().substr(0, 8),
					           memoryReply.mutations[memoryVerifyIdx].version,
					           version,
					           feedInfo->emptyVersion,
					           emptyVersion);

					fmt::print("  Memory: ({})\n", memoryReply.mutations[memoryVerifyIdx].mutations.size());
					for (auto& it : memoryReply.mutations[memoryVerifyIdx].mutations) {
						if (it.type == MutationRef::SetValue) {
							fmt::print("    {}=\n", it.param1.printable());
						} else {
							fmt::print("    {} - {}\n", it.param1.printable(), it.param2.printable());
						}
					}
					ASSERT(false);
				}
			}

			auto m = filterMutations(
			    reply.arena, MutationsAndVersionRef(mutations, version, knownCommittedVersion), req.range, inverted);
			if (m.mutations.size()) {
				reply.arena.dependsOn(mutations.arena());
				reply.mutations.push_back(reply.arena, m);

				if (memoryVerifyIdx < memoryReply.mutations.size() &&
				    version == memoryReply.mutations[memoryVerifyIdx].version) {
					// We could do validation of mutations here too, but it's complicated because clears can get split
					// and stuff
					memoryVerifyIdx++;
				}
			} else if (memoryVerifyIdx < memoryReply.mutations.size() &&
			           version == memoryReply.mutations[memoryVerifyIdx].version) {
				fmt::print("ERROR: SS {0} CF {1} SQ {2} has mutation at {3} in memory but all filtered out on disk!\n",
				           data->thisServerID.toString().substr(0, 4),
				           req.rangeID.printable().substr(0, 6),
				           streamUID.toString().substr(0, 8),
				           version);

				fmt::print("  Memory: ({})\n", memoryReply.mutations[memoryVerifyIdx].mutations.size());
				for (auto& it : memoryReply.mutations[memoryVerifyIdx].mutations) {
					if (it.type == MutationRef::SetValue) {
						fmt::print("    {}=\n", it.param1.printable().c_str());
					} else {
						fmt::print("    {} - {}\n", it.param1.printable().c_str(), it.param2.printable().c_str());
					}
				}
				ASSERT(false);
			}
			remainingDurableBytes -=
			    sizeof(KeyValueRef) +
			    kv.expectedSize(); // This is tracking the size on disk rather than the reply size
			                       // because we cannot add mutations from memory if there are potentially more on disk
			lastVersion = version;
			lastKnownCommitted = knownCommittedVersion;
		}
		if (remainingDurableBytes > 0) {
			reply.arena.dependsOn(memoryReply.arena);
			auto it = memoryReply.mutations.begin();
			int totalCount = memoryReply.mutations.size();
			while (it != memoryReply.mutations.end() && it->version <= lastVersion) {
				++it;
				--totalCount;
			}
			reply.mutations.append(reply.arena, it, totalCount);
			// If still empty, that means disk results were filtered out, but skipped all memory results. Add an empty,
			// either the last version from disk
			if (reply.mutations.empty() && res.size()) {
				CODE_PROBE(true, "Change feed adding empty version after disk + memory filtered");
				reply.mutations.push_back(reply.arena, MutationsAndVersionRef(lastVersion, lastKnownCommitted));
			}
		} else if (reply.mutations.empty() || reply.mutations.back().version < lastVersion) {
			CODE_PROBE(true, "Change feed adding empty version after disk filtered");
			reply.mutations.push_back(reply.arena, MutationsAndVersionRef(lastVersion, lastKnownCommitted));
		}
	} else {
		reply = memoryReply;
	}

	bool gotAll = remainingLimitBytes > 0 && remainingDurableBytes > 0 && data->version.get() == startVersion;
	Version finalVersion = std::min(req.end - 1, dequeVersion);
	if ((reply.mutations.empty() || reply.mutations.back().version < finalVersion) && remainingLimitBytes > 0 &&
	    remainingDurableBytes > 0) {
		CODE_PROBE(true, "Change feed adding empty version after empty results");
		reply.mutations.push_back(
		    reply.arena, MutationsAndVersionRef(finalVersion, finalVersion == dequeVersion ? dequeKnownCommit : 0));
		// if we add empty mutation after the last thing in memory, and didn't read from disk, gotAll is true
		if (data->version.get() == startVersion) {
			gotAll = true;
		}
	}

	// FIXME: clean all of this up, and just rely on client-side check
	// This check is done just before returning, after all waits in this function
	// Check if pop happened concurently
	if (!req.canReadPopped && req.begin <= feedInfo->emptyVersion) {
		// This can happen under normal circumstances if this part of a change feed got no updates, but then the feed
		// was popped. We can check by confirming that the client was sent empty versions as part of another feed's
		// response's minStorageVersion, or a ChangeFeedUpdateRequest. If this was the case, we know no updates could
		// have happened between req.begin and minVersion.
		Version minVersion = data->minFeedVersionForAddress(req.reply.getEndpoint().getPrimaryAddress());
		bool ok = atLatest && minVersion > feedInfo->emptyVersion;
		CODE_PROBE(ok, "feed popped while valid read waiting");
		CODE_PROBE(!ok, "feed popped while invalid read waiting");
		if (!ok) {
			TraceEvent("ChangeFeedMutationsPopped", data->thisServerID)
			    .detail("FeedID", req.rangeID)
			    .detail("StreamUID", streamUID)
			    .detail("Range", req.range)
			    .detail("Begin", req.begin)
			    .detail("End", req.end)
			    .detail("EmptyVersion", feedInfo->emptyVersion)
			    .detail("AtLatest", atLatest)
			    .detail("MinVersionSent", minVersion);
			// Disabling this check because it returns false positives when forcing a delta file flush at an empty
			// version that was not a mutation version throw change_feed_popped();
		}
	}

	if (MUTATION_TRACKING_ENABLED) {
		for (auto& mutations : reply.mutations) {
			for (auto& m : mutations.mutations) {
				DEBUG_MUTATION("ChangeFeedSSRead", mutations.version, m, data->thisServerID)
				    .detail("ChangeFeedID", req.rangeID)
				    .detail("StreamUID", streamUID)
				    .detail("ReqBegin", req.begin)
				    .detail("ReqEnd", req.end)
				    .detail("ReqRange", req.range);
			}
		}
	}

	if (DEBUG_CF_TRACE) {
		TraceEvent(SevDebug, "ChangeFeedMutationsDone", data->thisServerID)
		    .detail("FeedID", req.rangeID)
		    .detail("StreamUID", streamUID)
		    .detail("Range", req.range)
		    .detail("Begin", req.begin)
		    .detail("End", req.end)
		    .detail("FirstVersion", reply.mutations.empty() ? invalidVersion : reply.mutations.front().version)
		    .detail("LastVersion", reply.mutations.empty() ? invalidVersion : reply.mutations.back().version)
		    .detail("Count", reply.mutations.size())
		    .detail("GotAll", gotAll);
	}

	if (DEBUG_CF_MISSING(req.rangeID, req.range, req.begin, reply.mutations.back().version) && !req.canReadPopped) {
		bool foundVersion = false;
		bool foundKey = false;
		for (auto& it : reply.mutations) {
			if (it.version == DEBUG_CF_MISSING_VERSION) {
				foundVersion = true;
				for (auto& m : it.mutations) {
					if (m.type == MutationRef::SetValue && m.param1 == DEBUG_CF_MISSING_KEY) {
						foundKey = true;
						break;
					}
				}
				break;
			}
		}
		if (!foundVersion || !foundKey) {
			fmt::print("ERROR: SS {0} CF {1} SQ {2} missing {3} @ {4} from request for [{5} - {6}) {7} - {8}\n",
			           data->thisServerID.toString().substr(0, 4),
			           req.rangeID.printable().substr(0, 6),
			           streamUID.toString().substr(0, 8),
			           foundVersion ? "key" : "version",
			           DEBUG_CF_MISSING_VERSION,
			           req.range.begin.printable(),
			           req.range.end.printable(),
			           req.begin,
			           req.end);
			fmt::print("ERROR: {0} versions in response {1} - {2}:\n",
			           reply.mutations.size(),
			           reply.mutations.front().version,
			           reply.mutations.back().version);
			for (auto& it : reply.mutations) {
				fmt::print("ERROR:    {0} ({1}){2}\n",
				           it.version,
				           it.mutations.size(),
				           it.version == DEBUG_CF_MISSING_VERSION ? "<-------" : "");
			}
		} else {
			fmt::print("DBG: SS {0} CF {1} SQ {2} correct @ {3} from request for [{4} - {5}) {6} - {7}\n",
			           data->thisServerID.toString().substr(0, 4),
			           req.rangeID.printable().substr(0, 6),
			           streamUID.toString().substr(0, 8),
			           DEBUG_CF_MISSING_VERSION,
			           req.range.begin.printable(),
			           req.range.end.printable(),
			           req.begin,
			           req.end);
		}
	}

	reply.popVersion = feedInfo->emptyVersion + 1;

	// If the SS's version advanced at all during any of the waits, the read from memory may have missed some
	// mutations, so gotAll can only be true if data->version didn't change over the course of this actor
	return std::make_pair(reply, gotAll);
}

ACTOR Future<Void> localChangeFeedStream(StorageServer* data,
                                         PromiseStream<Standalone<MutationsAndVersionRef>> results,
                                         Key rangeID,
                                         Version begin,
                                         Version end,
                                         KeyRange range) {
	try {
		loop {
			state ChangeFeedStreamRequest feedRequest;
			feedRequest.rangeID = rangeID;
			feedRequest.begin = begin;
			feedRequest.end = end;
			feedRequest.range = range;
			state std::pair<ChangeFeedStreamReply, bool> feedReply =
			    wait(getChangeFeedMutations(data, feedRequest, true, false, UID()));
			begin = feedReply.first.mutations.back().version + 1;
			state int resultLoc = 0;
			while (resultLoc < feedReply.first.mutations.size()) {
				if (feedReply.first.mutations[resultLoc].mutations.size() ||
				    feedReply.first.mutations[resultLoc].version == end - 1) {
					wait(results.onEmpty());
					results.send(feedReply.first.mutations[resultLoc]);
				}
				resultLoc++;
			}

			if (begin == end) {
				return Void();
			}
		}
	} catch (Error& e) {
		if (e.code() == error_code_unknown_change_feed) {
			CODE_PROBE(true, "CF was moved away, no more local data to merge with");
			// Send endVersion so local stream is effectively done. We couldn't have send that already, because that
			// would mean the stream would have finished without error
			results.send(MutationsAndVersionRef(end, invalidVersion));
		} else {
			TraceEvent(SevError, "LocalChangeFeedError", data->thisServerID).error(e).detail("CFID", rangeID);
		}
		throw;
	}
}

// Change feed stream must be sent an error as soon as it is moved away, or change feed can get incorrect results
ACTOR Future<Void> stopChangeFeedOnMove(StorageServer* data, ChangeFeedStreamRequest req, UID streamUID) {
	wait(delay(0, TaskPriority::DefaultEndpoint));

	auto feed = data->uidChangeFeed.find(req.rangeID);
	if (feed == data->uidChangeFeed.end() || feed->second->removing) {
		req.reply.sendError(unknown_change_feed());
		return Void();
	}
	state Promise<Void> moved;
	feed->second->triggerOnMove(req.range, streamUID, moved);
	try {
		wait(moved.getFuture());
	} catch (Error& e) {
		ASSERT(e.code() == error_code_operation_cancelled);
		// remove from tracking

		auto feed = data->uidChangeFeed.find(req.rangeID);
		if (feed != data->uidChangeFeed.end()) {
			feed->second->removeOnMoveTrigger(req.range, streamUID);
		}
		return Void();
	}
	CODE_PROBE(true, "Change feed moved away cancelling queries");
	// DO NOT call req.reply.onReady before sending - we need to propagate this error through regardless of how far
	// behind client is
	req.reply.sendError(wrong_shard_server());
	return Void();
}

ACTOR Future<Void> changeFeedStreamQ(StorageServer* data, ChangeFeedStreamRequest req, UID streamUID) {
	state Span span("SS:getChangeFeedStream"_loc, req.spanContext);
	state bool atLatest = false;
	state bool removeUID = false;
	state Optional<Version> blockedVersion;
	if (req.replyBufferSize <= 0) {
		req.reply.setByteLimit(SERVER_KNOBS->CHANGEFEEDSTREAM_LIMIT_BYTES);
	} else {
		req.reply.setByteLimit(std::min((int64_t)req.replyBufferSize, SERVER_KNOBS->CHANGEFEEDSTREAM_LIMIT_BYTES));
	}

	++data->counters.feedStreamQueries;

	wait(delay(0, TaskPriority::DefaultEndpoint));

	try {
		if (DEBUG_CF_TRACE) {
			TraceEvent(SevDebug, "TraceChangeFeedStreamStart", data->thisServerID)
			    .detail("FeedID", req.rangeID)
			    .detail("StreamUID", streamUID)
			    .detail("Range", req.range)
			    .detail("Begin", req.begin)
			    .detail("End", req.end)
			    .detail("CanReadPopped", req.canReadPopped);
		}
		data->activeFeedQueries++;

		// send an empty version at begin - 1 to establish the stream quickly
		ChangeFeedStreamReply emptyInitialReply;
		MutationsAndVersionRef emptyInitialVersion;
		emptyInitialVersion.version = req.begin - 1;
		emptyInitialReply.mutations.push_back_deep(emptyInitialReply.arena, emptyInitialVersion);
		ASSERT(emptyInitialReply.atLatestVersion == false);
		ASSERT(emptyInitialReply.minStreamVersion == invalidVersion);
		req.reply.send(emptyInitialReply);

		if (DEBUG_CF_TRACE) {
			TraceEvent(SevDebug, "TraceChangeFeedStreamSentInitialEmpty", data->thisServerID)
			    .detail("FeedID", req.rangeID)
			    .detail("StreamUID", streamUID)
			    .detail("Range", req.range)
			    .detail("Begin", req.begin)
			    .detail("End", req.end)
			    .detail("CanReadPopped", req.canReadPopped)
			    .detail("Version", req.begin - 1);
		}

		loop {
			Future<Void> onReady = req.reply.onReady();
			if (atLatest && !onReady.isReady() && !removeUID) {
				data->changeFeedClientVersions[req.reply.getEndpoint().getPrimaryAddress()][streamUID] =
				    blockedVersion.present() ? blockedVersion.get() : data->prevVersion;
				if (DEBUG_CF_TRACE) {
					TraceEvent(SevDebug, "TraceChangeFeedStreamBlockedOnReady", data->thisServerID)
					    .detail("FeedID", req.rangeID)
					    .detail("StreamUID", streamUID)
					    .detail("Range", req.range)
					    .detail("Begin", req.begin)
					    .detail("End", req.end)
					    .detail("CanReadPopped", req.canReadPopped)
					    .detail("Version", blockedVersion.present() ? blockedVersion.get() : data->prevVersion);
				}
				removeUID = true;
			}
			wait(onReady);
			// keep this as not state variable so it is freed after sending to reduce memory
			Future<std::pair<ChangeFeedStreamReply, bool>> feedReplyFuture =
			    getChangeFeedMutations(data, req, false, atLatest, streamUID);
			if (atLatest && !removeUID && !feedReplyFuture.isReady()) {
				data->changeFeedClientVersions[req.reply.getEndpoint().getPrimaryAddress()][streamUID] =
				    blockedVersion.present() ? blockedVersion.get() : data->prevVersion;
				removeUID = true;
				if (DEBUG_CF_TRACE) {
					TraceEvent(SevDebug, "TraceChangeFeedStreamBlockedMutations", data->thisServerID)
					    .detail("FeedID", req.rangeID)
					    .detail("StreamUID", streamUID)
					    .detail("Range", req.range)
					    .detail("Begin", req.begin)
					    .detail("End", req.end)
					    .detail("CanReadPopped", req.canReadPopped)
					    .detail("Version", blockedVersion.present() ? blockedVersion.get() : data->prevVersion);
				}
			}
			std::pair<ChangeFeedStreamReply, bool> _feedReply = wait(feedReplyFuture);
			ChangeFeedStreamReply feedReply = _feedReply.first;
			bool gotAll = _feedReply.second;

			ASSERT(feedReply.mutations.size() > 0);
			req.begin = feedReply.mutations.back().version + 1;
			if (!atLatest && gotAll) {
				atLatest = true;
			}

			auto& clientVersions = data->changeFeedClientVersions[req.reply.getEndpoint().getPrimaryAddress()];
			Version minVersion = removeUID ? data->version.get() : data->prevVersion;
			if (removeUID) {
				if (gotAll || req.begin == req.end) {
					data->changeFeedClientVersions[req.reply.getEndpoint().getPrimaryAddress()].erase(streamUID);
					removeUID = false;
				} else {
					data->changeFeedClientVersions[req.reply.getEndpoint().getPrimaryAddress()][streamUID] =
					    feedReply.mutations.back().version;
				}
			}

			for (auto& it : clientVersions) {
				minVersion = std::min(minVersion, it.second);
			}
			feedReply.atLatestVersion = atLatest;
			feedReply.minStreamVersion = minVersion;

			data->counters.feedRowsQueried += feedReply.mutations.size();
			data->counters.feedBytesQueried += feedReply.mutations.expectedSize();

			req.reply.send(feedReply);
			if (req.begin == req.end) {
				data->activeFeedQueries--;
				req.reply.sendError(end_of_stream());
				return Void();
			}
			if (gotAll) {
				blockedVersion = Optional<Version>();
				auto feed = data->uidChangeFeed.find(req.rangeID);
				if (feed == data->uidChangeFeed.end() || feed->second->removing) {
					req.reply.sendError(unknown_change_feed());
					// throw to delete from changeFeedClientVersions if present
					throw unknown_change_feed();
				}
				choose {
					when(wait(feed->second->newMutations.onTrigger())) {}
					when(wait(req.end == std::numeric_limits<Version>::max() ? Future<Void>(Never())
					                                                         : data->version.whenAtLeast(req.end))) {}
				}
				auto feedItr = data->uidChangeFeed.find(req.rangeID);
				if (feedItr == data->uidChangeFeed.end() || feedItr->second->removing) {
					req.reply.sendError(unknown_change_feed());
					// throw to delete from changeFeedClientVersions if present
					throw unknown_change_feed();
				}
			} else {
				blockedVersion = feedReply.mutations.back().version;
			}
		}
	} catch (Error& e) {
		data->activeFeedQueries--;
		auto it = data->changeFeedClientVersions.find(req.reply.getEndpoint().getPrimaryAddress());
		if (it != data->changeFeedClientVersions.end()) {
			if (removeUID) {
				it->second.erase(streamUID);
			}
			if (it->second.empty()) {
				data->changeFeedClientVersions.erase(it);
			}
		}
		if (e.code() != error_code_operation_obsolete) {
			if (!canReplyWith(e))
				throw;
			req.reply.sendError(e);
		}
	}
	return Void();
}

ACTOR Future<Void> changeFeedVersionUpdateQ(StorageServer* data, ChangeFeedVersionUpdateRequest req) {
	++data->counters.feedVersionQueries;
	wait(data->version.whenAtLeast(req.minVersion));
	wait(delay(0));
	Version minVersion = data->minFeedVersionForAddress(req.reply.getEndpoint().getPrimaryAddress());
	req.reply.send(ChangeFeedVersionUpdateReply(minVersion));
	return Void();
}

#ifdef NO_INTELLISENSE
size_t WATCH_OVERHEAD_WATCHQ =
    sizeof(WatchValueSendReplyActorState<WatchValueSendReplyActor>) + sizeof(WatchValueSendReplyActor);
size_t WATCH_OVERHEAD_WATCHIMPL =
    sizeof(WatchWaitForValueChangeActorState<WatchWaitForValueChangeActor>) + sizeof(WatchWaitForValueChangeActor);
#else
size_t WATCH_OVERHEAD_WATCHQ = 0; // only used in IDE so value is irrelevant
size_t WATCH_OVERHEAD_WATCHIMPL = 0;
#endif

ACTOR Future<Void> getShardState_impl(StorageServer* data, GetShardStateRequest req) {
	ASSERT(req.mode != GetShardStateRequest::NO_WAIT);

	loop {
		std::vector<Future<Void>> onChange;

		for (auto t : data->shards.intersectingRanges(req.keys)) {
			if (!t.value()->assigned()) {
				onChange.push_back(delay(SERVER_KNOBS->SHARD_READY_DELAY));
				break;
			}

			if (req.mode == GetShardStateRequest::READABLE && !t.value()->isReadable())
				onChange.push_back(t.value()->adding->readWrite.getFuture());

			if (req.mode == GetShardStateRequest::FETCHING && !t.value()->isFetched())
				onChange.push_back(t.value()->adding->fetchComplete.getFuture());
		}

		if (!onChange.size()) {
			GetShardStateReply rep(data->version.get(), data->durableVersion.get());
			if (req.includePhysicalShard) {
				rep.shards = std::move(data->getStorageServerShards(req.keys));
			}
			req.reply.send(rep);
			return Void();
		}

		wait(waitForAll(onChange));
		wait(delay(0)); // onChange could have been triggered by cancellation, let things settle before rechecking
	}
}

ACTOR Future<Void> getShardStateQ(StorageServer* data, GetShardStateRequest req) {
	choose {
		when(wait(getShardState_impl(data, req))) {}
		when(wait(delay(g_network->isSimulated() ? 10 : 60))) {
			data->sendErrorWithPenalty(req.reply, timed_out(), data->getPenalty());
		}
	}
	return Void();
}

KeyRef addPrefix(KeyRef const& key, Optional<Key> prefix, Arena& arena) {
	if (prefix.present()) {
		return key.withPrefix(prefix.get(), arena);
	} else {
		return key;
	}
}

KeyValueRef removePrefix(KeyValueRef const& src, Optional<Key> prefix) {
	if (prefix.present()) {
		return KeyValueRef(src.key.removePrefix(prefix.get()), src.value);
	} else {
		return src;
	}
}

void merge(Arena& arena,
           VectorRef<KeyValueRef, VecSerStrategy::String>& output,
           VectorRef<KeyValueRef> const& vm_output,
           RangeResult const& base,
           int& vCount,
           int limit,
           bool stopAtEndOfBase,
           int& pos,
           int limitBytes,
           Optional<Key> tenantPrefix)
// Combines data from base (at an older version) with sets from newer versions in [start, end) and appends the first (up
// to) |limit| rows to output If limit<0, base and output are in descending order, and start->key()>end->key(), but
// start is still inclusive and end is exclusive
{
	ASSERT(limit != 0);
	// Add a dependency of the new arena on the result from the KVS so that we don't have to copy any of the KVS
	// results.
	arena.dependsOn(base.arena());

	bool forward = limit > 0;
	if (!forward)
		limit = -limit;
	int adjustedLimit = limit + output.size();
	int accumulatedBytes = 0;
	KeyValueRef const* baseStart = base.begin();
	KeyValueRef const* baseEnd = base.end();
	while (baseStart != baseEnd && vCount > 0 && output.size() < adjustedLimit && accumulatedBytes < limitBytes) {
		if (forward ? baseStart->key < vm_output[pos].key : baseStart->key > vm_output[pos].key) {
			output.push_back(arena, removePrefix(*baseStart++, tenantPrefix));
		} else {
			output.push_back_deep(arena, removePrefix(vm_output[pos], tenantPrefix));
			if (baseStart->key == vm_output[pos].key)
				++baseStart;
			++pos;
			vCount--;
		}
		accumulatedBytes += sizeof(KeyValueRef) + output.end()[-1].expectedSize();
	}
	while (baseStart != baseEnd && output.size() < adjustedLimit && accumulatedBytes < limitBytes) {
		output.push_back(arena, removePrefix(*baseStart++, tenantPrefix));
		accumulatedBytes += sizeof(KeyValueRef) + output.end()[-1].expectedSize();
	}
	if (!stopAtEndOfBase) {
		while (vCount > 0 && output.size() < adjustedLimit && accumulatedBytes < limitBytes) {
			output.push_back_deep(arena, removePrefix(vm_output[pos], tenantPrefix));
			accumulatedBytes += sizeof(KeyValueRef) + output.end()[-1].expectedSize();
			++pos;
			vCount--;
		}
	}
}

static inline void copyOptionalValue(Arena* a,
                                     GetValueReqAndResultRef& getValue,
                                     const Optional<Value>& optionalValue) {
	std::function<StringRef(Value)> contents = [](Value value) { return value.contents(); };
	getValue.result = optionalValue.map(contents);
	if (optionalValue.present()) {
		a->dependsOn(optionalValue.get().arena());
	}
}
ACTOR Future<GetValueReqAndResultRef> quickGetValue(StorageServer* data,
                                                    StringRef key,
                                                    Version version,
                                                    Arena* a,
                                                    // To provide span context, tags, debug ID to underlying lookups.
                                                    GetMappedKeyValuesRequest* pOriginalReq) {
	state GetValueReqAndResultRef getValue;
	state double getValueStart = g_network->timer();
	getValue.key = key;

	if (data->shards[key]->isReadable()) {
		try {
			// TODO: Use a lower level API may be better? Or tweak priorities?
			GetValueRequest req(pOriginalReq->spanContext,
			                    pOriginalReq->tenantInfo,
			                    key,
			                    version,
			                    pOriginalReq->tags,
			                    pOriginalReq->debugID,
			                    VersionVector());
			// Note that it does not use readGuard to avoid server being overloaded here. Throttling is enforced at the
			// original request level, rather than individual underlying lookups. The reason is that throttle any
			// individual underlying lookup will fail the original request, which is not productive.
			data->actors.add(getValueQ(data, req));
			GetValueReply reply = wait(req.reply.getFuture());
			if (!reply.error.present()) {
				++data->counters.quickGetValueHit;
				copyOptionalValue(a, getValue, reply.value);
				const double duration = g_network->timer() - getValueStart;
				data->counters.mappedRangeLocalSample.addMeasurement(duration);
				return getValue;
			}
			// Otherwise fallback.
		} catch (Error& e) {
			// Fallback.
		}
	}
	// Otherwise fallback.

	++data->counters.quickGetValueMiss;
	if (SERVER_KNOBS->QUICK_GET_VALUE_FALLBACK) {
		state Transaction tr(data->cx, pOriginalReq->tenantInfo.name);
		tr.setVersion(version);
		// TODO: is DefaultPromiseEndpoint the best priority for this?
		tr.trState->taskID = TaskPriority::DefaultPromiseEndpoint;
		Future<Optional<Value>> valueFuture = tr.get(key, Snapshot::True);
		// TODO: async in case it needs to read from other servers.
		Optional<Value> valueOption = wait(valueFuture);
		copyOptionalValue(a, getValue, valueOption);
		double duration = g_network->timer() - getValueStart;
		data->counters.mappedRangeRemoteSample.addMeasurement(duration);
		return getValue;
	} else {
		throw quick_get_value_miss();
	}
}

// If limit>=0, it returns the first rows in the range (sorted ascending), otherwise the last rows (sorted descending).
// readRange has O(|result|) + O(log |data|) cost
ACTOR Future<GetKeyValuesReply> readRange(StorageServer* data,
                                          Version version,
                                          KeyRange range,
                                          int limit,
                                          int* pLimitBytes,
                                          SpanContext parentSpan,
                                          IKeyValueStore::ReadType type,
                                          Optional<Key> tenantPrefix) {
	state GetKeyValuesReply result;
	state StorageServer::VersionedData::ViewAtVersion view = data->data().at(version);
	state StorageServer::VersionedData::iterator vCurrent = view.end();
	state KeyRef readBegin;
	state KeyRef readEnd;
	state Key readBeginTemp;
	state int vCount = 0;
	state Span span("SS:readRange"_loc, parentSpan);

	// for caching the storage queue results during the first PTree traversal
	state VectorRef<KeyValueRef> resultCache;

	// for remembering the position in the resultCache
	state int pos = 0;

	// Check if the desired key-range is cached
	auto containingRange = data->cachedRangeMap.rangeContaining(range.begin);
	if (containingRange.value() && containingRange->range().end >= range.end) {
		//TraceEvent(SevDebug, "SSReadRangeCached").detail("Size",data->cachedRangeMap.size()).detail("ContainingRangeBegin",containingRange->range().begin).detail("ContainingRangeEnd",containingRange->range().end).
		//	detail("Begin", range.begin).detail("End",range.end);
		result.cached = true;
	} else
		result.cached = false;

	// if (limit >= 0) we are reading forward, else backward
	if (limit >= 0) {
		// We might care about a clear beginning before start that
		//  runs into range
		vCurrent = view.lastLessOrEqual(range.begin);
		if (vCurrent && vCurrent->isClearTo() && vCurrent->getEndKey() > range.begin)
			readBegin = vCurrent->getEndKey();
		else
			readBegin = range.begin;

		if (vCurrent) {
			// We can get first greater or equal from the result of lastLessOrEqual
			if (vCurrent.key() != readBegin) {
				++vCurrent;
			}
		} else {
			// There's nothing less than or equal to readBegin in view, so
			// begin() is the first thing greater than readBegin, or end().
			// Either way that's the correct result for lower_bound.
			vCurrent = view.begin();
		}

		while (limit > 0 && *pLimitBytes > 0 && readBegin < range.end) {
			ASSERT(!vCurrent || vCurrent.key() >= readBegin);
			ASSERT(data->storageVersion() <= version);

			/* Traverse the PTree further, if thare are no unconsumed resultCache items */
			if (pos == resultCache.size()) {
				if (vCurrent) {
					auto b = vCurrent;
					--b;
					ASSERT(!b || b.key() < readBegin);
				}

				// Read up to limit items from the view, stopping at the next clear (or the end of the range)
				int vSize = 0;
				while (vCurrent && vCurrent.key() < range.end && !vCurrent->isClearTo() && vCount < limit &&
				       vSize < *pLimitBytes) {
					// Store the versionedData results in resultCache
					resultCache.emplace_back(result.arena, vCurrent.key(), vCurrent->getValue());
					vSize += sizeof(KeyValueRef) + resultCache.cback().expectedSize() -
					         (tenantPrefix.present() ? tenantPrefix.get().size() : 0);
					++vCount;
					++vCurrent;
				}
			}

			// Read the data on disk up to vCurrent (or the end of the range)
			readEnd = vCurrent ? std::min(vCurrent.key(), range.end) : range.end;
			RangeResult atStorageVersion =
			    wait(data->storage.readRange(KeyRangeRef(readBegin, readEnd), limit, *pLimitBytes, type));
			data->counters.kvScanBytes += atStorageVersion.logicalSize();

			ASSERT(atStorageVersion.size() <= limit);
			if (data->storageVersion() > version) {
				// TraceEvent(SevDebug, "ReadRangeThrow", data->thisServerID).detail("Version", version).detail("StorageVersion", data->storageVersion());
				throw transaction_too_old();
			}

			// merge the sets in resultCache with the sets on disk, stopping at the last key from disk if there is
			// 'more'
			int prevSize = result.data.size();
			merge(result.arena,
			      result.data,
			      resultCache,
			      atStorageVersion,
			      vCount,
			      limit,
			      atStorageVersion.more,
			      pos,
			      *pLimitBytes,
			      tenantPrefix);
			limit -= result.data.size() - prevSize;

			for (auto i = result.data.begin() + prevSize; i != result.data.end(); i++) {
				*pLimitBytes -= sizeof(KeyValueRef) + i->expectedSize();
			}

			if (limit <= 0 || *pLimitBytes <= 0) {
				break;
			}

			// Setup for the next iteration
			// If we hit our limits reading from disk but then combining with MVCC gave us back more room

			// if there might be more data, begin reading right after what we already found to find out
			if (atStorageVersion.more) {
				ASSERT(atStorageVersion.end()[-1].key.size() ==
				           result.data.end()[-1].key.size() + tenantPrefix.orDefault(""_sr).size() &&
				       atStorageVersion.end()[-1].key.endsWith(result.data.end()[-1].key) &&
				       atStorageVersion.end()[-1].key.startsWith(tenantPrefix.orDefault(""_sr)));

				readBegin = readBeginTemp = keyAfter(atStorageVersion.end()[-1].key);
			}

			// if vCurrent is a clear, skip it.
			else if (vCurrent && vCurrent->isClearTo()) {
				ASSERT(vCurrent->getEndKey() > readBegin);
				// next disk read should start at the end of the clear
				readBegin = vCurrent->getEndKey();
				++vCurrent;
			} else {
				ASSERT(readEnd == range.end);
				break;
			}
		}
	} else {
		vCurrent = view.lastLess(range.end);

		// A clear might extend all the way to range.end
		if (vCurrent && vCurrent->isClearTo() && vCurrent->getEndKey() >= range.end) {
			readEnd = vCurrent.key();
			--vCurrent;
		} else {
			readEnd = range.end;
		}

		while (limit < 0 && *pLimitBytes > 0 && readEnd > range.begin) {
			ASSERT(!vCurrent || vCurrent.key() < readEnd);
			ASSERT(data->storageVersion() <= version);

			/* Traverse the PTree further, if thare are no unconsumed resultCache items */
			if (pos == resultCache.size()) {
				if (vCurrent) {
					auto b = vCurrent;
					++b;
					ASSERT(!b || b.key() >= readEnd);
				}

				vCount = 0;
				int vSize = 0;
				while (vCurrent && vCurrent.key() >= range.begin && !vCurrent->isClearTo() && vCount < -limit &&
				       vSize < *pLimitBytes) {
					// Store the versionedData results in resultCache
					resultCache.emplace_back(result.arena, vCurrent.key(), vCurrent->getValue());
					vSize += sizeof(KeyValueRef) + resultCache.cback().expectedSize() -
					         (tenantPrefix.present() ? tenantPrefix.get().size() : 0);
					++vCount;
					--vCurrent;
				}
			}

			readBegin = vCurrent ? std::max(vCurrent->isClearTo() ? vCurrent->getEndKey() : vCurrent.key(), range.begin)
			                     : range.begin;
			RangeResult atStorageVersion =
			    wait(data->storage.readRange(KeyRangeRef(readBegin, readEnd), limit, *pLimitBytes, type));
			data->counters.kvScanBytes += atStorageVersion.logicalSize();

			ASSERT(atStorageVersion.size() <= -limit);
			if (data->storageVersion() > version)
				throw transaction_too_old();

			int prevSize = result.data.size();
			merge(result.arena,
			      result.data,
			      resultCache,
			      atStorageVersion,
			      vCount,
			      limit,
			      atStorageVersion.more,
			      pos,
			      *pLimitBytes,
			      tenantPrefix);
			limit += result.data.size() - prevSize;

			for (auto i = result.data.begin() + prevSize; i != result.data.end(); i++) {
				*pLimitBytes -= sizeof(KeyValueRef) + i->expectedSize();
			}

			if (limit >= 0 || *pLimitBytes <= 0) {
				break;
			}

			if (atStorageVersion.more) {
				ASSERT(atStorageVersion.end()[-1].key.size() ==
				           result.data.end()[-1].key.size() + tenantPrefix.orDefault(""_sr).size() &&
				       atStorageVersion.end()[-1].key.endsWith(result.data.end()[-1].key) &&
				       atStorageVersion.end()[-1].key.startsWith(tenantPrefix.orDefault(""_sr)));

				readEnd = atStorageVersion.end()[-1].key;
			} else if (vCurrent && vCurrent->isClearTo()) {
				ASSERT(vCurrent.key() < readEnd);
				readEnd = vCurrent.key();
				--vCurrent;
			} else {
				ASSERT(readBegin == range.begin);
				break;
			}
		}
	}

	// all but the last item are less than *pLimitBytes
	ASSERT(result.data.size() == 0 || *pLimitBytes + result.data.end()[-1].expectedSize() + sizeof(KeyValueRef) > 0);
	result.more = limit == 0 || *pLimitBytes <= 0; // FIXME: Does this have to be exact?
	result.version = version;
	return result;
}

KeyRangeRef StorageServer::clampRangeToTenant(KeyRangeRef range, Optional<TenantMapEntry> tenantEntry, Arena& arena) {
	if (tenantEntry.present()) {
		return KeyRangeRef(range.begin.startsWith(tenantEntry.get().prefix) ? range.begin : tenantEntry.get().prefix,
		                   range.end.startsWith(tenantEntry.get().prefix)
		                       ? range.end
		                       : allKeys.end.withPrefix(tenantEntry.get().prefix, arena));
	} else {
		return range;
	}
}

ACTOR Future<Key> findKey(StorageServer* data,
                          KeySelectorRef sel,
                          Version version,
                          KeyRange range,
                          int* pOffset,
                          SpanContext parentSpan,
                          IKeyValueStore::ReadType type)
// Attempts to find the key indicated by sel in the data at version, within range.
// Precondition: selectorInRange(sel, range)
// If it is found, offset is set to 0 and a key is returned which falls inside range.
// If the search would depend on any key outside range OR if the key selector offset is too large (range read returns
// too many bytes), it returns either
//   a negative offset and a key in [range.begin, sel.getKey()], indicating the key is (the first key <= returned key) +
//   offset, or a positive offset and a key in (sel.getKey(), range.end], indicating the key is (the first key >=
//   returned key) + offset-1
// The range passed in to this function should specify a shard.  If range.begin is repeatedly not the beginning of a
// shard, then it is possible to get stuck looping here
{
	ASSERT(version != latestVersion);
	ASSERT(selectorInRange(sel, range) && version >= data->oldestVersion.get());

	// Count forward or backward distance items, skipping the first one if it == key and skipEqualKey
	state bool forward = sel.offset > 0; // If forward, result >= sel.getKey(); else result <= sel.getKey()
	state int sign = forward ? +1 : -1;
	state bool skipEqualKey = sel.orEqual == forward;
	state int distance = forward ? sel.offset : 1 - sel.offset;
	state Span span("SS.findKey"_loc, parentSpan);

	// Don't limit the number of bytes if this is a trivial key selector (there will be at most two items returned from
	// the read range in this case)
	state int maxBytes;
	if (sel.offset <= 1 && sel.offset >= 0)
		maxBytes = std::numeric_limits<int>::max();
	else
		maxBytes = (g_network->isSimulated() && g_simulator.tssMode == ISimulator::TSSMode::Disabled && BUGGIFY)
		               ? SERVER_KNOBS->BUGGIFY_LIMIT_BYTES
		               : SERVER_KNOBS->STORAGE_LIMIT_BYTES;

	state GetKeyValuesReply rep = wait(
	    readRange(data,
	              version,
	              forward ? KeyRangeRef(sel.getKey(), range.end) : KeyRangeRef(range.begin, keyAfter(sel.getKey())),
	              (distance + skipEqualKey) * sign,
	              &maxBytes,
	              span.context,
	              type,
	              Optional<Key>()));
	state bool more = rep.more && rep.data.size() != distance + skipEqualKey;

	// If we get only one result in the reverse direction as a result of the data being too large, we could get stuck in
	// a loop
	if (more && !forward && rep.data.size() == 1) {
		CODE_PROBE(true, "Reverse key selector returned only one result in range read");
		maxBytes = std::numeric_limits<int>::max();
		GetKeyValuesReply rep2 = wait(readRange(data,
		                                        version,
		                                        KeyRangeRef(range.begin, keyAfter(sel.getKey())),
		                                        -2,
		                                        &maxBytes,
		                                        span.context,
		                                        type,
		                                        Optional<Key>()));
		rep = rep2;
		more = rep.more && rep.data.size() != distance + skipEqualKey;
		ASSERT(rep.data.size() == 2 || !more);
	}

	int index = distance - 1;
	if (skipEqualKey && rep.data.size() && rep.data[0].key == sel.getKey())
		++index;

	if (index < rep.data.size()) {
		*pOffset = 0;

		if (SERVER_KNOBS->READ_SAMPLING_ENABLED) {
			int64_t bytesReadPerKSecond =
			    std::max((int64_t)rep.data[index].key.size(), SERVER_KNOBS->EMPTY_READ_PENALTY);
			data->metrics.notifyBytesReadPerKSecond(sel.getKey(), bytesReadPerKSecond);
		}

		return rep.data[index].key;
	} else {
		if (SERVER_KNOBS->READ_SAMPLING_ENABLED) {
			int64_t bytesReadPerKSecond = SERVER_KNOBS->EMPTY_READ_PENALTY;
			data->metrics.notifyBytesReadPerKSecond(sel.getKey(), bytesReadPerKSecond);
		}

		// FIXME: If range.begin=="" && !forward, return success?
		*pOffset = index - rep.data.size() + 1;
		if (!forward)
			*pOffset = -*pOffset;

		if (more) {
			CODE_PROBE(true, "Key selector read range had more results");

			ASSERT(rep.data.size());
			Key returnKey = forward ? keyAfter(rep.data.back().key) : rep.data.back().key;

			// This is possible if key/value pairs are very large and only one result is returned on a last less than
			// query SOMEDAY: graceful handling of exceptionally sized values
			ASSERT(returnKey != sel.getKey());
			return returnKey;
		} else {
			return forward ? range.end : range.begin;
		}
	}
}

KeyRange getShardKeyRange(StorageServer* data, const KeySelectorRef& sel)
// Returns largest range such that the shard state isReadable and selectorInRange(sel, range) or wrong_shard_server if
// no such range exists
{
	auto i = sel.isBackward() ? data->shards.rangeContainingKeyBefore(sel.getKey())
	                          : data->shards.rangeContaining(sel.getKey());
	auto fullRange = data->shards.ranges();
	if (!i->value()->isReadable())
		throw wrong_shard_server();
	ASSERT(selectorInRange(sel, i->range()));
	Key begin, end;
	if (sel.isBackward()) {
		end = i->range().end;
		while (i != fullRange.begin() && i.value()->isReadable()) {
			begin = i->range().begin;
			--i;
		}
		if (i.value()->isReadable()) {
			begin = i->range().begin;
		}
	} else {
		begin = i->range().begin;
		while (i != fullRange.end() && i.value()->isReadable()) {
			end = i->range().end;
			++i;
		}
	}
	return KeyRangeRef(begin, end);
}

ACTOR Future<Void> getKeyValuesQ(StorageServer* data, GetKeyValuesRequest req)
// Throws a wrong_shard_server if the keys in the request or result depend on data outside this server OR if a large
// selector offset prevents all data from being read in one range read
{
	state Span span("SS:getKeyValues"_loc, req.spanContext);
	state int64_t resultSize = 0;
	state IKeyValueStore::ReadType type =
	    req.isFetchKeys ? IKeyValueStore::ReadType::FETCH : IKeyValueStore::ReadType::NORMAL;

	if (req.tenantInfo.name.present()) {
		span.addAttribute("tenant"_sr, req.tenantInfo.name.get());
	}

	getCurrentLineage()->modify(&TransactionLineage::txID) = req.spanContext.traceID;

	++data->counters.getRangeQueries;
	++data->counters.allQueries;
	data->maxQueryQueue = std::max<int>(
	    data->maxQueryQueue, data->counters.allQueries.getValue() - data->counters.finishedQueries.getValue());

	// Active load balancing runs at a very high priority (to obtain accurate queue lengths)
	// so we need to downgrade here
	if (SERVER_KNOBS->FETCH_KEYS_LOWER_PRIORITY && req.isFetchKeys) {
		wait(delay(0, TaskPriority::FetchKeys));
	} else {
		wait(data->getQueryDelay());
	}

	try {
		if (req.debugID.present())
			g_traceBatch.addEvent("TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValues.Before");

		Version commitVersion = getLatestCommitVersion(req.ssLatestCommitVersions, data->tag);
		state Version version = wait(waitForVersion(data, commitVersion, req.version, span.context));

		state Optional<TenantMapEntry> tenantEntry = data->getTenantEntry(version, req.tenantInfo);
		state Optional<Key> tenantPrefix = tenantEntry.map<Key>([](TenantMapEntry e) { return e.prefix; });
		if (tenantPrefix.present()) {
			req.begin.setKeyUnlimited(req.begin.getKey().withPrefix(tenantPrefix.get(), req.arena));
			req.end.setKeyUnlimited(req.end.getKey().withPrefix(tenantPrefix.get(), req.arena));
		}

		state uint64_t changeCounter = data->shardChangeCounter;
		//		try {
		state KeyRange shard = getShardKeyRange(data, req.begin);

		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValues.AfterVersion");
		//.detail("ShardBegin", shard.begin).detail("ShardEnd", shard.end);
		//} catch (Error& e) { TraceEvent("WrongShardServer", data->thisServerID).detail("Begin",
		// req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("Shard",
		//"None").detail("In", "getKeyValues>getShardKeyRange"); throw e; }

		if (!selectorInRange(req.end, shard) && !(req.end.isFirstGreaterOrEqual() && req.end.getKey() == shard.end)) {
			//			TraceEvent("WrongShardServer1", data->thisServerID).detail("Begin",
			// req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("ShardBegin",
			// shard.begin).detail("ShardEnd", shard.end).detail("In", "getKeyValues>checkShardExtents");
			throw wrong_shard_server();
		}

		KeyRangeRef searchRange = data->clampRangeToTenant(shard, tenantEntry, req.arena);

		state int offset1 = 0;
		state int offset2;
		state Future<Key> fBegin = req.begin.isFirstGreaterOrEqual()
		                               ? Future<Key>(req.begin.getKey())
		                               : findKey(data, req.begin, version, searchRange, &offset1, span.context, type);
		state Future<Key> fEnd = req.end.isFirstGreaterOrEqual()
		                             ? Future<Key>(req.end.getKey())
		                             : findKey(data, req.end, version, searchRange, &offset2, span.context, type);
		state Key begin = wait(fBegin);
		state Key end = wait(fEnd);

		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValues.AfterKeys");
		//.detail("Off1",offset1).detail("Off2",offset2).detail("ReqBegin",req.begin.getKey()).detail("ReqEnd",req.end.getKey());

		// Offsets of zero indicate begin/end keys in this shard, which obviously means we can answer the query
		// An end offset of 1 is also OK because the end key is exclusive, so if the first key of the next shard is the
		// end the last actual key returned must be from this shard. A begin offset of 1 is also OK because then either
		// begin is past end or equal to end (so the result is definitely empty)
		if ((offset1 && offset1 != 1) || (offset2 && offset2 != 1)) {
			CODE_PROBE(true, "wrong_shard_server due to offset");
			// We could detect when offset1 takes us off the beginning of the database or offset2 takes us off the end,
			// and return a clipped range rather than an error (since that is what the NativeAPI.getRange will do anyway
			// via its "slow path"), but we would have to add some flags to the response to encode whether we went off
			// the beginning and the end, since it needs that information.
			//TraceEvent("WrongShardServer2", data->thisServerID).detail("Begin", req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("ShardBegin", shard.begin).detail("ShardEnd", shard.end).detail("In", "getKeyValues>checkOffsets").detail("BeginKey", begin).detail("EndKey", end).detail("BeginOffset", offset1).detail("EndOffset", offset2);
			throw wrong_shard_server();
		}

		if (begin >= end) {
			if (req.debugID.present())
				g_traceBatch.addEvent("TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValues.Send");
			//.detail("Begin",begin).detail("End",end);

			GetKeyValuesReply none;
			none.version = version;
			none.more = false;
			none.penalty = data->getPenalty();

			data->checkChangeCounter(changeCounter,
			                         KeyRangeRef(std::min<KeyRef>(req.begin.getKey(), req.end.getKey()),
			                                     std::max<KeyRef>(req.begin.getKey(), req.end.getKey())));
			req.reply.send(none);
		} else {
			state int remainingLimitBytes = req.limitBytes;

			GetKeyValuesReply _r = wait(readRange(data,
			                                      version,
			                                      KeyRangeRef(begin, end),
			                                      req.limit,
			                                      &remainingLimitBytes,
			                                      span.context,
			                                      type,
			                                      tenantPrefix));
			GetKeyValuesReply r = _r;

			if (req.debugID.present())
				g_traceBatch.addEvent(
				    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValues.AfterReadRange");
			//.detail("Begin",begin).detail("End",end).detail("SizeOf",r.data.size());
			data->checkChangeCounter(
			    changeCounter,
			    KeyRangeRef(std::min<KeyRef>(begin, std::min<KeyRef>(req.begin.getKey(), req.end.getKey())),
			                std::max<KeyRef>(end, std::max<KeyRef>(req.begin.getKey(), req.end.getKey()))));
			if (EXPENSIVE_VALIDATION) {
				for (int i = 0; i < r.data.size(); i++) {
					if (tenantPrefix.present()) {
						ASSERT(r.data[i].key >= begin.removePrefix(tenantPrefix.get()) &&
						       r.data[i].key < end.removePrefix(tenantPrefix.get()));
					} else {
						ASSERT(r.data[i].key >= begin && r.data[i].key < end);
					}
				}
				ASSERT(r.data.size() <= std::abs(req.limit));
			}

			// For performance concerns, the cost of a range read is billed to the start key and end key of the range.
			int64_t totalByteSize = 0;
			for (int i = 0; i < r.data.size(); i++) {
				totalByteSize += r.data[i].expectedSize();
			}
			if (totalByteSize > 0 && SERVER_KNOBS->READ_SAMPLING_ENABLED) {
				int64_t bytesReadPerKSecond = std::max(totalByteSize, SERVER_KNOBS->EMPTY_READ_PENALTY) / 2;
				data->metrics.notifyBytesReadPerKSecond(addPrefix(r.data[0].key, tenantPrefix, req.arena),
				                                        bytesReadPerKSecond);
				data->metrics.notifyBytesReadPerKSecond(
				    addPrefix(r.data[r.data.size() - 1].key, tenantPrefix, req.arena), bytesReadPerKSecond);
			}

			r.penalty = data->getPenalty();
			req.reply.send(r);

			resultSize = req.limitBytes - remainingLimitBytes;
			data->counters.bytesQueried += resultSize;
			data->counters.rowsQueried += r.data.size();
			if (r.data.size() == 0) {
				++data->counters.emptyQueries;
			}
		}
	} catch (Error& e) {
		if (!canReplyWith(e))
			throw;
		data->sendErrorWithPenalty(req.reply, e, data->getPenalty());
	}

	data->transactionTagCounter.addRequest(req.tags, resultSize);
	++data->counters.finishedQueries;

	double duration = g_network->timer() - req.requestTime();
	data->counters.readLatencySample.addMeasurement(duration);
	if (data->latencyBandConfig.present()) {
		int maxReadBytes =
		    data->latencyBandConfig.get().readConfig.maxReadBytes.orDefault(std::numeric_limits<int>::max());
		int maxSelectorOffset =
		    data->latencyBandConfig.get().readConfig.maxKeySelectorOffset.orDefault(std::numeric_limits<int>::max());
		data->counters.readLatencyBands.addMeasurement(duration,
		                                               resultSize > maxReadBytes ||
		                                                   abs(req.begin.offset) > maxSelectorOffset ||
		                                                   abs(req.end.offset) > maxSelectorOffset);
	}

	return Void();
}

ACTOR Future<GetRangeReqAndResultRef> quickGetKeyValues(
    StorageServer* data,
    StringRef prefix,
    Version version,
    Arena* a,
    // To provide span context, tags, debug ID to underlying lookups.
    GetMappedKeyValuesRequest* pOriginalReq) {
	state GetRangeReqAndResultRef getRange;
	state double getValuesStart = g_network->timer();
	getRange.begin = firstGreaterOrEqual(KeyRef(*a, prefix));
	getRange.end = firstGreaterOrEqual(strinc(prefix, *a));
	try {
		// TODO: Use a lower level API may be better? Or tweak priorities?
		GetKeyValuesRequest req;
		req.spanContext = pOriginalReq->spanContext;
		req.arena = *a;
		req.begin = getRange.begin;
		req.end = getRange.end;
		req.version = version;
		req.tenantInfo = pOriginalReq->tenantInfo;
		// TODO: Validate when the underlying range query exceeds the limit.
		// TODO: Use remainingLimit, remainingLimitBytes rather than separate knobs.
		req.limit = SERVER_KNOBS->QUICK_GET_KEY_VALUES_LIMIT;
		req.limitBytes = SERVER_KNOBS->QUICK_GET_KEY_VALUES_LIMIT_BYTES;
		req.isFetchKeys = false;
		req.tags = pOriginalReq->tags;
		req.ssLatestCommitVersions = VersionVector();
		req.debugID = pOriginalReq->debugID;

		// Note that it does not use readGuard to avoid server being overloaded here. Throttling is enforced at the
		// original request level, rather than individual underlying lookups. The reason is that throttle any individual
		// underlying lookup will fail the original request, which is not productive.
		data->actors.add(getKeyValuesQ(data, req));
		GetKeyValuesReply reply = wait(req.reply.getFuture());
		if (!reply.error.present()) {
			++data->counters.quickGetKeyValuesHit;
			// Convert GetKeyValuesReply to RangeResult.
			a->dependsOn(reply.arena);
			getRange.result = RangeResultRef(reply.data, reply.more);
			const double duration = g_network->timer() - getValuesStart;
			data->counters.mappedRangeLocalSample.addMeasurement(duration);
			return getRange;
		}
		// Otherwise fallback.
	} catch (Error& e) {
		// Fallback.
	}

	++data->counters.quickGetKeyValuesMiss;
	if (SERVER_KNOBS->QUICK_GET_KEY_VALUES_FALLBACK) {
		state Transaction tr(data->cx, pOriginalReq->tenantInfo.name);
		tr.setVersion(version);
		// TODO: is DefaultPromiseEndpoint the best priority for this?
		tr.trState->taskID = TaskPriority::DefaultPromiseEndpoint;
		Future<RangeResult> rangeResultFuture =
		    tr.getRange(prefixRange(prefix), GetRangeLimits::ROW_LIMIT_UNLIMITED, Snapshot::True);
		// TODO: async in case it needs to read from other servers.
		RangeResult rangeResult = wait(rangeResultFuture);
		a->dependsOn(rangeResult.arena());
		getRange.result = rangeResult;
		const double duration = g_network->timer() - getValuesStart;
		data->counters.mappedRangeRemoteSample.addMeasurement(duration);
		return getRange;
	} else {
		throw quick_get_key_values_miss();
	}
}

void unpackKeyTuple(Tuple** referenceTuple, Optional<Tuple>& keyTuple, KeyValueRef* keyValue) {
	if (!keyTuple.present()) {
		// May throw exception if the key is not parsable as a tuple.
		try {
			keyTuple = Tuple::unpack(keyValue->key);
		} catch (Error& e) {
			TraceEvent("KeyNotTuple").error(e).detail("Key", keyValue->key.printable());
			throw key_not_tuple();
		}
	}
	*referenceTuple = &keyTuple.get();
}

void unpackValueTuple(Tuple** referenceTuple, Optional<Tuple>& valueTuple, KeyValueRef* keyValue) {
	if (!valueTuple.present()) {
		// May throw exception if the value is not parsable as a tuple.
		try {
			valueTuple = Tuple::unpack(keyValue->value);
		} catch (Error& e) {
			TraceEvent("ValueNotTuple").error(e).detail("Value", keyValue->value.printable());
			throw value_not_tuple();
		}
	}
	*referenceTuple = &valueTuple.get();
}

bool unescapeLiterals(std::string& s, std::string before, std::string after) {
	bool escaped = false;
	size_t p = 0;
	while (true) {
		size_t found = s.find(before, p);
		if (found == std::string::npos) {
			break;
		}
		s.replace(found, before.length(), after);
		p = found + after.length();
		escaped = true;
	}
	return escaped;
}

bool singleKeyOrValue(const std::string& s, size_t sz) {
	// format would be {K[??]} or {V[??]}
	return sz > 5 && s[0] == '{' && (s[1] == 'K' || s[1] == 'V') && s[2] == '[' && s[sz - 2] == ']' && s[sz - 1] == '}';
}

bool rangeQuery(const std::string& s) {
	return s == "{...}";
}

// create a vector of Optional<Tuple>
// in case of a singleKeyOrValue, insert an empty Tuple to vector as placeholder
// in case of a rangeQuery, insert Optional.empty as placeholder
// in other cases, insert the correct Tuple to be used.
void preprocessMappedKey(Tuple& mappedKeyFormatTuple, std::vector<Optional<Tuple>>& vt, bool& isRangeQuery) {
	vt.reserve(mappedKeyFormatTuple.size());

	for (int i = 0; i < mappedKeyFormatTuple.size(); i++) {
		Tuple::ElementType type = mappedKeyFormatTuple.getType(i);
		if (type == Tuple::BYTES || type == Tuple::UTF8) {
			std::string s = mappedKeyFormatTuple.getString(i).toString();
			auto sz = s.size();
			bool escaped = unescapeLiterals(s, "{{", "{");
			escaped = unescapeLiterals(s, "}}", "}") || escaped;
			if (escaped) {
				vt.emplace_back(Tuple::makeTuple(s));
			} else if (singleKeyOrValue(s, sz)) {
				// when it is SingleKeyOrValue, insert an empty Tuple to vector as placeholder
				vt.emplace_back(Tuple());
			} else if (rangeQuery(s)) {
				if (i != mappedKeyFormatTuple.size() - 1) {
					// It must be the last element of the mapper tuple
					throw mapper_bad_range_decriptor();
				}
				// when it is rangeQuery, insert Optional.empty as placeholder
				vt.emplace_back(Optional<Tuple>());
				isRangeQuery = true;
			} else {
				Tuple t;
				t.appendRaw(mappedKeyFormatTuple.subTupleRawString(i));
				vt.emplace_back(t);
			}
		} else {
			Tuple t;
			t.appendRaw(mappedKeyFormatTuple.subTupleRawString(i));
			vt.emplace_back(t);
		}
	}
}

Key constructMappedKey(KeyValueRef* keyValue,
                       std::vector<Optional<Tuple>>& vec,
                       Tuple& mappedKeyTuple,
                       Tuple& mappedKeyFormatTuple) {
	// Lazily parse key and/or value to tuple because they may not need to be a tuple if not used.
	Optional<Tuple> keyTuple;
	Optional<Tuple> valueTuple;
	mappedKeyTuple.clear();
	mappedKeyTuple.reserve(vec.size());

	for (int i = 0; i < vec.size(); i++) {
		if (!vec[i].present()) {
			// rangeQuery
			continue;
		}
		if (vec[i].get().size()) {
			mappedKeyTuple.append(vec[i].get());
		} else {
			// singleKeyOrValue is true
			std::string s = mappedKeyFormatTuple.getString(i).toString();
			auto sz = s.size();
			int idx;
			Tuple* referenceTuple;
			try {
				idx = std::stoi(s.substr(3, sz - 5));
			} catch (std::exception& e) {
				throw mapper_bad_index();
			}
			if (s[1] == 'K') {
				unpackKeyTuple(&referenceTuple, keyTuple, keyValue);
			} else if (s[1] == 'V') {
				unpackValueTuple(&referenceTuple, valueTuple, keyValue);
			} else {
				ASSERT(false);
				throw internal_error();
			}
			if (idx < 0 || idx >= referenceTuple->size()) {
				throw mapper_bad_index();
			}
			mappedKeyTuple.appendRaw(referenceTuple->subTupleRawString(idx));
		}
	}

	return mappedKeyTuple.pack();
}

TEST_CASE("/fdbserver/storageserver/constructMappedKey") {
	Key key = Tuple::makeTuple("key-0"_sr, "key-1"_sr, "key-2"_sr).getDataAsStandalone();
	Value value = Tuple::makeTuple("value-0"_sr, "value-1"_sr, "value-2"_sr).getDataAsStandalone();
	state KeyValueRef kvr(key, value);
	{
		Tuple mappedKeyFormatTuple =
		    Tuple::makeTuple("normal"_sr, "{{escaped}}"_sr, "{K[2]}"_sr, "{V[0]}"_sr, "{...}"_sr);

		Tuple mappedKeyTuple;
		std::vector<Optional<Tuple>> vt;
		bool isRangeQuery = false;
		preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);

		Key mappedKey = constructMappedKey(&kvr, vt, mappedKeyTuple, mappedKeyFormatTuple);

		Key expectedMappedKey =
		    Tuple::makeTuple("normal"_sr, "{escaped}"_sr, "key-2"_sr, "value-0"_sr).getDataAsStandalone();
		//		std::cout << printable(mappedKey) << " == " << printable(expectedMappedKey) << std::endl;
		ASSERT(mappedKey.compare(expectedMappedKey) == 0);
		ASSERT(isRangeQuery == true);
	}

	{
		Tuple mappedKeyFormatTuple = Tuple::makeTuple("{{{{}}"_sr, "}}"_sr);

		Tuple mappedKeyTuple;
		std::vector<Optional<Tuple>> vt;
		bool isRangeQuery = false;
		preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);
		Key mappedKey = constructMappedKey(&kvr, vt, mappedKeyTuple, mappedKeyFormatTuple);

		Key expectedMappedKey = Tuple::makeTuple("{{}"_sr, "}"_sr).getDataAsStandalone();
		//		std::cout << printable(mappedKey) << " == " << printable(expectedMappedKey) << std::endl;
		ASSERT(mappedKey.compare(expectedMappedKey) == 0);
		ASSERT(isRangeQuery == false);
	}
	{
		Tuple mappedKeyFormatTuple = Tuple::makeTuple("{{{{}}"_sr, "}}"_sr);

		Tuple mappedKeyTuple;
		std::vector<Optional<Tuple>> vt;
		bool isRangeQuery = false;
		preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);
		Key mappedKey = constructMappedKey(&kvr, vt, mappedKeyTuple, mappedKeyFormatTuple);

		Key expectedMappedKey = Tuple::makeTuple("{{}"_sr, "}"_sr).getDataAsStandalone();
		//		std::cout << printable(mappedKey) << " == " << printable(expectedMappedKey) << std::endl;
		ASSERT(mappedKey.compare(expectedMappedKey) == 0);
		ASSERT(isRangeQuery == false);
	}
	{
		Tuple mappedKeyFormatTuple = Tuple::makeTuple("{K[100]}"_sr);
		state bool throwException = false;
		try {
			Tuple mappedKeyTuple;
			std::vector<Optional<Tuple>> vt;
			bool isRangeQuery = false;
			preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);

			Key mappedKey = constructMappedKey(&kvr, vt, mappedKeyTuple, mappedKeyFormatTuple);
		} catch (Error& e) {
			ASSERT(e.code() == error_code_mapper_bad_index);
			throwException = true;
		}
		ASSERT(throwException);
	}
	{
		Tuple mappedKeyFormatTuple = Tuple::makeTuple("{...}"_sr, "last-element"_sr);
		state bool throwException2 = false;
		try {
			Tuple mappedKeyTuple;
			std::vector<Optional<Tuple>> vt;
			bool isRangeQuery = false;
			preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);

			Key mappedKey = constructMappedKey(&kvr, vt, mappedKeyTuple, mappedKeyFormatTuple);
		} catch (Error& e) {
			ASSERT(e.code() == error_code_mapper_bad_range_decriptor);
			throwException2 = true;
		}
		ASSERT(throwException2);
	}
	{
		Tuple mappedKeyFormatTuple = Tuple::makeTuple("{K[not-a-number]}"_sr);
		state bool throwException3 = false;
		try {
			Tuple mappedKeyTuple;
			std::vector<Optional<Tuple>> vt;
			bool isRangeQuery = false;
			preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);

			Key mappedKey = constructMappedKey(&kvr, vt, mappedKeyTuple, mappedKeyFormatTuple);
		} catch (Error& e) {
			ASSERT(e.code() == error_code_mapper_bad_index);
			throwException3 = true;
		}
		ASSERT(throwException3);
	}
	return Void();
}

// Issues a secondary query (either range and point read) and fills results into "kvm".
ACTOR Future<Void> mapSubquery(StorageServer* data,
                               Version version,
                               GetMappedKeyValuesRequest* pOriginalReq,
                               Arena* pArena,
                               int matchIndex,
                               bool isRangeQuery,
                               bool isBoundary,
                               KeyValueRef* it,
                               MappedKeyValueRef* kvm,
                               Key mappedKey) {
	if (isRangeQuery) {
		// Use the mappedKey as the prefix of the range query.
		GetRangeReqAndResultRef getRange = wait(quickGetKeyValues(data, mappedKey, version, pArena, pOriginalReq));
		if ((!getRange.result.empty() && matchIndex == MATCH_INDEX_MATCHED_ONLY) ||
		    (getRange.result.empty() && matchIndex == MATCH_INDEX_UNMATCHED_ONLY)) {
			kvm->key = it->key;
			kvm->value = it->value;
		}

		kvm->boundaryAndExist = isBoundary && !getRange.result.empty();
		kvm->reqAndResult = getRange;
	} else {
		GetValueReqAndResultRef getValue = wait(quickGetValue(data, mappedKey, version, pArena, pOriginalReq));
		kvm->reqAndResult = getValue;
		kvm->boundaryAndExist = isBoundary && getValue.result.present();
	}
	return Void();
}

ACTOR Future<GetMappedKeyValuesReply> mapKeyValues(StorageServer* data,
                                                   GetKeyValuesReply input,
                                                   StringRef mapper,
                                                   // To provide span context, tags, debug ID to underlying lookups.
                                                   GetMappedKeyValuesRequest* pOriginalReq,
                                                   Optional<Key> tenantPrefix,
                                                   int matchIndex) {
	state GetMappedKeyValuesReply result;
	result.version = input.version;
	result.more = input.more;
	result.cached = input.cached;
	result.arena.dependsOn(input.arena);

	result.data.reserve(result.arena, input.data.size());

	state Tuple mappedKeyFormatTuple;
	state Tuple mappedKeyTuple;

	try {
		mappedKeyFormatTuple = Tuple::unpack(mapper);
	} catch (Error& e) {
		TraceEvent("MapperNotTuple").error(e).detail("Mapper", mapper);
		throw mapper_not_tuple();
	}
	state std::vector<Optional<Tuple>> vt;
	state bool isRangeQuery = false;
	preprocessMappedKey(mappedKeyFormatTuple, vt, isRangeQuery);

	state int sz = input.data.size();
	const int k = std::min(sz, SERVER_KNOBS->MAX_PARALLEL_QUICK_GET_VALUE);
	state std::vector<MappedKeyValueRef> kvms(k);
	state std::vector<Future<Void>> subqueries;
	state int offset = 0;
	for (; offset < sz; offset += SERVER_KNOBS->MAX_PARALLEL_QUICK_GET_VALUE) {
		// Divide into batches of MAX_PARALLEL_QUICK_GET_VALUE subqueries
		for (int i = 0; i + offset < sz && i < SERVER_KNOBS->MAX_PARALLEL_QUICK_GET_VALUE; i++) {
			KeyValueRef* it = &input.data[i + offset];
			MappedKeyValueRef* kvm = &kvms[i];
			bool isBoundary = (i + offset) == 0 || (i + offset) == sz - 1;
			// need to keep the boundary, so that caller can use it as a continuation.
			if (isBoundary || matchIndex == MATCH_INDEX_ALL) {
				kvm->key = it->key;
				kvm->value = it->value;
			} else {
				// Clear key value to the default.
				kvm->key = ""_sr;
				kvm->value = ""_sr;
			}

			Key mappedKey = constructMappedKey(it, vt, mappedKeyTuple, mappedKeyFormatTuple);
			// Make sure the mappedKey is always available, so that it's good even we want to get key asynchronously.
			result.arena.dependsOn(mappedKey.arena());

			// std::cout << "key:" << printable(kvm->key) << ", value:" << printable(kvm->value)
			//          << ", mappedKey:" << printable(mappedKey) << std::endl;

			subqueries.push_back(mapSubquery(data,
			                                 input.version,
			                                 pOriginalReq,
			                                 &result.arena,
			                                 matchIndex,
			                                 isRangeQuery,
			                                 isBoundary,
			                                 it,
			                                 kvm,
			                                 mappedKey));
		}
		wait(waitForAll(subqueries));
		subqueries.clear();
		for (int i = 0; i + offset < sz && i < SERVER_KNOBS->MAX_PARALLEL_QUICK_GET_VALUE; i++) {
			result.data.push_back(result.arena, kvms[i]);
		}
	}
	return result;
}

bool rangeIntersectsAnyTenant(TenantPrefixIndex& prefixIndex, KeyRangeRef range, Version ver) {
	auto view = prefixIndex.at(ver);
	auto beginItr = view.lastLessOrEqual(range.begin);
	auto endItr = view.lastLess(range.end);

	// If the begin and end reference different spots in the tenant index, then the tenant pointed to
	// by endItr intersects the range
	if (beginItr != endItr) {
		return true;
	}

	// If the iterators point to the same entry and that entry contains begin, then we are wholly in
	// one tenant
	if (beginItr != view.end() && range.begin.startsWith(beginItr.key())) {
		return true;
	}

	return false;
}

TEST_CASE("/fdbserver/storageserver/rangeIntersectsAnyTenant") {
	std::map<TenantName, TenantMapEntry> entries = {
		std::make_pair("tenant0"_sr, TenantMapEntry(0, TenantState::READY)),
		std::make_pair("tenant2"_sr, TenantMapEntry(2, TenantState::READY)),
		std::make_pair("tenant3"_sr, TenantMapEntry(3, TenantState::READY)),
		std::make_pair("tenant4"_sr, TenantMapEntry(4, TenantState::READY)),
		std::make_pair("tenant6"_sr, TenantMapEntry(6, TenantState::READY))
	};
	TenantPrefixIndex index;
	index.createNewVersion(1);
	for (auto entry : entries) {
		index.insert(entry.second.prefix, entry.first);
	}

	// Before all tenants
	ASSERT(!rangeIntersectsAnyTenant(index, KeyRangeRef(""_sr, "\x00"_sr), index.getLatestVersion()));

	// After all tenants
	ASSERT(!rangeIntersectsAnyTenant(index, KeyRangeRef("\xfe"_sr, "\xff"_sr), index.getLatestVersion()));

	// In between tenants
	ASSERT(!rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(TenantMapEntry::idToPrefix(1), TenantMapEntry::idToPrefix(1).withSuffix("\xff"_sr)),
	    index.getLatestVersion()));

	// In between tenants with end intersecting tenant start
	ASSERT(!rangeIntersectsAnyTenant(
	    index, KeyRangeRef(TenantMapEntry::idToPrefix(5), entries["tenant6"_sr].prefix), index.getLatestVersion()));

	// Entire tenants
	ASSERT(rangeIntersectsAnyTenant(
	    index, KeyRangeRef(entries["tenant0"_sr].prefix, TenantMapEntry::idToPrefix(1)), index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(
	    index, KeyRangeRef(entries["tenant2"_sr].prefix, entries["tenant3"_sr].prefix), index.getLatestVersion()));

	// Partial tenants
	ASSERT(rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(entries["tenant0"_sr].prefix, entries["tenant0"_sr].prefix.withSuffix("foo"_sr)),
	    index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(entries["tenant3"_sr].prefix.withSuffix("foo"_sr), entries["tenant4"_sr].prefix),
	    index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(index,
	                                KeyRangeRef(entries["tenant4"_sr].prefix.withSuffix("bar"_sr),
	                                            entries["tenant4"_sr].prefix.withSuffix("foo"_sr)),
	                                index.getLatestVersion()));

	// Begin outside, end inside tenant
	ASSERT(rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(TenantMapEntry::idToPrefix(1), entries["tenant2"_sr].prefix.withSuffix("foo"_sr)),
	    index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(TenantMapEntry::idToPrefix(1), entries["tenant3"_sr].prefix.withSuffix("foo"_sr)),
	    index.getLatestVersion()));

	// Begin inside, end outside tenant
	ASSERT(rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(entries["tenant3"_sr].prefix.withSuffix("foo"_sr), TenantMapEntry::idToPrefix(5)),
	    index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(
	    index,
	    KeyRangeRef(entries["tenant4"_sr].prefix.withSuffix("foo"_sr), TenantMapEntry::idToPrefix(5)),
	    index.getLatestVersion()));

	// Both inside different tenants
	ASSERT(rangeIntersectsAnyTenant(index,
	                                KeyRangeRef(entries["tenant0"_sr].prefix.withSuffix("foo"_sr),
	                                            entries["tenant2"_sr].prefix.withSuffix("foo"_sr)),
	                                index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(index,
	                                KeyRangeRef(entries["tenant0"_sr].prefix.withSuffix("foo"_sr),
	                                            entries["tenant3"_sr].prefix.withSuffix("foo"_sr)),
	                                index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(index,
	                                KeyRangeRef(entries["tenant2"_sr].prefix.withSuffix("foo"_sr),
	                                            entries["tenant6"_sr].prefix.withSuffix("foo"_sr)),
	                                index.getLatestVersion()));

	// Both outside tenants with tenant in the middle
	ASSERT(rangeIntersectsAnyTenant(
	    index, KeyRangeRef(""_sr, TenantMapEntry::idToPrefix(1).withSuffix("foo"_sr)), index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(index, KeyRangeRef(""_sr, "\xff"_sr), index.getLatestVersion()));
	ASSERT(rangeIntersectsAnyTenant(
	    index, KeyRangeRef(TenantMapEntry::idToPrefix(5).withSuffix("foo"_sr), "\xff"_sr), index.getLatestVersion()));

	return Void();
}

// Most of the actor is copied from getKeyValuesQ. I tried to use templates but things become nearly impossible after
// combining actor shenanigans with template shenanigans.
ACTOR Future<Void> getMappedKeyValuesQ(StorageServer* data, GetMappedKeyValuesRequest req)
// Throws a wrong_shard_server if the keys in the request or result depend on data outside this server OR if a large
// selector offset prevents all data from being read in one range read
{
	state Span span("SS:getMappedKeyValues"_loc, req.spanContext);
	state int64_t resultSize = 0;
	state IKeyValueStore::ReadType type =
	    req.isFetchKeys ? IKeyValueStore::ReadType::FETCH : IKeyValueStore::ReadType::NORMAL;

	if (req.tenantInfo.name.present()) {
		span.addAttribute("tenant"_sr, req.tenantInfo.name.get());
	}

	getCurrentLineage()->modify(&TransactionLineage::txID) = req.spanContext.traceID;

	++data->counters.getMappedRangeQueries;
	++data->counters.allQueries;
	data->maxQueryQueue = std::max<int>(
	    data->maxQueryQueue, data->counters.allQueries.getValue() - data->counters.finishedQueries.getValue());

	// Active load balancing runs at a very high priority (to obtain accurate queue lengths)
	// so we need to downgrade here
	if (SERVER_KNOBS->FETCH_KEYS_LOWER_PRIORITY && req.isFetchKeys) {
		wait(delay(0, TaskPriority::FetchKeys));
	} else {
		wait(data->getQueryDelay());
	}

	try {
		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getMappedKeyValues.Before");
		// VERSION_VECTOR change
		Version commitVersion = getLatestCommitVersion(req.ssLatestCommitVersions, data->tag);
		state Version version = wait(waitForVersion(data, commitVersion, req.version, span.context));

		state Optional<TenantMapEntry> tenantEntry = data->getTenantEntry(req.version, req.tenantInfo);
		state Optional<Key> tenantPrefix = tenantEntry.map<Key>([](TenantMapEntry e) { return e.prefix; });
		if (tenantPrefix.present()) {
			req.begin.setKeyUnlimited(req.begin.getKey().withPrefix(tenantPrefix.get(), req.arena));
			req.end.setKeyUnlimited(req.end.getKey().withPrefix(tenantPrefix.get(), req.arena));
		}

		state uint64_t changeCounter = data->shardChangeCounter;
		//		try {
		state KeyRange shard = getShardKeyRange(data, req.begin);

		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getMappedKeyValues.AfterVersion");
		//.detail("ShardBegin", shard.begin).detail("ShardEnd", shard.end);
		//} catch (Error& e) { TraceEvent("WrongShardServer", data->thisServerID).detail("Begin",
		// req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("Shard",
		//"None").detail("In", "getMappedKeyValues>getShardKeyRange"); throw e; }

		if (!selectorInRange(req.end, shard) && !(req.end.isFirstGreaterOrEqual() && req.end.getKey() == shard.end)) {
			//			TraceEvent("WrongShardServer1", data->thisServerID).detail("Begin",
			// req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("ShardBegin",
			// shard.begin).detail("ShardEnd", shard.end).detail("In", "getMappedKeyValues>checkShardExtents");
			throw wrong_shard_server();
		}

		KeyRangeRef searchRange = data->clampRangeToTenant(shard, tenantEntry, req.arena);

		state int offset1 = 0;
		state int offset2;
		state Future<Key> fBegin = req.begin.isFirstGreaterOrEqual()
		                               ? Future<Key>(req.begin.getKey())
		                               : findKey(data, req.begin, version, searchRange, &offset1, span.context, type);
		state Future<Key> fEnd = req.end.isFirstGreaterOrEqual()
		                             ? Future<Key>(req.end.getKey())
		                             : findKey(data, req.end, version, searchRange, &offset2, span.context, type);
		state Key begin = wait(fBegin);
		state Key end = wait(fEnd);

		if (!tenantPrefix.present()) {
			// We do not support raw flat map requests when using tenants.
			// When tenants are required, we disable raw flat map requests entirely.
			// If tenants are optional, we check whether the range intersects a tenant and fail if it does.
			if (data->db->get().client.tenantMode == TenantMode::REQUIRED) {
				throw tenant_name_required();
			}

			if (rangeIntersectsAnyTenant(data->tenantPrefixIndex, KeyRangeRef(begin, end), req.version)) {
				throw tenant_name_required();
			}
		}

		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getMappedKeyValues.AfterKeys");
		//.detail("Off1",offset1).detail("Off2",offset2).detail("ReqBegin",req.begin.getKey()).detail("ReqEnd",req.end.getKey());

		// Offsets of zero indicate begin/end keys in this shard, which obviously means we can answer the query
		// An end offset of 1 is also OK because the end key is exclusive, so if the first key of the next shard is the
		// end the last actual key returned must be from this shard. A begin offset of 1 is also OK because then either
		// begin is past end or equal to end (so the result is definitely empty)
		if ((offset1 && offset1 != 1) || (offset2 && offset2 != 1)) {
			CODE_PROBE(true, "wrong_shard_server due to offset in getMappedKeyValuesQ");
			// We could detect when offset1 takes us off the beginning of the database or offset2 takes us off the end,
			// and return a clipped range rather than an error (since that is what the NativeAPI.getRange will do anyway
			// via its "slow path"), but we would have to add some flags to the response to encode whether we went off
			// the beginning and the end, since it needs that information.
			//TraceEvent("WrongShardServer2", data->thisServerID).detail("Begin", req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("ShardBegin", shard.begin).detail("ShardEnd", shard.end).detail("In", "getMappedKeyValues>checkOffsets").detail("BeginKey", begin).detail("EndKey", end).detail("BeginOffset", offset1).detail("EndOffset", offset2);
			throw wrong_shard_server();
		}

		if (begin >= end) {
			if (req.debugID.present())
				g_traceBatch.addEvent(
				    "TransactionDebug", req.debugID.get().first(), "storageserver.getMappedKeyValues.Send");
			//.detail("Begin",begin).detail("End",end);

			GetMappedKeyValuesReply none;
			none.version = version;
			none.more = false;
			none.penalty = data->getPenalty();

			data->checkChangeCounter(changeCounter,
			                         KeyRangeRef(std::min<KeyRef>(req.begin.getKey(), req.end.getKey()),
			                                     std::max<KeyRef>(req.begin.getKey(), req.end.getKey())));
			req.reply.send(none);
		} else {
			state int remainingLimitBytes = req.limitBytes;

			GetKeyValuesReply getKeyValuesReply = wait(readRange(data,
			                                                     version,
			                                                     KeyRangeRef(begin, end),
			                                                     req.limit,
			                                                     &remainingLimitBytes,
			                                                     span.context,
			                                                     type,
			                                                     tenantPrefix));

			state GetMappedKeyValuesReply r;
			try {
				// Map the scanned range to another list of keys and look up.
				GetMappedKeyValuesReply _r =
				    wait(mapKeyValues(data, getKeyValuesReply, req.mapper, &req, tenantPrefix, req.matchIndex));
				r = _r;
			} catch (Error& e) {
				TraceEvent("MapError").error(e);
				throw;
			}

			if (req.debugID.present())
				g_traceBatch.addEvent(
				    "TransactionDebug", req.debugID.get().first(), "storageserver.getMappedKeyValues.AfterReadRange");
			//.detail("Begin",begin).detail("End",end).detail("SizeOf",r.data.size());
			data->checkChangeCounter(
			    changeCounter,
			    KeyRangeRef(std::min<KeyRef>(begin, std::min<KeyRef>(req.begin.getKey(), req.end.getKey())),
			                std::max<KeyRef>(end, std::max<KeyRef>(req.begin.getKey(), req.end.getKey()))));
			if (EXPENSIVE_VALIDATION) {
				// TODO: GetMappedKeyValuesRequest doesn't respect limit yet.
				//                ASSERT(r.data.size() <= std::abs(req.limit));
			}

			// For performance concerns, the cost of a range read is billed to the start key and end key of the range.
			int64_t totalByteSize = 0;
			for (int i = 0; i < r.data.size(); i++) {
				totalByteSize += r.data[i].expectedSize();
			}
			if (totalByteSize > 0 && SERVER_KNOBS->READ_SAMPLING_ENABLED) {
				int64_t bytesReadPerKSecond = std::max(totalByteSize, SERVER_KNOBS->EMPTY_READ_PENALTY) / 2;
				data->metrics.notifyBytesReadPerKSecond(addPrefix(r.data[0].key, tenantPrefix, req.arena),
				                                        bytesReadPerKSecond);
				data->metrics.notifyBytesReadPerKSecond(
				    addPrefix(r.data[r.data.size() - 1].key, tenantPrefix, req.arena), bytesReadPerKSecond);
			}

			r.penalty = data->getPenalty();
			req.reply.send(r);

			resultSize = req.limitBytes - remainingLimitBytes;
			data->counters.bytesQueried += resultSize;
			data->counters.rowsQueried += r.data.size();
			if (r.data.size() == 0) {
				++data->counters.emptyQueries;
			}
		}
	} catch (Error& e) {
		if (!canReplyWith(e))
			throw;
		data->sendErrorWithPenalty(req.reply, e, data->getPenalty());
	}

	data->transactionTagCounter.addRequest(req.tags, resultSize);
	++data->counters.finishedQueries;

	double duration = g_network->timer() - req.requestTime();
	data->counters.readLatencySample.addMeasurement(duration);
	data->counters.mappedRangeSample.addMeasurement(duration);
	if (data->latencyBandConfig.present()) {
		int maxReadBytes =
		    data->latencyBandConfig.get().readConfig.maxReadBytes.orDefault(std::numeric_limits<int>::max());
		int maxSelectorOffset =
		    data->latencyBandConfig.get().readConfig.maxKeySelectorOffset.orDefault(std::numeric_limits<int>::max());
		data->counters.readLatencyBands.addMeasurement(duration,
		                                               resultSize > maxReadBytes ||
		                                                   abs(req.begin.offset) > maxSelectorOffset ||
		                                                   abs(req.end.offset) > maxSelectorOffset);
	}

	return Void();
}

ACTOR Future<Void> getKeyValuesStreamQ(StorageServer* data, GetKeyValuesStreamRequest req)
// Throws a wrong_shard_server if the keys in the request or result depend on data outside this server OR if a large
// selector offset prevents all data from being read in one range read
{
	state Span span("SS:getKeyValuesStream"_loc, req.spanContext);
	state int64_t resultSize = 0;
	state IKeyValueStore::ReadType type =
	    req.isFetchKeys ? IKeyValueStore::ReadType::FETCH : IKeyValueStore::ReadType::NORMAL;

	if (req.tenantInfo.name.present()) {
		span.addAttribute("tenant"_sr, req.tenantInfo.name.get());
	}

	req.reply.setByteLimit(SERVER_KNOBS->RANGESTREAM_LIMIT_BYTES);
	++data->counters.getRangeStreamQueries;
	++data->counters.allQueries;
	data->maxQueryQueue = std::max<int>(
	    data->maxQueryQueue, data->counters.allQueries.getValue() - data->counters.finishedQueries.getValue());

	// Active load balancing runs at a very high priority (to obtain accurate queue lengths)
	// so we need to downgrade here
	if (SERVER_KNOBS->FETCH_KEYS_LOWER_PRIORITY && req.isFetchKeys) {
		wait(delay(0, TaskPriority::FetchKeys));
	} else {
		wait(delay(0, TaskPriority::DefaultEndpoint));
	}

	try {
		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValuesStream.Before");

		Version commitVersion = getLatestCommitVersion(req.ssLatestCommitVersions, data->tag);
		state Version version = wait(waitForVersion(data, commitVersion, req.version, span.context));

		state Optional<TenantMapEntry> tenantEntry = data->getTenantEntry(version, req.tenantInfo);
		state Optional<Key> tenantPrefix = tenantEntry.map<Key>([](TenantMapEntry e) { return e.prefix; });
		if (tenantPrefix.present()) {
			req.begin.setKeyUnlimited(req.begin.getKey().withPrefix(tenantPrefix.get(), req.arena));
			req.end.setKeyUnlimited(req.end.getKey().withPrefix(tenantPrefix.get(), req.arena));
		}

		state uint64_t changeCounter = data->shardChangeCounter;
		//		try {
		state KeyRange shard = getShardKeyRange(data, req.begin);

		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValuesStream.AfterVersion");
		//.detail("ShardBegin", shard.begin).detail("ShardEnd", shard.end);
		//} catch (Error& e) { TraceEvent("WrongShardServer", data->thisServerID).detail("Begin",
		// req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("Shard",
		//"None").detail("In", "getKeyValues>getShardKeyRange"); throw e; }

		if (!selectorInRange(req.end, shard) && !(req.end.isFirstGreaterOrEqual() && req.end.getKey() == shard.end)) {
			//			TraceEvent("WrongShardServer1", data->thisServerID).detail("Begin",
			// req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("ShardBegin",
			// shard.begin).detail("ShardEnd", shard.end).detail("In", "getKeyValues>checkShardExtents");
			throw wrong_shard_server();
		}

		KeyRangeRef searchRange = data->clampRangeToTenant(shard, tenantEntry, req.arena);

		state int offset1 = 0;
		state int offset2;
		state Future<Key> fBegin = req.begin.isFirstGreaterOrEqual()
		                               ? Future<Key>(req.begin.getKey())
		                               : findKey(data, req.begin, version, searchRange, &offset1, span.context, type);
		state Future<Key> fEnd = req.end.isFirstGreaterOrEqual()
		                             ? Future<Key>(req.end.getKey())
		                             : findKey(data, req.end, version, searchRange, &offset2, span.context, type);
		state Key begin = wait(fBegin);
		state Key end = wait(fEnd);
		if (req.debugID.present())
			g_traceBatch.addEvent(
			    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValuesStream.AfterKeys");
		//.detail("Off1",offset1).detail("Off2",offset2).detail("ReqBegin",req.begin.getKey()).detail("ReqEnd",req.end.getKey());

		// Offsets of zero indicate begin/end keys in this shard, which obviously means we can answer the query
		// An end offset of 1 is also OK because the end key is exclusive, so if the first key of the next shard is the
		// end the last actual key returned must be from this shard. A begin offset of 1 is also OK because then either
		// begin is past end or equal to end (so the result is definitely empty)
		if ((offset1 && offset1 != 1) || (offset2 && offset2 != 1)) {
			CODE_PROBE(true, "wrong_shard_server due to offset in rangeStream");
			// We could detect when offset1 takes us off the beginning of the database or offset2 takes us off the end,
			// and return a clipped range rather than an error (since that is what the NativeAPI.getRange will do anyway
			// via its "slow path"), but we would have to add some flags to the response to encode whether we went off
			// the beginning and the end, since it needs that information.
			//TraceEvent("WrongShardServer2", data->thisServerID).detail("Begin", req.begin.toString()).detail("End", req.end.toString()).detail("Version", version).detail("ShardBegin", shard.begin).detail("ShardEnd", shard.end).detail("In", "getKeyValues>checkOffsets").detail("BeginKey", begin).detail("EndKey", end).detail("BeginOffset", offset1).detail("EndOffset", offset2);
			throw wrong_shard_server();
		}

		if (begin >= end) {
			if (req.debugID.present())
				g_traceBatch.addEvent(
				    "TransactionDebug", req.debugID.get().first(), "storageserver.getKeyValuesStream.Send");
			//.detail("Begin",begin).detail("End",end);

			GetKeyValuesStreamReply none;
			none.version = version;
			none.more = false;

			data->checkChangeCounter(changeCounter,
			                         KeyRangeRef(std::min<KeyRef>(req.begin.getKey(), req.end.getKey()),
			                                     std::max<KeyRef>(req.begin.getKey(), req.end.getKey())));
			req.reply.send(none);
			req.reply.sendError(end_of_stream());
		} else {
			loop {
				wait(req.reply.onReady());

				if (version < data->oldestVersion.get()) {
					throw transaction_too_old();
				}

				// Even if TSS mode is Disabled, this may be the second test in a restarting test where the first run
				// had it enabled.
				state int byteLimit = (BUGGIFY && g_simulator.tssMode == ISimulator::TSSMode::Disabled &&
				                       !data->isTss() && !data->isSSWithTSSPair())
				                          ? 1
				                          : CLIENT_KNOBS->REPLY_BYTE_LIMIT;
				GetKeyValuesReply _r = wait(readRange(
				    data, version, KeyRangeRef(begin, end), req.limit, &byteLimit, span.context, type, tenantPrefix));
				GetKeyValuesStreamReply r(_r);

				if (req.debugID.present())
					g_traceBatch.addEvent("TransactionDebug",
					                      req.debugID.get().first(),
					                      "storageserver.getKeyValuesStream.AfterReadRange");
				//.detail("Begin",begin).detail("End",end).detail("SizeOf",r.data.size());
				data->checkChangeCounter(
				    changeCounter,
				    KeyRangeRef(std::min<KeyRef>(begin, std::min<KeyRef>(req.begin.getKey(), req.end.getKey())),
				                std::max<KeyRef>(end, std::max<KeyRef>(req.begin.getKey(), req.end.getKey()))));
				if (EXPENSIVE_VALIDATION) {
					for (int i = 0; i < r.data.size(); i++) {
						if (tenantPrefix.present()) {
							ASSERT(r.data[i].key >= begin.removePrefix(tenantPrefix.get()) &&
							       r.data[i].key < end.removePrefix(tenantPrefix.get()));
						} else {
							ASSERT(r.data[i].key >= begin && r.data[i].key < end);
						}
					}
					ASSERT(r.data.size() <= std::abs(req.limit));
				}

				// For performance concerns, the cost of a range read is billed to the start key and end key of the
				// range.
				int64_t totalByteSize = 0;
				for (int i = 0; i < r.data.size(); i++) {
					totalByteSize += r.data[i].expectedSize();
				}

				KeyRef lastKey;
				if (!r.data.empty()) {
					lastKey = addPrefix(r.data.back().key, tenantPrefix, req.arena);
				}
				if (totalByteSize > 0 && SERVER_KNOBS->READ_SAMPLING_ENABLED) {
					int64_t bytesReadPerKSecond = std::max(totalByteSize, SERVER_KNOBS->EMPTY_READ_PENALTY) / 2;
					KeyRef firstKey = addPrefix(r.data[0].key, tenantPrefix, req.arena);
					data->metrics.notifyBytesReadPerKSecond(firstKey, bytesReadPerKSecond);
					data->metrics.notifyBytesReadPerKSecond(lastKey, bytesReadPerKSecond);
				}

				req.reply.send(r);

				data->counters.rowsQueried += r.data.size();
				if (r.data.size() == 0) {
					++data->counters.emptyQueries;
				}
				if (!r.more) {
					req.reply.sendError(end_of_stream());
					break;
				}
				ASSERT(r.data.size());

				if (req.limit >= 0) {
					begin = keyAfter(lastKey);
				} else {
					end = lastKey;
				}

				if (SERVER_KNOBS->FETCH_KEYS_LOWER_PRIORITY && req.isFetchKeys) {
					wait(delay(0, TaskPriority::FetchKeys));
				} else {
					wait(delay(0, TaskPriority::DefaultEndpoint));
				}

				data->transactionTagCounter.addRequest(req.tags, resultSize);
			}
		}
	} catch (Error& e) {
		if (e.code() != error_code_operation_obsolete) {
			if (!canReplyWith(e))
				throw;
			req.reply.sendError(e);
		}
	}

	data->transactionTagCounter.addRequest(req.tags, resultSize);
	++data->counters.finishedQueries;

	return Void();
}

ACTOR Future<Void> getKeyQ(StorageServer* data, GetKeyRequest req) {
	state Span span("SS:getKey"_loc, req.spanContext);
	if (req.tenantInfo.name.present()) {
		span.addAttribute("tenant"_sr, req.tenantInfo.name.get());
	}
	state int64_t resultSize = 0;
	getCurrentLineage()->modify(&TransactionLineage::txID) = req.spanContext.traceID;

	++data->counters.getKeyQueries;
	++data->counters.allQueries;
	data->maxQueryQueue = std::max<int>(
	    data->maxQueryQueue, data->counters.allQueries.getValue() - data->counters.finishedQueries.getValue());

	// Active load balancing runs at a very high priority (to obtain accurate queue lengths)
	// so we need to downgrade here
	wait(data->getQueryDelay());

	try {
		Version commitVersion = getLatestCommitVersion(req.ssLatestCommitVersions, data->tag);
		state Version version = wait(waitForVersion(data, commitVersion, req.version, req.spanContext));

		state Optional<TenantMapEntry> tenantEntry = data->getTenantEntry(version, req.tenantInfo);
		if (tenantEntry.present()) {
			req.sel.setKeyUnlimited(req.sel.getKey().withPrefix(tenantEntry.get().prefix, req.arena));
		}
		state uint64_t changeCounter = data->shardChangeCounter;

		KeyRange shard = getShardKeyRange(data, req.sel);
		KeyRangeRef searchRange = data->clampRangeToTenant(shard, tenantEntry, req.arena);

		state int offset;
		Key absoluteKey = wait(
		    findKey(data, req.sel, version, searchRange, &offset, req.spanContext, IKeyValueStore::ReadType::NORMAL));

		data->checkChangeCounter(changeCounter,
		                         KeyRangeRef(std::min<KeyRef>(req.sel.getKey(), absoluteKey),
		                                     std::max<KeyRef>(req.sel.getKey(), absoluteKey)));

		KeyRef k = absoluteKey;
		if (tenantEntry.present()) {
			k = k.removePrefix(tenantEntry.get().prefix);
		}

		KeySelector updated;
		if (offset < 0)
			updated = firstGreaterOrEqual(k) +
			          offset; // first thing on this shard OR (large offset case) smallest key retrieved in range read
		else if (offset > 0)
			updated =
			    firstGreaterOrEqual(k) + offset -
			    1; // first thing on next shard OR (large offset case) keyAfter largest key retrieved in range read
		else
			updated = KeySelectorRef(k, true, 0); // found

		resultSize = k.size();
		data->counters.bytesQueried += resultSize;
		++data->counters.rowsQueried;

		// Check if the desired key might be cached
		auto cached = data->cachedRangeMap[absoluteKey];
		// if (cached)
		//	TraceEvent(SevDebug, "SSGetKeyCached").detail("Key", k).detail("Begin",
		// shard.begin).detail("End", shard.end);

		GetKeyReply reply(updated, cached);
		reply.penalty = data->getPenalty();

		req.reply.send(reply);
	} catch (Error& e) {
		// if (e.code() == error_code_wrong_shard_server) TraceEvent("WrongShardServer").detail("In","getKey");
		if (!canReplyWith(e))
			throw;
		data->sendErrorWithPenalty(req.reply, e, data->getPenalty());
	}

	// SOMEDAY: The size reported here is an undercount of the bytes read due to the fact that we have to scan for the
	// key It would be more accurate to count all the read bytes, but it's not critical because this function is only
	// used if read-your-writes is disabled
	data->transactionTagCounter.addRequest(req.tags, resultSize);

	++data->counters.finishedQueries;

	double duration = g_network->timer() - req.requestTime();
	data->counters.readLatencySample.addMeasurement(duration);
	if (data->latencyBandConfig.present()) {
		int maxReadBytes =
		    data->latencyBandConfig.get().readConfig.maxReadBytes.orDefault(std::numeric_limits<int>::max());
		int maxSelectorOffset =
		    data->latencyBandConfig.get().readConfig.maxKeySelectorOffset.orDefault(std::numeric_limits<int>::max());
		data->counters.readLatencyBands.addMeasurement(
		    duration, resultSize > maxReadBytes || abs(req.sel.offset) > maxSelectorOffset);
	}

	return Void();
}

void getQueuingMetrics(StorageServer* self, StorageQueuingMetricsRequest const& req) {
	StorageQueuingMetricsReply reply;
	reply.localTime = now();
	reply.instanceID = self->instanceID;
	reply.bytesInput = self->counters.bytesInput.getValue();
	reply.bytesDurable = self->counters.bytesDurable.getValue();

	reply.storageBytes = self->storage.getStorageBytes();
	reply.localRateLimit = self->currentRate();

	reply.version = self->version.get();
	reply.cpuUsage = self->cpuUsage;
	reply.diskUsage = self->diskUsage;
	reply.durableVersion = self->durableVersion.get();

	reply.busiestTags = self->transactionTagCounter.getBusiestTags();

	req.reply.send(reply);
}

#ifndef __INTEL_COMPILER
#pragma endregion
#endif

/////////////////////////// Updates ////////////////////////////////
#ifndef __INTEL_COMPILER
#pragma region Updates
#endif

ACTOR Future<Void> doEagerReads(StorageServer* data, UpdateEagerReadInfo* eager) {
	eager->finishKeyBegin();

	if (SERVER_KNOBS->ENABLE_CLEAR_RANGE_EAGER_READS) {
		std::vector<Future<Key>> keyEnd(eager->keyBegin.size());
		for (int i = 0; i < keyEnd.size(); i++)
			keyEnd[i] = data->storage.readNextKeyInclusive(eager->keyBegin[i], IKeyValueStore::ReadType::EAGER);
		data->counters.eagerReadsKeys += keyEnd.size();

		state Future<std::vector<Key>> futureKeyEnds = getAll(keyEnd);
		state std::vector<Key> keyEndVal = wait(futureKeyEnds);
		for (const auto& key : keyEndVal) {
			data->counters.kvScanBytes += key.expectedSize();
		}
		eager->keyEnd = keyEndVal;
	}

	std::vector<Future<Optional<Value>>> value(eager->keys.size());
	for (int i = 0; i < value.size(); i++)
		value[i] =
		    data->storage.readValuePrefix(eager->keys[i].first, eager->keys[i].second, IKeyValueStore::ReadType::EAGER);

	state Future<std::vector<Optional<Value>>> futureValues = getAll(value);
	std::vector<Optional<Value>> optionalValues = wait(futureValues);
	for (const auto& value : optionalValues) {
		if (value.present()) {
			data->counters.kvGetBytes += value.expectedSize();
		}
	}
	data->counters.eagerReadsKeys += eager->keys.size();
	eager->value = optionalValues;

	return Void();
}

bool changeDurableVersion(StorageServer* data, Version desiredDurableVersion) {
	// Remove entries from the latest version of data->versionedData that haven't changed since they were inserted
	//   before or at desiredDurableVersion, to maintain the invariants for versionedData.
	// Such entries remain in older versions of versionedData until they are forgotten, because it is expensive to dig
	// them out. We also remove everything up to and including newDurableVersion from mutationLog, and everything
	//   up to but excluding desiredDurableVersion from freeable
	// May return false if only part of the work has been done, in which case the caller must call again with the same
	// parameters

	auto& verData = data->mutableData();
	ASSERT(verData.getLatestVersion() == data->version.get() || verData.getLatestVersion() == data->version.get() + 1);

	Version nextDurableVersion = desiredDurableVersion;

	auto mlv = data->getMutationLog().begin();
	if (mlv != data->getMutationLog().end() && mlv->second.version <= desiredDurableVersion) {
		auto& v = mlv->second;
		nextDurableVersion = v.version;
		data->freeable[data->version.get()].dependsOn(v.arena());

		if (verData.getLatestVersion() <= data->version.get())
			verData.createNewVersion(data->version.get() + 1);

		int64_t bytesDurable = VERSION_OVERHEAD;
		for (const auto& m : v.mutations) {
			bytesDurable += mvccStorageBytes(m);
			auto i = verData.atLatest().find(m.param1);
			if (i) {
				ASSERT(i.key() == m.param1);
				ASSERT(i.insertVersion() >= nextDurableVersion);
				if (i.insertVersion() == nextDurableVersion)
					verData.erase(i);
			}
			if (m.type == MutationRef::SetValue) {
				// A set can split a clear, so there might be another entry immediately after this one that should also
				// be cleaned up
				i = verData.atLatest().upper_bound(m.param1);
				if (i) {
					ASSERT(i.insertVersion() >= nextDurableVersion);
					if (i.insertVersion() == nextDurableVersion)
						verData.erase(i);
				}
			}
		}
		data->counters.bytesDurable += bytesDurable;
	}

	if (EXPENSIVE_VALIDATION) {
		// Check that the above loop did its job
		auto view = data->data().atLatest();
		for (auto i = view.begin(); i != view.end(); ++i)
			ASSERT(i.insertVersion() > nextDurableVersion);
	}
	data->getMutableMutationLog().erase(data->getMutationLog().begin(),
	                                    data->getMutationLog().upper_bound(nextDurableVersion));
	data->freeable.erase(data->freeable.begin(), data->freeable.lower_bound(nextDurableVersion));

	Future<Void> checkFatalError = data->otherError.getFuture();
	data->durableVersion.set(nextDurableVersion);
	setDataDurableVersion(data->thisServerID, data->durableVersion.get());
	if (checkFatalError.isReady())
		checkFatalError.get();

	// TraceEvent("ForgotVersionsBefore", data->thisServerID).detail("Version", nextDurableVersion);
	validate(data);

	return nextDurableVersion == desiredDurableVersion;
}

Optional<MutationRef> clipMutation(MutationRef const& m, KeyRangeRef range) {
	if (isSingleKeyMutation((MutationRef::Type)m.type)) {
		if (range.contains(m.param1))
			return m;
	} else if (m.type == MutationRef::ClearRange) {
		KeyRangeRef i = range & KeyRangeRef(m.param1, m.param2);
		if (!i.empty())
			return MutationRef((MutationRef::Type)m.type, i.begin, i.end);
	} else
		ASSERT(false);
	return Optional<MutationRef>();
}

bool convertAtomicOp(MutationRef& m, StorageServer::VersionedData const& data, UpdateEagerReadInfo* eager, Arena& ar) {
	// After this function call, m should be copied into an arena immediately (before modifying data, shards, or eager)
	if (m.type != MutationRef::ClearRange && m.type != MutationRef::SetValue) {
		Optional<StringRef> oldVal;
		auto it = data.atLatest().lastLessOrEqual(m.param1);
		if (it != data.atLatest().end() && it->isValue() && it.key() == m.param1)
			oldVal = it->getValue();
		else if (it != data.atLatest().end() && it->isClearTo() && it->getEndKey() > m.param1) {
			CODE_PROBE(true, "Atomic op right after a clear.");
		} else {
			Optional<Value>& oldThing = eager->getValue(m.param1);
			if (oldThing.present())
				oldVal = oldThing.get();
		}

		switch (m.type) {
		case MutationRef::AddValue:
			m.param2 = doLittleEndianAdd(oldVal, m.param2, ar);
			break;
		case MutationRef::And:
			m.param2 = doAnd(oldVal, m.param2, ar);
			break;
		case MutationRef::Or:
			m.param2 = doOr(oldVal, m.param2, ar);
			break;
		case MutationRef::Xor:
			m.param2 = doXor(oldVal, m.param2, ar);
			break;
		case MutationRef::AppendIfFits:
			m.param2 = doAppendIfFits(oldVal, m.param2, ar);
			break;
		case MutationRef::Max:
			m.param2 = doMax(oldVal, m.param2, ar);
			break;
		case MutationRef::Min:
			m.param2 = doMin(oldVal, m.param2, ar);
			break;
		case MutationRef::ByteMin:
			m.param2 = doByteMin(oldVal, m.param2, ar);
			break;
		case MutationRef::ByteMax:
			m.param2 = doByteMax(oldVal, m.param2, ar);
			break;
		case MutationRef::MinV2:
			m.param2 = doMinV2(oldVal, m.param2, ar);
			break;
		case MutationRef::AndV2:
			m.param2 = doAndV2(oldVal, m.param2, ar);
			break;
		case MutationRef::CompareAndClear:
			if (oldVal.present() && m.param2 == oldVal.get()) {
				m.type = MutationRef::ClearRange;
				m.param2 = keyAfter(m.param1, ar);
				return true;
			}
			return false;
		}
		m.type = MutationRef::SetValue;
	}
	return true;
}

void expandClear(MutationRef& m,
                 StorageServer::VersionedData const& data,
                 UpdateEagerReadInfo* eager,
                 KeyRef eagerTrustedEnd) {
	// After this function call, m should be copied into an arena immediately (before modifying data, shards, or eager)
	ASSERT(m.type == MutationRef::ClearRange);
	// Expand the clear
	const auto& d = data.atLatest();

	// If another clear overlaps the beginning of this one, engulf it
	auto i = d.lastLess(m.param1);
	if (i && i->isClearTo() && i->getEndKey() >= m.param1)
		m.param1 = i.key();

	// If another clear overlaps the end of this one, engulf it; otherwise expand
	i = d.lastLessOrEqual(m.param2);
	if (i && i->isClearTo() && i->getEndKey() >= m.param2) {
		m.param2 = i->getEndKey();
	} else if (SERVER_KNOBS->ENABLE_CLEAR_RANGE_EAGER_READS) {
		// Expand to the next set or clear (from storage or latestVersion), and if it
		// is a clear, engulf it as well
		i = d.lower_bound(m.param2);
		KeyRef endKeyAtStorageVersion =
		    m.param2 == eagerTrustedEnd ? eagerTrustedEnd : std::min(eager->getKeyEnd(m.param2), eagerTrustedEnd);
		if (!i || endKeyAtStorageVersion < i.key())
			m.param2 = endKeyAtStorageVersion;
		else if (i->isClearTo())
			m.param2 = i->getEndKey();
		else
			m.param2 = i.key();
	}
}

void applyMutation(StorageServer* self,
                   MutationRef const& m,
                   Arena& arena,
                   StorageServer::VersionedData& data,
                   Version version) {
	// m is expected to be in arena already
	// Clear split keys are added to arena
	StorageMetrics metrics;
	metrics.bytesPerKSecond = mvccStorageBytes(m) / 2;
	metrics.iosPerKSecond = 1;
	self->metrics.notify(m.param1, metrics);

	if (m.type == MutationRef::SetValue) {
		// VersionedMap (data) is bookkeeping all empty ranges. If the key to be set is new, it is supposed to be in a
		// range what was empty. Break the empty range into halves.
		auto prev = data.atLatest().lastLessOrEqual(m.param1);
		if (prev && prev->isClearTo() && prev->getEndKey() > m.param1) {
			ASSERT(prev.key() <= m.param1);
			KeyRef end = prev->getEndKey();
			// the insert version of the previous clear is preserved for the "left half", because in
			// changeDurableVersion() the previous clear is still responsible for removing it insert() invalidates prev,
			// so prev.key() is not safe to pass to it by reference
			data.insert(KeyRef(prev.key()),
			            ValueOrClearToRef::clearTo(m.param1),
			            prev.insertVersion()); // overwritten by below insert if empty
			KeyRef nextKey = keyAfter(m.param1, arena);
			if (end != nextKey) {
				ASSERT(end > nextKey);
				// the insert version of the "right half" is not preserved, because in changeDurableVersion() this set
				// is responsible for removing it
				// FIXME: This copy is technically an asymptotic problem, definitely a waste of memory (copy of keyAfter
				// is a waste, but not asymptotic)
				data.insert(nextKey, ValueOrClearToRef::clearTo(KeyRef(arena, end)));
			}
		}
		data.insert(m.param1, ValueOrClearToRef::value(m.param2));
		self->watches.trigger(m.param1);
	} else if (m.type == MutationRef::ClearRange) {
		data.erase(m.param1, m.param2);
		ASSERT(m.param2 > m.param1);
		ASSERT(!data.isClearContaining(data.atLatest(), m.param1));
		data.insert(m.param1, ValueOrClearToRef::clearTo(m.param2));
		self->watches.triggerRange(m.param1, m.param2);
	}
}

void applyChangeFeedMutation(StorageServer* self, MutationRef const& m, Version version) {
	if (m.type == MutationRef::SetValue) {
		for (auto& it : self->keyChangeFeed[m.param1]) {
			if (version < it->stopVersion && !it->removing && version > it->emptyVersion) {
				if (it->mutations.empty() || it->mutations.back().version != version) {
					it->mutations.push_back(MutationsAndVersionRef(version, self->knownCommittedVersion.get()));
				}
				it->mutations.back().mutations.push_back_deep(it->mutations.back().arena(), m);
				self->currentChangeFeeds.insert(it->id);

				DEBUG_MUTATION("ChangeFeedWriteSet", version, m, self->thisServerID)
				    .detail("Range", it->range)
				    .detail("ChangeFeedID", it->id);
			} else {
				CODE_PROBE(version <= it->emptyVersion, "Skip CF write because version <= emptyVersion");
				CODE_PROBE(it->removing, "Skip CF write because removing");
				CODE_PROBE(version >= it->stopVersion, "Skip CF write because stopped");
				DEBUG_MUTATION("ChangeFeedWriteSetIgnore", version, m, self->thisServerID)
				    .detail("Range", it->range)
				    .detail("ChangeFeedID", it->id)
				    .detail("StopVersion", it->stopVersion)
				    .detail("EmptyVersion", it->emptyVersion)
				    .detail("Removing", it->removing);
			}
		}
	} else if (m.type == MutationRef::ClearRange) {
		auto ranges = self->keyChangeFeed.intersectingRanges(KeyRangeRef(m.param1, m.param2));
		for (auto& r : ranges) {
			for (auto& it : r.value()) {
				if (version < it->stopVersion && !it->removing && version > it->emptyVersion) {
					if (it->mutations.empty() || it->mutations.back().version != version) {
						it->mutations.push_back(MutationsAndVersionRef(version, self->knownCommittedVersion.get()));
					}
					it->mutations.back().mutations.push_back_deep(it->mutations.back().arena(), m);
					self->currentChangeFeeds.insert(it->id);
					DEBUG_MUTATION("ChangeFeedWriteClear", version, m, self->thisServerID)
					    .detail("Range", it->range)
					    .detail("ChangeFeedID", it->id);
				} else {
					CODE_PROBE(version <= it->emptyVersion, "Skip CF clear because version <= emptyVersion");
					CODE_PROBE(it->removing, "Skip CF clear because removing");
					CODE_PROBE(version >= it->stopVersion, "Skip CF clear because stopped");
					DEBUG_MUTATION("ChangeFeedWriteClearIgnore", version, m, self->thisServerID)
					    .detail("Range", it->range)
					    .detail("ChangeFeedID", it->id)
					    .detail("StopVersion", it->stopVersion)
					    .detail("EmptyVersion", it->emptyVersion)
					    .detail("Removing", it->removing);
				}
			}
		}
	}
}

void removeDataRange(StorageServer* ss,
                     Standalone<VerUpdateRef>& mLV,
                     KeyRangeMap<Reference<ShardInfo>>& shards,
                     KeyRangeRef range) {
	// modify the latest version of data to remove all sets and trim all clears to exclude range.
	// Add a clear to mLV (mutationLog[data.getLatestVersion()]) that ensures all keys in range are removed from the
	// disk when this latest version becomes durable mLV is also modified if necessary to ensure that split clears can
	// be forgotten

	MutationRef clearRange(MutationRef::ClearRange, range.begin, range.end);
	clearRange = ss->addMutationToMutationLog(mLV, clearRange);

	auto& data = ss->mutableData();

	// Expand the range to the right to include other shards not in versionedData
	for (auto r = shards.rangeContaining(range.end); r != shards.ranges().end() && !r->value()->isInVersionedData();
	     ++r)
		range = KeyRangeRef(range.begin, r->end());

	auto endClear = data.atLatest().lastLess(range.end);
	if (endClear && endClear->isClearTo() && endClear->getEndKey() > range.end) {
		// This clear has been bumped up to insertVersion==data.getLatestVersion and needs a corresponding mutation log
		// entry to forget
		MutationRef m(MutationRef::ClearRange, range.end, endClear->getEndKey());
		m = ss->addMutationToMutationLog(mLV, m);
		data.insert(m.param1, ValueOrClearToRef::clearTo(m.param2));
		++ss->counters.kvSystemClearRanges;
	}

	auto beginClear = data.atLatest().lastLess(range.begin);
	if (beginClear && beginClear->isClearTo() && beginClear->getEndKey() > range.begin) {
		// We don't need any special mutationLog entry - because the begin key and insert version are unchanged the
		// original clear
		//   mutation works to forget this one - but we need range.begin in the right arena
		KeyRef rb(mLV.arena(), range.begin);
		// insert() invalidates beginClear, so beginClear.key() is not safe to pass to it by reference
		data.insert(KeyRef(beginClear.key()), ValueOrClearToRef::clearTo(rb), beginClear.insertVersion());
	}

	data.erase(range.begin, range.end);
}

void setAvailableStatus(StorageServer* self, KeyRangeRef keys, bool available);
void setAssignedStatus(StorageServer* self, KeyRangeRef keys, bool nowAssigned);
void updateStorageShard(StorageServer* self, StorageServerShard shard);

void coalescePhysicalShards(StorageServer* data, KeyRangeRef keys) {
	auto shardRanges = data->shards.intersectingRanges(keys);
	auto fullRange = data->shards.ranges();

	auto iter = shardRanges.begin();
	if (iter != fullRange.begin()) {
		--iter;
	}
	auto iterEnd = shardRanges.end();
	if (iterEnd != fullRange.end()) {
		++iterEnd;
	}

	KeyRangeMap<Reference<ShardInfo>>::iterator lastShard = iter;
	++iter;

	for (; iter != iterEnd; ++iter) {
		if (ShardInfo::canMerge(lastShard.value().getPtr(), iter->value().getPtr())) {
			ShardInfo* newShard = lastShard.value().extractPtr();
			ASSERT(newShard->mergeWith(iter->value().getPtr()));
			data->addShard(newShard);
			iter = data->shards.rangeContaining(newShard->keys.begin);
		}
		lastShard = iter;
	}
}

void coalesceShards(StorageServer* data, KeyRangeRef keys) {
	auto shardRanges = data->shards.intersectingRanges(keys);
	auto fullRange = data->shards.ranges();

	auto iter = shardRanges.begin();
	if (iter != fullRange.begin())
		--iter;
	auto iterEnd = shardRanges.end();
	if (iterEnd != fullRange.end())
		++iterEnd;

	bool lastReadable = false;
	bool lastNotAssigned = false;
	KeyRangeMap<Reference<ShardInfo>>::iterator lastRange;

	for (; iter != iterEnd; ++iter) {
		if (lastReadable && iter->value()->isReadable()) {
			KeyRange range = KeyRangeRef(lastRange->begin(), iter->end());
			data->addShard(ShardInfo::newReadWrite(range, data));
			iter = data->shards.rangeContaining(range.begin);
		} else if (lastNotAssigned && iter->value()->notAssigned()) {
			KeyRange range = KeyRangeRef(lastRange->begin(), iter->end());
			data->addShard(ShardInfo::newNotAssigned(range));
			iter = data->shards.rangeContaining(range.begin);
		}

		lastReadable = iter->value()->isReadable();
		lastNotAssigned = iter->value()->notAssigned();
		lastRange = iter;
	}
}

template <class T>
void addMutation(T& target, Version version, bool fromFetch, MutationRef const& mutation) {
	target.addMutation(version, fromFetch, mutation);
}

template <class T>
void addMutation(Reference<T>& target, Version version, bool fromFetch, MutationRef const& mutation) {
	addMutation(*target, version, fromFetch, mutation);
}

template <class T>
void splitMutations(StorageServer* data, KeyRangeMap<T>& map, VerUpdateRef const& update) {
	for (int i = 0; i < update.mutations.size(); i++) {
		splitMutation(data, map, update.mutations[i], update.version, update.version);
	}
}

template <class T>
void splitMutation(StorageServer* data, KeyRangeMap<T>& map, MutationRef const& m, Version ver, bool fromFetch) {
	if (isSingleKeyMutation((MutationRef::Type)m.type)) {
		if (!SHORT_CIRCUT_ACTUAL_STORAGE || !normalKeys.contains(m.param1))
			addMutation(map.rangeContaining(m.param1)->value(), ver, fromFetch, m);
	} else if (m.type == MutationRef::ClearRange) {
		KeyRangeRef mKeys(m.param1, m.param2);
		if (!SHORT_CIRCUT_ACTUAL_STORAGE || !normalKeys.contains(mKeys)) {
			auto r = map.intersectingRanges(mKeys);
			for (auto i = r.begin(); i != r.end(); ++i) {
				KeyRangeRef k = mKeys & i->range();
				addMutation(i->value(), ver, fromFetch, MutationRef((MutationRef::Type)m.type, k.begin, k.end));
			}
		}
	} else
		ASSERT(false); // Unknown mutation type in splitMutations
}

ACTOR Future<Void> logFetchKeysWarning(AddingShard* shard) {
	state double startTime = now();
	loop {
		state double waitSeconds = BUGGIFY ? 5.0 : 600.0;
		wait(delay(waitSeconds));

		const auto traceEventLevel =
		    waitSeconds > SERVER_KNOBS->FETCH_KEYS_TOO_LONG_TIME_CRITERIA ? SevWarnAlways : SevInfo;
		TraceEvent(traceEventLevel, "FetchKeysTooLong")
		    .detail("Duration", now() - startTime)
		    .detail("Phase", shard->phase)
		    .detail("Begin", shard->keys.begin)
		    .detail("End", shard->keys.end);
	}
}

class FetchKeysMetricReporter {
	const UID uid;
	const double startTime;
	int fetchedBytes;
	StorageServer::FetchKeysHistograms& histograms;
	StorageServer::CurrentRunningFetchKeys& currentRunning;
	Counter& bytesFetchedCounter;
	Counter& kvFetchedCounter;

public:
	FetchKeysMetricReporter(const UID& uid_,
	                        const double startTime_,
	                        const KeyRange& keyRange,
	                        StorageServer::FetchKeysHistograms& histograms_,
	                        StorageServer::CurrentRunningFetchKeys& currentRunning_,
	                        Counter& bytesFetchedCounter,
	                        Counter& kvFetchedCounter)
	  : uid(uid_), startTime(startTime_), fetchedBytes(0), histograms(histograms_), currentRunning(currentRunning_),
	    bytesFetchedCounter(bytesFetchedCounter), kvFetchedCounter(kvFetchedCounter) {

		currentRunning.recordStart(uid, keyRange);
	}

	void addFetchedBytes(const int bytes, const int kvCount) {
		fetchedBytes += bytes;
		bytesFetchedCounter += bytes;
		kvFetchedCounter += kvCount;
	}

	~FetchKeysMetricReporter() {
		double latency = now() - startTime;

		// If fetchKeys is *NOT* run, i.e. returning immediately, still report a record.
		if (latency == 0)
			latency = 1e6;

		const uint32_t bandwidth = fetchedBytes / latency;

		histograms.latency->sampleSeconds(latency);
		histograms.bytes->sample(fetchedBytes);
		histograms.bandwidth->sample(bandwidth);

		currentRunning.recordFinish(uid);
	}
};

ACTOR Future<Void> tryGetRange(PromiseStream<RangeResult> results, Transaction* tr, KeyRange keys) {
	state KeySelectorRef begin = firstGreaterOrEqual(keys.begin);
	state KeySelectorRef end = firstGreaterOrEqual(keys.end);

	try {
		loop {
			GetRangeLimits limits(GetRangeLimits::ROW_LIMIT_UNLIMITED, SERVER_KNOBS->FETCH_BLOCK_BYTES);
			limits.minRows = 0;
			state RangeResult rep = wait(tr->getRange(begin, end, limits, Snapshot::True));
			if (!rep.more) {
				rep.readThrough = keys.end;
			}
			results.send(rep);

			if (!rep.more) {
				results.sendError(end_of_stream());
				return Void();
			}

			if (rep.readThrough.present()) {
				begin = firstGreaterOrEqual(rep.readThrough.get());
			} else {
				begin = firstGreaterThan(rep.end()[-1].key);
			}
		}
	} catch (Error& e) {
		if (e.code() == error_code_actor_cancelled) {
			throw;
		}
		results.sendError(e);
		throw;
	}
}

// We have to store the version the change feed was stopped at in the SS instead of just the stopped status
// In addition to simplifying stopping logic, it enables communicating stopped status when fetching change feeds
// from other SS correctly
const Value changeFeedSSValue(KeyRangeRef const& range, Version popVersion, Version stopVersion) {
	BinaryWriter wr(IncludeVersion(ProtocolVersion::withChangeFeed()));
	wr << range;
	wr << popVersion;
	wr << stopVersion;
	return wr.toValue();
}

std::tuple<KeyRange, Version, Version> decodeChangeFeedSSValue(ValueRef const& value) {
	KeyRange range;
	Version popVersion, stopVersion;
	BinaryReader reader(value, IncludeVersion());
	reader >> range;
	reader >> popVersion;
	reader >> stopVersion;
	return std::make_tuple(range, popVersion, stopVersion);
}

ACTOR Future<Void> changeFeedPopQ(StorageServer* self, ChangeFeedPopRequest req) {
	// if a SS restarted and is way behind, wait for it to at least have caught up through the pop version
	wait(self->version.whenAtLeast(req.version));
	wait(delay(0));

	if (!self->isReadable(req.range)) {
		req.reply.sendError(wrong_shard_server());
		return Void();
	}
	auto feed = self->uidChangeFeed.find(req.rangeID);
	if (feed == self->uidChangeFeed.end()) {
		req.reply.sendError(unknown_change_feed());
		return Void();
	}

	TraceEvent(SevDebug, "ChangeFeedPopQuery", self->thisServerID)
	    .detail("RangeID", req.rangeID)
	    .detail("Version", req.version)
	    .detail("SSVersion", self->version.get())
	    .detail("Range", req.range);

	if (req.version - 1 > feed->second->emptyVersion) {
		feed->second->emptyVersion = req.version - 1;
		while (!feed->second->mutations.empty() && feed->second->mutations.front().version < req.version) {
			feed->second->mutations.pop_front();
		}
		if (!feed->second->destroyed) {
			Version durableVersion = self->data().getLatestVersion();
			auto& mLV = self->addVersionToMutationLog(durableVersion);
			self->addMutationToMutationLog(
			    mLV,
			    MutationRef(
			        MutationRef::SetValue,
			        persistChangeFeedKeys.begin.toString() + feed->second->id.toString(),
			        changeFeedSSValue(feed->second->range, feed->second->emptyVersion + 1, feed->second->stopVersion)));
			if (feed->second->storageVersion != invalidVersion) {
				++self->counters.kvSystemClearRanges;
				self->addMutationToMutationLog(mLV,
				                               MutationRef(MutationRef::ClearRange,
				                                           changeFeedDurableKey(feed->second->id, 0),
				                                           changeFeedDurableKey(feed->second->id, req.version)));
				if (req.version > feed->second->storageVersion) {
					feed->second->storageVersion = invalidVersion;
					feed->second->durableVersion = invalidVersion;
				}
			}
			wait(self->durableVersion.whenAtLeast(durableVersion));
		}
	}
	req.reply.send(Void());
	return Void();
}

// FIXME: there's a decent amount of duplicated code around fetching and popping change feeds
// Returns max version fetched
ACTOR Future<Version> fetchChangeFeedApplier(StorageServer* data,
                                             Reference<ChangeFeedInfo> changeFeedInfo,
                                             Key rangeId,
                                             KeyRange range,
                                             Version emptyVersion,
                                             Version beginVersion,
                                             Version endVersion) {

	state Version startVersion = beginVersion;
	startVersion = std::max(startVersion, emptyVersion + 1);
	startVersion = std::max(startVersion, changeFeedInfo->fetchVersion + 1);
	startVersion = std::max(startVersion, changeFeedInfo->durableFetchVersion.get() + 1);

	ASSERT(startVersion >= 0);

	if (startVersion >= endVersion || (changeFeedInfo->removing)) {
		CODE_PROBE(true, "Change Feed popped before fetch");
		TraceEvent(SevDebug, "FetchChangeFeedNoOp", data->thisServerID)
		    .detail("RangeID", rangeId)
		    .detail("Range", range)
		    .detail("StartVersion", startVersion)
		    .detail("EndVersion", endVersion)
		    .detail("Removing", changeFeedInfo->removing);
		return invalidVersion;
	}

	state Reference<ChangeFeedData> feedResults = makeReference<ChangeFeedData>();
	state Future<Void> feed = data->cx->getChangeFeedStream(
	    feedResults, rangeId, startVersion, endVersion, range, SERVER_KNOBS->CHANGEFEEDSTREAM_LIMIT_BYTES, true);

	state Version firstVersion = invalidVersion;
	state Version lastVersion = invalidVersion;
	state int64_t versionsFetched = 0;

	state PromiseStream<Standalone<MutationsAndVersionRef>> localResults;

	// Add 1 to fetch version to make sure the local stream will have more versions in the stream than the remote stream
	// to avoid edge cases in the merge logic

	state Future<Void> localStream =
	    localChangeFeedStream(data, localResults, rangeId, startVersion, endVersion + 1, range);
	state Standalone<MutationsAndVersionRef> localResult;

	Standalone<MutationsAndVersionRef> _localResult = waitNext(localResults.getFuture());
	localResult = _localResult;
	try {
		loop {
			while (data->fetchKeysBudgetUsed.get()) {
				wait(data->fetchKeysBudgetUsed.onChange());
			}

			state Standalone<VectorRef<MutationsAndVersionRef>> remoteResult =
			    waitNext(feedResults->mutations.getFuture());
			state int remoteLoc = 0;

			while (remoteLoc < remoteResult.size()) {
				if (feedResults->popVersion - 1 > changeFeedInfo->emptyVersion) {
					CODE_PROBE(true, "CF fetched updated popped version from src SS");
					changeFeedInfo->emptyVersion = feedResults->popVersion - 1;
					// pop mutations
					while (!changeFeedInfo->mutations.empty() &&
					       changeFeedInfo->mutations.front().version <= changeFeedInfo->emptyVersion) {
						changeFeedInfo->mutations.pop_front();
					}
					auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
					data->addMutationToMutationLog(
					    mLV,
					    MutationRef(MutationRef::SetValue,
					                persistChangeFeedKeys.begin.toString() + changeFeedInfo->id.toString(),
					                changeFeedSSValue(changeFeedInfo->range,
					                                  changeFeedInfo->emptyVersion + 1,
					                                  changeFeedInfo->stopVersion)));
					data->addMutationToMutationLog(
					    mLV,
					    MutationRef(MutationRef::ClearRange,
					                changeFeedDurableKey(changeFeedInfo->id, 0),
					                changeFeedDurableKey(changeFeedInfo->id, feedResults->popVersion)));
					++data->counters.kvSystemClearRanges;
				}

				Version localVersion = localResult.version;
				Version remoteVersion = remoteResult[remoteLoc].version;

				if (remoteVersion <= localVersion) {
					if (remoteVersion > changeFeedInfo->emptyVersion) {
						// merge if same version
						if (remoteVersion == localVersion && remoteResult[remoteLoc].mutations.size() &&
						    remoteResult[remoteLoc].mutations.back().param1 != lastEpochEndPrivateKey) {
							int remoteSize = remoteResult[remoteLoc].mutations.size();
							ASSERT(localResult.mutations.size());
							remoteResult[remoteLoc].mutations.append(
							    remoteResult.arena(), localResult.mutations.begin(), localResult.mutations.size());
							if (MUTATION_TRACKING_ENABLED) {
								int midx = 0;
								for (auto& m : remoteResult[remoteLoc].mutations) {
									DEBUG_MUTATION("ChangeFeedWriteMoveMerge", remoteVersion, m, data->thisServerID)
									    .detail("Range", range)
									    .detail("FromLocal", midx >= remoteSize)
									    .detail("ChangeFeedID", rangeId);
									midx++;
								}
							}
						} else {
							if (MUTATION_TRACKING_ENABLED) {
								for (auto& m : remoteResult[remoteLoc].mutations) {
									DEBUG_MUTATION("ChangeFeedWriteMove", remoteVersion, m, data->thisServerID)
									    .detail("Range", range)
									    .detail("ChangeFeedID", rangeId);
								}
							}
						}

						data->storage.writeKeyValue(
						    KeyValueRef(changeFeedDurableKey(rangeId, remoteVersion),
						                changeFeedDurableValue(remoteResult[remoteLoc].mutations,
						                                       remoteResult[remoteLoc].knownCommittedVersion)));
						++data->counters.kvSystemClearRanges;
						changeFeedInfo->fetchVersion = std::max(changeFeedInfo->fetchVersion, remoteVersion);

						if (firstVersion == invalidVersion) {
							firstVersion = remoteVersion;
						}
						lastVersion = remoteVersion;
						versionsFetched++;
					} else {
						CODE_PROBE(true, "Change feed ignoring write on move because it was popped concurrently");
						if (MUTATION_TRACKING_ENABLED) {
							for (auto& m : remoteResult[remoteLoc].mutations) {
								DEBUG_MUTATION("ChangeFeedWriteMoveIgnore", remoteVersion, m, data->thisServerID)
								    .detail("Range", range)
								    .detail("ChangeFeedID", rangeId)
								    .detail("EmptyVersion", changeFeedInfo->emptyVersion);
							}
						}
						if (versionsFetched > 0) {
							ASSERT(firstVersion != invalidVersion);
							ASSERT(lastVersion != invalidVersion);
							data->storage.clearRange(
							    KeyRangeRef(changeFeedDurableKey(changeFeedInfo->id, firstVersion),
							                changeFeedDurableKey(changeFeedInfo->id, lastVersion + 1)));
							++data->counters.kvSystemClearRanges;
							firstVersion = invalidVersion;
							lastVersion = invalidVersion;
							versionsFetched = 0;
						}
					}
					remoteLoc++;
				}
				if (localVersion <= remoteVersion) {
					// Do this once per wait instead of once per version for efficiency
					data->fetchingChangeFeeds.insert(changeFeedInfo->id);
					Standalone<MutationsAndVersionRef> _localResult = waitNext(localResults.getFuture());
					localResult = _localResult;
				}
			}
			// Do this once per wait instead of once per version for efficiency
			data->fetchingChangeFeeds.insert(changeFeedInfo->id);

			data->counters.feedBytesFetched += remoteResult.expectedSize();
			data->fetchKeysBytesBudget -= remoteResult.expectedSize();
			if (data->fetchKeysBytesBudget <= 0) {
				data->fetchKeysBudgetUsed.set(true);
			}
			wait(yield());
		}
	} catch (Error& e) {
		if (e.code() != error_code_end_of_stream) {
			TraceEvent(SevDebug, "FetchChangeFeedError", data->thisServerID)
			    .errorUnsuppressed(e)
			    .detail("RangeID", rangeId)
			    .detail("Range", range)
			    .detail("EndVersion", endVersion)
			    .detail("Removing", changeFeedInfo->removing)
			    .detail("Destroyed", changeFeedInfo->destroyed);
			throw;
		}
	}

	if (feedResults->popVersion - 1 > changeFeedInfo->emptyVersion) {
		CODE_PROBE(true, "CF fetched updated popped version from src SS at end");
		changeFeedInfo->emptyVersion = feedResults->popVersion - 1;
		while (!changeFeedInfo->mutations.empty() &&
		       changeFeedInfo->mutations.front().version <= changeFeedInfo->emptyVersion) {
			changeFeedInfo->mutations.pop_front();
		}
		auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
		data->addMutationToMutationLog(
		    mLV,
		    MutationRef(MutationRef::SetValue,
		                persistChangeFeedKeys.begin.toString() + changeFeedInfo->id.toString(),
		                changeFeedSSValue(
		                    changeFeedInfo->range, changeFeedInfo->emptyVersion + 1, changeFeedInfo->stopVersion)));
		data->addMutationToMutationLog(mLV,
		                               MutationRef(MutationRef::ClearRange,
		                                           changeFeedDurableKey(changeFeedInfo->id, 0),
		                                           changeFeedDurableKey(changeFeedInfo->id, feedResults->popVersion)));
		++data->counters.kvSystemClearRanges;
	}

	// if we were popped or removed while fetching but it didn't pass the fetch version while writing, clean up here
	if (versionsFetched > 0 && startVersion < changeFeedInfo->emptyVersion) {
		CODE_PROBE(true, "Change feed cleaning up popped data after move");
		ASSERT(firstVersion != invalidVersion);
		ASSERT(lastVersion != invalidVersion);
		Version endClear = std::min(lastVersion + 1, changeFeedInfo->emptyVersion);
		if (endClear > firstVersion) {
			auto& mLV2 = data->addVersionToMutationLog(data->data().getLatestVersion());
			data->addMutationToMutationLog(mLV2,
			                               MutationRef(MutationRef::ClearRange,
			                                           changeFeedDurableKey(changeFeedInfo->id, firstVersion),
			                                           changeFeedDurableKey(changeFeedInfo->id, endClear)));
			++data->counters.kvSystemClearRanges;
		}
	}

	TraceEvent(SevDebug, "FetchChangeFeedDone", data->thisServerID)
	    .detail("RangeID", rangeId)
	    .detail("Range", range)
	    .detail("StartVersion", startVersion)
	    .detail("EndVersion", endVersion)
	    .detail("EmptyVersion", changeFeedInfo->emptyVersion)
	    .detail("FirstFetchedVersion", firstVersion)
	    .detail("LastFetchedVersion", lastVersion)
	    .detail("VersionsFetched", versionsFetched)
	    .detail("Removed", changeFeedInfo->removing);
	return lastVersion;
}

// returns largest version fetched
ACTOR Future<Version> fetchChangeFeed(StorageServer* data,
                                      Reference<ChangeFeedInfo> changeFeedInfo,
                                      Version beginVersion,
                                      Version endVersion) {
	wait(delay(0)); // allow this actor to be cancelled by removals

	// bound active change feed fetches
	wait(data->fetchChangeFeedParallelismLock.take(TaskPriority::DefaultYield));
	state FlowLock::Releaser holdingFCFPL(data->fetchChangeFeedParallelismLock);

	TraceEvent(SevDebug, "FetchChangeFeed", data->thisServerID)
	    .detail("RangeID", changeFeedInfo->id)
	    .detail("Range", changeFeedInfo->range)
	    .detail("BeginVersion", beginVersion)
	    .detail("EndVersion", endVersion);

	auto cleanupPending = data->changeFeedCleanupDurable.find(changeFeedInfo->id);
	if (cleanupPending != data->changeFeedCleanupDurable.end()) {
		CODE_PROBE(true, "Change feed waiting for dirty previous move to finish");
		TraceEvent(SevDebug, "FetchChangeFeedWaitCleanup", data->thisServerID)
		    .detail("RangeID", changeFeedInfo->id)
		    .detail("Range", changeFeedInfo->range)
		    .detail("CleanupVersion", cleanupPending->second)
		    .detail("EmptyVersion", changeFeedInfo->emptyVersion)
		    .detail("BeginVersion", beginVersion)
		    .detail("EndVersion", endVersion);
		wait(data->durableVersion.whenAtLeast(cleanupPending->second + 1));
		wait(delay(0));
		// shard might have gotten moved away (again) while we were waiting
		auto cleanupPendingAfter = data->changeFeedCleanupDurable.find(changeFeedInfo->id);
		if (cleanupPendingAfter != data->changeFeedCleanupDurable.end()) {
			ASSERT(cleanupPendingAfter->second >= endVersion);
			TraceEvent(SevDebug, "FetchChangeFeedCancelledByCleanup", data->thisServerID)
			    .detail("RangeID", changeFeedInfo->id)
			    .detail("Range", changeFeedInfo->range)
			    .detail("BeginVersion", beginVersion)
			    .detail("EndVersion", endVersion);
			return invalidVersion;
		}
	}

	state bool seenNotRegistered = false;
	loop {
		try {
			Version maxFetched = wait(fetchChangeFeedApplier(data,
			                                                 changeFeedInfo,
			                                                 changeFeedInfo->id,
			                                                 changeFeedInfo->range,
			                                                 changeFeedInfo->emptyVersion,
			                                                 beginVersion,
			                                                 endVersion));
			data->fetchingChangeFeeds.insert(changeFeedInfo->id);
			return maxFetched;
		} catch (Error& e) {
			if (e.code() != error_code_change_feed_not_registered) {
				throw;
			}
		}

		/*fmt::print("DBG: SS {} Feed {} possibly destroyed {}, {} metadata create, {} desired committed\n",
		           data->thisServerID.toString().substr(0, 4),
		           changeFeedInfo->id.printable(),
		           changeFeedInfo->possiblyDestroyed,
		           changeFeedInfo->metadataCreateVersion,
		           data->desiredOldestVersion.get());*/

		// There are two reasons for change_feed_not_registered:
		//   1. The feed was just created, but the ss mutation stream is ahead of the GRV that fetchChangeFeedApplier
		//   uses to read the change feed data from the database. In this case we need to wait and retry
		//   2. The feed was destroyed, but we missed a metadata update telling us this. In this case we need to destroy
		//   the feed
		// endVersion >= the metadata create version, so we can safely use it as a proxy
		if (beginVersion != 0 || seenNotRegistered || endVersion <= data->desiredOldestVersion.get()) {
			// If any of these are true, the feed must be destroyed.
			Version cleanupVersion = data->data().getLatestVersion();

			TraceEvent(SevDebug, "DestroyingChangeFeedFromFetch", data->thisServerID)
			    .detail("RangeID", changeFeedInfo->id)
			    .detail("Range", changeFeedInfo->range)
			    .detail("Version", cleanupVersion);

			if (g_network->isSimulated()) {
				ASSERT(g_simulator.validationData.allDestroyedChangeFeedIDs.count(changeFeedInfo->id.toString()));
			}

			Key beginClearKey = changeFeedInfo->id.withPrefix(persistChangeFeedKeys.begin);

			auto& mLV = data->addVersionToMutationLog(cleanupVersion);
			data->addMutationToMutationLog(
			    mLV, MutationRef(MutationRef::ClearRange, beginClearKey, keyAfter(beginClearKey)));
			++data->counters.kvSystemClearRanges;
			data->addMutationToMutationLog(mLV,
			                               MutationRef(MutationRef::ClearRange,
			                                           changeFeedDurableKey(changeFeedInfo->id, 0),
			                                           changeFeedDurableKey(changeFeedInfo->id, cleanupVersion)));
			++data->counters.kvSystemClearRanges;

			changeFeedInfo->destroy(cleanupVersion);

			if (data->uidChangeFeed.count(changeFeedInfo->id)) {
				// only register range for cleanup if it has not been already cleaned up
				data->changeFeedCleanupDurable[changeFeedInfo->id] = cleanupVersion;
			}

			for (auto& it : data->changeFeedRemovals) {
				it.second.send(changeFeedInfo->id);
			}

			return invalidVersion;
		}

		// otherwise assume the feed just hasn't been created on the SS we tried to read it from yet, wait for it to
		// definitely be committed and retry
		seenNotRegistered = true;
		wait(data->desiredOldestVersion.whenAtLeast(endVersion));
	}
}

ACTOR Future<std::vector<Key>> fetchChangeFeedMetadata(StorageServer* data,
                                                       KeyRange keys,
                                                       PromiseStream<Key> removals,
                                                       UID fetchKeysID) {

	// Wait for current TLog batch to finish to ensure that we're fetching metadata at a version >= the version of the
	// ChangeServerKeys mutation. This guarantees we don't miss any metadata between the previous batch's version
	// (data->version) and the mutation version.
	wait(data->version.whenAtLeast(data->version.get() + 1));
	state Version fetchVersion = data->version.get();

	TraceEvent(SevDebug, "FetchChangeFeedMetadata", data->thisServerID)
	    .detail("Range", keys)
	    .detail("FetchVersion", fetchVersion)
	    .detail("FKID", fetchKeysID);

	state std::set<Key> refreshedFeedIds;
	state std::set<Key> destroyedFeedIds;
	// before fetching feeds from other SS's, refresh any feeds we already have that are being marked as removed
	auto ranges = data->keyChangeFeed.intersectingRanges(keys);
	for (auto& r : ranges) {
		for (auto& cfInfo : r.value()) {
			auto feedCleanup = data->changeFeedCleanupDurable.find(cfInfo->id);
			if (feedCleanup != data->changeFeedCleanupDurable.end() && cfInfo->removing && !cfInfo->destroyed) {
				CODE_PROBE(true, "re-fetching feed scheduled for deletion! Un-mark it as removing");
				destroyedFeedIds.insert(cfInfo->id);

				cfInfo->removing = false;
				// because we now have a gap in the metadata, it's possible this feed was destroyed
				cfInfo->possiblyDestroyed = true;
				// Set refreshInProgress, so that if this actor is replaced by an expanded move actor, the new actor
				// picks up the refresh
				cfInfo->refreshInProgress = true;
				// reset fetch versions because everything previously fetched was cleaned up
				cfInfo->fetchVersion = invalidVersion;

				cfInfo->durableFetchVersion = NotifiedVersion();

				TraceEvent(SevDebug, "ResetChangeFeedInfo", data->thisServerID)
				    .detail("RangeID", cfInfo->id)
				    .detail("Range", cfInfo->range)
				    .detail("FetchVersion", fetchVersion)
				    .detail("EmptyVersion", cfInfo->emptyVersion)
				    .detail("StopVersion", cfInfo->stopVersion)
				    .detail("FKID", fetchKeysID);
			} else if (cfInfo->refreshInProgress) {
				CODE_PROBE(true, "Racing refreshes for same change feed in fetch");
				destroyedFeedIds.insert(cfInfo->id);
			}
		}
	}

	state std::vector<OverlappingChangeFeedEntry> feeds = wait(data->cx->getOverlappingChangeFeeds(keys, fetchVersion));
	// handle change feeds removed while fetching overlapping
	while (removals.getFuture().isReady()) {
		Key remove = waitNext(removals.getFuture());
		for (int i = 0; i < feeds.size(); i++) {
			if (feeds[i].rangeId == remove) {
				swapAndPop(&feeds, i--);
			}
		}
	}

	std::vector<Key> feedIds;
	feedIds.reserve(feeds.size());
	// create change feed metadata if it does not exist
	for (auto& cfEntry : feeds) {
		auto cleanupEntry = data->changeFeedCleanupDurable.find(cfEntry.rangeId);
		bool cleanupPending = cleanupEntry != data->changeFeedCleanupDurable.end();
		feedIds.push_back(cfEntry.rangeId);
		auto existingEntry = data->uidChangeFeed.find(cfEntry.rangeId);
		bool existing = existingEntry != data->uidChangeFeed.end();

		TraceEvent(SevDebug, "FetchedChangeFeedInfo", data->thisServerID)
		    .detail("RangeID", cfEntry.rangeId)
		    .detail("Range", cfEntry.range)
		    .detail("FetchVersion", fetchVersion)
		    .detail("EmptyVersion", cfEntry.emptyVersion)
		    .detail("StopVersion", cfEntry.stopVersion)
		    .detail("Existing", existing)
		    .detail("CleanupPendingVersion", cleanupPending ? cleanupEntry->second : invalidVersion)
		    .detail("FKID", fetchKeysID);

		bool addMutationToLog = false;
		Reference<ChangeFeedInfo> changeFeedInfo;

		auto fid = destroyedFeedIds.find(cfEntry.rangeId);
		if (fid != destroyedFeedIds.end()) {
			refreshedFeedIds.insert(cfEntry.rangeId);
			destroyedFeedIds.erase(fid);
		}

		if (!existing) {
			CODE_PROBE(cleanupPending,
			           "Fetch change feed which is cleanup pending. This means there was a move away and a move back, "
			           "this will remake the metadata");

			changeFeedInfo = Reference<ChangeFeedInfo>(new ChangeFeedInfo());
			changeFeedInfo->range = cfEntry.range;
			changeFeedInfo->id = cfEntry.rangeId;

			changeFeedInfo->emptyVersion = cfEntry.emptyVersion;
			changeFeedInfo->stopVersion = cfEntry.stopVersion;
			data->uidChangeFeed[cfEntry.rangeId] = changeFeedInfo;
			auto rs = data->keyChangeFeed.modify(cfEntry.range);
			for (auto r = rs.begin(); r != rs.end(); ++r) {
				r->value().push_back(changeFeedInfo);
			}
			data->keyChangeFeed.coalesce(cfEntry.range.contents());

			addMutationToLog = true;
		} else {
			changeFeedInfo = existingEntry->second;

			if (changeFeedInfo->destroyed) {
				// race where multiple feeds fetched overlapping change feed, one realized feed was missing and marked
				// it removed+destroyed, then this one fetched the same info
				continue;
			}

			// we checked all feeds we already owned in this range at the start to reset them if they were removing, and
			// this actor would have been cancelled if a later remove happened
			ASSERT(!changeFeedInfo->removing);
			if (cfEntry.stopVersion < changeFeedInfo->stopVersion) {
				CODE_PROBE(true, "Change feed updated stop version from fetch metadata");
				changeFeedInfo->stopVersion = cfEntry.stopVersion;
				addMutationToLog = true;
			}

			// don't update empty version past SS version if SS is behind, it can cause issues
			if (cfEntry.emptyVersion < data->version.get() && cfEntry.emptyVersion > changeFeedInfo->emptyVersion) {
				CODE_PROBE(true, "Change feed updated empty version from fetch metadata");
				changeFeedInfo->emptyVersion = cfEntry.emptyVersion;
				addMutationToLog = true;
			}
		}
		if (addMutationToLog) {
			ASSERT(changeFeedInfo.isValid());
			auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
			data->addMutationToMutationLog(
			    mLV,
			    MutationRef(
			        MutationRef::SetValue,
			        persistChangeFeedKeys.begin.toString() + cfEntry.rangeId.toString(),
			        changeFeedSSValue(cfEntry.range, changeFeedInfo->emptyVersion + 1, changeFeedInfo->stopVersion)));
			// if we updated pop version, remove mutations
			while (!changeFeedInfo->mutations.empty() &&
			       changeFeedInfo->mutations.front().version <= changeFeedInfo->emptyVersion) {
				changeFeedInfo->mutations.pop_front();
			}
		}
	}

	CODE_PROBE(!refreshedFeedIds.empty(), "Feed refreshed between move away and move back");
	CODE_PROBE(!destroyedFeedIds.empty(), "Feed destroyed between move away and move back");
	for (auto& feedId : refreshedFeedIds) {
		auto existingEntry = data->uidChangeFeed.find(feedId);
		if (existingEntry == data->uidChangeFeed.end() || existingEntry->second->destroyed ||
		    !existingEntry->second->refreshInProgress) {
			CODE_PROBE(true, "feed refreshed");
			continue;
		}

		// Since cleanup put a mutation in the log to delete the change feed data, put one in the log to restore
		// it
		// We may just want to refactor this so updateStorage does explicit deletes based on
		// changeFeedCleanupDurable and not use the mutation log at all for the change feed metadata cleanup.
		// Then we wouldn't have to reset anything here or above
		// Do the mutation log update here instead of above to ensure we only add it back to the mutation log if we're
		// sure it wasn't deleted in the metadata gap
		Version metadataVersion = data->data().getLatestVersion();
		auto& mLV = data->addVersionToMutationLog(metadataVersion);
		data->addMutationToMutationLog(
		    mLV,
		    MutationRef(MutationRef::SetValue,
		                persistChangeFeedKeys.begin.toString() + existingEntry->second->id.toString(),
		                changeFeedSSValue(existingEntry->second->range,
		                                  existingEntry->second->emptyVersion + 1,
		                                  existingEntry->second->stopVersion)));
		TraceEvent(SevDebug, "PersistingResetChangeFeedInfo", data->thisServerID)
		    .detail("RangeID", existingEntry->second->id)
		    .detail("Range", existingEntry->second->range)
		    .detail("FetchVersion", fetchVersion)
		    .detail("EmptyVersion", existingEntry->second->emptyVersion)
		    .detail("StopVersion", existingEntry->second->stopVersion)
		    .detail("FKID", fetchKeysID)
		    .detail("MetadataVersion", metadataVersion);
		existingEntry->second->refreshInProgress = false;
	}
	for (auto& feedId : destroyedFeedIds) {
		auto existingEntry = data->uidChangeFeed.find(feedId);
		if (existingEntry == data->uidChangeFeed.end() || existingEntry->second->destroyed) {
			CODE_PROBE(true, "feed refreshed but then destroyed elsewhere");
			continue;
		}

		/*fmt::print("DBG: SS {} fetching feed {} was refreshed but not present!! assuming destroyed\n",
		           data->thisServerID.toString().substr(0, 4),
		           feedId.printable());*/
		Version cleanupVersion = data->data().getLatestVersion();

		TraceEvent(SevDebug, "DestroyingChangeFeedFromFetchMetadata", data->thisServerID)
		    .detail("RangeID", feedId)
		    .detail("Range", existingEntry->second->range)
		    .detail("Version", cleanupVersion)
		    .detail("FKID", fetchKeysID);

		if (g_network->isSimulated()) {
			ASSERT(g_simulator.validationData.allDestroyedChangeFeedIDs.count(feedId.toString()));
		}

		Key beginClearKey = feedId.withPrefix(persistChangeFeedKeys.begin);

		auto& mLV = data->addVersionToMutationLog(cleanupVersion);
		data->addMutationToMutationLog(mLV,
		                               MutationRef(MutationRef::ClearRange, beginClearKey, keyAfter(beginClearKey)));
		++data->counters.kvSystemClearRanges;
		data->addMutationToMutationLog(mLV,
		                               MutationRef(MutationRef::ClearRange,
		                                           changeFeedDurableKey(feedId, 0),
		                                           changeFeedDurableKey(feedId, cleanupVersion)));
		++data->counters.kvSystemClearRanges;

		existingEntry->second->destroy(cleanupVersion);
		data->changeFeedCleanupDurable[feedId] = cleanupVersion;

		for (auto& it : data->changeFeedRemovals) {
			it.second.send(feedId);
		}
	}
	return feedIds;
}

// returns max version fetched for each feed
// newFeedIds is used for the second fetch to get data for new feeds that weren't there for the first fetch
ACTOR Future<std::unordered_map<Key, Version>> dispatchChangeFeeds(StorageServer* data,
                                                                   UID fetchKeysID,
                                                                   KeyRange keys,
                                                                   Version beginVersion,
                                                                   Version endVersion,
                                                                   PromiseStream<Key> removals,
                                                                   std::vector<Key>* feedIds,
                                                                   std::unordered_set<Key> newFeedIds) {
	state std::unordered_map<Key, Version> feedMaxFetched;
	if (feedIds->empty() && newFeedIds.empty()) {
		return feedMaxFetched;
	}

	// find overlapping range feeds
	state std::map<Key, Future<Version>> feedFetches;

	try {
		for (auto& feedId : *feedIds) {
			auto feedIt = data->uidChangeFeed.find(feedId);
			// feed may have been moved away or deleted after move was scheduled, do nothing in that case
			if (feedIt != data->uidChangeFeed.end() && !feedIt->second->removing) {
				feedFetches[feedIt->second->id] = fetchChangeFeed(data, feedIt->second, beginVersion, endVersion);
			}
		}
		for (auto& feedId : newFeedIds) {
			auto feedIt = data->uidChangeFeed.find(feedId);
			// we just read the change feed data map earlier in fetchKeys without yielding, so these feeds must exist
			ASSERT(feedIt != data->uidChangeFeed.end());
			ASSERT(!feedIt->second->removing);
			feedFetches[feedIt->second->id] = fetchChangeFeed(data, feedIt->second, 0, endVersion);
		}

		loop {
			Future<Version> nextFeed = Never();
			if (!removals.getFuture().isReady()) {
				bool done = true;
				while (!feedFetches.empty()) {
					if (feedFetches.begin()->second.isReady()) {
						Version maxFetched = feedFetches.begin()->second.get();
						if (maxFetched != invalidVersion) {
							feedFetches[feedFetches.begin()->first] = maxFetched;
						}
						feedFetches.erase(feedFetches.begin());
					} else {
						nextFeed = feedFetches.begin()->second;
						done = false;
						break;
					}
				}
				if (done) {
					return feedMaxFetched;
				}
			}
			choose {
				when(state Key remove = waitNext(removals.getFuture())) {
					wait(delay(0));
					feedFetches.erase(remove);
					for (int i = 0; i < feedIds->size(); i++) {
						if ((*feedIds)[i] == remove) {
							swapAndPop(feedIds, i--);
						}
					}
				}
				when(wait(success(nextFeed))) {}
			}
		}

	} catch (Error& e) {
		if (!data->shuttingDown) {
			data->changeFeedRemovals.erase(fetchKeysID);
		}
		throw;
	}
}

ACTOR Future<Void> fetchKeys(StorageServer* data, AddingShard* shard) {
	state const UID fetchKeysID = deterministicRandom()->randomUniqueID();
	state TraceInterval interval("FetchKeys");
	state KeyRange keys = shard->keys;
	state Future<Void> warningLogger = logFetchKeysWarning(shard);
	state const double startTime = now();
	state Version fetchVersion = invalidVersion;
	state FetchKeysMetricReporter metricReporter(fetchKeysID,
	                                             startTime,
	                                             keys,
	                                             data->fetchKeysHistograms,
	                                             data->currentRunningFetchKeys,
	                                             data->counters.bytesFetched,
	                                             data->counters.kvFetched);

	// delay(0) to force a return to the run loop before the work of fetchKeys is started.
	//  This allows adding->start() to be called inline with CSK.
	wait(data->coreStarted.getFuture() && delay(0));

	// On SS Reboot, durableVersion == latestVersion, so any mutations we add to the mutation log would be skipped if
	// added before latest version advances.
	// To ensure this doesn't happen, we wait for version to increase by one if this fetchKeys was initiated by a
	// changeServerKeys from restoreDurableState
	if (data->version.get() == data->durableVersion.get()) {
		wait(data->version.whenAtLeast(data->version.get() + 1));
		wait(delay(0));
	}

	try {
		DEBUG_KEY_RANGE("fetchKeysBegin", data->version.get(), shard->keys, data->thisServerID);

		TraceEvent(SevDebug, interval.begin(), data->thisServerID)
		    .detail("KeyBegin", shard->keys.begin)
		    .detail("KeyEnd", shard->keys.end)
		    .detail("Version", data->version.get())
		    .detail("FKID", fetchKeysID);

		state PromiseStream<Key> removals;
		data->changeFeedRemovals[fetchKeysID] = removals;
		state Future<std::vector<Key>> fetchCFMetadata = fetchChangeFeedMetadata(data, keys, removals, fetchKeysID);

		validate(data);

		// Wait (if necessary) for the latest version at which any key in keys was previously available (+1) to be
		// durable
		auto navr = data->newestAvailableVersion.intersectingRanges(keys);
		Version lastAvailable = invalidVersion;
		for (auto r = navr.begin(); r != navr.end(); ++r) {
			ASSERT(r->value() != latestVersion);
			lastAvailable = std::max(lastAvailable, r->value());
		}
		auto ndvr = data->newestDirtyVersion.intersectingRanges(keys);
		for (auto r = ndvr.begin(); r != ndvr.end(); ++r)
			lastAvailable = std::max(lastAvailable, r->value());

		if (lastAvailable != invalidVersion && lastAvailable >= data->durableVersion.get()) {
			CODE_PROBE(true, "FetchKeys waits for previous available version to be durable");
			wait(data->durableVersion.whenAtLeast(lastAvailable + 1));
		}

		TraceEvent(SevDebug, "FetchKeysVersionSatisfied", data->thisServerID).detail("FKID", interval.pairID);

		wait(data->fetchKeysParallelismLock.take(TaskPriority::DefaultYield));
		state FlowLock::Releaser holdingFKPL(data->fetchKeysParallelismLock);

		state double executeStart = now();
		++data->counters.fetchWaitingCount;
		data->counters.fetchWaitingMS += 1000 * (executeStart - startTime);

		// Fetch keys gets called while the update actor is processing mutations. data->version will not be updated
		// until all mutations for a version have been processed. We need to take the durableVersionLock to ensure
		// data->version is greater than the version of the mutation which caused the fetch to be initiated.

		// We must also ensure we have fetched all change feed metadata BEFORE changing the phase to fetching to ensure
		// change feed mutations get applied correctly
		state std::vector<Key> changeFeedsToFetch;
		std::vector<Key> _cfToFetch = wait(fetchCFMetadata);
		changeFeedsToFetch = _cfToFetch;
		wait(data->durableVersionLock.take());

		shard->phase = AddingShard::Fetching;

		data->durableVersionLock.release();

		wait(delay(0));

		// Get the history
		state int debug_getRangeRetries = 0;
		state int debug_nextRetryToLog = 1;
		state Error lastError;

		// FIXME: The client cache does not notice when servers are added to a team. To read from a local storage server
		// we must refresh the cache manually.
		data->cx->invalidateCache(Key(), keys);

		loop {
			state Transaction tr(data->cx);
			// fetchVersion = data->version.get();
			// A quick fix:
			// By default, we use data->version as the fetchVersion.
			// In the case where dest SS falls far behind src SS, we use GRV as the fetchVersion instead of
			// data->version, and then the dest SS waits for catching up the fetchVersion outside the
			// fetchKeysParallelismLock.
			// For example, consider dest SS falls far behind src SS.
			// At iteration 0, dest SS selects its version as fetchVersion,
			// but cannot read src SS and result in error_code_transaction_too_old.
			// Due to error_code_transaction_too_old, dest SS starts iteration 1.
			// At iteration 1, dest SS selects GRV as fetchVersion and (suppose) can read the data from src SS.
			// Then dest SS waits its version catch up with this GRV version and write the data to disk.
			// Note that dest SS waits outside the fetchKeysParallelismLock.
			if (lastError.code() == error_code_transaction_too_old) {
				Version grvVersion = wait(tr.getRawReadVersion());
				fetchVersion = std::max(grvVersion, data->version.get());
			} else {
				fetchVersion = std::max(shard->fetchVersion, data->version.get());
			}
			ASSERT(fetchVersion >= shard->fetchVersion); // at this point, shard->fetchVersion is the last fetchVersion
			shard->fetchVersion = fetchVersion;
			TraceEvent(SevDebug, "FetchKeysUnblocked", data->thisServerID)
			    .detail("FKID", interval.pairID)
			    .detail("Version", fetchVersion);

			while (!shard->updates.empty() && shard->updates[0].version <= fetchVersion)
				shard->updates.pop_front();
			tr.setVersion(fetchVersion);
			tr.trState->taskID = TaskPriority::FetchKeys;
			state PromiseStream<RangeResult> results;
			state Future<Void> hold = SERVER_KNOBS->FETCH_USING_STREAMING
			                              ? tr.getRangeStream(results, keys, GetRangeLimits(), Snapshot::True)
			                              : tryGetRange(results, &tr, keys);
			state Key nfk = keys.begin;

			try {
				loop {
					CODE_PROBE(true, "Fetching keys for transferred shard");
					while (data->fetchKeysBudgetUsed.get()) {
						wait(data->fetchKeysBudgetUsed.onChange());
					}
					state RangeResult this_block = waitNext(results.getFuture());

					state int expectedBlockSize =
					    (int)this_block.expectedSize() + (8 - (int)sizeof(KeyValueRef)) * this_block.size();

					TraceEvent(SevDebug, "FetchKeysBlock", data->thisServerID)
					    .detail("FKID", interval.pairID)
					    .detail("BlockRows", this_block.size())
					    .detail("BlockBytes", expectedBlockSize)
					    .detail("KeyBegin", keys.begin)
					    .detail("KeyEnd", keys.end)
					    .detail("Last", this_block.size() ? this_block.end()[-1].key : std::string())
					    .detail("Version", fetchVersion)
					    .detail("More", this_block.more);

					DEBUG_KEY_RANGE("fetchRange", fetchVersion, keys, data->thisServerID);
					if (MUTATION_TRACKING_ENABLED) {
						for (auto k = this_block.begin(); k != this_block.end(); ++k) {
							DEBUG_MUTATION("fetch",
							               fetchVersion,
							               MutationRef(MutationRef::SetValue, k->key, k->value),
							               data->thisServerID);
						}
					}

					metricReporter.addFetchedBytes(expectedBlockSize, this_block.size());

					// Write this_block to storage
					state KeyValueRef* kvItr = this_block.begin();
					for (; kvItr != this_block.end(); ++kvItr) {
						data->storage.writeKeyValue(*kvItr);
						wait(yield());
					}

					kvItr = this_block.begin();
					for (; kvItr != this_block.end(); ++kvItr) {
						data->byteSampleApplySet(*kvItr, invalidVersion);
						wait(yield());
					}

					ASSERT(this_block.readThrough.present() || this_block.size());
					nfk = this_block.readThrough.present() ? this_block.readThrough.get()
					                                       : keyAfter(this_block.end()[-1].key);
					this_block = RangeResult();

					data->fetchKeysBytesBudget -= expectedBlockSize;
					if (data->fetchKeysBytesBudget <= 0) {
						data->fetchKeysBudgetUsed.set(true);
					}
				}
			} catch (Error& e) {
				if (e.code() != error_code_end_of_stream && e.code() != error_code_connection_failed &&
				    e.code() != error_code_transaction_too_old && e.code() != error_code_future_version &&
				    e.code() != error_code_process_behind && e.code() != error_code_server_overloaded) {
					throw;
				}
				lastError = e;
				if (nfk == keys.begin) {
					TraceEvent("FKBlockFail", data->thisServerID)
					    .errorUnsuppressed(e)
					    .suppressFor(1.0)
					    .detail("FKID", interval.pairID);

					// FIXME: remove when we no longer support upgrades from 5.X
					if (debug_getRangeRetries >= 100) {
						data->cx->enableLocalityLoadBalance = EnableLocalityLoadBalance::False;
						TraceEvent(SevWarnAlways, "FKDisableLB").detail("FKID", fetchKeysID);
					}

					debug_getRangeRetries++;
					if (debug_nextRetryToLog == debug_getRangeRetries) {
						debug_nextRetryToLog += std::min(debug_nextRetryToLog, 1024);
						TraceEvent(SevWarn, "FetchPast", data->thisServerID)
						    .detail("TotalAttempts", debug_getRangeRetries)
						    .detail("FKID", interval.pairID)
						    .detail("N", fetchVersion)
						    .detail("E", data->version.get());
					}
					wait(delayJittered(FLOW_KNOBS->PREVENT_FAST_SPIN_DELAY));
					continue;
				}
				if (nfk < keys.end) {
					std::deque<Standalone<VerUpdateRef>> updatesToSplit = std::move(shard->updates);

					// This actor finishes committing the keys [keys.begin,nfk) that we already fetched.
					// The remaining unfetched keys [nfk,keys.end) will become a separate AddingShard with its own
					// fetchKeys.
					if (data->shardAware) {
						StorageServerShard rightShard = data->shards[keys.begin]->toStorageServerShard();
						rightShard.range = KeyRangeRef(nfk, keys.end);
						shard->server->addShard(ShardInfo::addingSplitLeft(KeyRangeRef(keys.begin, nfk), shard));
						shard->server->addShard(ShardInfo::newShard(data, rightShard));
						data->shards[keys.begin]->populateShard(rightShard);
					} else {
						shard->server->addShard(ShardInfo::addingSplitLeft(KeyRangeRef(keys.begin, nfk), shard));
						shard->server->addShard(ShardInfo::newAdding(data, KeyRangeRef(nfk, keys.end)));
					}
					shard = data->shards.rangeContaining(keys.begin).value()->adding.get();
					warningLogger = logFetchKeysWarning(shard);
					AddingShard* otherShard = data->shards.rangeContaining(nfk).value()->adding.get();
					keys = shard->keys;

					// Split our prior updates.  The ones that apply to our new, restricted key range will go back into
					// shard->updates, and the ones delivered to the new shard will be discarded because it is in
					// WaitPrevious phase (hasn't chosen a fetchVersion yet). What we are doing here is expensive and
					// could get more expensive if we started having many more blocks per shard. May need optimization
					// in the future.
					std::deque<Standalone<VerUpdateRef>>::iterator u = updatesToSplit.begin();
					for (; u != updatesToSplit.end(); ++u) {
						splitMutations(data, data->shards, *u);
					}

					CODE_PROBE(true, "fetchkeys has more");
					CODE_PROBE(shard->updates.size(), "Shard has updates");
					ASSERT(otherShard->updates.empty());
				}
				break;
			}
		}

		// FIXME: remove when we no longer support upgrades from 5.X
		data->cx->enableLocalityLoadBalance = EnableLocalityLoadBalance::True;
		TraceEvent(SevWarnAlways, "FKReenableLB").detail("FKID", fetchKeysID);

		// We have completed the fetch and write of the data, now we wait for MVCC window to pass.
		//  As we have finished this work, we will allow more work to start...
		shard->fetchComplete.send(Void());

		TraceEvent(SevDebug, "FKBeforeFinalCommit", data->thisServerID)
		    .detail("FKID", interval.pairID)
		    .detail("SV", data->storageVersion())
		    .detail("DV", data->durableVersion.get());
		// Directly commit()ing the IKVS would interfere with updateStorage, possibly resulting in an incomplete version
		// being recovered. Instead we wait for the updateStorage loop to commit something (and consequently also what
		// we have written)

		state Future<std::unordered_map<Key, Version>> feedFetchMain = dispatchChangeFeeds(
		    data, fetchKeysID, keys, 0, fetchVersion + 1, removals, &changeFeedsToFetch, std::unordered_set<Key>());

		state Future<Void> fetchDurable = data->durableVersion.whenAtLeast(data->storageVersion() + 1);
		state Future<Void> dataArrive = data->version.whenAtLeast(fetchVersion);

		holdingFKPL.release();
		wait(dataArrive && fetchDurable);

		state std::unordered_map<Key, Version> feedFetchedVersions = wait(feedFetchMain);

		TraceEvent(SevDebug, "FKAfterFinalCommit", data->thisServerID)
		    .detail("FKID", interval.pairID)
		    .detail("SV", data->storageVersion())
		    .detail("DV", data->durableVersion.get());

		// Wait to run during update(), after a new batch of versions is received from the tlog but before eager reads
		// take place.
		Promise<FetchInjectionInfo*> p;
		data->readyFetchKeys.push_back(p);

		// After we add to the promise readyFetchKeys, update() would provide a pointer to FetchInjectionInfo that we
		// can put mutation in.
		FetchInjectionInfo* batch = wait(p.getFuture());
		TraceEvent(SevDebug, "FKUpdateBatch", data->thisServerID).detail("FKID", interval.pairID);

		shard->phase = AddingShard::FetchingCF;
		ASSERT(data->version.get() >= fetchVersion);
		// Choose a transferredVersion.  This choice and timing ensure that
		//   * The transferredVersion can be mutated in versionedData
		//   * The transferredVersion isn't yet committed to storage (so we can write the availability status change)
		//   * The transferredVersion is <= the version of any of the updates in batch, and if there is an equal version
		//     its mutations haven't been processed yet
		shard->transferredVersion = data->version.get() + 1;
		// shard->transferredVersion = batch->changes[0].version;  //< FIXME: This obeys the documented properties, and
		// seems "safer" because it never introduces extra versions into the data structure, but violates some ASSERTs
		// currently
		data->mutableData().createNewVersion(shard->transferredVersion);
		ASSERT(shard->transferredVersion > data->storageVersion());
		ASSERT(shard->transferredVersion == data->data().getLatestVersion());

		// find new change feeds for this range that didn't exist when we started the fetch
		auto ranges = data->keyChangeFeed.intersectingRanges(keys);
		std::unordered_set<Key> newChangeFeeds;
		for (auto& r : ranges) {
			for (auto& cfInfo : r.value()) {
				CODE_PROBE(true, "SS fetching new change feed that didn't exist when fetch started");
				if (!cfInfo->removing) {
					newChangeFeeds.insert(cfInfo->id);
				}
			}
		}
		for (auto& cfId : changeFeedsToFetch) {
			newChangeFeeds.erase(cfId);
		}
		// This is split into two fetches to reduce tail. Fetch [0 - fetchVersion+1)
		// once fetchVersion is finalized, and [fetchVersion+1, transferredVersion) here once transferredVersion is
		// finalized. Also fetch new change feeds alongside it
		state Future<std::unordered_map<Key, Version>> feedFetchTransferred =
		    dispatchChangeFeeds(data,
		                        fetchKeysID,
		                        keys,
		                        fetchVersion + 1,
		                        shard->transferredVersion,
		                        removals,
		                        &changeFeedsToFetch,
		                        newChangeFeeds);

		TraceEvent(SevDebug, "FetchKeysHaveData", data->thisServerID)
		    .detail("FKID", interval.pairID)
		    .detail("Version", shard->transferredVersion)
		    .detail("StorageVersion", data->storageVersion());
		validate(data);

		// the minimal version in updates must be larger than fetchVersion
		ASSERT(shard->updates.empty() || shard->updates[0].version > fetchVersion);

		// Put the updates that were collected during the FinalCommit phase into the batch at the transferredVersion.
		// Eager reads will be done for them by update(), and the mutations will come back through
		// AddingShard::addMutations and be applied to versionedMap and mutationLog as normal. The lie about their
		// version is acceptable because this shard will never be read at versions < transferredVersion

		for (auto i = shard->updates.begin(); i != shard->updates.end(); ++i) {
			i->version = shard->transferredVersion;
			batch->arena.dependsOn(i->arena());
		}

		int startSize = batch->changes.size();
		CODE_PROBE(startSize, "Adding fetch data to a batch which already has changes");
		batch->changes.resize(batch->changes.size() + shard->updates.size());

		// FIXME: pass the deque back rather than copy the data
		std::copy(shard->updates.begin(), shard->updates.end(), batch->changes.begin() + startSize);
		Version checkv = shard->transferredVersion;

		for (auto b = batch->changes.begin() + startSize; b != batch->changes.end(); ++b) {
			ASSERT(b->version >= checkv);
			checkv = b->version;
			if (MUTATION_TRACKING_ENABLED) {
				for (auto& m : b->mutations) {
					DEBUG_MUTATION("fetchKeysFinalCommitInject", batch->changes[0].version, m, data->thisServerID);
				}
			}
		}

		shard->updates.clear();

		// wait on change feed fetch to complete writing to storage before marking data as available
		std::unordered_map<Key, Version> feedFetchedVersions2 = wait(feedFetchTransferred);
		for (auto& newFetch : feedFetchedVersions2) {
			auto prevFetch = feedFetchedVersions.find(newFetch.first);
			if (prevFetch != feedFetchedVersions.end()) {
				prevFetch->second = std::max(prevFetch->second, newFetch.second);
			} else {
				feedFetchedVersions[newFetch.first] = newFetch.second;
			}
		}

		data->changeFeedRemovals.erase(fetchKeysID);

		shard->phase = AddingShard::Waiting;

		// Similar to transferred version, but wait for all feed data and
		Version feedTransferredVersion = data->version.get() + 1;

		TraceEvent(SevDebug, "FetchKeysHaveFeedData", data->thisServerID)
		    .detail("FKID", interval.pairID)
		    .detail("Version", feedTransferredVersion)
		    .detail("StorageVersion", data->storageVersion());

		if (data->shardAware) {
			state StorageServerShard newShard = data->shards[keys.begin]->toStorageServerShard();
			ASSERT(newShard.range == keys);
			ASSERT(newShard.getShardState() == StorageServerShard::ReadWritePending);
			updateStorageShard(data, newShard);
		}
		setAvailableStatus(data,
		                   keys,
		                   true); // keys will be available when getLatestVersion()==transferredVersion is durable

		// Note that since it receives a pointer to FetchInjectionInfo, the thread does not leave this actor until this
		// point.

		// Wait for the transferred version (and therefore the shard data) to be committed and durable.
		wait(data->durableVersion.whenAtLeast(feedTransferredVersion));

		ASSERT(data->shards[shard->keys.begin]->assigned() &&
		       data->shards[shard->keys.begin]->keys ==
		           shard->keys); // We aren't changing whether the shard is assigned
		data->newestAvailableVersion.insert(shard->keys, latestVersion);
		shard->readWrite.send(Void());
		if (data->shardAware) {
			newShard.setShardState(StorageServerShard::ReadWrite);
			data->addShard(ShardInfo::newShard(data, newShard)); // invalidates shard!
			coalescePhysicalShards(data, keys);
		} else {
			data->addShard(ShardInfo::newReadWrite(shard->keys, data)); // invalidates shard!
			coalesceShards(data, keys);
		}

		validate(data);

		++data->counters.fetchExecutingCount;
		data->counters.fetchExecutingMS += 1000 * (now() - executeStart);

		TraceEvent(SevDebug, interval.end(), data->thisServerID);
	} catch (Error& e) {
		TraceEvent(SevDebug, interval.end(), data->thisServerID)
		    .errorUnsuppressed(e)
		    .detail("Version", data->version.get());
		if (!data->shuttingDown) {
			data->changeFeedRemovals.erase(fetchKeysID);
		}
		if (e.code() == error_code_actor_cancelled && !data->shuttingDown && shard->phase >= AddingShard::Fetching) {
			if (shard->phase < AddingShard::FetchingCF) {
				data->storage.clearRange(keys);
				++data->counters.kvSystemClearRanges;
				data->byteSampleApplyClear(keys, invalidVersion);
			} else {
				ASSERT(data->data().getLatestVersion() > data->version.get());
				removeDataRange(
				    data, data->addVersionToMutationLog(data->data().getLatestVersion()), data->shards, keys);
				setAvailableStatus(data, keys, false);
				// Prevent another, overlapping fetchKeys from entering the Fetching phase until
				// data->data().getLatestVersion() is durable
				data->newestDirtyVersion.insert(keys, data->data().getLatestVersion());
			}
		}

		TraceEvent(SevError, "FetchKeysError", data->thisServerID)
		    .error(e)
		    .detail("Elapsed", now() - startTime)
		    .detail("KeyBegin", keys.begin)
		    .detail("KeyEnd", keys.end);
		if (e.code() != error_code_actor_cancelled)
			data->otherError.sendError(e); // Kill the storage server.  Are there any recoverable errors?
		throw; // goes nowhere
	}

	return Void();
}

AddingShard::AddingShard(StorageServer* server, KeyRangeRef const& keys)
  : keys(keys), server(server), transferredVersion(invalidVersion), fetchVersion(invalidVersion), phase(WaitPrevious) {
	fetchClient = fetchKeys(server, this);
}

void AddingShard::addMutation(Version version, bool fromFetch, MutationRef const& mutation) {
	if (version <= fetchVersion) {
		return;
	}

	server->counters.logicalBytesMoveInOverhead += mutation.expectedSize();
	if (mutation.type == mutation.ClearRange) {
		ASSERT(keys.begin <= mutation.param1 && mutation.param2 <= keys.end);
	} else if (isSingleKeyMutation((MutationRef::Type)mutation.type)) {
		ASSERT(keys.contains(mutation.param1));
	}

	if (phase == WaitPrevious) {
		// Updates can be discarded
	} else if (phase == Fetching) {
		// Save incoming mutations (See the comments of member variable `updates`).

		// Create a new VerUpdateRef in updates queue if it is a new version.
		if (!updates.size() || version > updates.end()[-1].version) {
			VerUpdateRef v;
			v.version = version;
			v.isPrivateData = false;
			updates.push_back(v);
		} else {
			ASSERT(version == updates.end()[-1].version);
		}
		// Add the mutation to the version.
		updates.back().mutations.push_back_deep(updates.back().arena(), mutation);
	} else if (phase == FetchingCF || phase == Waiting) {
		server->addMutation(version, fromFetch, mutation, keys, server->updateEagerReads);
	} else
		ASSERT(false);
}

void ShardInfo::addMutation(Version version, bool fromFetch, MutationRef const& mutation) {
	ASSERT((void*)this);
	ASSERT(keys.contains(mutation.param1));
	if (adding)
		adding->addMutation(version, fromFetch, mutation);
	else if (readWrite)
		readWrite->addMutation(version, fromFetch, mutation, this->keys, readWrite->updateEagerReads);
	else if (mutation.type != MutationRef::ClearRange) {
		TraceEvent(SevError, "DeliveredToNotAssigned").detail("Version", version).detail("Mutation", mutation);
		ASSERT(false); // Mutation delivered to notAssigned shard!
	}
}

enum ChangeServerKeysContext { CSK_UPDATE, CSK_RESTORE, CSK_ASSIGN_EMPTY };
const char* changeServerKeysContextName[] = { "Update", "Restore" };

ACTOR Future<Void> restoreShards(StorageServer* data,
                                 Version version,
                                 RangeResult storageShards,
                                 RangeResult assignedShards,
                                 RangeResult availableShards) {
	TraceEvent(SevInfo, "StorageServerRestoreShardsBegin", data->thisServerID)
	    .detail("StorageShard", storageShards.size())
	    .detail("Version", version);

	state int mLoc;
	for (mLoc = 0; mLoc < storageShards.size(); ++mLoc) {
		const KeyRangeRef shardRange(storageShards[mLoc].key.removePrefix(persistStorageServerShardKeys.begin),
		                             mLoc + 1 == storageShards.size() ? allKeys.end
		                                                              : storageShards[mLoc + 1].key.removePrefix(
		                                                                    persistStorageServerShardKeys.begin));
		StorageServerShard shard =
		    ObjectReader::fromStringRef<StorageServerShard>(storageShards[mLoc].value, IncludeVersion());
		shard.range = shardRange;
		TraceEvent(SevVerbose, "RestoreShardsStorageShard", data->thisServerID)
		    .detail("Range", shardRange)
		    .detail("StorageShard", shard.toString());

		// TODO(psm): Schedule deletion of finished moveInShard.
		const StorageServerShard::ShardState shardState = shard.getShardState();
		auto existingShards = data->shards.intersectingRanges(shardRange);
		for (auto it = existingShards.begin(); it != existingShards.end(); ++it) {
			TraceEvent(SevVerbose, "RestoreShardsIntersectingRange", data->thisServerID)
			    .detail("StorageShard", shard.toString())
			    .detail("IntersectingShardRange", it->value()->keys)
			    .detail("IntersectingShardState", it->value()->debugDescribeState())
			    .log();
			ASSERT(it->value()->notAssigned());
		}

		if (shardState == StorageServerShard::NotAssigned) {
			continue;
		}

		auto ranges = data->shards.getAffectedRangesAfterInsertion(shard.range, Reference<ShardInfo>());
		for (int i = 0; i < ranges.size(); i++) {
			KeyRangeRef& range = static_cast<KeyRangeRef&>(ranges[i]);
			TraceEvent(SevVerbose, "RestoreShardsInstallPhysicalShard", data->thisServerID)
			    .detail("Shard", shard.toString())
			    .detail("Range", range);
			if (range == shard.range) {
				data->addShard(ShardInfo::newShard(data, shard));
			} else {
				StorageServerShard rightShard = ranges[i].value->toStorageServerShard();
				rightShard.range = range;
				data->addShard(ShardInfo::newShard(data, rightShard));
			}
		}

		const bool nowAvailable = shard.getShardState() == StorageServerShard::ReadWrite;
		data->newestAvailableVersion.insert(shard.range, nowAvailable ? latestVersion : invalidVersion);

		wait(yield());
	}

	state int availableLoc;
	for (availableLoc = 0; availableLoc < availableShards.size(); availableLoc++) {
		KeyRangeRef shardRange(
		    availableShards[availableLoc].key.removePrefix(persistShardAvailableKeys.begin),
		    availableLoc + 1 == availableShards.size()
		        ? allKeys.end
		        : availableShards[availableLoc + 1].key.removePrefix(persistShardAvailableKeys.begin));
		ASSERT(!shardRange.empty());

		const bool nowAvailable = availableShards[availableLoc].value != LiteralStringRef("0");
		auto existingShards = data->shards.intersectingRanges(shardRange);
		for (auto it = existingShards.begin(); it != existingShards.end(); ++it) {
			TraceEvent(SevVerbose, "RestoreShardsValidateAvailable", data->thisServerID)
			    .detail("Range", shardRange)
			    .detail("Available", nowAvailable)
			    .detail("IntersectingShardRange", it->value()->keys)
			    .detail("IntersectingShardState", it->value()->debugDescribeState())
			    .log();
			if (nowAvailable) {
				ASSERT(it->value()->isReadable());
				ASSERT(data->newestAvailableVersion.allEqual(shardRange, latestVersion));
			}
		}

		wait(yield());
	}

	state int assignedLoc;
	for (assignedLoc = 0; assignedLoc < assignedShards.size(); ++assignedLoc) {
		KeyRangeRef shardRange(assignedShards[assignedLoc].key.removePrefix(persistShardAssignedKeys.begin),
		                       assignedLoc + 1 == assignedShards.size()
		                           ? allKeys.end
		                           : assignedShards[assignedLoc + 1].key.removePrefix(persistShardAssignedKeys.begin));
		ASSERT(!shardRange.empty());
		const bool nowAssigned = assignedShards[assignedLoc].value != LiteralStringRef("0");

		auto existingShards = data->shards.intersectingRanges(shardRange);
		for (auto it = existingShards.begin(); it != existingShards.end(); ++it) {
			TraceEvent(SevVerbose, "RestoreShardsValidateAssigned", data->thisServerID)
			    .detail("Range", shardRange)
			    .detail("Assigned", nowAssigned)
			    .detail("IntersectingShardRange", it->value()->keys)
			    .detail("IntersectingShardState", it->value()->debugDescribeState())
			    .log();

			ASSERT_EQ(it->value()->assigned(), nowAssigned);
			if (!nowAssigned) {
				ASSERT(data->newestAvailableVersion.allEqual(shardRange, invalidVersion));
			}
		}

		wait(yield());
	}

	TraceEvent(SevVerbose, "StorageServerRestoreShardsCoalesce", data->thisServerID).detail("Version", version);
	coalescePhysicalShards(data, allKeys);
	TraceEvent(SevVerbose, "StorageServerRestoreShardsValidate", data->thisServerID).detail("Version", version);
	validate(data, /*force=*/true);
	TraceEvent(SevInfo, "StorageServerRestoreShardsEnd", data->thisServerID).detail("Version", version);

	return Void();
}

// Finds any change feeds that no longer have shards on this server, and clean them up
void cleanUpChangeFeeds(StorageServer* data, const KeyRangeRef& keys, Version version) {
	std::map<Key, KeyRange> candidateFeeds;
	auto ranges = data->keyChangeFeed.intersectingRanges(keys);
	for (auto r : ranges) {
		for (auto feed : r.value()) {
			candidateFeeds[feed->id] = feed->range;
		}
	}
	for (auto f : candidateFeeds) {
		bool foundAssigned = false;
		auto shards = data->shards.intersectingRanges(f.second);
		for (auto shard : shards) {
			if (shard->value()->assigned()) {
				foundAssigned = true;
				break;
			}
		}

		if (!foundAssigned) {
			Version durableVersion = data->data().getLatestVersion();
			TraceEvent(SevDebug, "ChangeFeedCleanup", data->thisServerID)
			    .detail("FeedID", f.first)
			    .detail("Version", version)
			    .detail("DurableVersion", durableVersion);

			data->changeFeedCleanupDurable[f.first] = durableVersion;

			Key beginClearKey = f.first.withPrefix(persistChangeFeedKeys.begin);
			auto& mLV = data->addVersionToMutationLog(durableVersion);
			data->addMutationToMutationLog(
			    mLV, MutationRef(MutationRef::ClearRange, beginClearKey, keyAfter(beginClearKey)));
			++data->counters.kvSystemClearRanges;
			data->addMutationToMutationLog(mLV,
			                               MutationRef(MutationRef::ClearRange,
			                                           changeFeedDurableKey(f.first, 0),
			                                           changeFeedDurableKey(f.first, version)));

			// We can't actually remove this change feed fully until the mutations clearing its data become durable.
			// If the SS restarted at version R before the clearing mutations became durable at version D (R < D),
			// then the restarted SS would restore the change feed clients would be able to read data and would miss
			// mutations from versions [R, D), up until we got the private mutation triggering the cleanup again.

			auto feed = data->uidChangeFeed.find(f.first);
			if (feed != data->uidChangeFeed.end()) {
				feed->second->removing = true;
				feed->second->refreshInProgress = false;
				feed->second->moved(feed->second->range);
				feed->second->newMutations.trigger();
			}
		} else {
			// if just part of feed's range is moved away
			auto feed = data->uidChangeFeed.find(f.first);
			if (feed != data->uidChangeFeed.end()) {
				feed->second->moved(keys);
			}
		}
	}
}

void changeServerKeys(StorageServer* data,
                      const KeyRangeRef& keys,
                      bool nowAssigned,
                      Version version,
                      ChangeServerKeysContext context) {
	ASSERT(!keys.empty());

	// TraceEvent("ChangeServerKeys", data->thisServerID)
	//     .detail("KeyBegin", keys.begin)
	//     .detail("KeyEnd", keys.end)
	//     .detail("NowAssigned", nowAssigned)
	//     .detail("Version", version)
	//     .detail("Context", changeServerKeysContextName[(int)context]);
	validate(data);

	// TODO(alexmiller): Figure out how to selectively enable spammy data distribution events.
	DEBUG_KEY_RANGE(nowAssigned ? "KeysAssigned" : "KeysUnassigned", version, keys, data->thisServerID);

	bool isDifferent = false;
	auto existingShards = data->shards.intersectingRanges(keys);
	for (auto it = existingShards.begin(); it != existingShards.end(); ++it) {
		if (nowAssigned != it->value()->assigned()) {
			isDifferent = true;
			TraceEvent("CSKRangeDifferent", data->thisServerID)
			    .detail("KeyBegin", it->range().begin)
			    .detail("KeyEnd", it->range().end);
			break;
		}
	}
	if (!isDifferent) {
		// TraceEvent("CSKShortCircuit", data->thisServerID).detail("KeyBegin", keys.begin).detail("KeyEnd", keys.end);
		return;
	}

	// Save a backup of the ShardInfo references before we start messing with shards, in order to defer fetchKeys
	// cancellation (and its potential call to removeDataRange()) until shards is again valid
	std::vector<Reference<ShardInfo>> oldShards;
	auto os = data->shards.intersectingRanges(keys);
	for (auto r = os.begin(); r != os.end(); ++r)
		oldShards.push_back(r->value());

	// As addShard (called below)'s documentation requires, reinitialize any overlapping range(s)
	auto ranges = data->shards.getAffectedRangesAfterInsertion(
	    keys, Reference<ShardInfo>()); // null reference indicates the range being changed
	for (int i = 0; i < ranges.size(); i++) {
		if (!ranges[i].value) {
			ASSERT((KeyRangeRef&)ranges[i] == keys); // there shouldn't be any nulls except for the range being inserted
		} else if (ranges[i].value->notAssigned())
			data->addShard(ShardInfo::newNotAssigned(ranges[i]));
		else if (ranges[i].value->isReadable())
			data->addShard(ShardInfo::newReadWrite(ranges[i], data));
		else {
			ASSERT(ranges[i].value->adding);
			data->addShard(ShardInfo::newAdding(data, ranges[i]));
			CODE_PROBE(true, "ChangeServerKeys reFetchKeys");
		}
	}

	// Shard state depends on nowAssigned and whether the data is available (actually assigned in memory or on the disk)
	// up to the given version.  The latter depends on data->newestAvailableVersion, so loop over the ranges of that.
	// SOMEDAY: Could this just use shards?  Then we could explicitly do the removeDataRange here when an
	// adding/transferred shard is cancelled
	auto vr = data->newestAvailableVersion.intersectingRanges(keys);
	std::vector<std::pair<KeyRange, Version>> changeNewestAvailable;
	std::vector<KeyRange> removeRanges;
	std::vector<KeyRange> newEmptyRanges;
	for (auto r = vr.begin(); r != vr.end(); ++r) {
		KeyRangeRef range = keys & r->range();
		bool dataAvailable = r->value() == latestVersion || r->value() >= version;
		// TraceEvent("CSKRange", data->thisServerID)
		//     .detail("KeyBegin", range.begin)
		//     .detail("KeyEnd", range.end)
		//     .detail("Available", dataAvailable)
		//     .detail("NowAssigned", nowAssigned)
		//     .detail("NewestAvailable", r->value())
		//     .detail("ShardState0", data->shards[range.begin]->debugDescribeState());
		if (context == CSK_ASSIGN_EMPTY && !dataAvailable) {
			ASSERT(nowAssigned);
			TraceEvent("ChangeServerKeysAddEmptyRange", data->thisServerID)
			    .detail("Begin", range.begin)
			    .detail("End", range.end);
			newEmptyRanges.push_back(range);
			data->addShard(ShardInfo::newReadWrite(range, data));
		} else if (!nowAssigned) {
			if (dataAvailable) {
				ASSERT(r->value() ==
				       latestVersion); // Not that we care, but this used to be checked instead of dataAvailable
				ASSERT(data->mutableData().getLatestVersion() > version || context == CSK_RESTORE);
				changeNewestAvailable.emplace_back(range, version);
				removeRanges.push_back(range);
			}
			data->addShard(ShardInfo::newNotAssigned(range));
			data->watches.triggerRange(range.begin, range.end);
		} else if (!dataAvailable) {
			// SOMEDAY: Avoid restarting adding/transferred shards
			// bypass fetchkeys; shard is known empty at initial cluster version
			if (version == data->initialClusterVersion - 1) {
				TraceEvent("ChangeServerKeysInitialRange", data->thisServerID)
				    .detail("Begin", range.begin)
				    .detail("End", range.end);
				changeNewestAvailable.emplace_back(range, latestVersion);
				data->addShard(ShardInfo::newReadWrite(range, data));
				setAvailableStatus(data, range, true);
			} else {
				auto& shard = data->shards[range.begin];
				if (!shard->assigned() || shard->keys != range)
					data->addShard(ShardInfo::newAdding(data, range));
			}
		} else {
			changeNewestAvailable.emplace_back(range, latestVersion);
			data->addShard(ShardInfo::newReadWrite(range, data));
		}
	}
	// Update newestAvailableVersion when a shard becomes (un)available (in a separate loop to avoid invalidating vr
	// above)
	for (auto r = changeNewestAvailable.begin(); r != changeNewestAvailable.end(); ++r)
		data->newestAvailableVersion.insert(r->first, r->second);

	if (!nowAssigned)
		data->metrics.notifyNotReadable(keys);

	coalesceShards(data, KeyRangeRef(ranges[0].begin, ranges[ranges.size() - 1].end));

	// Now it is OK to do removeDataRanges, directly and through fetchKeys cancellation (and we have to do so before
	// validate())
	oldShards.clear();
	ranges.clear();
	for (auto r = removeRanges.begin(); r != removeRanges.end(); ++r) {
		removeDataRange(data, data->addVersionToMutationLog(data->data().getLatestVersion()), data->shards, *r);
		setAvailableStatus(data, *r, false);
	}

	// Clear the moving-in empty range, and set it available at the latestVersion.
	for (const auto& range : newEmptyRanges) {
		MutationRef clearRange(MutationRef::ClearRange, range.begin, range.end);
		data->addMutation(data->data().getLatestVersion(), true, clearRange, range, data->updateEagerReads);
		data->newestAvailableVersion.insert(range, latestVersion);
		setAvailableStatus(data, range, true);
		++data->counters.kvSystemClearRanges;
	}
	validate(data);

	if (!nowAssigned) {
		cleanUpChangeFeeds(data, keys, version);
	}
}

void changeServerKeysWithPhysicalShards(StorageServer* data,
                                        const KeyRangeRef& keys,
                                        const UID& dataMoveId,
                                        bool nowAssigned,
                                        Version version,
                                        ChangeServerKeysContext context) {
	ASSERT(!keys.empty());
	TraceEvent(SevDebug, "ChangeServerKeysWithPhysicalShards", data->thisServerID)
	    .detail("DataMoveID", dataMoveId)
	    .detail("Range", keys)
	    .detail("NowAssigned", nowAssigned)
	    .detail("Version", version)
	    .detail("Context", changeServerKeysContextName[(int)context]);

	validate(data);

	DEBUG_KEY_RANGE(nowAssigned ? "KeysAssigned" : "KeysUnassigned", version, keys, data->thisServerID);

	const uint64_t desiredId = dataMoveId.first();
	const Version cVer = version + 1;
	ASSERT(data->data().getLatestVersion() == cVer);

	// Save a backup of the ShardInfo references before we start messing with shards, in order to defer fetchKeys
	// cancellation (and its potential call to removeDataRange()) until shards is again valid
	std::vector<Reference<ShardInfo>> oldShards;
	auto os = data->shards.intersectingRanges(keys);
	for (auto r = os.begin(); r != os.end(); ++r) {
		oldShards.push_back(r->value());
	}

	auto ranges = data->shards.getAffectedRangesAfterInsertion(
	    keys,
	    Reference<ShardInfo>()); // null reference indicates the range being changed
	for (int i = 0; i < ranges.size(); i++) {
		const Reference<ShardInfo> currentShard = ranges[i].value;
		const KeyRangeRef currentRange = static_cast<KeyRangeRef>(ranges[i]);
		if (!currentShard.isValid()) {
			ASSERT(currentRange == keys); // there shouldn't be any nulls except for the range being inserted
		} else if (currentShard->notAssigned()) {
			ASSERT(nowAssigned); // Adding a new range to the server.
			StorageServerShard newShard = currentShard->toStorageServerShard();
			newShard.range = currentRange;
			data->addShard(ShardInfo::newShard(data, newShard));
			TraceEvent(SevVerbose, "SSSplitShardNotAssigned", data->thisServerID)
			    .detail("Range", keys)
			    .detail("NowAssigned", nowAssigned)
			    .detail("Version", cVer)
			    .detail("ResultingShard", newShard.toString());
		} else if (currentShard->isReadable()) {
			StorageServerShard newShard = currentShard->toStorageServerShard();
			newShard.range = currentRange;
			data->addShard(ShardInfo::newShard(data, newShard));
			TraceEvent(SevVerbose, "SSSplitShardReadable", data->thisServerID)
			    .detail("Range", keys)
			    .detail("NowAssigned", nowAssigned)
			    .detail("Version", cVer)
			    .detail("ResultingShard", newShard.toString());
		} else if (ranges[i].value->adding) {
			ASSERT(!nowAssigned);
			StorageServerShard newShard = currentShard->toStorageServerShard();
			newShard.range = currentRange;
			// TODO(psm): Cancel or update the moving-in shard when physical shard move is enabled.
			data->addShard(ShardInfo::newShard(data, newShard));
			TraceEvent(SevVerbose, "SSSplitShardAdding", data->thisServerID)
			    .detail("Range", keys)
			    .detail("NowAssigned", nowAssigned)
			    .detail("Version", cVer)
			    .detail("ResultingShard", newShard.toString());
		} else {
			ASSERT(false);
		}
	}

	auto vr = data->shards.intersectingRanges(keys);
	std::vector<std::pair<KeyRange, Version>> changeNewestAvailable;
	std::vector<KeyRange> removeRanges;
	std::vector<KeyRange> newEmptyRanges;
	std::vector<StorageServerShard> updatedShards;
	int totalAssignedAtVer = 0;
	for (auto r = vr.begin(); r != vr.end(); ++r) {
		KeyRangeRef range = keys & r->range();
		const bool dataAvailable = r->value()->isReadable();
		TraceEvent(SevVerbose, "CSKPhysicalShard", data->thisServerID)
		    .detail("Range", range)
		    .detail("ExistingShardRange", r->range())
		    .detail("Available", dataAvailable)
		    .detail("NowAssigned", nowAssigned)
		    .detail("ShardState", r->value()->debugDescribeState());
		ASSERT(keys.contains(r->range()));
		if (context == CSK_ASSIGN_EMPTY && !dataAvailable) {
			ASSERT(nowAssigned);
			TraceEvent(SevVerbose, "ChangeServerKeysAddEmptyRange", data->thisServerID)
			    .detail("Range", range)
			    .detail("Version", cVer);
			newEmptyRanges.push_back(range);
			updatedShards.emplace_back(range, cVer, desiredId, desiredId, StorageServerShard::ReadWrite);
		} else if (!nowAssigned) {
			if (dataAvailable) {
				ASSERT(data->newestAvailableVersion[range.begin] ==
				       latestVersion); // Not that we care, but this used to be checked instead of dataAvailable
				ASSERT(data->mutableData().getLatestVersion() > version || context == CSK_RESTORE);
				changeNewestAvailable.emplace_back(range, version);
				removeRanges.push_back(range);
			}
			updatedShards.push_back(StorageServerShard::notAssigned(range, cVer));
			data->watches.triggerRange(range.begin, range.end);
			data->pendingRemoveRanges[cVer].push_back(range);
			// TODO(psm): When fetchKeys() is not used, make sure KV will remove the data, otherwise, removeDataShard()
			// here.
			TraceEvent(SevVerbose, "SSUnassignShard", data->thisServerID)
			    .detail("Range", range)
			    .detail("NowAssigned", nowAssigned)
			    .detail("Version", cVer)
			    .detail("NewShard", updatedShards.back().toString());
		} else if (!dataAvailable) {
			if (version == data->initialClusterVersion - 1) {
				TraceEvent(SevVerbose, "CSKWithPhysicalShardsSeedRange", data->thisServerID)
				    .detail("ShardID", desiredId)
				    .detail("Range", range);
				changeNewestAvailable.emplace_back(range, latestVersion);
				updatedShards.push_back(
				    StorageServerShard(range, version, desiredId, desiredId, StorageServerShard::ReadWrite));
				setAvailableStatus(data, range, true);
				// Note: The initial range is available, however, the shard won't be created in the storage engine
				// untill version is committed.
				data->pendingAddRanges[cVer].emplace_back(desiredId, range);
				TraceEvent(SevVerbose, "SSInitialShard", data->thisServerID)
				    .detail("Range", range)
				    .detail("NowAssigned", nowAssigned)
				    .detail("Version", cVer)
				    .detail("NewShard", updatedShards.back().toString());
			} else {
				auto& shard = data->shards[range.begin];
				if (!shard->assigned()) {
					updatedShards.push_back(
					    StorageServerShard(range, cVer, desiredId, desiredId, StorageServerShard::MovingIn));
					data->pendingAddRanges[cVer].emplace_back(desiredId, range);
					data->newestDirtyVersion.insert(range, cVer);
					TraceEvent(SevVerbose, "SSAssignShard", data->thisServerID)
					    .detail("Range", range)
					    .detail("NowAssigned", nowAssigned)
					    .detail("Version", cVer)
					    .detail("TotalAssignedAtVer", ++totalAssignedAtVer)
					    .detail("NewShard", updatedShards.back().toString());
				} else {
					ASSERT(shard->adding != nullptr);
					if (shard->desiredShardId != desiredId) {
						TraceEvent(SevError, "CSKConflictingMoveInShards", data->thisServerID)
						    .detail("DataMoveID", dataMoveId)
						    .detail("Range", range)
						    .detail("TargetShard", desiredId)
						    .detail("CurrentShard", shard->desiredShardId)
						    .detail("Version", cVer);
						// TODO(psm): Replace this with moveInShard->cancel().
						ASSERT(false);
					} else {
						TraceEvent(SevVerbose, "CSKMoveInToSameShard", data->thisServerID)
						    .detail("DataMoveID", dataMoveId)
						    .detailf("TargetShard", "%016llx", desiredId)
						    .detail("MoveRange", keys)
						    .detail("Range", range)
						    .detail("ExistingShardRange", shard->keys)
						    .detail("Version", cVer);
					}
				}
			}
		} else {
			updatedShards.push_back(StorageServerShard(
			    range, cVer, data->shards[range.begin]->shardId, desiredId, StorageServerShard::ReadWrite));
			changeNewestAvailable.emplace_back(range, latestVersion);
			TraceEvent(SevVerbose, "SSAssignShardAlreadyAvailable", data->thisServerID)
			    .detail("Range", range)
			    .detail("NowAssigned", nowAssigned)
			    .detail("Version", cVer)
			    .detail("NewShard", updatedShards.back().toString());
		}
	}

	for (const auto& shard : updatedShards) {
		data->addShard(ShardInfo::newShard(data, shard));
		updateStorageShard(data, shard);
	}

	// Update newestAvailableVersion when a shard becomes (un)available (in a separate loop to avoid invalidating vr
	// above)
	for (auto r = changeNewestAvailable.begin(); r != changeNewestAvailable.end(); ++r) {
		data->newestAvailableVersion.insert(r->first, r->second);
	}

	if (!nowAssigned) {
		data->metrics.notifyNotReadable(keys);
	}

	coalescePhysicalShards(data, KeyRangeRef(ranges[0].begin, ranges[ranges.size() - 1].end));

	// Now it is OK to do removeDataRanges, directly and through fetchKeys cancellation (and we have to do so before
	// validate())
	oldShards.clear();
	ranges.clear();
	for (auto r = removeRanges.begin(); r != removeRanges.end(); ++r) {
		removeDataRange(data, data->addVersionToMutationLog(data->data().getLatestVersion()), data->shards, *r);
		setAvailableStatus(data, *r, false);
	}

	// Clear the moving-in empty range, and set it available at the latestVersion.
	for (const auto& range : newEmptyRanges) {
		MutationRef clearRange(MutationRef::ClearRange, range.begin, range.end);
		data->addMutation(data->data().getLatestVersion(), true, clearRange, range, data->updateEagerReads);
		data->newestAvailableVersion.insert(range, latestVersion);
		setAvailableStatus(data, range, true);
		++data->counters.kvSystemClearRanges;
	}
	validate(data);

	// find any change feeds that no longer have shards on this server, and clean them up
	if (!nowAssigned) {
		cleanUpChangeFeeds(data, keys, version);
	}
}

void rollback(StorageServer* data, Version rollbackVersion, Version nextVersion) {
	CODE_PROBE(true, "call to shard rollback");
	DEBUG_KEY_RANGE("Rollback", rollbackVersion, allKeys, data->thisServerID);

	// We used to do a complicated dance to roll back in MVCC history.  It's much simpler, and more testable,
	// to simply restart the storage server actor and restore from the persistent disk state, and then roll
	// forward from the TLog's history.  It's not quite as efficient, but we rarely have to do this in practice.

	// FIXME: This code is relying for liveness on an undocumented property of the log system implementation: that after
	// a rollback the rolled back versions will eventually be missing from the peeked log.  A more sophisticated
	// approach would be to make the rollback range durable and, after reboot, skip over those versions if they appear
	// in peek results.

	throw please_reboot();
}

void StorageServer::addMutation(Version version,
                                bool fromFetch,
                                MutationRef const& mutation,
                                KeyRangeRef const& shard,
                                UpdateEagerReadInfo* eagerReads) {
	MutationRef expanded = mutation;
	MutationRef
	    nonExpanded; // need to keep non-expanded but atomic converted version of clear mutations for change feeds
	auto& mLog = addVersionToMutationLog(version);

	if (!convertAtomicOp(expanded, data(), eagerReads, mLog.arena())) {
		return;
	}
	if (expanded.type == MutationRef::ClearRange) {
		nonExpanded = expanded;
		expandClear(expanded, data(), eagerReads, shard.end);
	}
	expanded = addMutationToMutationLog(mLog, expanded);
	DEBUG_MUTATION("applyMutation", version, expanded, thisServerID)
	    .detail("ShardBegin", shard.begin)
	    .detail("ShardEnd", shard.end);

	if (!fromFetch) {
		// have to do change feed before applyMutation because nonExpanded wasn't copied into the mutation log arena,
		// and thus would go out of scope if it wasn't copied into the change feed arena
		applyChangeFeedMutation(this, expanded.type == MutationRef::ClearRange ? nonExpanded : expanded, version);
	}
	applyMutation(this, expanded, mLog.arena(), mutableData(), version);

	// printf("\nSSUpdate: Printing versioned tree after applying mutation\n");
	// mutableData().printTree(version);
}

struct OrderByVersion {
	bool operator()(const VerUpdateRef& a, const VerUpdateRef& b) {
		if (a.version != b.version)
			return a.version < b.version;
		if (a.isPrivateData != b.isPrivateData)
			return a.isPrivateData;
		return false;
	}
};

class StorageUpdater {
public:
	StorageUpdater()
	  : currentVersion(invalidVersion), fromVersion(invalidVersion), restoredVersion(invalidVersion),
	    processedStartKey(false), processedCacheStartKey(false) {}
	StorageUpdater(Version fromVersion, Version restoredVersion)
	  : currentVersion(fromVersion), fromVersion(fromVersion), restoredVersion(restoredVersion),
	    processedStartKey(false), processedCacheStartKey(false) {}

	void applyMutation(StorageServer* data, MutationRef const& m, Version ver, bool fromFetch) {
		//TraceEvent("SSNewVersion", data->thisServerID).detail("VerWas", data->mutableData().latestVersion).detail("ChVer", ver);

		if (currentVersion != ver) {
			fromVersion = currentVersion;
			currentVersion = ver;
			data->mutableData().createNewVersion(ver);
		}

		if (m.param1.startsWith(systemKeys.end)) {
			if ((m.type == MutationRef::SetValue) && m.param1.substr(1).startsWith(storageCachePrefix)) {
				applyPrivateCacheData(data, m);
			} else if ((m.type == MutationRef::SetValue) && m.param1.substr(1).startsWith(checkpointPrefix)) {
				registerPendingCheckpoint(data, m, ver);
			} else {
				applyPrivateData(data, ver, m);
			}
		} else {
			if (MUTATION_TRACKING_ENABLED) {
				DEBUG_MUTATION("SSUpdateMutation", ver, m, data->thisServerID).detail("FromFetch", fromFetch);
			}

			splitMutation(data, data->shards, m, ver, fromFetch);
		}

		if (data->otherError.getFuture().isReady())
			data->otherError.getFuture().get();
	}

	Version currentVersion;

private:
	Version fromVersion;
	Version restoredVersion;

	KeyRef startKey;
	bool nowAssigned;
	bool emptyRange;
	UID dataMoveId;
	bool processedStartKey;

	KeyRef cacheStartKey;
	bool processedCacheStartKey;

	void applyPrivateData(StorageServer* data, Version ver, MutationRef const& m) {
		TraceEvent(SevDebug, "SSPrivateMutation", data->thisServerID).detail("Mutation", m).detail("Version", ver);

		if (processedStartKey) {
			// Because of the implementation of the krm* functions, we expect changes in pairs, [begin,end)
			// We can also ignore clearRanges, because they are always accompanied by such a pair of sets with the same
			// keys
			ASSERT(m.type == MutationRef::SetValue && m.param1.startsWith(data->sk));
			KeyRangeRef keys(startKey.removePrefix(data->sk), m.param1.removePrefix(data->sk));

			// ignore data movements for tss in quarantine
			if (!data->isTSSInQuarantine()) {
				const ChangeServerKeysContext context = emptyRange ? CSK_ASSIGN_EMPTY : CSK_UPDATE;
				if (data->shardAware) {
					setAssignedStatus(data, keys, nowAssigned);
					TraceEvent(SevDebug, "SSSetAssignedStatus", data->thisServerID)
					    .detail("Range", keys)
					    .detail("NowAssigned", nowAssigned)
					    .detail("Version", ver);
					changeServerKeysWithPhysicalShards(
					    data, keys, dataMoveId, nowAssigned, currentVersion - 1, context);
				} else {
					// add changes in shard assignment to the mutation log
					setAssignedStatus(data, keys, nowAssigned);

					// The changes for version have already been received (and are being processed now).  We need to
					// fetch the data for change.version-1 (changes from versions < change.version) If emptyRange, treat
					// the shard as empty, see removeKeysFromFailedServer() for more details about this scenario.
					changeServerKeys(data, keys, nowAssigned, currentVersion - 1, context);
				}
			}

			processedStartKey = false;
		} else if (m.type == MutationRef::SetValue && m.param1.startsWith(data->sk)) {
			// Because of the implementation of the krm* functions, we expect changes in pairs, [begin,end)
			// We can also ignore clearRanges, because they are always accompanied by such a pair of sets with the same
			// keys
			startKey = m.param1;
			decodeServerKeysValue(m.param2, nowAssigned, emptyRange, dataMoveId);
			processedStartKey = true;
		} else if (m.type == MutationRef::SetValue && m.param1 == lastEpochEndPrivateKey) {
			// lastEpochEnd transactions are guaranteed by the master to be alone in their own batch (version)
			// That means we don't have to worry about the impact on changeServerKeys
			// ASSERT( /*isFirstVersionUpdateFromTLog && */!std::next(it) );

			Version rollbackVersion;
			BinaryReader br(m.param2, Unversioned());
			br >> rollbackVersion;

			if (rollbackVersion < fromVersion && rollbackVersion > restoredVersion) {
				CODE_PROBE(true, "ShardApplyPrivateData shard rollback");
				TraceEvent(SevWarn, "Rollback", data->thisServerID)
				    .detail("FromVersion", fromVersion)
				    .detail("ToVersion", rollbackVersion)
				    .detail("AtVersion", currentVersion)
				    .detail("RestoredVersion", restoredVersion)
				    .detail("StorageVersion", data->storageVersion());
				ASSERT(rollbackVersion >= data->storageVersion());
				rollback(data, rollbackVersion, currentVersion);
			} else {
				TraceEvent(SevDebug, "RollbackSkip", data->thisServerID)
				    .detail("FromVersion", fromVersion)
				    .detail("ToVersion", rollbackVersion)
				    .detail("AtVersion", currentVersion)
				    .detail("RestoredVersion", restoredVersion)
				    .detail("StorageVersion", data->storageVersion());
			}
			for (auto& it : data->uidChangeFeed) {
				if (!it.second->removing && currentVersion < it.second->stopVersion) {
					it.second->mutations.push_back(MutationsAndVersionRef(currentVersion, rollbackVersion));
					it.second->mutations.back().mutations.push_back_deep(it.second->mutations.back().arena(), m);
					data->currentChangeFeeds.insert(it.first);
				}
			}

			data->recoveryVersionSkips.emplace_back(rollbackVersion, currentVersion - rollbackVersion);
		} else if (m.type == MutationRef::SetValue && m.param1 == killStoragePrivateKey) {
			TraceEvent("StorageServerWorkerRemoved", data->thisServerID).detail("Reason", "KillStorage");
			throw worker_removed();
		} else if ((m.type == MutationRef::SetValue || m.type == MutationRef::ClearRange) &&
		           m.param1.substr(1).startsWith(serverTagPrefix)) {
			UID serverTagKey = decodeServerTagKey(m.param1.substr(1));
			bool matchesThisServer = serverTagKey == data->thisServerID;
			bool matchesTssPair = data->isTss() ? serverTagKey == data->tssPairID.get() : false;
			// Remove SS if another SS is now assigned our tag, or this server was removed by deleting our tag entry
			// Since TSS don't have tags, they check for their pair's tag. If a TSS is in quarantine, it will stick
			// around until its pair is removed or it is finished quarantine.
			if ((m.type == MutationRef::SetValue &&
			     ((!data->isTss() && !matchesThisServer) || (data->isTss() && !matchesTssPair))) ||
			    (m.type == MutationRef::ClearRange &&
			     ((!data->isTSSInQuarantine() && matchesThisServer) || (data->isTss() && matchesTssPair)))) {
				TraceEvent("StorageServerWorkerRemoved", data->thisServerID)
				    .detail("Reason", "ServerTag")
				    .detail("MutationType", getTypeString(m.type))
				    .detail("TagMatches", matchesThisServer)
				    .detail("IsTSS", data->isTss());
				throw worker_removed();
			}
			if (!data->isTss() && m.type == MutationRef::ClearRange && data->ssPairID.present() &&
			    serverTagKey == data->ssPairID.get()) {
				data->clearSSWithTssPair();
				// Add ss pair id change to mutation log to make durable
				auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
				data->addMutationToMutationLog(
				    mLV, MutationRef(MutationRef::ClearRange, persistSSPairID, keyAfter(persistSSPairID)));
			}
		} else if (m.type == MutationRef::SetValue && m.param1 == rebootWhenDurablePrivateKey) {
			data->rebootAfterDurableVersion = currentVersion;
			TraceEvent("RebootWhenDurableSet", data->thisServerID)
			    .detail("DurableVersion", data->durableVersion.get())
			    .detail("RebootAfterDurableVersion", data->rebootAfterDurableVersion);
		} else if (m.type == MutationRef::SetValue && m.param1 == primaryLocalityPrivateKey) {
			data->primaryLocality = BinaryReader::fromStringRef<int8_t>(m.param2, Unversioned());
			auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
			data->addMutationToMutationLog(mLV, MutationRef(MutationRef::SetValue, persistPrimaryLocality, m.param2));
		} else if (m.type == MutationRef::SetValue && m.param1.startsWith(changeFeedPrivatePrefix)) {
			Key changeFeedId = m.param1.removePrefix(changeFeedPrivatePrefix);
			KeyRange changeFeedRange;
			Version popVersion;
			ChangeFeedStatus status;
			std::tie(changeFeedRange, popVersion, status) = decodeChangeFeedValue(m.param2);
			auto feed = data->uidChangeFeed.find(changeFeedId);

			TraceEvent(SevDebug, "ChangeFeedPrivateMutation", data->thisServerID)
			    .detail("RangeID", changeFeedId)
			    .detail("Range", changeFeedRange)
			    .detail("Version", currentVersion)
			    .detail("PopVersion", popVersion)
			    .detail("Status", status);

			// Because of data moves, we can get mutations operating on a change feed we don't yet know about, because
			// the fetch hasn't started yet
			bool createdFeed = false;
			if (feed == data->uidChangeFeed.end() && status != ChangeFeedStatus::CHANGE_FEED_DESTROY) {
				createdFeed = true;

				Reference<ChangeFeedInfo> changeFeedInfo(new ChangeFeedInfo());
				changeFeedInfo->range = changeFeedRange;
				changeFeedInfo->id = changeFeedId;
				if (status == ChangeFeedStatus::CHANGE_FEED_CREATE && popVersion == invalidVersion) {
					// for a create, the empty version should be now, otherwise it will be set in a later pop
					changeFeedInfo->emptyVersion = currentVersion - 1;
				} else {
					CODE_PROBE(true, "SS got non-create change feed private mutation before move created its metadata");
					changeFeedInfo->emptyVersion = invalidVersion;
				}
				changeFeedInfo->metadataCreateVersion = currentVersion;
				data->uidChangeFeed[changeFeedId] = changeFeedInfo;

				feed = data->uidChangeFeed.find(changeFeedId);
				ASSERT(feed != data->uidChangeFeed.end());

				TraceEvent(SevDebug, "AddingChangeFeed", data->thisServerID)
				    .detail("RangeID", changeFeedId)
				    .detail("Range", changeFeedRange)
				    .detail("EmptyVersion", feed->second->emptyVersion);

				auto rs = data->keyChangeFeed.modify(changeFeedRange);
				for (auto r = rs.begin(); r != rs.end(); ++r) {
					r->value().push_back(changeFeedInfo);
				}
				data->keyChangeFeed.coalesce(changeFeedRange.contents());
			}

			bool popMutationLog = false;
			bool addMutationToLog = false;
			if (popVersion != invalidVersion && status != ChangeFeedStatus::CHANGE_FEED_DESTROY) {
				// pop the change feed at pop version, no matter what state it is in
				if (popVersion - 1 > feed->second->emptyVersion) {
					feed->second->emptyVersion = popVersion - 1;
					while (!feed->second->mutations.empty() && feed->second->mutations.front().version < popVersion) {
						feed->second->mutations.pop_front();
					}
					if (feed->second->storageVersion != invalidVersion) {
						++data->counters.kvSystemClearRanges;
						// do this clear in the mutation log, as we want it to be committed consistently with the
						// popVersion update
						popMutationLog = true;
						if (popVersion > feed->second->storageVersion) {
							feed->second->storageVersion = invalidVersion;
							feed->second->durableVersion = invalidVersion;
						}
					}
					if (!feed->second->destroyed) {
						// if feed is destroyed, adding an extra mutation here would re-create it if SS restarted
						addMutationToLog = true;
					}
				}

			} else if (status == ChangeFeedStatus::CHANGE_FEED_CREATE && createdFeed) {
				TraceEvent(SevDebug, "CreatingChangeFeed", data->thisServerID)
				    .detail("RangeID", changeFeedId)
				    .detail("Range", changeFeedRange)
				    .detail("Version", currentVersion);
				// no-op, already created metadata
				addMutationToLog = true;
			}
			if (status == ChangeFeedStatus::CHANGE_FEED_STOP && currentVersion < feed->second->stopVersion) {
				TraceEvent(SevDebug, "StoppingChangeFeed", data->thisServerID)
				    .detail("RangeID", changeFeedId)
				    .detail("Range", changeFeedRange)
				    .detail("Version", currentVersion);
				feed->second->stopVersion = currentVersion;
				addMutationToLog = true;
			}
			if (status == ChangeFeedStatus::CHANGE_FEED_DESTROY && !createdFeed && feed != data->uidChangeFeed.end()) {
				TraceEvent(SevDebug, "DestroyingChangeFeed", data->thisServerID)
				    .detail("RangeID", changeFeedId)
				    .detail("Range", changeFeedRange)
				    .detail("Version", currentVersion);
				Key beginClearKey = changeFeedId.withPrefix(persistChangeFeedKeys.begin);
				Version cleanupVersion = data->data().getLatestVersion();
				auto& mLV = data->addVersionToMutationLog(cleanupVersion);
				data->addMutationToMutationLog(
				    mLV, MutationRef(MutationRef::ClearRange, beginClearKey, keyAfter(beginClearKey)));
				++data->counters.kvSystemClearRanges;
				data->addMutationToMutationLog(mLV,
				                               MutationRef(MutationRef::ClearRange,
				                                           changeFeedDurableKey(feed->second->id, 0),
				                                           changeFeedDurableKey(feed->second->id, currentVersion)));
				++data->counters.kvSystemClearRanges;

				feed->second->destroy(currentVersion);
				data->changeFeedCleanupDurable[feed->first] = cleanupVersion;
			}

			if (status == ChangeFeedStatus::CHANGE_FEED_DESTROY) {
				for (auto& it : data->changeFeedRemovals) {
					it.second.send(changeFeedId);
				}
			}

			if (addMutationToLog) {
				auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
				data->addMutationToMutationLog(
				    mLV,
				    MutationRef(MutationRef::SetValue,
				                persistChangeFeedKeys.begin.toString() + changeFeedId.toString(),
				                changeFeedSSValue(
				                    feed->second->range, feed->second->emptyVersion + 1, feed->second->stopVersion)));
				if (popMutationLog) {
					++data->counters.kvSystemClearRanges;
					data->addMutationToMutationLog(mLV,
					                               MutationRef(MutationRef::ClearRange,
					                                           changeFeedDurableKey(feed->second->id, 0),
					                                           changeFeedDurableKey(feed->second->id, popVersion)));
				}
			}
		} else if ((m.type == MutationRef::SetValue || m.type == MutationRef::ClearRange) &&
		           m.param1.startsWith(TenantMetadata::tenantMapPrivatePrefix)) {
			if (m.type == MutationRef::SetValue) {
				data->insertTenant(
				    m.param1.removePrefix(TenantMetadata::tenantMapPrivatePrefix), m.param2, currentVersion);
			} else if (m.type == MutationRef::ClearRange) {
				data->clearTenants(m.param1.removePrefix(TenantMetadata::tenantMapPrivatePrefix),
				                   m.param2.removePrefix(TenantMetadata::tenantMapPrivatePrefix),
				                   currentVersion);
			}
		} else if (m.param1.substr(1).startsWith(tssMappingKeys.begin) &&
		           (m.type == MutationRef::SetValue || m.type == MutationRef::ClearRange)) {
			if (!data->isTss()) {
				UID ssId = TupleCodec<UID>::unpack(m.param1.substr(1).removePrefix(tssMappingKeys.begin));
				ASSERT(ssId == data->thisServerID);
				// Add ss pair id change to mutation log to make durable
				auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());
				if (m.type == MutationRef::SetValue) {
					UID tssId = TupleCodec<UID>::unpack(m.param2);
					data->setSSWithTssPair(tssId);
					data->addMutationToMutationLog(mLV,
					                               MutationRef(MutationRef::SetValue,
					                                           persistSSPairID,
					                                           BinaryWriter::toValue(tssId, Unversioned())));
				} else {
					data->clearSSWithTssPair();
					data->addMutationToMutationLog(
					    mLV, MutationRef(MutationRef::ClearRange, persistSSPairID, keyAfter(persistSSPairID)));
				}
			}
		} else if (m.param1.substr(1).startsWith(tssQuarantineKeys.begin) &&
		           (m.type == MutationRef::SetValue || m.type == MutationRef::ClearRange)) {
			if (data->isTss()) {
				UID ssId = decodeTssQuarantineKey(m.param1.substr(1));
				ASSERT(ssId == data->thisServerID);
				if (m.type == MutationRef::SetValue) {
					CODE_PROBE(true, "Putting TSS in quarantine");
					TraceEvent(SevWarn, "TSSQuarantineStart", data->thisServerID).log();
					data->startTssQuarantine();
				} else {
					TraceEvent(SevWarn, "TSSQuarantineStop", data->thisServerID).log();
					TraceEvent("StorageServerWorkerRemoved", data->thisServerID).detail("Reason", "TSSQuarantineStop");
					// dipose of this TSS
					throw worker_removed();
				}
			}
		} else {
			ASSERT(false); // Unknown private mutation
		}
	}

	void applyPrivateCacheData(StorageServer* data, MutationRef const& m) {
		//TraceEvent(SevDebug, "SSPrivateCacheMutation", data->thisServerID).detail("Mutation", m);

		if (processedCacheStartKey) {
			// Because of the implementation of the krm* functions, we expect changes in pairs, [begin,end)
			ASSERT((m.type == MutationRef::SetValue) && m.param1.substr(1).startsWith(storageCachePrefix));
			KeyRangeRef keys(cacheStartKey.removePrefix(systemKeys.begin).removePrefix(storageCachePrefix),
			                 m.param1.removePrefix(systemKeys.begin).removePrefix(storageCachePrefix));
			data->cachedRangeMap.insert(keys, true);

			// Figure out the affected shard ranges and maintain the cached key-range information in the in-memory map
			// TODO revisit- we are not splitting the cached ranges based on shards as of now.
			if (0) {
				auto cachedRanges = data->shards.intersectingRanges(keys);
				for (auto shard = cachedRanges.begin(); shard != cachedRanges.end(); ++shard) {
					KeyRangeRef intersectingRange = shard.range() & keys;
					TraceEvent(SevDebug, "SSPrivateCacheMutationInsertUnexpected", data->thisServerID)
					    .detail("Begin", intersectingRange.begin)
					    .detail("End", intersectingRange.end);
					data->cachedRangeMap.insert(intersectingRange, true);
				}
			}
			processedStartKey = false;
		} else if ((m.type == MutationRef::SetValue) && m.param1.substr(1).startsWith(storageCachePrefix)) {
			// Because of the implementation of the krm* functions, we expect changes in pairs, [begin,end)
			cacheStartKey = m.param1;
			processedCacheStartKey = true;
		} else {
			ASSERT(false); // Unknown private mutation
		}
	}

	// Registers a pending checkpoint request, it will be fullfilled when the desired version is durable.
	void registerPendingCheckpoint(StorageServer* data, const MutationRef& m, Version ver) {
		CheckpointMetaData checkpoint = decodeCheckpointValue(m.param2);
		ASSERT(checkpoint.getState() == CheckpointMetaData::Pending);
		const UID checkpointID = decodeCheckpointKey(m.param1.substr(1));
		checkpoint.version = ver;
		data->pendingCheckpoints[ver].push_back(checkpoint);

		auto& mLV = data->addVersionToMutationLog(ver);
		const Key pendingCheckpointKey(persistPendingCheckpointKeys.begin.toString() + checkpointID.toString());
		data->addMutationToMutationLog(
		    mLV, MutationRef(MutationRef::SetValue, pendingCheckpointKey, checkpointValue(checkpoint)));

		TraceEvent("RegisterPendingCheckpoint", data->thisServerID)
		    .detail("Key", pendingCheckpointKey)
		    .detail("Checkpoint", checkpoint.toString());
	}
};

bool StorageServer::insertTenant(TenantNameRef tenantName, TenantMapEntry tenantEntry, Version version) {
	if (version >= tenantMap.getLatestVersion()) {
		tenantMap.createNewVersion(version);
		tenantPrefixIndex.createNewVersion(version);

		tenantMap.insert(tenantName, tenantEntry);
		tenantPrefixIndex.insert(tenantEntry.prefix, tenantName);

		TraceEvent("InsertTenant", thisServerID).detail("Tenant", tenantName).detail("Version", version);
		return true;
	} else {
		return false;
	}
}

void StorageServer::insertTenant(TenantNameRef tenantName, ValueRef value, Version version) {
	if (insertTenant(tenantName, TenantMapEntry::decode(value), version)) {
		auto& mLV = addVersionToMutationLog(version);
		addMutationToMutationLog(
		    mLV, MutationRef(MutationRef::SetValue, tenantName.withPrefix(persistTenantMapKeys.begin), value));
	}
}

void StorageServer::clearTenants(TenantNameRef startTenant, TenantNameRef endTenant, Version version) {
	if (version >= tenantMap.getLatestVersion()) {
		tenantMap.createNewVersion(version);
		tenantPrefixIndex.createNewVersion(version);

		auto view = tenantMap.at(version);
		for (auto itr = view.lower_bound(startTenant); itr != view.lower_bound(endTenant); ++itr) {
			// Trigger any watches on the prefix associated with the tenant.
			watches.triggerRange(itr->prefix, strinc(itr->prefix));
			tenantPrefixIndex.erase(itr->prefix);
			TraceEvent("EraseTenant", thisServerID).detail("Tenant", itr.key()).detail("Version", version);
		}

		tenantMap.erase(startTenant, endTenant);

		auto& mLV = addVersionToMutationLog(version);
		addMutationToMutationLog(mLV,
		                         MutationRef(MutationRef::ClearRange,
		                                     startTenant.withPrefix(persistTenantMapKeys.begin),
		                                     endTenant.withPrefix(persistTenantMapKeys.begin)));
	}
}

ACTOR Future<Void> tssDelayForever() {
	loop {
		wait(delay(5.0));
		if (g_simulator.speedUpSimulation) {
			return Void();
		}
	}
}

ACTOR Future<Void> update(StorageServer* data, bool* pReceivedUpdate) {
	state double start;
	try {

		// If we are disk bound and durableVersion is very old, we need to block updates or we could run out of
		// memory. This is often referred to as the storage server e-brake (emergency brake)

		// We allow the storage server to make some progress between e-brake periods, referreed to as "overage", in
		// order to ensure that it advances desiredOldestVersion enough for updateStorage to make enough progress on
		// freeing up queue size.
		state double waitStartT = 0;
		if (data->queueSize() >= SERVER_KNOBS->STORAGE_HARD_LIMIT_BYTES &&
		    data->durableVersion.get() < data->desiredOldestVersion.get() &&
		    ((data->desiredOldestVersion.get() - SERVER_KNOBS->STORAGE_HARD_LIMIT_VERSION_OVERAGE >
		      data->lastDurableVersionEBrake) ||
		     (data->counters.bytesInput.getValue() - SERVER_KNOBS->STORAGE_HARD_LIMIT_BYTES_OVERAGE >
		      data->lastBytesInputEBrake))) {

			while (data->queueSize() >= SERVER_KNOBS->STORAGE_HARD_LIMIT_BYTES &&
			       data->durableVersion.get() < data->desiredOldestVersion.get()) {
				if (now() - waitStartT >= 1) {
					TraceEvent(SevWarn, "StorageServerUpdateLag", data->thisServerID)
					    .detail("Version", data->version.get())
					    .detail("DurableVersion", data->durableVersion.get())
					    .detail("DesiredOldestVersion", data->desiredOldestVersion.get())
					    .detail("QueueSize", data->queueSize())
					    .detail("LastBytesInputEBrake", data->lastBytesInputEBrake)
					    .detail("LastDurableVersionEBrake", data->lastDurableVersionEBrake);
					waitStartT = now();
				}

				data->behind = true;
				wait(delayJittered(.005, TaskPriority::TLogPeekReply));
			}
			data->lastBytesInputEBrake = data->counters.bytesInput.getValue();
			data->lastDurableVersionEBrake = data->durableVersion.get();
		}

		if (g_network->isSimulated() && data->isTss() && g_simulator.tssMode == ISimulator::TSSMode::EnabledAddDelay &&
		    !g_simulator.speedUpSimulation && data->tssFaultInjectTime.present() &&
		    data->tssFaultInjectTime.get() < now()) {
			if (deterministicRandom()->random01() < 0.01) {
				TraceEvent(SevWarnAlways, "TSSInjectDelayForever", data->thisServerID).log();
				// small random chance to just completely get stuck here, each tss should eventually hit this in
				// this mode
				wait(tssDelayForever());
			} else {
				// otherwise pause for part of a second
				double delayTime = deterministicRandom()->random01();
				TraceEvent(SevWarnAlways, "TSSInjectDelay", data->thisServerID).detail("Delay", delayTime);
				wait(delay(delayTime));
			}
		}

		while (data->byteSampleClearsTooLarge.get()) {
			wait(data->byteSampleClearsTooLarge.onChange());
		}

		state Reference<ILogSystem::IPeekCursor> cursor = data->logCursor;

		state double beforeTLogCursorReads = now();
		loop {
			wait(cursor->getMore());
			if (!cursor->isExhausted()) {
				break;
			}
		}
		data->tlogCursorReadsLatencyHistogram->sampleSeconds(now() - beforeTLogCursorReads);
		if (cursor->popped() > 0) {
			TraceEvent("StorageServerWorkerRemoved", data->thisServerID)
			    .detail("Reason", "PeekPoppedTLogData")
			    .detail("Version", cursor->popped());
			throw worker_removed();
		}

		++data->counters.updateBatches;
		data->lastTLogVersion = cursor->getMaxKnownVersion();
		if (cursor->getMinKnownCommittedVersion() > data->knownCommittedVersion.get()) {
			data->knownCommittedVersion.set(cursor->getMinKnownCommittedVersion());
		}
		data->versionLag = std::max<int64_t>(0, data->lastTLogVersion - data->version.get());

		ASSERT(*pReceivedUpdate == false);
		*pReceivedUpdate = true;

		start = now();
		wait(data->durableVersionLock.take(TaskPriority::TLogPeekReply, 1));
		state FlowLock::Releaser holdingDVL(data->durableVersionLock);
		if (now() - start > 0.1)
			TraceEvent("SSSlowTakeLock1", data->thisServerID)
			    .detailf("From", "%016llx", debug_lastLoadBalanceResultEndpointToken)
			    .detail("Duration", now() - start)
			    .detail("Version", data->version.get());
		data->ssVersionLockLatencyHistogram->sampleSeconds(now() - start);

		start = now();
		state UpdateEagerReadInfo eager;
		state FetchInjectionInfo fii;
		state Reference<ILogSystem::IPeekCursor> cloneCursor2;
		state Optional<std::unordered_map<BlobCipherDetails, Reference<BlobCipherKey>>> cipherKeys;
		state bool collectingCipherKeys = false;

		// Collect eager read keys.
		// If encrypted mutation is encountered, we collect cipher details and fetch cipher keys, then start over.
		loop {
			state uint64_t changeCounter = data->shardChangeCounter;
			bool epochEnd = false;
			bool hasPrivateData = false;
			bool firstMutation = true;
			bool dbgLastMessageWasProtocol = false;

			std::unordered_set<BlobCipherDetails> cipherDetails;

			Reference<ILogSystem::IPeekCursor> cloneCursor1 = cursor->cloneNoMore();
			cloneCursor2 = cursor->cloneNoMore();

			cloneCursor1->setProtocolVersion(data->logProtocol);

			for (; cloneCursor1->hasMessage(); cloneCursor1->nextMessage()) {
				ArenaReader& cloneReader = *cloneCursor1->reader();

				if (LogProtocolMessage::isNextIn(cloneReader)) {
					LogProtocolMessage lpm;
					cloneReader >> lpm;
					//TraceEvent(SevDebug, "SSReadingLPM", data->thisServerID).detail("Mutation", lpm);
					dbgLastMessageWasProtocol = true;
					cloneCursor1->setProtocolVersion(cloneReader.protocolVersion());
				} else if (cloneReader.protocolVersion().hasSpanContext() &&
				           SpanContextMessage::isNextIn(cloneReader)) {
					SpanContextMessage scm;
					cloneReader >> scm;
				} else if (cloneReader.protocolVersion().hasOTELSpanContext() &&
				           OTELSpanContextMessage::isNextIn(cloneReader)) {
					OTELSpanContextMessage scm;
					cloneReader >> scm;
				} else if (cloneReader.protocolVersion().hasEncryptionAtRest() &&
				           EncryptedMutationMessage::isNextIn(cloneReader) && !cipherKeys.present()) {
					// Encrypted mutation found, but cipher keys haven't been fetch.
					// Collect cipher details to fetch cipher keys in one batch.
					EncryptedMutationMessage emm;
					cloneReader >> emm;
					cipherDetails.insert(emm.header.cipherTextDetails);
					cipherDetails.insert(emm.header.cipherHeaderDetails);
					collectingCipherKeys = true;
				} else {
					MutationRef msg;
					if (cloneReader.protocolVersion().hasEncryptionAtRest() &&
					    EncryptedMutationMessage::isNextIn(cloneReader)) {
						assert(cipherKeys.present());
						msg = EncryptedMutationMessage::decrypt(cloneReader, eager.arena, cipherKeys.get());
					} else {
						cloneReader >> msg;
					}
					// TraceEvent(SevDebug, "SSReadingLog", data->thisServerID).detail("Mutation", msg);

					if (!collectingCipherKeys) {
						if (firstMutation && msg.param1.startsWith(systemKeys.end))
							hasPrivateData = true;
						firstMutation = false;

						if (msg.param1 == lastEpochEndPrivateKey) {
							epochEnd = true;
							ASSERT(dbgLastMessageWasProtocol);
						}

						eager.addMutation(msg);
						dbgLastMessageWasProtocol = false;
					}
				}
			}

			if (collectingCipherKeys) {
				std::unordered_map<BlobCipherDetails, Reference<BlobCipherKey>> getCipherKeysResult =
				    wait(getEncryptCipherKeys(data->db, cipherDetails));
				cipherKeys = getCipherKeysResult;
				collectingCipherKeys = false;
				eager = UpdateEagerReadInfo();
			} else {
				// Any fetchKeys which are ready to transition their shards to the adding,transferred state do so now.
				// If there is an epoch end we skip this step, to increase testability and to prevent inserting a
				// version in the middle of a rolled back version range.
				while (!hasPrivateData && !epochEnd && !data->readyFetchKeys.empty()) {
					auto fk = data->readyFetchKeys.back();
					data->readyFetchKeys.pop_back();
					fk.send(&fii);
					// fetchKeys() would put the data it fetched into the fii. The thread will not return back to this
					// actor until it was completed.
				}

				for (auto& c : fii.changes)
					eager.addMutations(c.mutations);

				wait(doEagerReads(data, &eager));
				if (data->shardChangeCounter == changeCounter)
					break;
				CODE_PROBE(
				    true,
				    "A fetchKeys completed while we were doing this, so eager might be outdated.  Read it again.");
				// SOMEDAY: Theoretically we could check the change counters of individual shards and retry the reads
				// only selectively
				eager = UpdateEagerReadInfo();
			}
		}
		data->eagerReadsLatencyHistogram->sampleSeconds(now() - start);

		if (now() - start > 0.1)
			TraceEvent("SSSlowTakeLock2", data->thisServerID)
			    .detailf("From", "%016llx", debug_lastLoadBalanceResultEndpointToken)
			    .detail("Duration", now() - start)
			    .detail("Version", data->version.get());

		data->updateEagerReads = &eager;
		data->debug_inApplyUpdate = true;

		state StorageUpdater updater(data->lastVersionWithData, data->restoredVersion);

		if (EXPENSIVE_VALIDATION)
			data->data().atLatest().validate();
		validate(data);

		state bool injectedChanges = false;
		state int changeNum = 0;
		state int mutationBytes = 0;
		state double beforeFetchKeysUpdates = now();
		for (; changeNum < fii.changes.size(); changeNum++) {
			state int mutationNum = 0;
			state VerUpdateRef* pUpdate = &fii.changes[changeNum];
			for (; mutationNum < pUpdate->mutations.size(); mutationNum++) {
				updater.applyMutation(data, pUpdate->mutations[mutationNum], pUpdate->version, true);
				mutationBytes += pUpdate->mutations[mutationNum].totalSize();
				// data->counters.mutationBytes or data->counters.mutations should not be updated because they
				// should have counted when the mutations arrive from cursor initially.
				injectedChanges = true;
				if (mutationBytes > SERVER_KNOBS->DESIRED_UPDATE_BYTES) {
					mutationBytes = 0;
					wait(delay(SERVER_KNOBS->UPDATE_DELAY));
				}
			}
		}
		data->fetchKeysPTreeUpdatesLatencyHistogram->sampleSeconds(now() - beforeFetchKeysUpdates);

		state Version ver = invalidVersion;
		cloneCursor2->setProtocolVersion(data->logProtocol);
		state SpanContext spanContext = SpanContext();
		state double beforeTLogMsgsUpdates = now();
		state std::set<Key> updatedChangeFeeds;
		for (; cloneCursor2->hasMessage(); cloneCursor2->nextMessage()) {
			if (mutationBytes > SERVER_KNOBS->DESIRED_UPDATE_BYTES) {
				mutationBytes = 0;
				// Instead of just yielding, leave time for the storage server to respond to reads
				wait(delay(SERVER_KNOBS->UPDATE_DELAY));
			}

			if (cloneCursor2->version().version > ver) {
				ASSERT(cloneCursor2->version().version > data->version.get());
			}

			auto& rd = *cloneCursor2->reader();

			if (cloneCursor2->version().version > ver && cloneCursor2->version().version > data->version.get()) {
				++data->counters.updateVersions;
				if (data->currentChangeFeeds.size()) {
					data->changeFeedVersions.emplace_back(
					    std::vector<Key>(data->currentChangeFeeds.begin(), data->currentChangeFeeds.end()), ver);
					updatedChangeFeeds.insert(data->currentChangeFeeds.begin(), data->currentChangeFeeds.end());
					data->currentChangeFeeds.clear();
				}
				ver = cloneCursor2->version().version;
			}

			if (LogProtocolMessage::isNextIn(rd)) {
				LogProtocolMessage lpm;
				rd >> lpm;

				data->logProtocol = rd.protocolVersion();
				data->storage.changeLogProtocol(ver, data->logProtocol);
				cloneCursor2->setProtocolVersion(rd.protocolVersion());
				spanContext.traceID = UID();
			} else if (rd.protocolVersion().hasSpanContext() && SpanContextMessage::isNextIn(rd)) {
				SpanContextMessage scm;
				rd >> scm;
				CODE_PROBE(true, "storageserveractor converting SpanContextMessage into OTEL SpanContext");
				spanContext =
				    SpanContext(UID(scm.spanContext.first(), scm.spanContext.second()),
				                0,
				                scm.spanContext.first() != 0 && scm.spanContext.second() != 0 ? TraceFlags::sampled
				                                                                              : TraceFlags::unsampled);
			} else if (rd.protocolVersion().hasOTELSpanContext() && OTELSpanContextMessage::isNextIn(rd)) {
				CODE_PROBE(true, "storageserveractor reading OTELSpanContextMessage");
				OTELSpanContextMessage scm;
				rd >> scm;
				spanContext = scm.spanContext;
			} else {
				MutationRef msg;
				if (rd.protocolVersion().hasEncryptionAtRest() && EncryptedMutationMessage::isNextIn(rd)) {
					ASSERT(cipherKeys.present());
					msg = EncryptedMutationMessage::decrypt(rd, rd.arena(), cipherKeys.get());
				} else {
					rd >> msg;
				}

				Span span("SS:update"_loc, spanContext);
				span.addAttribute("key"_sr, msg.param1);

				// Drop non-private mutations if TSS fault injection is enabled in simulation, or if this is a TSS in
				// quarantine.
				if (g_network->isSimulated() && data->isTss() && !g_simulator.speedUpSimulation &&
				    g_simulator.tssMode == ISimulator::TSSMode::EnabledDropMutations &&
				    data->tssFaultInjectTime.present() && data->tssFaultInjectTime.get() < now() &&
				    (msg.type == MutationRef::SetValue || msg.type == MutationRef::ClearRange) &&
				    (msg.param1.size() < 2 || msg.param1[0] != 0xff || msg.param1[1] != 0xff) &&
				    deterministicRandom()->random01() < 0.05) {
					TraceEvent(SevWarnAlways, "TSSInjectDropMutation", data->thisServerID)
					    .detail("Mutation", msg)
					    .detail("Version", cloneCursor2->version().toString());
				} else if (data->isTSSInQuarantine() &&
				           (msg.param1.size() < 2 || msg.param1[0] != 0xff || msg.param1[1] != 0xff)) {
					TraceEvent("TSSQuarantineDropMutation", data->thisServerID)
					    .suppressFor(10.0)
					    .detail("Version", cloneCursor2->version().toString());
				} else if (ver != invalidVersion) { // This change belongs to a version < minVersion
					DEBUG_MUTATION("SSPeek", ver, msg, data->thisServerID);
					if (ver == data->initialClusterVersion) {
						//TraceEvent("SSPeekMutation", data->thisServerID).log();
						// The following trace event may produce a value with special characters
						TraceEvent("SSPeekMutation", data->thisServerID)
						    .detail("Mutation", msg)
						    .detail("Version", cloneCursor2->version().toString());
					}

					updater.applyMutation(data, msg, ver, false);
					mutationBytes += msg.totalSize();
					data->counters.mutationBytes += msg.totalSize();
					data->counters.logicalBytesInput += msg.expectedSize();
					++data->counters.mutations;
					switch (msg.type) {
					case MutationRef::SetValue:
						++data->counters.setMutations;
						break;
					case MutationRef::ClearRange:
						++data->counters.clearRangeMutations;
						break;
					case MutationRef::AddValue:
					case MutationRef::And:
					case MutationRef::AndV2:
					case MutationRef::AppendIfFits:
					case MutationRef::ByteMax:
					case MutationRef::ByteMin:
					case MutationRef::Max:
					case MutationRef::Min:
					case MutationRef::MinV2:
					case MutationRef::Or:
					case MutationRef::Xor:
					case MutationRef::CompareAndClear:
						++data->counters.atomicMutations;
						break;
					}
				} else
					TraceEvent(SevError, "DiscardingPeekedData", data->thisServerID)
					    .detail("Mutation", msg)
					    .detail("Version", cloneCursor2->version().toString());
			}
		}
		data->tLogMsgsPTreeUpdatesLatencyHistogram->sampleSeconds(now() - beforeTLogMsgsUpdates);
		if (data->currentChangeFeeds.size()) {
			data->changeFeedVersions.emplace_back(
			    std::vector<Key>(data->currentChangeFeeds.begin(), data->currentChangeFeeds.end()), ver);
			updatedChangeFeeds.insert(data->currentChangeFeeds.begin(), data->currentChangeFeeds.end());
			data->currentChangeFeeds.clear();
		}

		if (ver != invalidVersion) {
			data->lastVersionWithData = ver;
		}
		ver = cloneCursor2->version().version - 1;

		if (injectedChanges)
			data->lastVersionWithData = ver;

		data->updateEagerReads = nullptr;
		data->debug_inApplyUpdate = false;

		if (ver == invalidVersion && !fii.changes.empty()) {
			ver = updater.currentVersion;
		}

		if (ver != invalidVersion && ver > data->version.get()) {
			// TODO(alexmiller): Update to version tracking.
			// DEBUG_KEY_RANGE("SSUpdate", ver, KeyRangeRef());

			data->mutableData().createNewVersion(ver);
			if (data->otherError.getFuture().isReady())
				data->otherError.getFuture().get();

			data->counters.fetchedVersions += (ver - data->version.get());
			++data->counters.fetchesFromLogs;
			Optional<UID> curSourceTLogID = cursor->getCurrentPeekLocation();

			if (curSourceTLogID != data->sourceTLogID) {
				data->sourceTLogID = curSourceTLogID;

				TraceEvent("StorageServerSourceTLogID", data->thisServerID)
				    .detail("SourceTLogID",
				            data->sourceTLogID.present() ? data->sourceTLogID.get().toString() : "unknown")
				    .trackLatest(data->storageServerSourceTLogIDEventHolder->trackingKey);
			}

			data->noRecentUpdates.set(false);
			data->lastUpdate = now();

			data->prevVersion = data->version.get();
			data->version.set(ver); // Triggers replies to waiting gets for new version(s)

			for (auto& it : updatedChangeFeeds) {
				auto feed = data->uidChangeFeed.find(it);
				if (feed != data->uidChangeFeed.end()) {
					feed->second->newMutations.trigger();
				}
			}

			setDataVersion(data->thisServerID, data->version.get());
			if (data->otherError.getFuture().isReady())
				data->otherError.getFuture().get();

			Version maxVersionsInMemory =
			    (g_network->isSimulated() && g_simulator.speedUpSimulation)
			        ? std::max(5 * SERVER_KNOBS->VERSIONS_PER_SECOND, SERVER_KNOBS->MAX_READ_TRANSACTION_LIFE_VERSIONS)
			        : SERVER_KNOBS->MAX_READ_TRANSACTION_LIFE_VERSIONS;
			for (int i = 0; i < data->recoveryVersionSkips.size(); i++) {
				maxVersionsInMemory += data->recoveryVersionSkips[i].second;
			}

			// Trigger updateStorage if necessary
			Version proposedOldestVersion =
			    std::max(data->version.get(), cursor->getMinKnownCommittedVersion()) - maxVersionsInMemory;
			if (data->primaryLocality == tagLocalitySpecial || data->tag.locality == data->primaryLocality) {
				proposedOldestVersion = std::max(proposedOldestVersion, data->lastTLogVersion - maxVersionsInMemory);
			}
			proposedOldestVersion = std::min(proposedOldestVersion, data->version.get() - 1);
			proposedOldestVersion = std::max(proposedOldestVersion, data->oldestVersion.get());
			proposedOldestVersion = std::max(proposedOldestVersion, data->desiredOldestVersion.get());
			proposedOldestVersion = std::max(proposedOldestVersion, data->initialClusterVersion);

			//TraceEvent("StorageServerUpdated", data->thisServerID).detail("Ver", ver).detail("DataVersion", data->version.get())
			//	.detail("LastTLogVersion", data->lastTLogVersion).detail("NewOldest",
			// data->oldestVersion.get()).detail("DesiredOldest",data->desiredOldestVersion.get())
			//	.detail("MaxVersionInMemory", maxVersionsInMemory).detail("Proposed",
			// proposedOldestVersion).detail("PrimaryLocality", data->primaryLocality).detail("Tag",
			// data->tag.toString());

			while (!data->recoveryVersionSkips.empty() &&
			       proposedOldestVersion > data->recoveryVersionSkips.front().first) {
				data->recoveryVersionSkips.pop_front();
			}
			data->desiredOldestVersion.set(proposedOldestVersion);
		}

		validate(data);

		if ((data->lastTLogVersion - data->version.get()) < SERVER_KNOBS->STORAGE_RECOVERY_VERSION_LAG_LIMIT) {
			if (data->registerInterfaceAcceptingRequests.canBeSet()) {
				data->registerInterfaceAcceptingRequests.send(Void());
				ErrorOr<Void> e = wait(errorOr(data->interfaceRegistered));
				if (e.isError()) {
					TraceEvent(SevWarn, "StorageInterfaceRegistrationFailed", data->thisServerID).error(e.getError());
				}
			}
		}

		data->logCursor->advanceTo(cloneCursor2->version());
		if (cursor->version().version >= data->lastTLogVersion) {
			if (data->behind) {
				TraceEvent("StorageServerNoLongerBehind", data->thisServerID)
				    .detail("CursorVersion", cursor->version().version)
				    .detail("TLogVersion", data->lastTLogVersion);
			}
			data->behind = false;
		}

		return Void(); // update will get called again ASAP
	} catch (Error& err) {
		state Error e = err;
		if (e.code() == error_code_encrypt_keys_fetch_failed) {
			TraceEvent(SevWarn, "SSUpdateError", data->thisServerID).error(e).backtrace();
		} else if (e.code() != error_code_worker_removed && e.code() != error_code_please_reboot) {
			TraceEvent(SevError, "SSUpdateError", data->thisServerID).error(e).backtrace();
		} else if (e.code() == error_code_please_reboot) {
			wait(data->durableInProgress);
		}
		throw e;
	}
}

ACTOR Future<Void> createCheckpoint(StorageServer* data, CheckpointMetaData metaData) {
	ASSERT(metaData.ssID == data->thisServerID);
	const CheckpointRequest req(metaData.version,
	                            metaData.range,
	                            static_cast<CheckpointFormat>(metaData.format),
	                            metaData.checkpointID,
	                            data->folder + rocksdbCheckpointDirPrefix + metaData.checkpointID.toString());
	state CheckpointMetaData checkpointResult;
	try {
		state CheckpointMetaData res = wait(data->storage.checkpoint(req));
		checkpointResult = res;
		checkpointResult.ssID = data->thisServerID;
		ASSERT(checkpointResult.getState() == CheckpointMetaData::Complete);
		data->checkpoints[checkpointResult.checkpointID] = checkpointResult;
		TraceEvent("StorageCreatedCheckpoint", data->thisServerID).detail("Checkpoint", checkpointResult.toString());
	} catch (Error& e) {
		// If checkpoint creation fails, the failure is persisted.
		checkpointResult = metaData;
		checkpointResult.setState(CheckpointMetaData::Fail);
		TraceEvent("StorageCreatedCheckpointFailure", data->thisServerID)
		    .detail("PendingCheckpoint", checkpointResult.toString());
	}

	// Persist the checkpoint meta data.
	try {
		Key pendingCheckpointKey(persistPendingCheckpointKeys.begin.toString() +
		                         checkpointResult.checkpointID.toString());
		Key persistCheckpointKey(persistCheckpointKeys.begin.toString() + checkpointResult.checkpointID.toString());
		data->storage.clearRange(singleKeyRange(pendingCheckpointKey));
		data->storage.writeKeyValue(KeyValueRef(persistCheckpointKey, checkpointValue(checkpointResult)));
		wait(data->storage.commit());
		TraceEvent("StorageCreateCheckpointPersisted", data->thisServerID)
		    .detail("Checkpoint", checkpointResult.toString());
	} catch (Error& e) {
		// If the checkpoint meta data is not persisted successfully, remove the checkpoint.
		TraceEvent(SevWarn, "StorageCreateCheckpointPersistFailure", data->thisServerID)
		    .errorUnsuppressed(e)
		    .detail("Checkpoint", checkpointResult.toString());
		data->checkpoints[checkpointResult.checkpointID].setState(CheckpointMetaData::Deleting);
		data->actors.add(deleteCheckpointQ(data, metaData.version, checkpointResult));
	}

	return Void();
}

ACTOR Future<Void> updateStorage(StorageServer* data) {
	state UnlimitedCommitBytes unlimitedCommitBytes = UnlimitedCommitBytes::False;
	loop {
		unlimitedCommitBytes = UnlimitedCommitBytes::False;
		ASSERT(data->durableVersion.get() == data->storageVersion());
		if (g_network->isSimulated()) {
			double endTime =
			    g_simulator.checkDisabled(format("%s/updateStorage", data->thisServerID.toString().c_str()));
			if (endTime > now()) {
				wait(delay(endTime - now(), TaskPriority::UpdateStorage));
			}
		}
		wait(data->desiredOldestVersion.whenAtLeast(data->storageVersion() + 1));
		wait(delay(0, TaskPriority::UpdateStorage));

		state Promise<Void> durableInProgress;
		data->durableInProgress = durableInProgress.getFuture();

		state Version startOldestVersion = data->storageVersion();
		state Version newOldestVersion = data->storageVersion();
		state Version desiredVersion = data->desiredOldestVersion.get();
		state int64_t bytesLeft = SERVER_KNOBS->STORAGE_COMMIT_BYTES;

		// Clean up stale checkpoint requests, this is not supposed to happen, since checkpoints are cleaned up on
		// failures. This is kept as a safeguard.
		while (!data->pendingCheckpoints.empty() && data->pendingCheckpoints.begin()->first <= startOldestVersion) {
			for (int idx = 0; idx < data->pendingCheckpoints.begin()->second.size(); ++idx) {
				auto& metaData = data->pendingCheckpoints.begin()->second[idx];
				data->actors.add(deleteCheckpointQ(data, startOldestVersion, metaData));
				TraceEvent(SevWarnAlways, "StorageStaleCheckpointRequest", data->thisServerID)
				    .detail("PendingCheckpoint", metaData.toString())
				    .detail("DurableVersion", startOldestVersion);
			}
			data->pendingCheckpoints.erase(data->pendingCheckpoints.begin());
		}

		// Create checkpoint if the pending request version is within (startOldestVersion, desiredVersion].
		// Versions newer than the checkpoint version won't be committed before the checkpoint is created.
		state bool requireCheckpoint = false;
		if (!data->pendingCheckpoints.empty()) {
			const Version cVer = data->pendingCheckpoints.begin()->first;
			if (cVer <= desiredVersion) {
				TraceEvent(SevDebug, "CheckpointVersionSatisfied", data->thisServerID)
				    .detail("DesiredVersion", desiredVersion)
				    .detail("DurableVersion", data->durableVersion.get())
				    .detail("CheckPointVersion", cVer);
				desiredVersion = cVer;
				requireCheckpoint = true;
			}
		}

		state bool removeKVSRanges = false;
		if (!data->pendingRemoveRanges.empty()) {
			const Version aVer = data->pendingRemoveRanges.begin()->first;
			if (aVer <= desiredVersion) {
				TraceEvent(SevDebug, "RemoveRangeVersionSatisfied", data->thisServerID)
				    .detail("DesiredVersion", desiredVersion)
				    .detail("DurableVersion", data->durableVersion.get())
				    .detail("RemoveRangeVersion", aVer);
				desiredVersion = aVer;
				removeKVSRanges = true;
			}
		}

		state bool addedRanges = false;
		if (!data->pendingAddRanges.empty()) {
			const Version aVer = data->pendingAddRanges.begin()->first;
			if (aVer <= desiredVersion) {
				TraceEvent(SevDebug, "AddRangeVersionSatisfied", data->thisServerID)
				    .detail("DesiredVersion", desiredVersion)
				    .detail("DurableVersion", data->durableVersion.get())
				    .detail("AddRangeVersion", aVer);
				desiredVersion = aVer;
				ASSERT(!data->pendingAddRanges.begin()->second.empty());
				TraceEvent(SevVerbose, "SSAddKVSRangeBegin", data->thisServerID)
				    .detail("Version", data->pendingAddRanges.begin()->first)
				    .detail("DurableVersion", data->durableVersion.get())
				    .detail("NewRanges", describe(data->pendingAddRanges.begin()->second));
				state std::vector<Future<Void>> fAddRanges;
				for (const auto& shard : data->pendingAddRanges.begin()->second) {
					TraceEvent(SevInfo, "SSAddKVSRange", data->thisServerID)
					    .detail("Range", shard.range)
					    .detail("PhysicalShardID", shard.shardId);
					fAddRanges.push_back(data->storage.addRange(shard.range, shard.shardId));
				}
				wait(waitForAll(fAddRanges));
				TraceEvent(SevVerbose, "SSAddKVSRangeEnd", data->thisServerID)
				    .detail("Version", data->pendingAddRanges.begin()->first)
				    .detail("DurableVersion", data->durableVersion.get());
				addedRanges = true;
				// Remove commit byte limit to make sure the private mutaiton(s) associated with the
				// `addRange` are committed.
				unlimitedCommitBytes = UnlimitedCommitBytes::True;
			}
		}

		// Write mutations to storage until we reach the desiredVersion or have written too much (bytesleft)
		state double beforeStorageUpdates = now();
		loop {
			state bool done = data->storage.makeVersionMutationsDurable(
			    newOldestVersion, desiredVersion, bytesLeft, unlimitedCommitBytes);
			if (data->tenantMap.getLatestVersion() < newOldestVersion) {
				data->tenantMap.createNewVersion(newOldestVersion);
				data->tenantPrefixIndex.createNewVersion(newOldestVersion);
			}
			// We want to forget things from these data structures atomically with changing oldestVersion (and "before",
			// since oldestVersion.set() may trigger waiting actors) forgetVersionsBeforeAsync visibly forgets
			// immediately (without waiting) but asynchronously frees memory.
			Future<Void> finishedForgetting =
			    data->mutableData().forgetVersionsBeforeAsync(newOldestVersion, TaskPriority::UpdateStorage) &&
			    data->tenantMap.forgetVersionsBeforeAsync(newOldestVersion, TaskPriority::UpdateStorage) &&
			    data->tenantPrefixIndex.forgetVersionsBeforeAsync(newOldestVersion, TaskPriority::UpdateStorage);
			data->oldestVersion.set(newOldestVersion);
			wait(finishedForgetting);
			wait(yield(TaskPriority::UpdateStorage));
			if (done)
				break;
		}

		if (addedRanges) {
			TraceEvent(SevVerbose, "SSAddKVSRangeMetaData", data->thisServerID)
			    .detail("NewDurableVersion", newOldestVersion)
			    .detail("DesiredVersion", desiredVersion)
			    .detail("OldestRemoveKVSRangesVersion", data->pendingAddRanges.begin()->first);
			ASSERT(newOldestVersion == data->pendingAddRanges.begin()->first);
			ASSERT(newOldestVersion == desiredVersion);
			for (const auto& shard : data->pendingAddRanges.begin()->second) {
				data->storage.persistRangeMapping(shard.range, true);
			}
			data->pendingAddRanges.erase(data->pendingAddRanges.begin());
		}

		if (removeKVSRanges) {
			TraceEvent(SevDebug, "RemoveKVSRangesVersionDurable", data->thisServerID)
			    .detail("NewDurableVersion", newOldestVersion)
			    .detail("DesiredVersion", desiredVersion)
			    .detail("OldestRemoveKVSRangesVersion", data->pendingRemoveRanges.begin()->first);
			ASSERT(newOldestVersion <= data->pendingRemoveRanges.begin()->first);
			if (newOldestVersion == data->pendingRemoveRanges.begin()->first) {
				for (const auto& range : data->pendingRemoveRanges.begin()->second) {
					data->storage.persistRangeMapping(range, false);
				}
			}
		}

		std::set<Key> modifiedChangeFeeds = data->fetchingChangeFeeds;
		data->fetchingChangeFeeds.clear();
		while (!data->changeFeedVersions.empty() && data->changeFeedVersions.front().second <= newOldestVersion) {
			modifiedChangeFeeds.insert(data->changeFeedVersions.front().first.begin(),
			                           data->changeFeedVersions.front().first.end());
			data->changeFeedVersions.pop_front();
		}

		state std::vector<std::pair<Key, Version>> feedFetchVersions;

		state std::vector<Key> updatedChangeFeeds(modifiedChangeFeeds.begin(), modifiedChangeFeeds.end());
		state int curFeed = 0;
		while (curFeed < updatedChangeFeeds.size()) {
			auto info = data->uidChangeFeed.find(updatedChangeFeeds[curFeed]);
			if (info != data->uidChangeFeed.end()) {
				// Cannot yield in mutation updating loop because of race with fetchVersion
				Version alreadyFetched = std::max(info->second->fetchVersion, info->second->durableFetchVersion.get());
				for (auto& it : info->second->mutations) {
					if (it.version <= alreadyFetched) {
						continue;
					} else if (it.version > newOldestVersion) {
						break;
					}
					data->storage.writeKeyValue(
					    KeyValueRef(changeFeedDurableKey(info->second->id, it.version),
					                changeFeedDurableValue(it.mutations, it.knownCommittedVersion)));
					// FIXME: there appears to be a bug somewhere where the exact same mutation appears twice in a row
					// in the stream. We should fix this assert to be strictly > and re-enable it
					ASSERT(it.version >= info->second->storageVersion);
					info->second->storageVersion = it.version;
				}

				if (info->second->fetchVersion != invalidVersion && !info->second->removing) {
					feedFetchVersions.push_back(std::pair(info->second->id, info->second->fetchVersion));
				}
				// handle case where fetch had version ahead of last in-memory mutation
				if (alreadyFetched > info->second->storageVersion) {
					info->second->storageVersion = std::min(alreadyFetched, newOldestVersion);
					if (alreadyFetched > info->second->storageVersion) {
						// This change feed still has pending mutations fetched and written to storage that are higher
						// than the new durableVersion. To ensure its storage and durable version get updated, we need
						// to add it back to fetchingChangeFeeds
						data->fetchingChangeFeeds.insert(info->first);
					}
				}
				wait(yield(TaskPriority::UpdateStorage));
			}
			curFeed++;
		}

		// Set the new durable version as part of the outstanding change set, before commit
		if (startOldestVersion != newOldestVersion)
			data->storage.makeVersionDurable(newOldestVersion);
		data->storageUpdatesDurableLatencyHistogram->sampleSeconds(now() - beforeStorageUpdates);

		debug_advanceMaxCommittedVersion(data->thisServerID, newOldestVersion);
		state double beforeStorageCommit = now();
		wait(data->storage.canCommit());
		state Future<Void> durable = data->storage.commit();
		++data->counters.kvCommits;
		state Future<Void> durableDelay = Void();

		if (bytesLeft > 0) {
			durableDelay = delay(SERVER_KNOBS->STORAGE_COMMIT_INTERVAL, TaskPriority::UpdateStorage);
		}

		wait(ioTimeoutError(durable, SERVER_KNOBS->MAX_STORAGE_COMMIT_TIME));
		data->storageCommitLatencyHistogram->sampleSeconds(now() - beforeStorageCommit);

		debug_advanceMinCommittedVersion(data->thisServerID, newOldestVersion);

		if (removeKVSRanges) {
			TraceEvent(SevDebug, "RemoveKVSRangesComitted", data->thisServerID)
			    .detail("NewDurableVersion", newOldestVersion)
			    .detail("DesiredVersion", desiredVersion)
			    .detail("OldestRemoveKVSRangesVersion", data->pendingRemoveRanges.begin()->first);
			ASSERT(newOldestVersion <= data->pendingRemoveRanges.begin()->first);
			if (newOldestVersion == data->pendingRemoveRanges.begin()->first) {
				for (const auto& range : data->pendingRemoveRanges.begin()->second) {
					data->storage.removeRange(range);
					TraceEvent(SevVerbose, "RemoveKVSRange", data->thisServerID).detail("Range", range);
				}
				data->pendingRemoveRanges.erase(data->pendingRemoveRanges.begin());
			}
			removeKVSRanges = false;
		}

		if (requireCheckpoint) {
			// `pendingCheckpoints` is a queue of checkpoint requests ordered by their versoins, and
			// `newOldestVersion` is chosen such that it is no larger than the smallest pending checkpoing
			// version. When the exact desired checkpoint version is committed, updateStorage() is blocked
			// and a checkpoint will be created at that version from the underlying storage engine.
			// Note a pending checkpoint is only dequeued after the corresponding checkpoint is created
			// successfully.
			TraceEvent(SevDebug, "CheckpointVersionDurable", data->thisServerID)
			    .detail("NewDurableVersion", newOldestVersion)
			    .detail("DesiredVersion", desiredVersion)
			    .detail("SmallestCheckPointVersion", data->pendingCheckpoints.begin()->first);
			// newOldestVersion could be smaller than the desired version due to byte limit.
			ASSERT(newOldestVersion <= data->pendingCheckpoints.begin()->first);
			if (newOldestVersion == data->pendingCheckpoints.begin()->first) {
				std::vector<Future<Void>> createCheckpoints;
				// TODO: Combine these checkpoints if necessary.
				for (int idx = 0; idx < data->pendingCheckpoints.begin()->second.size(); ++idx) {
					createCheckpoints.push_back(createCheckpoint(data, data->pendingCheckpoints.begin()->second[idx]));
				}
				wait(waitForAll(createCheckpoints));
				// Erase the pending checkpoint after the checkpoint has been created successfully.
				ASSERT(newOldestVersion == data->pendingCheckpoints.begin()->first);
				data->pendingCheckpoints.erase(data->pendingCheckpoints.begin());
			}
			requireCheckpoint = false;
		}

		if (newOldestVersion > data->rebootAfterDurableVersion) {
			TraceEvent("RebootWhenDurableTriggered", data->thisServerID)
			    .detail("NewOldestVersion", newOldestVersion)
			    .detail("RebootAfterDurableVersion", data->rebootAfterDurableVersion);
			// To avoid brokenPromise error, which is caused by the sender of the durableInProgress (i.e., this
			// process) never sets durableInProgress, we should set durableInProgress before send the
			// please_reboot() error. Otherwise, in the race situation when storage server receives both reboot and
			// brokenPromise of durableInProgress, the worker of the storage server will die.
			// We will eventually end up with no worker for storage server role.
			// The data distributor's buildTeam() will get stuck in building a team
			durableInProgress.sendError(please_reboot());
			throw please_reboot();
		}

		curFeed = 0;
		while (curFeed < updatedChangeFeeds.size()) {
			auto info = data->uidChangeFeed.find(updatedChangeFeeds[curFeed]);
			if (info != data->uidChangeFeed.end()) {
				while (!info->second->mutations.empty() && info->second->mutations.front().version < newOldestVersion) {
					info->second->mutations.pop_front();
				}
				ASSERT(info->second->storageVersion >= info->second->durableVersion);
				info->second->durableVersion = info->second->storageVersion;
				wait(yield(TaskPriority::UpdateStorage));
			}
			curFeed++;
		}

		// if commit included fetched data from this change feed, update the fetched durable version
		curFeed = 0;
		while (curFeed < feedFetchVersions.size()) {
			auto info = data->uidChangeFeed.find(feedFetchVersions[curFeed].first);
			// Don't update if the feed is pending cleanup. Either it will get cleaned up and destroyed, or it will get
			// fetched again, where the fetch version will get reset.
			if (info != data->uidChangeFeed.end() && !data->changeFeedCleanupDurable.count(info->second->id)) {
				if (feedFetchVersions[curFeed].second > info->second->durableFetchVersion.get()) {
					info->second->durableFetchVersion.set(feedFetchVersions[curFeed].second);
				}
				if (feedFetchVersions[curFeed].second == info->second->fetchVersion) {
					// haven't fetched anything else since commit started, reset fetch version
					info->second->fetchVersion = invalidVersion;
				}
			}
			curFeed++;
		}

		// remove any entries from changeFeedCleanupPending that were persisted
		auto cfCleanup = data->changeFeedCleanupDurable.begin();
		while (cfCleanup != data->changeFeedCleanupDurable.end()) {
			if (cfCleanup->second <= newOldestVersion) {
				// remove from the data structure here, if it wasn't added back by another fetch or something
				auto feed = data->uidChangeFeed.find(cfCleanup->first);
				ASSERT(feed != data->uidChangeFeed.end());
				if (feed->second->removing) {
					auto rs = data->keyChangeFeed.modify(feed->second->range);
					for (auto r = rs.begin(); r != rs.end(); ++r) {
						auto& feedList = r->value();
						for (int i = 0; i < feedList.size(); i++) {
							if (feedList[i]->id == cfCleanup->first) {
								swapAndPop(&feedList, i--);
							}
						}
					}
					data->keyChangeFeed.coalesce(feed->second->range.contents());

					data->uidChangeFeed.erase(feed);
				} else {
					CODE_PROBE(true, "Feed re-fetched after remove");
				}
				cfCleanup = data->changeFeedCleanupDurable.erase(cfCleanup);
			} else {
				cfCleanup++;
			}
		}

		durableInProgress.send(Void());
		wait(delay(0, TaskPriority::UpdateStorage)); // Setting durableInProgess could cause the storage server to
		                                             // shut down, so delay to check for cancellation

		// Taking and releasing the durableVersionLock ensures that no eager reads both begin before the commit was
		// effective and are applied after we change the durable version. Also ensure that we have to lock while
		// calling changeDurableVersion, because otherwise the latest version of mutableData might be partially
		// loaded.
		state double beforeSSDurableVersionUpdate = now();
		wait(data->durableVersionLock.take());
		data->popVersion(data->durableVersion.get() + 1);

		while (!changeDurableVersion(data, newOldestVersion)) {
			if (g_network->check_yield(TaskPriority::UpdateStorage)) {
				data->durableVersionLock.release();
				wait(delay(0, TaskPriority::UpdateStorage));
				wait(data->durableVersionLock.take());
			}
		}

		data->durableVersionLock.release();
		data->ssDurableVersionUpdateLatencyHistogram->sampleSeconds(now() - beforeSSDurableVersionUpdate);

		//TraceEvent("StorageServerDurable", data->thisServerID).detail("Version", newOldestVersion);
		data->fetchKeysBytesBudget = SERVER_KNOBS->STORAGE_FETCH_BYTES;

		data->fetchKeysBudgetUsed.set(false);
		if (!data->fetchKeysBudgetUsed.get()) {
			wait(durableDelay || data->fetchKeysBudgetUsed.onChange());
		}
	}
}

#ifndef __INTEL_COMPILER
#pragma endregion
#endif

////////////////////////////////// StorageServerDisk ///////////////////////////////////////
#ifndef __INTEL_COMPILER
#pragma region StorageServerDisk
#endif

void StorageServerDisk::makeNewStorageServerDurable(const bool shardAware) {
	if (shardAware) {
		storage->set(persistShardAwareFormat);
	} else {
		storage->set(persistFormat);
	}
	storage->set(KeyValueRef(persistID, BinaryWriter::toValue(data->thisServerID, Unversioned())));
	if (data->tssPairID.present()) {
		storage->set(KeyValueRef(persistTssPairID, BinaryWriter::toValue(data->tssPairID.get(), Unversioned())));
	}
	ASSERT(data->clusterId.getFuture().isReady() && data->clusterId.getFuture().get().isValid());
	storage->set(
	    KeyValueRef(persistClusterIdKey, BinaryWriter::toValue(data->clusterId.getFuture().get(), Unversioned())));
	storage->set(KeyValueRef(persistVersion, BinaryWriter::toValue(data->version.get(), Unversioned())));

	if (shardAware) {
		storage->set(KeyValueRef(persistStorageServerShardKeys.begin.toString(),
		                         ObjectWriter::toValue(StorageServerShard::notAssigned(allKeys, 0), IncludeVersion())));
	} else {
		storage->set(KeyValueRef(persistShardAssignedKeys.begin.toString(), LiteralStringRef("0")));
		storage->set(KeyValueRef(persistShardAvailableKeys.begin.toString(), LiteralStringRef("0")));
	}

	auto view = data->tenantMap.atLatest();
	for (auto itr = view.begin(); itr != view.end(); ++itr) {
		storage->set(KeyValueRef(itr.key().withPrefix(persistTenantMapKeys.begin), itr->encode()));
	}
}

void setAvailableStatus(StorageServer* self, KeyRangeRef keys, bool available) {
	// ASSERT( self->debug_inApplyUpdate );
	ASSERT(!keys.empty());

	auto& mLV = self->addVersionToMutationLog(self->data().getLatestVersion());

	KeyRange availableKeys = KeyRangeRef(persistShardAvailableKeys.begin.toString() + keys.begin.toString(),
	                                     persistShardAvailableKeys.begin.toString() + keys.end.toString());
	//TraceEvent("SetAvailableStatus", self->thisServerID).detail("Version", mLV.version).detail("RangeBegin", availableKeys.begin).detail("RangeEnd", availableKeys.end);

	self->addMutationToMutationLog(mLV, MutationRef(MutationRef::ClearRange, availableKeys.begin, availableKeys.end));
	++self->counters.kvSystemClearRanges;
	self->addMutationToMutationLog(mLV,
	                               MutationRef(MutationRef::SetValue,
	                                           availableKeys.begin,
	                                           available ? LiteralStringRef("1") : LiteralStringRef("0")));
	if (keys.end != allKeys.end) {
		bool endAvailable = self->shards.rangeContaining(keys.end)->value()->isCFInVersionedData();
		self->addMutationToMutationLog(mLV,
		                               MutationRef(MutationRef::SetValue,
		                                           availableKeys.end,
		                                           endAvailable ? LiteralStringRef("1") : LiteralStringRef("0")));
	}

	// When a shard is moved out, delete all related checkpoints created for data move.
	if (!available) {
		for (auto& [id, checkpoint] : self->checkpoints) {
			if (checkpoint.range.intersects(keys)) {
				Key persistCheckpointKey(persistCheckpointKeys.begin.toString() + checkpoint.checkpointID.toString());
				checkpoint.setState(CheckpointMetaData::Deleting);
				self->addMutationToMutationLog(
				    mLV, MutationRef(MutationRef::SetValue, persistCheckpointKey, checkpointValue(checkpoint)));
			}
			self->actors.add(deleteCheckpointQ(self, mLV.version + 1, checkpoint));
			TraceEvent("SSDeleteCheckpointScheduled", self->thisServerID)
			    .detail("MovedOutRange", keys.toString())
			    .detail("Checkpoint", checkpoint.toString())
			    .detail("DeleteVersion", mLV.version + 1);
		}
	}
}

void updateStorageShard(StorageServer* data, StorageServerShard shard) {
	if (shard.getShardState() == StorageServerShard::ReadWritePending) {
		shard.setShardState(StorageServerShard::ReadWrite);
	}

	auto& mLV = data->addVersionToMutationLog(data->data().getLatestVersion());

	KeyRange shardKeys = KeyRangeRef(persistStorageServerShardKeys.begin.toString() + shard.range.begin.toString(),
	                                 persistStorageServerShardKeys.begin.toString() + shard.range.end.toString());
	TraceEvent(SevVerbose, "UpdateStorageServerShard", data->thisServerID)
	    .detail("Version", mLV.version)
	    .detail("Shard", shard.toString())
	    .detail("ShardKey", shardKeys.begin);

	data->addMutationToMutationLog(mLV, MutationRef(MutationRef::ClearRange, shardKeys.begin, shardKeys.end));
	++data->counters.kvSystemClearRanges;
	data->addMutationToMutationLog(
	    mLV, MutationRef(MutationRef::SetValue, shardKeys.begin, ObjectWriter::toValue(shard, IncludeVersion())));
	if (shard.range.end != allKeys.end) {
		StorageServerShard endShard = data->shards.rangeContaining(shard.range.end)->value()->toStorageServerShard();
		if (endShard.getShardState() == StorageServerShard::ReadWritePending) {
			endShard.setShardState(StorageServerShard::ReadWrite);
		}
		TraceEvent(SevVerbose, "UpdateStorageServerShardEndShard", data->thisServerID)
		    .detail("Version", mLV.version)
		    .detail("Shard", endShard.toString())
		    .detail("ShardKey", shardKeys.end);
		data->addMutationToMutationLog(
		    mLV, MutationRef(MutationRef::SetValue, shardKeys.end, ObjectWriter::toValue(endShard, IncludeVersion())));
	}
}

void setAssignedStatus(StorageServer* self, KeyRangeRef keys, bool nowAssigned) {
	ASSERT(!keys.empty());
	auto& mLV = self->addVersionToMutationLog(self->data().getLatestVersion());
	KeyRange assignedKeys = KeyRangeRef(persistShardAssignedKeys.begin.toString() + keys.begin.toString(),
	                                    persistShardAssignedKeys.begin.toString() + keys.end.toString());
	//TraceEvent("SetAssignedStatus", self->thisServerID).detail("Version", mLV.version).detail("RangeBegin", assignedKeys.begin).detail("RangeEnd", assignedKeys.end);
	self->addMutationToMutationLog(mLV, MutationRef(MutationRef::ClearRange, assignedKeys.begin, assignedKeys.end));
	++self->counters.kvSystemClearRanges;
	self->addMutationToMutationLog(mLV,
	                               MutationRef(MutationRef::SetValue,
	                                           assignedKeys.begin,
	                                           nowAssigned ? LiteralStringRef("1") : LiteralStringRef("0")));
	if (keys.end != allKeys.end) {
		bool endAssigned = self->shards.rangeContaining(keys.end)->value()->assigned();
		self->addMutationToMutationLog(mLV,
		                               MutationRef(MutationRef::SetValue,
		                                           assignedKeys.end,
		                                           endAssigned ? LiteralStringRef("1") : LiteralStringRef("0")));
	}
}

void StorageServerDisk::clearRange(KeyRangeRef keys) {
	storage->clear(keys);
	++(*kvClearRanges);
}

void StorageServerDisk::writeKeyValue(KeyValueRef kv) {
	storage->set(kv);
	*kvCommitLogicalBytes += kv.expectedSize();
}

void StorageServerDisk::writeMutation(MutationRef mutation) {
	if (mutation.type == MutationRef::SetValue) {
		storage->set(KeyValueRef(mutation.param1, mutation.param2));
		*kvCommitLogicalBytes += mutation.expectedSize();
	} else if (mutation.type == MutationRef::ClearRange) {
		storage->clear(KeyRangeRef(mutation.param1, mutation.param2));
		++(*kvClearRanges);
	} else
		ASSERT(false);
}

void StorageServerDisk::writeMutations(const VectorRef<MutationRef>& mutations,
                                       Version debugVersion,
                                       const char* debugContext) {
	for (const auto& m : mutations) {
		DEBUG_MUTATION(debugContext, debugVersion, m, data->thisServerID);
		if (m.type == MutationRef::SetValue) {
			storage->set(KeyValueRef(m.param1, m.param2));
			*kvCommitLogicalBytes += m.expectedSize();
		} else if (m.type == MutationRef::ClearRange) {
			storage->clear(KeyRangeRef(m.param1, m.param2));
			++(*kvClearRanges);
		}
	}
}

bool StorageServerDisk::makeVersionMutationsDurable(Version& prevStorageVersion,
                                                    Version newStorageVersion,
                                                    int64_t& bytesLeft,
                                                    UnlimitedCommitBytes unlimitedCommitBytes) {
	if (!unlimitedCommitBytes && bytesLeft <= 0)
		return true;

	// Apply mutations from the mutationLog
	auto u = data->getMutationLog().upper_bound(prevStorageVersion);
	if (u != data->getMutationLog().end() && u->first <= newStorageVersion) {
		VerUpdateRef const& v = u->second;
		ASSERT(v.version > prevStorageVersion && v.version <= newStorageVersion);
		// TODO(alexmiller): Update to version tracking.
		// DEBUG_KEY_RANGE("makeVersionMutationsDurable", v.version, KeyRangeRef());
		writeMutations(v.mutations, v.version, "makeVersionDurable");
		for (const auto& m : v.mutations)
			bytesLeft -= mvccStorageBytes(m);
		prevStorageVersion = v.version;
		return false;
	} else {
		prevStorageVersion = newStorageVersion;
		return true;
	}
}

// Update data->storage to persist the changes from (data->storageVersion(),version]
void StorageServerDisk::makeVersionDurable(Version version) {
	storage->set(KeyValueRef(persistVersion, BinaryWriter::toValue(version, Unversioned())));
	*kvCommitLogicalBytes += persistVersion.expectedSize() + sizeof(Version);

	// TraceEvent("MakeDurable", data->thisServerID)
	//     .detail("FromVersion", prevStorageVersion)
	//     .detail("ToVersion", version);
}

// Update data->storage to persist tss quarantine state
void StorageServerDisk::makeTssQuarantineDurable() {
	storage->set(KeyValueRef(persistTssQuarantine, LiteralStringRef("1")));
}

void StorageServerDisk::changeLogProtocol(Version version, ProtocolVersion protocol) {
	data->addMutationToMutationLogOrStorage(
	    version,
	    MutationRef(MutationRef::SetValue, persistLogProtocol, BinaryWriter::toValue(protocol, Unversioned())));
}

ACTOR Future<Void> applyByteSampleResult(StorageServer* data,
                                         IKeyValueStore* storage,
                                         Key begin,
                                         Key end,
                                         std::vector<Standalone<VectorRef<KeyValueRef>>>* results = nullptr) {
	state int totalFetches = 0;
	state int totalKeys = 0;
	state int totalBytes = 0;
	loop {
		RangeResult bs = wait(storage->readRange(
		    KeyRangeRef(begin, end), SERVER_KNOBS->STORAGE_LIMIT_BYTES, SERVER_KNOBS->STORAGE_LIMIT_BYTES));
		if (results) {
			results->push_back(bs.castTo<VectorRef<KeyValueRef>>());
			data->bytesRestored += bs.logicalSize();
			data->counters.kvScanBytes += bs.logicalSize();
		}
		int rangeSize = bs.expectedSize();
		totalFetches++;
		totalKeys += bs.size();
		totalBytes += rangeSize;
		for (int j = 0; j < bs.size(); j++) {
			KeyRef key = bs[j].key.removePrefix(persistByteSampleKeys.begin);
			if (!data->byteSampleClears.rangeContaining(key).value()) {
				data->metrics.byteSample.sample.insert(
				    key, BinaryReader::fromStringRef<int32_t>(bs[j].value, Unversioned()), false);
			}
		}
		if (rangeSize >= SERVER_KNOBS->STORAGE_LIMIT_BYTES) {
			Key nextBegin = keyAfter(bs.back().key);
			data->byteSampleClears.insert(KeyRangeRef(begin, nextBegin).removePrefix(persistByteSampleKeys.begin),
			                              true);
			data->byteSampleClearsTooLarge.set(data->byteSampleClears.size() >
			                                   SERVER_KNOBS->MAX_BYTE_SAMPLE_CLEAR_MAP_SIZE);
			begin = nextBegin;
			if (begin == end) {
				break;
			}
		} else {
			data->byteSampleClears.insert(KeyRangeRef(begin.removePrefix(persistByteSampleKeys.begin),
			                                          end == persistByteSampleKeys.end
			                                              ? LiteralStringRef("\xff\xff\xff")
			                                              : end.removePrefix(persistByteSampleKeys.begin)),
			                              true);
			data->byteSampleClearsTooLarge.set(data->byteSampleClears.size() >
			                                   SERVER_KNOBS->MAX_BYTE_SAMPLE_CLEAR_MAP_SIZE);
			break;
		}

		if (!results) {
			wait(delay(SERVER_KNOBS->BYTE_SAMPLE_LOAD_DELAY));
		}
	}
	TraceEvent("RecoveredByteSampleRange", data->thisServerID)
	    .detail("Begin", begin)
	    .detail("End", end)
	    .detail("Fetches", totalFetches)
	    .detail("Keys", totalKeys)
	    .detail("ReadBytes", totalBytes);
	return Void();
}

ACTOR Future<Void> restoreByteSample(StorageServer* data,
                                     IKeyValueStore* storage,
                                     Promise<Void> byteSampleSampleRecovered,
                                     Future<Void> startRestore) {
	state std::vector<Standalone<VectorRef<KeyValueRef>>> byteSampleSample;
	wait(applyByteSampleResult(
	    data, storage, persistByteSampleSampleKeys.begin, persistByteSampleSampleKeys.end, &byteSampleSample));
	byteSampleSampleRecovered.send(Void());
	wait(startRestore);
	wait(delay(SERVER_KNOBS->BYTE_SAMPLE_START_DELAY));

	size_t bytes_per_fetch = 0;
	// Since the expected size also includes (as of now) the space overhead of the container, we calculate our own
	// number here
	for (auto& it : byteSampleSample) {
		for (auto& kv : it) {
			bytes_per_fetch += BinaryReader::fromStringRef<int32_t>(kv.value, Unversioned());
		}
	}
	bytes_per_fetch = (bytes_per_fetch / SERVER_KNOBS->BYTE_SAMPLE_LOAD_PARALLELISM) + 1;

	state std::vector<Future<Void>> sampleRanges;
	int accumulatedSize = 0;
	Key lastStart =
	    persistByteSampleKeys.begin; // make sure the first range starts at the absolute beginning of the byte sample
	for (auto& it : byteSampleSample) {
		for (auto& kv : it) {
			if (accumulatedSize >= bytes_per_fetch) {
				accumulatedSize = 0;
				Key realKey = kv.key.removePrefix(persistByteSampleKeys.begin);
				sampleRanges.push_back(applyByteSampleResult(data, storage, lastStart, realKey));
				lastStart = realKey;
			}
			accumulatedSize += BinaryReader::fromStringRef<int32_t>(kv.value, Unversioned());
		}
	}
	// make sure that the last range goes all the way to the end of the byte sample
	sampleRanges.push_back(applyByteSampleResult(data, storage, lastStart, persistByteSampleKeys.end));

	wait(waitForAll(sampleRanges));
	TraceEvent("RecoveredByteSampleChunkedRead", data->thisServerID).detail("Ranges", sampleRanges.size());

	if (BUGGIFY)
		wait(delay(deterministicRandom()->random01() * 10.0));

	return Void();
}

// Reads the cluster ID from the transaction state store.
ACTOR Future<UID> getClusterId(StorageServer* self) {
	state ReadYourWritesTransaction tr(self->cx);
	loop {
		try {
			self->cx->invalidateCache(Key(), systemKeys);
			tr.setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
			tr.setOption(FDBTransactionOptions::LOCK_AWARE);
			Optional<Value> clusterId = wait(tr.get(clusterIdKey));
			ASSERT(clusterId.present());
			return BinaryReader::fromStringRef<UID>(clusterId.get(), Unversioned());
		} catch (Error& e) {
			wait(tr.onError(e));
		}
	}
}

// Read the cluster ID from the transaction state store and persist it to local
// storage. This function should only be necessary during an upgrade when the
// prior FDB version did not support cluster IDs. The normal path for storage
// server recruitment will include the cluster ID in the initial recruitment
// message.
ACTOR Future<Void> persistClusterId(StorageServer* self) {
	state Transaction tr(self->cx);
	loop {
		try {
			Optional<Value> clusterId = wait(tr.get(clusterIdKey));
			if (clusterId.present()) {
				auto uid = BinaryReader::fromStringRef<UID>(clusterId.get(), Unversioned());
				self->storage.writeKeyValue(
				    KeyValueRef(persistClusterIdKey, BinaryWriter::toValue(uid, Unversioned())));
				// Purposely not calling commit here, and letting the recurring
				// commit handle save this value to disk
				self->clusterId.send(uid);
			}
			break;
		} catch (Error& e) {
			wait(tr.onError(e));
		}
	}
	return Void();
}

ACTOR Future<bool> restoreDurableState(StorageServer* data, IKeyValueStore* storage) {
	state Future<Optional<Value>> fFormat = storage->readValue(persistFormat.key);
	state Future<Optional<Value>> fID = storage->readValue(persistID);
	state Future<Optional<Value>> fClusterID = storage->readValue(persistClusterIdKey);
	state Future<Optional<Value>> ftssPairID = storage->readValue(persistTssPairID);
	state Future<Optional<Value>> fssPairID = storage->readValue(persistSSPairID);
	state Future<Optional<Value>> fTssQuarantine = storage->readValue(persistTssQuarantine);
	state Future<Optional<Value>> fVersion = storage->readValue(persistVersion);
	state Future<Optional<Value>> fLogProtocol = storage->readValue(persistLogProtocol);
	state Future<Optional<Value>> fPrimaryLocality = storage->readValue(persistPrimaryLocality);
	state Future<RangeResult> fShardAssigned = storage->readRange(persistShardAssignedKeys);
	state Future<RangeResult> fShardAvailable = storage->readRange(persistShardAvailableKeys);
	state Future<RangeResult> fChangeFeeds = storage->readRange(persistChangeFeedKeys);
	state Future<RangeResult> fPendingCheckpoints = storage->readRange(persistPendingCheckpointKeys);
	state Future<RangeResult> fCheckpoints = storage->readRange(persistCheckpointKeys);
	state Future<RangeResult> fTenantMap = storage->readRange(persistTenantMapKeys);
	state Future<RangeResult> fStorageShards = storage->readRange(persistStorageServerShardKeys);

	state Promise<Void> byteSampleSampleRecovered;
	state Promise<Void> startByteSampleRestore;
	data->byteSampleRecovery =
	    restoreByteSample(data, storage, byteSampleSampleRecovered, startByteSampleRestore.getFuture());

	TraceEvent("ReadingDurableState", data->thisServerID).log();
	wait(waitForAll(std::vector{
	    fFormat, fID, fClusterID, ftssPairID, fssPairID, fTssQuarantine, fVersion, fLogProtocol, fPrimaryLocality }));
	wait(waitForAll(std::vector{ fShardAssigned,
	                             fShardAvailable,
	                             fChangeFeeds,
	                             fPendingCheckpoints,
	                             fCheckpoints,
	                             fTenantMap,
	                             fStorageShards }));
	wait(byteSampleSampleRecovered.getFuture());
	TraceEvent("RestoringDurableState", data->thisServerID).log();

	if (!fFormat.get().present()) {
		// The DB was never initialized
		TraceEvent("DBNeverInitialized", data->thisServerID).log();
		storage->dispose();
		data->thisServerID = UID();
		data->sk = Key();
		return false;
	} else {
		TraceEvent(SevVerbose, "RestoringStorageServerWithPhysicalShards", data->thisServerID).log();
		data->shardAware = fFormat.get().get() == persistShardAwareFormat.value;
	}
	data->bytesRestored += fFormat.get().expectedSize();
	if (!persistFormatReadableRange.contains(fFormat.get().get())) {
		TraceEvent(SevError, "UnsupportedDBFormat")
		    .detail("Format", fFormat.get().get().toString())
		    .detail("Expected", persistFormat.value.toString());
		throw worker_recovery_failed();
	}
	data->thisServerID = BinaryReader::fromStringRef<UID>(fID.get().get(), Unversioned());
	data->bytesRestored += fID.get().expectedSize();
	if (ftssPairID.get().present()) {
		data->setTssPair(BinaryReader::fromStringRef<UID>(ftssPairID.get().get(), Unversioned()));
		data->bytesRestored += ftssPairID.get().expectedSize();
	}

	if (fssPairID.get().present()) {
		data->setSSWithTssPair(BinaryReader::fromStringRef<UID>(fssPairID.get().get(), Unversioned()));
		data->bytesRestored += fssPairID.get().expectedSize();
	}

	if (fClusterID.get().present()) {
		data->clusterId.send(BinaryReader::fromStringRef<UID>(fClusterID.get().get(), Unversioned()));
		data->bytesRestored += fClusterID.get().expectedSize();
	} else {
		CODE_PROBE(true, "storage server upgraded to version supporting cluster IDs");
		data->actors.add(persistClusterId(data));
	}

	// It's a bit sketchy to rely on an untrusted storage engine to persist its quarantine state when the quarantine
	// state means the storage engine already had a durability or correctness error, but it should get
	// re-quarantined very quickly because of a mismatch if it starts trying to do things again
	if (fTssQuarantine.get().present()) {
		CODE_PROBE(true, "TSS restarted while quarantined");
		data->tssInQuarantine = true;
		data->bytesRestored += fTssQuarantine.get().expectedSize();
	}

	data->sk = serverKeysPrefixFor((data->tssPairID.present()) ? data->tssPairID.get() : data->thisServerID)
	               .withPrefix(systemKeys.begin); // FFFF/serverKeys/[this server]/

	if (fLogProtocol.get().present()) {
		data->logProtocol = BinaryReader::fromStringRef<ProtocolVersion>(fLogProtocol.get().get(), Unversioned());
		data->bytesRestored += fLogProtocol.get().expectedSize();
	}

	if (fPrimaryLocality.get().present()) {
		data->primaryLocality = BinaryReader::fromStringRef<int8_t>(fPrimaryLocality.get().get(), Unversioned());
		data->bytesRestored += fPrimaryLocality.get().expectedSize();
	}

	state Version version = BinaryReader::fromStringRef<Version>(fVersion.get().get(), Unversioned());
	debug_checkRestoredVersion(data->thisServerID, version, "StorageServer");
	data->setInitialVersion(version);
	data->bytesRestored += fVersion.get().expectedSize();

	state RangeResult pendingCheckpoints = fPendingCheckpoints.get();
	state int pCLoc;
	for (pCLoc = 0; pCLoc < pendingCheckpoints.size(); ++pCLoc) {
		CheckpointMetaData metaData = decodeCheckpointValue(pendingCheckpoints[pCLoc].value);
		data->pendingCheckpoints[metaData.version].push_back(metaData);
		wait(yield());
	}

	state RangeResult checkpoints = fCheckpoints.get();
	state int cLoc;
	for (cLoc = 0; cLoc < checkpoints.size(); ++cLoc) {
		CheckpointMetaData metaData = decodeCheckpointValue(checkpoints[cLoc].value);
		data->checkpoints[metaData.checkpointID] = metaData;
		if (metaData.getState() == CheckpointMetaData::Deleting) {
			data->actors.add(deleteCheckpointQ(data, version, metaData));
		}
		wait(yield());
	}

	state RangeResult available = fShardAvailable.get();
	data->bytesRestored += available.logicalSize();
	state int availableLoc;
	for (availableLoc = 0; availableLoc < available.size(); availableLoc++) {
		KeyRangeRef keys(available[availableLoc].key.removePrefix(persistShardAvailableKeys.begin),
		                 availableLoc + 1 == available.size()
		                     ? allKeys.end
		                     : available[availableLoc + 1].key.removePrefix(persistShardAvailableKeys.begin));
		ASSERT(!keys.empty());

		bool nowAvailable = available[availableLoc].value != LiteralStringRef("0");
		/*if(nowAvailable)
		  TraceEvent("AvailableShard", data->thisServerID).detail("RangeBegin", keys.begin).detail("RangeEnd", keys.end);*/
		data->newestAvailableVersion.insert(keys, nowAvailable ? latestVersion : invalidVersion);
		wait(yield());
	}

	state RangeResult assigned = fShardAssigned.get();
	data->bytesRestored += assigned.logicalSize();
	state int assignedLoc;
	if (data->shardAware) {
		// TODO(psm): Avoid copying RangeResult around.
		wait(restoreShards(data, version, fStorageShards.get(), assigned, available));
	} else {
		for (assignedLoc = 0; assignedLoc < assigned.size(); assignedLoc++) {
			KeyRangeRef keys(assigned[assignedLoc].key.removePrefix(persistShardAssignedKeys.begin),
			                 assignedLoc + 1 == assigned.size()
			                     ? allKeys.end
			                     : assigned[assignedLoc + 1].key.removePrefix(persistShardAssignedKeys.begin));
			ASSERT(!keys.empty());
			bool nowAssigned = assigned[assignedLoc].value != LiteralStringRef("0");
			/*if(nowAssigned)
			  TraceEvent("AssignedShard", data->thisServerID).detail("RangeBegin", keys.begin).detail("RangeEnd", keys.end);*/
			changeServerKeys(data, keys, nowAssigned, version, CSK_RESTORE);

			if (!nowAssigned)
				ASSERT(data->newestAvailableVersion.allEqual(keys, invalidVersion));
			wait(yield());
		}
	}

	state RangeResult changeFeeds = fChangeFeeds.get();
	data->bytesRestored += changeFeeds.logicalSize();
	state int feedLoc;
	for (feedLoc = 0; feedLoc < changeFeeds.size(); feedLoc++) {
		Key changeFeedId = changeFeeds[feedLoc].key.removePrefix(persistChangeFeedKeys.begin);
		KeyRange changeFeedRange;
		Version popVersion, stopVersion;
		std::tie(changeFeedRange, popVersion, stopVersion) = decodeChangeFeedSSValue(changeFeeds[feedLoc].value);
		TraceEvent(SevDebug, "RestoringChangeFeed", data->thisServerID)
		    .detail("RangeID", changeFeedId)
		    .detail("Range", changeFeedRange)
		    .detail("StopVersion", stopVersion)
		    .detail("PopVer", popVersion);
		Reference<ChangeFeedInfo> changeFeedInfo(new ChangeFeedInfo());
		changeFeedInfo->range = changeFeedRange;
		changeFeedInfo->id = changeFeedId;
		changeFeedInfo->durableVersion = version;
		changeFeedInfo->storageVersion = version;
		changeFeedInfo->emptyVersion = popVersion - 1;
		changeFeedInfo->stopVersion = stopVersion;
		data->uidChangeFeed[changeFeedId] = changeFeedInfo;
		auto rs = data->keyChangeFeed.modify(changeFeedRange);
		for (auto r = rs.begin(); r != rs.end(); ++r) {
			r->value().push_back(changeFeedInfo);
		}
		wait(yield());
	}
	data->keyChangeFeed.coalesce(allKeys);

	state RangeResult tenantMap = fTenantMap.get();
	state int tenantMapLoc;
	for (tenantMapLoc = 0; tenantMapLoc < tenantMap.size(); tenantMapLoc++) {
		auto const& result = tenantMap[tenantMapLoc];
		TenantName tenantName = result.key.substr(persistTenantMapKeys.begin.size());
		TenantMapEntry tenantEntry = TenantMapEntry::decode(result.value);

		data->tenantMap.insert(tenantName, tenantEntry);
		data->tenantPrefixIndex.insert(tenantEntry.prefix, tenantName);

		TraceEvent("RestoringTenant", data->thisServerID)
		    .detail("Key", tenantMap[tenantMapLoc].key)
		    .detail("TenantName", tenantName)
		    .detail("Prefix", tenantEntry.prefix);

		wait(yield());
	}

	// TODO: why is this seemingly random delay here?
	wait(delay(0.0001));

	{
		// Erase data which isn't available (it is from some fetch at a later version)
		// SOMEDAY: Keep track of keys that might be fetching, make sure we don't have any data elsewhere?
		for (auto it = data->newestAvailableVersion.ranges().begin(); it != data->newestAvailableVersion.ranges().end();
		     ++it) {
			if (it->value() == invalidVersion) {
				KeyRangeRef clearRange(it->begin(), it->end());
				++data->counters.kvSystemClearRanges;
				// TODO(alexmiller): Figure out how to selectively enable spammy data distribution events.
				// DEBUG_KEY_RANGE("clearInvalidVersion", invalidVersion, clearRange);
				storage->clear(clearRange);
				++data->counters.kvSystemClearRanges;
				data->byteSampleApplyClear(clearRange, invalidVersion);
			}
		}
	}

	validate(data, true);
	startByteSampleRestore.send(Void());

	return true;
}

Future<bool> StorageServerDisk::restoreDurableState() {
	return ::restoreDurableState(data, storage);
}

// Determines whether a key-value pair should be included in a byte sample
// Also returns size information about the sample
ByteSampleInfo isKeyValueInSample(KeyValueRef keyValue) {
	ByteSampleInfo info;

	const KeyRef key = keyValue.key;
	info.size = key.size() + keyValue.value.size();

	uint32_t a = 0;
	uint32_t b = 0;
	hashlittle2(key.begin(), key.size(), &a, &b);

	double probability =
	    (double)info.size / (key.size() + SERVER_KNOBS->BYTE_SAMPLING_OVERHEAD) / SERVER_KNOBS->BYTE_SAMPLING_FACTOR;
	info.inSample = a / ((1 << 30) * 4.0) < probability;
	info.sampledSize = info.size / std::min(1.0, probability);

	return info;
}

void StorageServer::addMutationToMutationLogOrStorage(Version ver, MutationRef m) {
	if (ver != invalidVersion) {
		addMutationToMutationLog(addVersionToMutationLog(ver), m);
	} else {
		storage.writeMutation(m);
		byteSampleApplyMutation(m, ver);
	}
}

void StorageServer::byteSampleApplySet(KeyValueRef kv, Version ver) {
	// Update byteSample in memory and (eventually) on disk and notify waiting metrics

	ByteSampleInfo sampleInfo = isKeyValueInSample(kv);
	auto& byteSample = metrics.byteSample.sample;

	int64_t delta = 0;
	const KeyRef key = kv.key;

	auto old = byteSample.find(key);
	if (old != byteSample.end())
		delta = -byteSample.getMetric(old);
	if (sampleInfo.inSample) {
		delta += sampleInfo.sampledSize;
		byteSample.insert(key, sampleInfo.sampledSize);
		addMutationToMutationLogOrStorage(ver,
		                                  MutationRef(MutationRef::SetValue,
		                                              key.withPrefix(persistByteSampleKeys.begin),
		                                              BinaryWriter::toValue(sampleInfo.sampledSize, Unversioned())));
	} else {
		bool any = old != byteSample.end();
		if (!byteSampleRecovery.isReady()) {
			if (!byteSampleClears.rangeContaining(key).value()) {
				byteSampleClears.insert(key, true);
				byteSampleClearsTooLarge.set(byteSampleClears.size() > SERVER_KNOBS->MAX_BYTE_SAMPLE_CLEAR_MAP_SIZE);
				any = true;
			}
		}
		if (any) {
			byteSample.erase(old);
			auto diskRange = singleKeyRange(key.withPrefix(persistByteSampleKeys.begin));
			addMutationToMutationLogOrStorage(ver,
			                                  MutationRef(MutationRef::ClearRange, diskRange.begin, diskRange.end));
			++counters.kvSystemClearRanges;
		}
	}

	if (delta)
		metrics.notifyBytes(key, delta);
}

void StorageServer::byteSampleApplyClear(KeyRangeRef range, Version ver) {
	// Update byteSample in memory and (eventually) on disk via the mutationLog and notify waiting metrics

	auto& byteSample = metrics.byteSample.sample;
	bool any = false;

	if (range.begin < allKeys.end) {
		// NotifyBytes should not be called for keys past allKeys.end
		KeyRangeRef searchRange = KeyRangeRef(range.begin, std::min(range.end, allKeys.end));
		counters.sampledBytesCleared += byteSample.sumRange(searchRange.begin, searchRange.end);

		auto r = metrics.waitMetricsMap.intersectingRanges(searchRange);
		for (auto shard = r.begin(); shard != r.end(); ++shard) {
			KeyRangeRef intersectingRange = shard.range() & range;
			int64_t bytes = byteSample.sumRange(intersectingRange.begin, intersectingRange.end);
			metrics.notifyBytes(shard, -bytes);
			any = any || bytes > 0;
		}
	}

	if (range.end > allKeys.end && byteSample.sumRange(std::max(allKeys.end, range.begin), range.end) > 0)
		any = true;

	if (!byteSampleRecovery.isReady()) {
		auto clearRanges = byteSampleClears.intersectingRanges(range);
		for (auto it : clearRanges) {
			if (!it.value()) {
				byteSampleClears.insert(range, true);
				byteSampleClearsTooLarge.set(byteSampleClears.size() > SERVER_KNOBS->MAX_BYTE_SAMPLE_CLEAR_MAP_SIZE);
				any = true;
				break;
			}
		}
	}

	if (any) {
		byteSample.eraseAsync(range.begin, range.end);
		auto diskRange = range.withPrefix(persistByteSampleKeys.begin);
		addMutationToMutationLogOrStorage(ver, MutationRef(MutationRef::ClearRange, diskRange.begin, diskRange.end));
		++counters.kvSystemClearRanges;
	}
}

ACTOR Future<Void> waitMetrics(StorageServerMetrics* self, WaitMetricsRequest req, Future<Void> timeout) {
	state PromiseStream<StorageMetrics> change;
	state StorageMetrics metrics = self->getMetrics(req.keys);
	state Error error = success();
	state bool timedout = false;

	if (!req.min.allLessOrEqual(metrics) || !metrics.allLessOrEqual(req.max)) {
		CODE_PROBE(true, "ShardWaitMetrics return case 1 (quickly)");
		req.reply.send(metrics);
		return Void();
	}

	{
		auto rs = self->waitMetricsMap.modify(req.keys);
		for (auto r = rs.begin(); r != rs.end(); ++r)
			r->value().push_back(change);
		loop {
			try {
				choose {
					when(StorageMetrics c = waitNext(change.getFuture())) {
						metrics += c;

						// SOMEDAY: validation! The changes here are possibly partial changes (we receive multiple
						// messages per
						//  update to our requested range). This means that the validation would have to occur after
						//  all the messages for one clear or set have been dispatched.

						/*StorageMetrics m = getMetrics( data, req.keys );
						  bool b = ( m.bytes != metrics.bytes || m.bytesPerKSecond != metrics.bytesPerKSecond ||
						  m.iosPerKSecond != metrics.iosPerKSecond ); if (b) { printf("keys: '%s' - '%s' @%p\n",
						  printable(req.keys.begin).c_str(), printable(req.keys.end).c_str(), this);
						  printf("waitMetrics: desync %d (%lld %lld %lld) != (%lld %lld %lld); +(%lld %lld %lld)\n",
						  b, m.bytes, m.bytesPerKSecond, m.iosPerKSecond, metrics.bytes, metrics.bytesPerKSecond,
						  metrics.iosPerKSecond, c.bytes, c.bytesPerKSecond, c.iosPerKSecond);

						  }*/
					}
					when(wait(timeout)) { timedout = true; }
				}
			} catch (Error& e) {
				if (e.code() == error_code_actor_cancelled)
					throw; // This is only cancelled when the main loop had exited...no need in this case to clean
					       // up self
				error = e;
				break;
			}

			if (timedout) {
				CODE_PROBE(true, "ShardWaitMetrics return on timeout");
				// FIXME: instead of using random chance, send wrong_shard_server when the call in from
				// waitMetricsMultiple (requires additional information in the request)
				if (deterministicRandom()->random01() < SERVER_KNOBS->WAIT_METRICS_WRONG_SHARD_CHANCE) {
					req.reply.sendError(wrong_shard_server());
				} else {
					req.reply.send(metrics);
				}
				break;
			}

			if (!req.min.allLessOrEqual(metrics) || !metrics.allLessOrEqual(req.max)) {
				CODE_PROBE(true, "ShardWaitMetrics return case 2 (delayed)");
				req.reply.send(metrics);
				break;
			}
		}

		wait(delay(0)); // prevent iterator invalidation of functions sending changes
	}

	auto rs = self->waitMetricsMap.modify(req.keys);
	for (auto i = rs.begin(); i != rs.end(); ++i) {
		auto& x = i->value();
		for (int j = 0; j < x.size(); j++) {
			if (x[j] == change) {
				swapAndPop(&x, j);
				break;
			}
		}
	}
	self->waitMetricsMap.coalesce(req.keys);

	if (error.code() != error_code_success) {
		if (error.code() != error_code_wrong_shard_server)
			throw error;
		CODE_PROBE(true, "ShardWaitMetrics delayed wrong_shard_server()");
		req.reply.sendError(error);
	}

	return Void();
}

Future<Void> StorageServerMetrics::waitMetrics(WaitMetricsRequest req, Future<Void> delay) {
	return ::waitMetrics(this, req, delay);
}

#ifndef __INTEL_COMPILER
#pragma endregion
#endif

/////////////////////////////// Core //////////////////////////////////////
#ifndef __INTEL_COMPILER
#pragma region Core
#endif

ACTOR Future<Void> metricsCore(StorageServer* self, StorageServerInterface ssi) {
	state Future<Void> doPollMetrics = Void();

	wait(self->byteSampleRecovery);
	TraceEvent("StorageServerRestoreDurableState", self->thisServerID).detail("RestoredBytes", self->bytesRestored);

	// Logs all counters in `counters.cc` and reset the interval.
	self->actors.add(traceCounters("StorageMetrics",
	                               self->thisServerID,
	                               SERVER_KNOBS->STORAGE_LOGGING_DELAY,
	                               &self->counters.cc,
	                               self->thisServerID.toString() + "/StorageMetrics",
	                               [self = self](TraceEvent& te) {
		                               te.detail("StorageEngine", self->storage.getKeyValueStoreType().toString());
		                               te.detail("Tag", self->tag.toString());
		                               StorageBytes sb = self->storage.getStorageBytes();
		                               te.detail("KvstoreBytesUsed", sb.used);
		                               te.detail("KvstoreBytesFree", sb.free);
		                               te.detail("KvstoreBytesAvailable", sb.available);
		                               te.detail("KvstoreBytesTotal", sb.total);
		                               te.detail("KvstoreBytesTemp", sb.temp);
		                               if (self->isTss()) {
			                               te.detail("TSSPairID", self->tssPairID);
			                               te.detail("TSSJointID",
			                                         UID(self->thisServerID.first() ^ self->tssPairID.get().first(),
			                                             self->thisServerID.second() ^ self->tssPairID.get().second()));
		                               } else if (self->isSSWithTSSPair()) {
			                               te.detail("SSPairID", self->ssPairID);
			                               te.detail("TSSJointID",
			                                         UID(self->thisServerID.first() ^ self->ssPairID.get().first(),
			                                             self->thisServerID.second() ^ self->ssPairID.get().second()));
		                               }
	                               }));

	loop {
		choose {
			when(WaitMetricsRequest req = waitNext(ssi.waitMetrics.getFuture())) {
				if (!self->isReadable(req.keys)) {
					CODE_PROBE(true, "waitMetrics immediate wrong_shard_server()");
					self->sendErrorWithPenalty(req.reply, wrong_shard_server(), self->getPenalty());
				} else {
					self->actors.add(
					    self->metrics.waitMetrics(req, delayJittered(SERVER_KNOBS->STORAGE_METRIC_TIMEOUT)));
				}
			}
			when(SplitMetricsRequest req = waitNext(ssi.splitMetrics.getFuture())) {
				if (!self->isReadable(req.keys)) {
					CODE_PROBE(true, "splitMetrics immediate wrong_shard_server()");
					self->sendErrorWithPenalty(req.reply, wrong_shard_server(), self->getPenalty());
				} else {
					self->metrics.splitMetrics(req);
				}
			}
			when(GetStorageMetricsRequest req = waitNext(ssi.getStorageMetrics.getFuture())) {
				StorageBytes sb = self->storage.getStorageBytes();
				self->metrics.getStorageMetrics(
				    req, sb, self->counters.bytesInput.getRate(), self->versionLag, self->lastUpdate);
			}
			when(ReadHotSubRangeRequest req = waitNext(ssi.getReadHotRanges.getFuture())) {
				if (!self->isReadable(req.keys)) {
					CODE_PROBE(true, "readHotSubRanges immediate wrong_shard_server()");
					self->sendErrorWithPenalty(req.reply, wrong_shard_server(), self->getPenalty());
				} else {
					self->metrics.getReadHotRanges(req);
				}
			}
			when(SplitRangeRequest req = waitNext(ssi.getRangeSplitPoints.getFuture())) {
				if (!self->isReadable(req.keys)) {
					CODE_PROBE(true, "getSplitPoints immediate wrong_shard_server()");
					self->sendErrorWithPenalty(req.reply, wrong_shard_server(), self->getPenalty());
				} else {
					self->getSplitPoints(req);
				}
			}
			when(wait(doPollMetrics)) {
				self->metrics.poll();
				doPollMetrics = delay(SERVER_KNOBS->STORAGE_SERVER_POLL_METRICS_DELAY);
			}
		}
	}
}

ACTOR Future<Void> logLongByteSampleRecovery(Future<Void> recovery) {
	choose {
		when(wait(recovery)) {}
		when(wait(delay(SERVER_KNOBS->LONG_BYTE_SAMPLE_RECOVERY_DELAY))) {
			TraceEvent(g_network->isSimulated() ? SevWarn : SevWarnAlways, "LongByteSampleRecovery");
		}
	}

	return Void();
}

ACTOR Future<Void> checkBehind(StorageServer* self) {
	state int behindCount = 0;
	loop {
		wait(delay(SERVER_KNOBS->BEHIND_CHECK_DELAY));
		state Transaction tr(self->cx);
		loop {
			try {
				Version readVersion = wait(tr.getRawReadVersion());
				if (readVersion > self->version.get() + SERVER_KNOBS->BEHIND_CHECK_VERSIONS) {
					behindCount++;
				} else {
					behindCount = 0;
				}
				self->versionBehind = behindCount >= SERVER_KNOBS->BEHIND_CHECK_COUNT;
				break;
			} catch (Error& e) {
				wait(tr.onError(e));
			}
		}
	}
}

ACTOR Future<Void> serveGetValueRequests(StorageServer* self, FutureStream<GetValueRequest> getValue) {
	getCurrentLineage()->modify(&TransactionLineage::operation) = TransactionLineage::Operation::GetValue;
	loop {
		GetValueRequest req = waitNext(getValue);
		// Warning: This code is executed at extremely high priority (TaskPriority::LoadBalancedEndpoint), so
		// downgrade before doing real work
		if (req.debugID.present())
			g_traceBatch.addEvent("GetValueDebug",
			                      req.debugID.get().first(),
			                      "storageServer.received"); //.detail("TaskID", g_network->getCurrentTask());

		if (SHORT_CIRCUT_ACTUAL_STORAGE && normalKeys.contains(req.key))
			req.reply.send(GetValueReply());
		else
			self->actors.add(self->readGuard(req, getValueQ));
	}
}

ACTOR Future<Void> serveGetKeyValuesRequests(StorageServer* self, FutureStream<GetKeyValuesRequest> getKeyValues) {
	getCurrentLineage()->modify(&TransactionLineage::operation) = TransactionLineage::Operation::GetKeyValues;
	loop {
		GetKeyValuesRequest req = waitNext(getKeyValues);

		// Warning: This code is executed at extremely high priority (TaskPriority::LoadBalancedEndpoint), so
		// downgrade before doing real work
		self->actors.add(self->readGuard(req, getKeyValuesQ));
	}
}

ACTOR Future<Void> serveGetMappedKeyValuesRequests(StorageServer* self,
                                                   FutureStream<GetMappedKeyValuesRequest> getMappedKeyValues) {
	// TODO: Is it fine to keep TransactionLineage::Operation::GetKeyValues here?
	getCurrentLineage()->modify(&TransactionLineage::operation) = TransactionLineage::Operation::GetKeyValues;
	loop {
		GetMappedKeyValuesRequest req = waitNext(getMappedKeyValues);

		// Warning: This code is executed at extremely high priority (TaskPriority::LoadBalancedEndpoint), so downgrade
		// before doing real work
		self->actors.add(self->readGuard(req, getMappedKeyValuesQ));
	}
}

ACTOR Future<Void> serveGetKeyValuesStreamRequests(StorageServer* self,
                                                   FutureStream<GetKeyValuesStreamRequest> getKeyValuesStream) {
	loop {
		GetKeyValuesStreamRequest req = waitNext(getKeyValuesStream);
		// Warning: This code is executed at extremely high priority (TaskPriority::LoadBalancedEndpoint), so
		// downgrade before doing real work
		// FIXME: add readGuard again
		self->actors.add(getKeyValuesStreamQ(self, req));
	}
}

ACTOR Future<Void> serveGetKeyRequests(StorageServer* self, FutureStream<GetKeyRequest> getKey) {
	getCurrentLineage()->modify(&TransactionLineage::operation) = TransactionLineage::Operation::GetKey;
	loop {
		GetKeyRequest req = waitNext(getKey);
		// Warning: This code is executed at extremely high priority (TaskPriority::LoadBalancedEndpoint), so
		// downgrade before doing real work
		self->actors.add(self->readGuard(req, getKeyQ));
	}
}

ACTOR Future<Void> watchValueWaitForVersion(StorageServer* self,
                                            WatchValueRequest req,
                                            PromiseStream<WatchValueRequest> stream) {
	state Span span("SS:watchValueWaitForVersion"_loc, req.spanContext);
	if (req.tenantInfo.name.present()) {
		span.addAttribute("tenant"_sr, req.tenantInfo.name.get());
	}
	getCurrentLineage()->modify(&TransactionLineage::txID) = req.spanContext.traceID;
	try {
		wait(success(waitForVersionNoTooOld(self, req.version)));
		Optional<TenantMapEntry> entry = self->getTenantEntry(latestVersion, req.tenantInfo);
		if (entry.present()) {
			req.key = req.key.withPrefix(entry.get().prefix);
		}
		stream.send(req);
	} catch (Error& e) {
		if (!canReplyWith(e))
			throw e;
		self->sendErrorWithPenalty(req.reply, e, self->getPenalty());
	}
	return Void();
}

ACTOR Future<Void> serveWatchValueRequestsImpl(StorageServer* self, FutureStream<WatchValueRequest> stream) {
	loop {
		getCurrentLineage()->modify(&TransactionLineage::txID) = UID();
		state WatchValueRequest req = waitNext(stream);
		state Reference<ServerWatchMetadata> metadata = self->getWatchMetadata(req.key.contents());
		state Span span("SS:serveWatchValueRequestsImpl"_loc, req.spanContext);
		getCurrentLineage()->modify(&TransactionLineage::txID) = req.spanContext.traceID;

		// case 1: no watch set for the current key
		if (!metadata.isValid()) {
			metadata = makeReference<ServerWatchMetadata>(req.key, req.value, req.version, req.tags, req.debugID);
			KeyRef key = self->setWatchMetadata(metadata);
			metadata->watch_impl = forward(watchWaitForValueChange(self, span.context, key), metadata->versionPromise);
			self->actors.add(watchValueSendReply(self, req, metadata->versionPromise.getFuture(), span.context));
		}
		// case 2: there is a watch in the map and it has the same value so just update version
		else if (metadata->value == req.value) {
			if (req.version > metadata->version) {
				metadata->version = req.version;
				metadata->tags = req.tags;
				metadata->debugID = req.debugID;
			}
			self->actors.add(watchValueSendReply(self, req, metadata->versionPromise.getFuture(), span.context));
		}
		// case 3: version in map has a lower version so trigger watch and create a new entry in map
		else if (req.version > metadata->version) {
			self->deleteWatchMetadata(req.key.contents());
			metadata->versionPromise.send(req.version);
			metadata->watch_impl.cancel();

			metadata = makeReference<ServerWatchMetadata>(req.key, req.value, req.version, req.tags, req.debugID);
			KeyRef key = self->setWatchMetadata(metadata);
			metadata->watch_impl = forward(watchWaitForValueChange(self, span.context, key), metadata->versionPromise);

			self->actors.add(watchValueSendReply(self, req, metadata->versionPromise.getFuture(), span.context));
		}
		// case 4: version in the map is higher so immediately trigger watch
		else if (req.version < metadata->version) {
			CODE_PROBE(true, "watch version in map is higher so trigger watch (case 4)");
			req.reply.send(WatchValueReply{ metadata->version });
		}
		// case 5: watch value differs but their versions are the same (rare case) so check with the SS
		else {
			CODE_PROBE(true, "watch version in the map is the same but value is different (case 5)");
			loop {
				try {
					state Version latest = self->version.get();
					GetValueRequest getReq(span.context,
					                       TenantInfo(),
					                       metadata->key,
					                       latest,
					                       metadata->tags,
					                       metadata->debugID,
					                       VersionVector());
					state Future<Void> getValue = getValueQ(self, getReq);
					GetValueReply reply = wait(getReq.reply.getFuture());
					metadata = self->getWatchMetadata(req.key.contents());

					if (metadata.isValid() && reply.value != metadata->value) { // valSS != valMap
						self->deleteWatchMetadata(req.key.contents());
						metadata->versionPromise.send(req.version);
						metadata->watch_impl.cancel();
					}

					if (reply.value == req.value) { // valSS == valreq
						metadata =
						    makeReference<ServerWatchMetadata>(req.key, req.value, req.version, req.tags, req.debugID);
						KeyRef key = self->setWatchMetadata(metadata);
						metadata->watch_impl =
						    forward(watchWaitForValueChange(self, span.context, key), metadata->versionPromise);
						self->actors.add(
						    watchValueSendReply(self, req, metadata->versionPromise.getFuture(), span.context));
					} else {
						req.reply.send(WatchValueReply{ latest });
					}
					break;
				} catch (Error& e) {
					if (e.code() != error_code_transaction_too_old) {
						if (!canReplyWith(e))
							throw e;
						self->sendErrorWithPenalty(req.reply, e, self->getPenalty());
						break;
					}
					CODE_PROBE(true, "Reading a watched key failed with transaction_too_old case 5");
				}
			}
		}
	}
}

ACTOR Future<Void> serveWatchValueRequests(StorageServer* self, FutureStream<WatchValueRequest> watchValue) {
	state PromiseStream<WatchValueRequest> stream;
	getCurrentLineage()->modify(&TransactionLineage::operation) = TransactionLineage::Operation::WatchValue;
	self->actors.add(serveWatchValueRequestsImpl(self, stream.getFuture()));

	loop {
		WatchValueRequest req = waitNext(watchValue);
		// TODO: fast load balancing?
		if (self->shouldRead(req)) {
			self->actors.add(watchValueWaitForVersion(self, req, stream));
		}
	}
}

ACTOR Future<Void> serveChangeFeedStreamRequests(StorageServer* self,
                                                 FutureStream<ChangeFeedStreamRequest> changeFeedStream) {
	loop {
		ChangeFeedStreamRequest req = waitNext(changeFeedStream);
		// must notify change feed that its shard is moved away ASAP
		self->actors.add(changeFeedStreamQ(self, req, req.debugUID) || stopChangeFeedOnMove(self, req, req.debugUID));
	}
}

ACTOR Future<Void> serveOverlappingChangeFeedsRequests(
    StorageServer* self,
    FutureStream<OverlappingChangeFeedsRequest> overlappingChangeFeeds) {
	loop {
		OverlappingChangeFeedsRequest req = waitNext(overlappingChangeFeeds);
		self->actors.add(self->readGuard(req, overlappingChangeFeedsQ));
	}
}

ACTOR Future<Void> serveChangeFeedPopRequests(StorageServer* self, FutureStream<ChangeFeedPopRequest> changeFeedPops) {
	loop {
		ChangeFeedPopRequest req = waitNext(changeFeedPops);
		self->actors.add(self->readGuard(req, changeFeedPopQ));
	}
}

ACTOR Future<Void> serveChangeFeedVersionUpdateRequests(
    StorageServer* self,
    FutureStream<ChangeFeedVersionUpdateRequest> changeFeedVersionUpdate) {
	loop {
		ChangeFeedVersionUpdateRequest req = waitNext(changeFeedVersionUpdate);
		self->actors.add(self->readGuard(req, changeFeedVersionUpdateQ));
	}
}

ACTOR Future<Void> reportStorageServerState(StorageServer* self) {
	if (!SERVER_KNOBS->REPORT_DD_METRICS) {
		return Void();
	}

	loop {
		wait(delay(SERVER_KNOBS->DD_METRICS_REPORT_INTERVAL));

		const auto numRunningFetchKeys = self->currentRunningFetchKeys.numRunning();
		if (numRunningFetchKeys == 0) {
			continue;
		}

		const auto longestRunningFetchKeys = self->currentRunningFetchKeys.longestTime();

		auto level = SevInfo;
		if (longestRunningFetchKeys.first >= SERVER_KNOBS->FETCH_KEYS_TOO_LONG_TIME_CRITERIA) {
			level = SevWarnAlways;
		}

		TraceEvent(level, "FetchKeysCurrentStatus", self->thisServerID)
		    .detail("Timestamp", now())
		    .detail("LongestRunningTime", longestRunningFetchKeys.first)
		    .detail("StartKey", longestRunningFetchKeys.second.begin)
		    .detail("EndKey", longestRunningFetchKeys.second.end)
		    .detail("NumRunning", numRunningFetchKeys);
	}
}

ACTOR Future<Void> storageServerCore(StorageServer* self, StorageServerInterface ssi) {
	state Future<Void> doUpdate = Void();
	state bool updateReceived = false; // true iff the current update() actor assigned to doUpdate has already
	                                   // received an update from the tlog
	state double lastLoopTopTime = now();
	state Future<Void> dbInfoChange = Void();
	state Future<Void> checkLastUpdate = Void();
	state Future<Void> updateProcessStatsTimer = delay(SERVER_KNOBS->FASTRESTORE_UPDATE_PROCESS_STATS_INTERVAL);

	self->actors.add(updateStorage(self));
	self->actors.add(waitFailureServer(ssi.waitFailure.getFuture()));
	self->actors.add(self->otherError.getFuture());
	self->actors.add(metricsCore(self, ssi));
	self->actors.add(logLongByteSampleRecovery(self->byteSampleRecovery));
	self->actors.add(checkBehind(self));
	self->actors.add(serveGetValueRequests(self, ssi.getValue.getFuture()));
	self->actors.add(serveGetKeyValuesRequests(self, ssi.getKeyValues.getFuture()));
	self->actors.add(serveGetMappedKeyValuesRequests(self, ssi.getMappedKeyValues.getFuture()));
	self->actors.add(serveGetKeyValuesStreamRequests(self, ssi.getKeyValuesStream.getFuture()));
	self->actors.add(serveGetKeyRequests(self, ssi.getKey.getFuture()));
	self->actors.add(serveWatchValueRequests(self, ssi.watchValue.getFuture()));
	self->actors.add(serveChangeFeedStreamRequests(self, ssi.changeFeedStream.getFuture()));
	self->actors.add(serveOverlappingChangeFeedsRequests(self, ssi.overlappingChangeFeeds.getFuture()));
	self->actors.add(serveChangeFeedPopRequests(self, ssi.changeFeedPop.getFuture()));
	self->actors.add(serveChangeFeedVersionUpdateRequests(self, ssi.changeFeedVersionUpdate.getFuture()));
	self->actors.add(traceRole(Role::STORAGE_SERVER, ssi.id()));
	self->actors.add(reportStorageServerState(self));

	self->transactionTagCounter.startNewInterval();
	self->actors.add(
	    recurring([&]() { self->transactionTagCounter.startNewInterval(); }, SERVER_KNOBS->TAG_MEASUREMENT_INTERVAL));

	self->coreStarted.send(Void());

	loop {
		++self->counters.loops;

		double loopTopTime = now();
		double elapsedTime = loopTopTime - lastLoopTopTime;
		if (elapsedTime > 0.050) {
			if (deterministicRandom()->random01() < 0.01)
				TraceEvent(SevWarn, "SlowSSLoopx100", self->thisServerID).detail("Elapsed", elapsedTime);
		}
		lastLoopTopTime = loopTopTime;

		choose {
			when(wait(checkLastUpdate)) {
				if (now() - self->lastUpdate >= CLIENT_KNOBS->NO_RECENT_UPDATES_DURATION) {
					self->noRecentUpdates.set(true);
					checkLastUpdate = delay(CLIENT_KNOBS->NO_RECENT_UPDATES_DURATION);
				} else {
					checkLastUpdate =
					    delay(std::max(CLIENT_KNOBS->NO_RECENT_UPDATES_DURATION - (now() - self->lastUpdate), 0.1));
				}
			}
			when(wait(dbInfoChange)) {
				CODE_PROBE(self->logSystem, "shardServer dbInfo changed");
				dbInfoChange = self->db->onChange();
				if (self->db->get().recoveryState >= RecoveryState::ACCEPTING_COMMITS) {
					self->logSystem = ILogSystem::fromServerDBInfo(self->thisServerID, self->db->get());
					if (self->logSystem) {
						if (self->db->get().logSystemConfig.recoveredAt.present()) {
							self->poppedAllAfter = self->db->get().logSystemConfig.recoveredAt.get();
						}
						self->logCursor = self->logSystem->peekSingle(
						    self->thisServerID, self->version.get() + 1, self->tag, self->history);
						self->popVersion(self->durableVersion.get() + 1, true);
					}
					// If update() is waiting for results from the tlog, it might never get them, so needs to be
					// cancelled.  But if it is waiting later, cancelling it could cause problems (e.g. fetchKeys
					// that already committed to transitioning to waiting state)
					if (!updateReceived) {
						doUpdate = Void();
					}
				}

				Optional<LatencyBandConfig> newLatencyBandConfig = self->db->get().latencyBandConfig;
				if (newLatencyBandConfig.present() != self->latencyBandConfig.present() ||
				    (newLatencyBandConfig.present() &&
				     newLatencyBandConfig.get().readConfig != self->latencyBandConfig.get().readConfig)) {
					self->latencyBandConfig = newLatencyBandConfig;
					self->counters.readLatencyBands.clearBands();
					TraceEvent("LatencyBandReadUpdatingConfig").detail("Present", newLatencyBandConfig.present());
					if (self->latencyBandConfig.present()) {
						for (auto band : self->latencyBandConfig.get().readConfig.bands) {
							self->counters.readLatencyBands.addThreshold(band);
						}
					}
				}
			}
			when(GetShardStateRequest req = waitNext(ssi.getShardState.getFuture())) {
				if (req.mode == GetShardStateRequest::NO_WAIT) {
					if (self->isReadable(req.keys))
						req.reply.send(GetShardStateReply{ self->version.get(), self->durableVersion.get() });
					else
						req.reply.sendError(wrong_shard_server());
				} else {
					self->actors.add(getShardStateQ(self, req));
				}
			}
			when(StorageQueuingMetricsRequest req = waitNext(ssi.getQueuingMetrics.getFuture())) {
				getQueuingMetrics(self, req);
			}
			when(ReplyPromise<KeyValueStoreType> reply = waitNext(ssi.getKeyValueStoreType.getFuture())) {
				reply.send(self->storage.getKeyValueStoreType());
			}
			when(wait(doUpdate)) {
				updateReceived = false;
				if (!self->logSystem)
					doUpdate = Never();
				else
					doUpdate = update(self, &updateReceived);
			}
			when(GetCheckpointRequest req = waitNext(ssi.checkpoint.getFuture())) {
				if (!self->isReadable(req.range)) {
					req.reply.sendError(wrong_shard_server());
					continue;
				} else {
					self->actors.add(getCheckpointQ(self, req));
				}
			}
			when(FetchCheckpointRequest req = waitNext(ssi.fetchCheckpoint.getFuture())) {
				self->actors.add(fetchCheckpointQ(self, req));
			}
			when(FetchCheckpointKeyValuesRequest req = waitNext(ssi.fetchCheckpointKeyValues.getFuture())) {
				self->actors.add(fetchCheckpointKeyValuesQ(self, req));
			}
			when(wait(updateProcessStatsTimer)) {
				updateProcessStats(self);
				updateProcessStatsTimer = delay(SERVER_KNOBS->FASTRESTORE_UPDATE_PROCESS_STATS_INTERVAL);
			}
			when(wait(self->actors.getResult())) {}
		}
	}
}

bool storageServerTerminated(StorageServer& self, IKeyValueStore* persistentData, Error const& e) {
	self.shuttingDown = true;

	// Clearing shards shuts down any fetchKeys actors; these may do things on cancellation that are best done with
	// self still valid
	self.shards.insert(allKeys, Reference<ShardInfo>());

	// Dispose the IKVS (destroying its data permanently) only if this shutdown is definitely permanent.  Otherwise
	// just close it.
	if (e.code() == error_code_please_reboot) {
		// do nothing.
	} else if (e.code() == error_code_worker_removed || e.code() == error_code_recruitment_failed) {
		// SOMEDAY: could close instead of dispose if tss in quarantine gets removed so it could still be
		// investigated?
		persistentData->dispose();
	} else {
		persistentData->close();
	}

	if (e.code() == error_code_worker_removed || e.code() == error_code_recruitment_failed ||
	    e.code() == error_code_file_not_found || e.code() == error_code_actor_cancelled ||
	    e.code() == error_code_remote_kvs_cancelled) {
		TraceEvent("StorageServerTerminated", self.thisServerID).errorUnsuppressed(e);
		return true;
	} else
		return false;
}

ACTOR Future<Void> memoryStoreRecover(IKeyValueStore* store, Reference<IClusterConnectionRecord> connRecord, UID id) {
	if (store->getType() != KeyValueStoreType::MEMORY || connRecord.getPtr() == nullptr) {
		return Never();
	}

	// create a temp client connect to DB
	Database cx = Database::createDatabase(connRecord, Database::API_VERSION_LATEST);

	state Reference<ReadYourWritesTransaction> tr = makeReference<ReadYourWritesTransaction>(cx);
	state int noCanRemoveCount = 0;
	loop {
		try {
			tr->setOption(FDBTransactionOptions::PRIORITY_SYSTEM_IMMEDIATE);
			tr->setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);

			state bool canRemove = wait(canRemoveStorageServer(tr, id));
			if (!canRemove) {
				CODE_PROBE(true,
				           "it's possible that the caller had a transaction in flight that assigned keys to the "
				           "server. Wait for it to reverse its mistake.");
				wait(delayJittered(SERVER_KNOBS->REMOVE_RETRY_DELAY, TaskPriority::UpdateStorage));
				tr->reset();
				TraceEvent("RemoveStorageServerRetrying")
				    .detail("Count", noCanRemoveCount++)
				    .detail("ServerID", id)
				    .detail("CanRemove", canRemove);
			} else {
				return Void();
			}
		} catch (Error& e) {
			state Error err = e;
			wait(tr->onError(e));
			TraceEvent("RemoveStorageServerRetrying").error(err);
		}
	}
}

ACTOR Future<Void> initTenantMap(StorageServer* self) {
	state Reference<ReadYourWritesTransaction> tr = makeReference<ReadYourWritesTransaction>(self->cx);

	loop {
		try {
			tr->setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
			state Version version = wait(tr->getReadVersion());
			// This limits the number of tenants, but eventually we shouldn't need to do this at all
			// when SSs store only the local tenants
			KeyBackedRangeResult<std::pair<TenantName, TenantMapEntry>> entries =
			    wait(TenantMetadata::tenantMap.getRange(
			        tr, Optional<TenantName>(), Optional<TenantName>(), CLIENT_KNOBS->TOO_MANY));

			TraceEvent("InitTenantMap", self->thisServerID)
			    .detail("Version", version)
			    .detail("NumTenants", entries.results.size());

			for (auto entry : entries.results) {
				self->insertTenant(entry.first, entry.second, version);
			}
			break;
		} catch (Error& e) {
			wait(tr->onError(e));
		}
	}

	return Void();
}

ACTOR Future<Void> replaceInterface(StorageServer* self, StorageServerInterface ssi) {
	ASSERT(!ssi.isTss());
	state Transaction tr(self->cx);

	loop {
		state Future<Void> infoChanged = self->db->onChange();
		state Reference<CommitProxyInfo> commitProxies(new CommitProxyInfo(self->db->get().client.commitProxies));
		choose {
			when(GetStorageServerRejoinInfoReply _rep =
			         wait(commitProxies->size()
			                  ? basicLoadBalance(commitProxies,
			                                     &CommitProxyInterface::getStorageServerRejoinInfo,
			                                     GetStorageServerRejoinInfoRequest(ssi.id(), ssi.locality.dcId()))
			                  : Never())) {
				state GetStorageServerRejoinInfoReply rep = _rep;

				try {
					tr.reset();
					tr.setOption(FDBTransactionOptions::PRIORITY_SYSTEM_IMMEDIATE);
					tr.setVersion(rep.version);

					tr.addReadConflictRange(singleKeyRange(serverListKeyFor(ssi.id())));
					tr.addReadConflictRange(singleKeyRange(serverTagKeyFor(ssi.id())));
					tr.addReadConflictRange(serverTagHistoryRangeFor(ssi.id()));
					tr.addReadConflictRange(singleKeyRange(tagLocalityListKeyFor(ssi.locality.dcId())));

					tr.set(serverListKeyFor(ssi.id()), serverListValue(ssi));

					if (rep.newLocality) {
						tr.addReadConflictRange(tagLocalityListKeys);
						tr.set(tagLocalityListKeyFor(ssi.locality.dcId()),
						       tagLocalityListValue(rep.newTag.get().locality));
					}

					// this only should happen if SS moved datacenters
					if (rep.newTag.present()) {
						KeyRange conflictRange = singleKeyRange(serverTagConflictKeyFor(rep.newTag.get()));
						tr.addReadConflictRange(conflictRange);
						tr.addWriteConflictRange(conflictRange);
						tr.setOption(FDBTransactionOptions::FIRST_IN_BATCH);
						tr.set(serverTagKeyFor(ssi.id()), serverTagValue(rep.newTag.get()));
						tr.atomicOp(serverTagHistoryKeyFor(ssi.id()),
						            serverTagValue(rep.tag),
						            MutationRef::SetVersionstampedKey);
					}

					if (rep.history.size() && rep.history.back().first < self->version.get()) {
						tr.clear(serverTagHistoryRangeBefore(ssi.id(), self->version.get()));
					}

					choose {
						when(wait(tr.commit())) {
							self->history = rep.history;

							if (rep.newTag.present()) {
								self->tag = rep.newTag.get();
								self->history.insert(self->history.begin(),
								                     std::make_pair(tr.getCommittedVersion(), rep.tag));
							} else {
								self->tag = rep.tag;
							}
							self->allHistory = self->history;

							TraceEvent("SSTag", self->thisServerID).detail("MyTag", self->tag.toString());
							for (auto it : self->history) {
								TraceEvent("SSHistory", self->thisServerID)
								    .detail("Ver", it.first)
								    .detail("Tag", it.second.toString());
							}

							if (self->history.size() && BUGGIFY) {
								TraceEvent("SSHistoryReboot", self->thisServerID).log();
								throw please_reboot();
							}

							break;
						}
						when(wait(infoChanged)) {}
					}
				} catch (Error& e) {
					wait(tr.onError(e));
				}
			}
			when(wait(infoChanged)) {}
		}
	}

	return Void();
}

ACTOR Future<Void> replaceTSSInterface(StorageServer* self, StorageServerInterface ssi) {
	// RYW for KeyBackedMap
	state Reference<ReadYourWritesTransaction> tr = makeReference<ReadYourWritesTransaction>(self->cx);
	state KeyBackedMap<UID, UID> tssMapDB = KeyBackedMap<UID, UID>(tssMappingKeys.begin);

	ASSERT(ssi.isTss());

	loop {
		try {
			state Tag myTag;

			tr->reset();
			tr->setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
			tr->setOption(FDBTransactionOptions::PRIORITY_SYSTEM_IMMEDIATE);

			Optional<Value> pairTagValue = wait(tr->get(serverTagKeyFor(self->tssPairID.get())));

			if (!pairTagValue.present()) {
				CODE_PROBE(true, "Race where tss was down, pair was removed, tss starts back up");
				TraceEvent("StorageServerWorkerRemoved", self->thisServerID).detail("Reason", "TssPairMissing");
				throw worker_removed();
			}

			myTag = decodeServerTagValue(pairTagValue.get());

			tr->addReadConflictRange(singleKeyRange(serverListKeyFor(ssi.id())));
			tr->set(serverListKeyFor(ssi.id()), serverListValue(ssi));

			// add itself back to tss mapping
			if (!self->isTSSInQuarantine()) {
				tssMapDB.set(tr, self->tssPairID.get(), ssi.id());
			}

			wait(tr->commit());
			self->tag = myTag;

			break;
		} catch (Error& e) {
			wait(tr->onError(e));
		}
	}

	return Void();
}

ACTOR Future<Void> storageInterfaceRegistration(StorageServer* self,
                                                StorageServerInterface ssi,
                                                Optional<Future<Void>> readyToAcceptRequests) {

	if (readyToAcceptRequests.present()) {
		wait(readyToAcceptRequests.get());
		ssi.startAcceptingRequests();
	} else {
		ssi.stopAcceptingRequests();
	}

	try {
		if (self->isTss()) {
			wait(replaceTSSInterface(self, ssi));
		} else {
			wait(replaceInterface(self, ssi));
		}
	} catch (Error& e) {
		throw;
	}

	return Void();
}

// for creating a new storage server
ACTOR Future<Void> storageServer(IKeyValueStore* persistentData,
                                 StorageServerInterface ssi,
                                 Tag seedTag,
                                 UID clusterId,
                                 Version startVersion,
                                 Version tssSeedVersion,
                                 ReplyPromise<InitializeStorageReply> recruitReply,
                                 Reference<AsyncVar<ServerDBInfo> const> db,
                                 std::string folder) {
	state StorageServer self(persistentData, db, ssi);
	self.shardAware = CLIENT_KNOBS->SHARD_ENCODE_LOCATION_METADATA &&
	                  (SERVER_KNOBS->STORAGE_SERVER_SHARD_AWARE || persistentData->shardAware());
	state Future<Void> ssCore;
	self.clusterId.send(clusterId);
	self.initialClusterVersion = startVersion;
	if (ssi.isTss()) {
		self.setTssPair(ssi.tssPairID.get());
		ASSERT(self.isTss());
	}

	self.sk = serverKeysPrefixFor(self.tssPairID.present() ? self.tssPairID.get() : self.thisServerID)
	              .withPrefix(systemKeys.begin); // FFFF/serverKeys/[this server]/
	self.folder = folder;

	try {
		wait(self.storage.init());
		wait(self.storage.commit());
		++self.counters.kvCommits;

		if (seedTag == invalidTag) {
			ssi.startAcceptingRequests();
			self.registerInterfaceAcceptingRequests.send(Void());

			// Might throw recruitment_failed in case of simultaneous master failure
			std::pair<Version, Tag> verAndTag = wait(addStorageServer(self.cx, ssi));

			self.tag = verAndTag.second;
			if (ssi.isTss()) {
				self.setInitialVersion(tssSeedVersion);
			} else {
				self.setInitialVersion(verAndTag.first - 1);
			}

			wait(initTenantMap(&self));
		} else {
			self.tag = seedTag;
		}

		self.storage.makeNewStorageServerDurable(self.shardAware);
		wait(self.storage.commit());
		++self.counters.kvCommits;

		self.interfaceRegistered =
		    storageInterfaceRegistration(&self, ssi, self.registerInterfaceAcceptingRequests.getFuture());
		wait(delay(0));

		TraceEvent("StorageServerInit", ssi.id())
		    .detail("Version", self.version.get())
		    .detail("SeedTag", seedTag.toString())
		    .detail("TssPair", ssi.isTss() ? ssi.tssPairID.get().toString() : "");
		InitializeStorageReply rep;
		rep.interf = ssi;
		rep.addedVersion = self.version.get();
		recruitReply.send(rep);
		self.byteSampleRecovery = Void();

		ssCore = storageServerCore(&self, ssi);
		wait(ssCore);

		throw internal_error();
	} catch (Error& e) {
		// If we die with an error before replying to the recruitment request, send the error to the recruiter
		// (ClusterController, and from there to the DataDistributionTeamCollection)
		if (!recruitReply.isSet())
			recruitReply.sendError(recruitment_failed());

		// If the storage server dies while something that uses self is still on the stack,
		// we want that actor to complete before we terminate and that memory goes out of scope
		state Error err = e;
		if (storageServerTerminated(self, persistentData, err)) {
			ssCore.cancel();
			self.actors.clear(true);
			wait(delay(0));
			return Void();
		}
		ssCore.cancel();
		self.actors.clear(true);
		wait(delay(0));
		throw err;
	}
}

// for recovering an existing storage server
ACTOR Future<Void> storageServer(IKeyValueStore* persistentData,
                                 StorageServerInterface ssi,
                                 Reference<AsyncVar<ServerDBInfo> const> db,
                                 std::string folder,
                                 Promise<Void> recovered,
                                 Reference<IClusterConnectionRecord> connRecord) {
	state StorageServer self(persistentData, db, ssi);
	state Future<Void> ssCore;
	self.folder = folder;

	try {
		state double start = now();
		TraceEvent("StorageServerRebootStart", self.thisServerID).log();

		wait(self.storage.init());
		choose {
			// after a rollback there might be uncommitted changes.
			// for memory storage engine type, wait until recovery is done before commit
			when(wait(self.storage.commit())) {}

			when(wait(memoryStoreRecover(persistentData, connRecord, self.thisServerID))) {
				TraceEvent("DisposeStorageServer", self.thisServerID).log();
				throw worker_removed();
			}
		}
		++self.counters.kvCommits;

		bool ok = wait(self.storage.restoreDurableState());
		if (!ok) {
			if (recovered.canBeSet())
				recovered.send(Void());
			return Void();
		}
		TraceEvent("SSTimeRestoreDurableState", self.thisServerID).detail("TimeTaken", now() - start);

		// if this is a tss storage file, use that as source of truth for this server being a tss instead of the
		// presence of the tss pair key in the storage engine
		if (ssi.isTss()) {
			ASSERT(self.isTss());
			ssi.tssPairID = self.tssPairID.get();
		} else {
			ASSERT(!self.isTss());
		}

		ASSERT(self.thisServerID == ssi.id());

		self.sk = serverKeysPrefixFor(self.tssPairID.present() ? self.tssPairID.get() : self.thisServerID)
		              .withPrefix(systemKeys.begin); // FFFF/serverKeys/[this server]/

		TraceEvent("StorageServerReboot", self.thisServerID).detail("Version", self.version.get());

		if (recovered.canBeSet())
			recovered.send(Void());

		state Future<Void> f = storageInterfaceRegistration(&self, ssi, {});
		wait(delay(0));
		ErrorOr<Void> e = wait(errorOr(f));
		if (e.isError()) {
			Error e = f.getError();

			throw e;
			// TODO: #5375
			/*
			            if (e.code() != error_code_worker_removed) {
			                throw e;
			            }
			            state UID clusterId = wait(getClusterId(&self));
			            ASSERT(self.clusterId.isValid());
			            UID durableClusterId = wait(self.clusterId.getFuture());
			            ASSERT(durableClusterId.isValid());
			            if (clusterId == durableClusterId) {
			                throw worker_removed();
			            }
			            // When a storage server connects to a new cluster, it deletes its
			            // old data and creates a new, empty data file for the new cluster.
			            // We want to avoid this and force a manual removal of the storage
			            // servers' old data when being assigned to a new cluster to avoid
			            // accidental data loss.
			            TraceEvent(SevWarn, "StorageServerBelongsToExistingCluster")
			                .detail("ServerID", ssi.id())
			                .detail("ClusterID", durableClusterId)
			                .detail("NewClusterID", clusterId);
			            wait(Future<Void>(Never()));
			*/
		}

		self.interfaceRegistered =
		    storageInterfaceRegistration(&self, ssi, self.registerInterfaceAcceptingRequests.getFuture());
		wait(delay(0));

		TraceEvent("StorageServerStartingCore", self.thisServerID).detail("TimeTaken", now() - start);

		ssCore = storageServerCore(&self, ssi);
		wait(ssCore);

		throw internal_error();
	} catch (Error& e) {
		if (self.byteSampleRecovery.isValid()) {
			self.byteSampleRecovery.cancel();
		}

		if (recovered.canBeSet())
			recovered.send(Void());

		// If the storage server dies while something that uses self is still on the stack,
		// we want that actor to complete before we terminate and that memory goes out of scope
		state Error err = e;
		if (storageServerTerminated(self, persistentData, err)) {
			ssCore.cancel();
			self.actors.clear(true);
			wait(delay(0));
			return Void();
		}
		ssCore.cancel();
		self.actors.clear(true);
		wait(delay(0));
		throw err;
	}
}

#ifndef __INTEL_COMPILER
#pragma endregion
#endif

/*
4 Reference count
4 priority
24 pointers
8 lastUpdateVersion
2 updated, replacedPointer
--
42 PTree overhead

8 Version insertVersion
--
50 VersionedMap overhead

12 KeyRef
12 ValueRef
1  isClear
--
25 payload


50 overhead
25 payload
21 structure padding
32 allocator rounds up
---
128 allocated

To reach 64, need to save: 11 bytes + all padding

Possibilities:
  -8 Combine lastUpdateVersion, insertVersion?
  -2 Fold together updated, replacedPointer, isClear bits
  -3 Fold away updated, replacedPointer, isClear
  -8 Move value lengths into arena
  -4 Replace priority with H(pointer)
  -12 Compress pointers (using special allocator)
  -4 Modular lastUpdateVersion (make sure no node survives 4 billion updates)
*/

void versionedMapTest() {
	VersionedMap<int, int> vm;

	printf("SS Ptree node is %zu bytes\n", sizeof(StorageServer::VersionedData::PTreeT));

	const int NSIZE = sizeof(VersionedMap<int, int>::PTreeT);
	const int ASIZE = NSIZE <= 64 ? 64 : nextFastAllocatedSize(NSIZE);

	auto before = FastAllocator<ASIZE>::getTotalMemory();

	for (int v = 1; v <= 1000; ++v) {
		vm.createNewVersion(v);
		for (int i = 0; i < 1000; i++) {
			int k = deterministicRandom()->randomInt(0, 2000000);
			/*for(int k2=k-5; k2<k+5; k2++)
			    if (vm.atLatest().find(k2) != vm.atLatest().end())
			        vm.erase(k2);*/
			vm.erase(k - 5, k + 5);
			vm.insert(k, v);
		}
	}

	auto after = FastAllocator<ASIZE>::getTotalMemory();

	int count = 0;
	for (auto i = vm.atLatest().begin(); i != vm.atLatest().end(); ++i)
		++count;

	printf("PTree node is %d bytes, allocated as %d bytes\n", NSIZE, ASIZE);
	printf("%d distinct after %d insertions\n", count, 1000 * 1000);
	printf("Memory used: %f MB\n", (after - before) / 1e6);
}