foundationdb/fdbserver/masterserver.actor.cpp

/*
 * masterserver.actor.cpp
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2013-2018 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 <iterator>

#include "fdbclient/NativeAPI.actor.h"
#include "fdbclient/Notified.h"
#include "fdbclient/SystemData.h"
#include "fdbrpc/FailureMonitor.h"
#include "fdbrpc/PerfMetric.h"
#include "fdbrpc/sim_validation.h"
#include "fdbrpc/simulator.h"
#include "fdbserver/ApplyMetadataMutation.h"
#include "fdbserver/BackupProgress.actor.h"
#include "fdbserver/ConflictSet.h"
#include "fdbserver/CoordinatedState.h"
#include "fdbserver/CoordinationInterface.h" // copy constructors for ServerCoordinators class
#include "fdbserver/DBCoreState.h"
#include "fdbserver/DataDistribution.actor.h"
#include "fdbserver/IKeyValueStore.h"
#include "fdbserver/Knobs.h"
#include "fdbserver/LogSystem.h"
#include "fdbserver/LogSystemDiskQueueAdapter.h"
#include "fdbserver/MasterInterface.h"
#include "fdbserver/ProxyCommitData.actor.h"
#include "fdbserver/RecoveryState.h"
#include "fdbserver/ServerDBInfo.h"
#include "fdbserver/WaitFailure.h"
#include "fdbserver/WorkerInterface.actor.h"
#include "flow/ActorCollection.h"
#include "flow/Trace.h"

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

using std::max;
using std::min;
using std::vector;

struct CommitProxyVersionReplies {
	std::map<uint64_t, GetCommitVersionReply> replies;
	NotifiedVersion latestRequestNum;

	CommitProxyVersionReplies(CommitProxyVersionReplies&& r) noexcept
	  : replies(std::move(r.replies)), latestRequestNum(std::move(r.latestRequestNum)) {}
	void operator=(CommitProxyVersionReplies&& r) noexcept {
		replies = std::move(r.replies);
		latestRequestNum = std::move(r.latestRequestNum);
	}

	CommitProxyVersionReplies() : latestRequestNum(0) {}
};

ACTOR Future<Void> masterTerminateOnConflict(UID dbgid,
                                             Promise<Void> fullyRecovered,
                                             Future<Void> onConflict,
                                             Future<Void> switchedState) {
	choose {
		when(wait(onConflict)) {
			if (!fullyRecovered.isSet()) {
				TraceEvent("MasterTerminated", dbgid).detail("Reason", "Conflict");
				TEST(true); // Coordinated state conflict, master dying
				throw worker_removed();
			}
			return Void();
		}
		when(wait(switchedState)) { return Void(); }
	}
}

class ReusableCoordinatedState : NonCopyable {
public:
	Promise<Void> fullyRecovered;
	DBCoreState prevDBState;
	DBCoreState myDBState;
	bool finalWriteStarted;
	Future<Void> previousWrite;

	ReusableCoordinatedState(ServerCoordinators const& coordinators,
	                         PromiseStream<Future<Void>> const& addActor,
	                         UID const& dbgid)
	  : coordinators(coordinators), cstate(coordinators), addActor(addActor), dbgid(dbgid), finalWriteStarted(false),
	    previousWrite(Void()) {}

	Future<Void> read() { return _read(this); }

	Future<Void> write(DBCoreState newState, bool finalWrite = false) {
		previousWrite = _write(this, newState, finalWrite);
		return previousWrite;
	}

	Future<Void> move(ClusterConnectionString const& nc) { return cstate.move(nc); }

private:
	MovableCoordinatedState cstate;
	ServerCoordinators coordinators;
	PromiseStream<Future<Void>> addActor;
	Promise<Void> switchedState;
	UID dbgid;

	ACTOR Future<Void> _read(ReusableCoordinatedState* self) {
		Value prevDBStateRaw = wait(self->cstate.read());
		Future<Void> onConflict = masterTerminateOnConflict(
		    self->dbgid, self->fullyRecovered, self->cstate.onConflict(), self->switchedState.getFuture());
		if (onConflict.isReady() && onConflict.isError()) {
			throw onConflict.getError();
		}
		self->addActor.send(onConflict);

		if (prevDBStateRaw.size()) {
			self->prevDBState = BinaryReader::fromStringRef<DBCoreState>(prevDBStateRaw, IncludeVersion());
			self->myDBState = self->prevDBState;
		}

		return Void();
	}

	ACTOR Future<Void> _write(ReusableCoordinatedState* self, DBCoreState newState, bool finalWrite) {
		if (self->finalWriteStarted) {
			wait(Future<Void>(Never()));
		}

		if (finalWrite) {
			self->finalWriteStarted = true;
		}

		try {
			wait(self->cstate.setExclusive(
			    BinaryWriter::toValue(newState, IncludeVersion(ProtocolVersion::withDBCoreState()))));
		} catch (Error& e) {
			TEST(true); // Master displaced during writeMasterState
			throw;
		}

		self->myDBState = newState;

		if (!finalWrite) {
			self->switchedState.send(Void());
			self->cstate = MovableCoordinatedState(self->coordinators);
			Value rereadDBStateRaw = wait(self->cstate.read());
			DBCoreState readState;
			if (rereadDBStateRaw.size())
				readState = BinaryReader::fromStringRef<DBCoreState>(rereadDBStateRaw, IncludeVersion());

			if (readState != newState) {
				TraceEvent("MasterTerminated", self->dbgid).detail("Reason", "CStateChanged");
				TEST(true); // Coordinated state changed between writing and reading, master dying
				throw worker_removed();
			}
			self->switchedState = Promise<Void>();
			self->addActor.send(masterTerminateOnConflict(
			    self->dbgid, self->fullyRecovered, self->cstate.onConflict(), self->switchedState.getFuture()));
		} else {
			self->fullyRecovered.send(Void());
		}

		return Void();
	}
};

struct MasterData : NonCopyable, ReferenceCounted<MasterData> {
	UID dbgid;

	AsyncTrigger registrationTrigger;
	Version lastEpochEnd, // The last version in the old epoch not (to be) rolled back in this recovery
	    recoveryTransactionVersion; // The first version in this epoch
	double lastCommitTime;

	Version liveCommittedVersion; // The largest live committed version reported by commit proxies.
	bool databaseLocked;
	Optional<Value> proxyMetadataVersion;
	Version minKnownCommittedVersion;

	DatabaseConfiguration originalConfiguration;
	DatabaseConfiguration configuration;
	std::vector<Optional<Key>> primaryDcId;
	std::vector<Optional<Key>> remoteDcIds;
	bool hasConfiguration;

	ServerCoordinators coordinators;

	Reference<ILogSystem> logSystem;
	Version version; // The last version assigned to a proxy by getVersion()
	double lastVersionTime;
	LogSystemDiskQueueAdapter* txnStateLogAdapter;
	IKeyValueStore* txnStateStore;
	int64_t memoryLimit;
	std::map<Optional<Value>, int8_t> dcId_locality;
	std::vector<Tag> allTags;

	int8_t getNextLocality() {
		int8_t maxLocality = -1;
		for (auto it : dcId_locality) {
			maxLocality = std::max(maxLocality, it.second);
		}
		return maxLocality + 1;
	}

	std::vector<CommitProxyInterface> commitProxies;
	std::vector<CommitProxyInterface> provisionalCommitProxies;
	std::vector<GrvProxyInterface> grvProxies;
	std::vector<GrvProxyInterface> provisionalGrvProxies;
	std::vector<ResolverInterface> resolvers;

	std::map<UID, CommitProxyVersionReplies> lastCommitProxyVersionReplies;

	Standalone<StringRef> dbId;

	MasterInterface myInterface;
	const ClusterControllerFullInterface
	    clusterController; // If the cluster controller changes, this master will die, so this is immutable.

	ReusableCoordinatedState cstate;
	Promise<Void> cstateUpdated;
	Reference<AsyncVar<ServerDBInfo>> dbInfo;
	int64_t registrationCount; // Number of different MasterRegistrationRequests sent to clusterController

	RecoveryState recoveryState;

	AsyncVar<Standalone<VectorRef<ResolverMoveRef>>> resolverChanges;
	Version resolverChangesVersion;
	std::set<UID> resolverNeedingChanges;

	PromiseStream<Future<Void>> addActor;
	Reference<AsyncVar<bool>> recruitmentStalled;
	bool forceRecovery;
	bool neverCreated;
	int8_t safeLocality;
	int8_t primaryLocality;

	std::vector<WorkerInterface> backupWorkers; // Recruited backup workers from cluster controller.

	CounterCollection cc;
	Counter changeCoordinatorsRequests;
	Counter getCommitVersionRequests;
	Counter backupWorkerDoneRequests;
	Counter getLiveCommittedVersionRequests;
	Counter reportLiveCommittedVersionRequests;

	Future<Void> logger;

	MasterData(Reference<AsyncVar<ServerDBInfo>> const& dbInfo,
	           MasterInterface const& myInterface,
	           ServerCoordinators const& coordinators,
	           ClusterControllerFullInterface const& clusterController,
	           Standalone<StringRef> const& dbId,
	           PromiseStream<Future<Void>> const& addActor,
	           bool forceRecovery)
	  : dbgid(myInterface.id()), myInterface(myInterface), dbInfo(dbInfo), cstate(coordinators, addActor, dbgid),
	    coordinators(coordinators), clusterController(clusterController), dbId(dbId), forceRecovery(forceRecovery),
	    safeLocality(tagLocalityInvalid), primaryLocality(tagLocalityInvalid), neverCreated(false),
	    lastEpochEnd(invalidVersion), liveCommittedVersion(invalidVersion), databaseLocked(false),
	    minKnownCommittedVersion(invalidVersion), recoveryTransactionVersion(invalidVersion), lastCommitTime(0),
	    registrationCount(0), version(invalidVersion), lastVersionTime(0), txnStateStore(0), memoryLimit(2e9),
	    addActor(addActor), hasConfiguration(false), recruitmentStalled(makeReference<AsyncVar<bool>>(false)),
	    cc("Master", dbgid.toString()), changeCoordinatorsRequests("ChangeCoordinatorsRequests", cc),
	    getCommitVersionRequests("GetCommitVersionRequests", cc),
	    backupWorkerDoneRequests("BackupWorkerDoneRequests", cc),
	    getLiveCommittedVersionRequests("GetLiveCommittedVersionRequests", cc),
	    reportLiveCommittedVersionRequests("ReportLiveCommittedVersionRequests", cc) {
		logger = traceCounters("MasterMetrics", dbgid, SERVER_KNOBS->WORKER_LOGGING_INTERVAL, &cc, "MasterMetrics");
		if (forceRecovery && !myInterface.locality.dcId().present()) {
			TraceEvent(SevError, "ForcedRecoveryRequiresDcID");
			forceRecovery = false;
		}
	}
	~MasterData() {
		if (txnStateStore)
			txnStateStore->close();
	}
};

ACTOR Future<Void> newCommitProxies(Reference<MasterData> self, RecruitFromConfigurationReply recr) {
	vector<Future<CommitProxyInterface>> initializationReplies;
	for (int i = 0; i < recr.commitProxies.size(); i++) {
		InitializeCommitProxyRequest req;
		req.master = self->myInterface;
		req.recoveryCount = self->cstate.myDBState.recoveryCount + 1;
		req.recoveryTransactionVersion = self->recoveryTransactionVersion;
		req.firstProxy = i == 0;
		TraceEvent("CommitProxyReplies", self->dbgid).detail("WorkerID", recr.commitProxies[i].id());
		initializationReplies.push_back(
		    transformErrors(throwErrorOr(recr.commitProxies[i].commitProxy.getReplyUnlessFailedFor(
		                        req, SERVER_KNOBS->TLOG_TIMEOUT, SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
		                    master_recovery_failed()));
	}

	vector<CommitProxyInterface> newRecruits = wait(getAll(initializationReplies));
	// It is required for the correctness of COMMIT_ON_FIRST_PROXY that self->commitProxies[0] is the firstCommitProxy.
	self->commitProxies = newRecruits;

	return Void();
}

ACTOR Future<Void> newGrvProxies(Reference<MasterData> self, RecruitFromConfigurationReply recr) {
	vector<Future<GrvProxyInterface>> initializationReplies;
	for (int i = 0; i < recr.grvProxies.size(); i++) {
		InitializeGrvProxyRequest req;
		req.master = self->myInterface;
		req.recoveryCount = self->cstate.myDBState.recoveryCount + 1;
		TraceEvent("GrvProxyReplies", self->dbgid).detail("WorkerID", recr.grvProxies[i].id());
		initializationReplies.push_back(
		    transformErrors(throwErrorOr(recr.grvProxies[i].grvProxy.getReplyUnlessFailedFor(
		                        req, SERVER_KNOBS->TLOG_TIMEOUT, SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
		                    master_recovery_failed()));
	}

	vector<GrvProxyInterface> newRecruits = wait(getAll(initializationReplies));
	self->grvProxies = newRecruits;
	return Void();
}

ACTOR Future<Void> newResolvers(Reference<MasterData> self, RecruitFromConfigurationReply recr) {
	vector<Future<ResolverInterface>> initializationReplies;
	for (int i = 0; i < recr.resolvers.size(); i++) {
		InitializeResolverRequest req;
		req.recoveryCount = self->cstate.myDBState.recoveryCount + 1;
		req.commitProxyCount = recr.commitProxies.size();
		req.resolverCount = recr.resolvers.size();
		TraceEvent("ResolverReplies", self->dbgid).detail("WorkerID", recr.resolvers[i].id());
		initializationReplies.push_back(
		    transformErrors(throwErrorOr(recr.resolvers[i].resolver.getReplyUnlessFailedFor(
		                        req, SERVER_KNOBS->TLOG_TIMEOUT, SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
		                    master_recovery_failed()));
	}

	vector<ResolverInterface> newRecruits = wait(getAll(initializationReplies));
	self->resolvers = newRecruits;

	return Void();
}

ACTOR Future<Void> newTLogServers(Reference<MasterData> self,
                                  RecruitFromConfigurationReply recr,
                                  Reference<ILogSystem> oldLogSystem,
                                  vector<Standalone<CommitTransactionRef>>* initialConfChanges) {
	if (self->configuration.usableRegions > 1) {
		state Optional<Key> remoteDcId = self->remoteDcIds.size() ? self->remoteDcIds[0] : Optional<Key>();
		if (!self->dcId_locality.count(recr.dcId)) {
			int8_t loc = self->getNextLocality();
			Standalone<CommitTransactionRef> tr;
			tr.set(tr.arena(), tagLocalityListKeyFor(recr.dcId), tagLocalityListValue(loc));
			initialConfChanges->push_back(tr);
			self->dcId_locality[recr.dcId] = loc;
			TraceEvent(SevWarn, "UnknownPrimaryDCID", self->dbgid).detail("PrimaryId", recr.dcId).detail("Loc", loc);
		}

		if (!self->dcId_locality.count(remoteDcId)) {
			int8_t loc = self->getNextLocality();
			Standalone<CommitTransactionRef> tr;
			tr.set(tr.arena(), tagLocalityListKeyFor(remoteDcId), tagLocalityListValue(loc));
			initialConfChanges->push_back(tr);
			self->dcId_locality[remoteDcId] = loc;
			TraceEvent(SevWarn, "UnknownRemoteDCID", self->dbgid).detail("RemoteId", remoteDcId).detail("Loc", loc);
		}

		std::vector<UID> exclusionWorkerIds;
		std::transform(recr.tLogs.begin(),
		               recr.tLogs.end(),
		               std::back_inserter(exclusionWorkerIds),
		               [](const WorkerInterface& in) { return in.id(); });
		std::transform(recr.satelliteTLogs.begin(),
		               recr.satelliteTLogs.end(),
		               std::back_inserter(exclusionWorkerIds),
		               [](const WorkerInterface& in) { return in.id(); });
		Future<RecruitRemoteFromConfigurationReply> fRemoteWorkers = brokenPromiseToNever(
		    self->clusterController.recruitRemoteFromConfiguration.getReply(RecruitRemoteFromConfigurationRequest(
		        self->configuration,
		        remoteDcId,
		        recr.tLogs.size() *
		            std::max<int>(1, self->configuration.desiredLogRouterCount / std::max<int>(1, recr.tLogs.size())),
		        exclusionWorkerIds)));

		self->primaryLocality = self->dcId_locality[recr.dcId];
		self->logSystem = Reference<ILogSystem>(); // Cancels the actors in the previous log system.
		Reference<ILogSystem> newLogSystem = wait(oldLogSystem->newEpoch(recr,
		                                                                 fRemoteWorkers,
		                                                                 self->configuration,
		                                                                 self->cstate.myDBState.recoveryCount + 1,
		                                                                 self->primaryLocality,
		                                                                 self->dcId_locality[remoteDcId],
		                                                                 self->allTags,
		                                                                 self->recruitmentStalled));
		self->logSystem = newLogSystem;
	} else {
		self->primaryLocality = tagLocalitySpecial;
		self->logSystem = Reference<ILogSystem>(); // Cancels the actors in the previous log system.
		Reference<ILogSystem> newLogSystem = wait(oldLogSystem->newEpoch(recr,
		                                                                 Never(),
		                                                                 self->configuration,
		                                                                 self->cstate.myDBState.recoveryCount + 1,
		                                                                 self->primaryLocality,
		                                                                 tagLocalitySpecial,
		                                                                 self->allTags,
		                                                                 self->recruitmentStalled));
		self->logSystem = newLogSystem;
	}
	return Void();
}

ACTOR Future<Void> newSeedServers(Reference<MasterData> self,
                                  RecruitFromConfigurationReply recruits,
                                  vector<StorageServerInterface>* servers) {
	// This is only necessary if the database is at version 0
	servers->clear();
	if (self->lastEpochEnd)
		return Void();

	state int idx = 0;
	state std::map<Optional<Value>, Tag> dcId_tags;
	state int8_t nextLocality = 0;
	while (idx < recruits.storageServers.size()) {
		TraceEvent("MasterRecruitingInitialStorageServer", self->dbgid)
		    .detail("CandidateWorker", recruits.storageServers[idx].locality.toString());

		InitializeStorageRequest isr;
		isr.seedTag = dcId_tags.count(recruits.storageServers[idx].locality.dcId())
		                  ? dcId_tags[recruits.storageServers[idx].locality.dcId()]
		                  : Tag(nextLocality, 0);
		isr.storeType = self->configuration.storageServerStoreType;
		isr.reqId = deterministicRandom()->randomUniqueID();
		isr.interfaceId = deterministicRandom()->randomUniqueID();

		ErrorOr<InitializeStorageReply> newServer = wait(recruits.storageServers[idx].storage.tryGetReply(isr));

		if (newServer.isError()) {
			if (!newServer.isError(error_code_recruitment_failed) &&
			    !newServer.isError(error_code_request_maybe_delivered))
				throw newServer.getError();

			TEST(true); // masterserver initial storage recuitment loop failed to get new server
			wait(delay(SERVER_KNOBS->STORAGE_RECRUITMENT_DELAY));
		} else {
			if (!dcId_tags.count(recruits.storageServers[idx].locality.dcId())) {
				dcId_tags[recruits.storageServers[idx].locality.dcId()] = Tag(nextLocality, 0);
				nextLocality++;
			}

			Tag& tag = dcId_tags[recruits.storageServers[idx].locality.dcId()];
			tag.id++;
			idx++;

			servers->push_back(newServer.get().interf);
		}
	}

	self->dcId_locality.clear();
	for (auto& it : dcId_tags) {
		self->dcId_locality[it.first] = it.second.locality;
	}

	TraceEvent("MasterRecruitedInitialStorageServers", self->dbgid)
	    .detail("TargetCount", self->configuration.storageTeamSize)
	    .detail("Servers", describe(*servers));

	return Void();
}

Future<Void> waitCommitProxyFailure(vector<CommitProxyInterface> const& commitProxies) {
	std::vector<Future<Void>> failed;
	failed.reserve(commitProxies.size());
	for (auto commitProxy : commitProxies) {
		failed.push_back(waitFailureClient(commitProxy.waitFailure,
		                                   SERVER_KNOBS->TLOG_TIMEOUT,
		                                   -SERVER_KNOBS->TLOG_TIMEOUT / SERVER_KNOBS->SECONDS_BEFORE_NO_FAILURE_DELAY,
		                                   /*trace=*/true));
	}
	ASSERT(failed.size() >= 1);
	return tagError<Void>(quorum(failed, 1), commit_proxy_failed());
}

Future<Void> waitGrvProxyFailure(vector<GrvProxyInterface> const& grvProxies) {
	vector<Future<Void>> failed;
	failed.reserve(grvProxies.size());
	for (int i = 0; i < grvProxies.size(); i++)
		failed.push_back(waitFailureClient(grvProxies[i].waitFailure,
		                                   SERVER_KNOBS->TLOG_TIMEOUT,
		                                   -SERVER_KNOBS->TLOG_TIMEOUT / SERVER_KNOBS->SECONDS_BEFORE_NO_FAILURE_DELAY,
		                                   /*trace=*/true));
	ASSERT(failed.size() >= 1);
	return tagError<Void>(quorum(failed, 1), grv_proxy_failed());
}

Future<Void> waitResolverFailure(vector<ResolverInterface> const& resolvers) {
	std::vector<Future<Void>> failed;
	failed.reserve(resolvers.size());
	for (auto resolver : resolvers) {
		failed.push_back(waitFailureClient(resolver.waitFailure,
		                                   SERVER_KNOBS->TLOG_TIMEOUT,
		                                   -SERVER_KNOBS->TLOG_TIMEOUT / SERVER_KNOBS->SECONDS_BEFORE_NO_FAILURE_DELAY,
		                                   /*trace=*/true));
	}
	ASSERT(failed.size() >= 1);
	return tagError<Void>(quorum(failed, 1), master_resolver_failed());
}

ACTOR Future<Void> updateLogsValue(Reference<MasterData> self, Database cx) {
	state Transaction tr(cx);
	loop {
		try {
			Optional<Standalone<StringRef>> value = wait(tr.get(logsKey));
			ASSERT(value.present());
			auto logs = decodeLogsValue(value.get());

			std::set<UID> logIds;
			for (auto& log : logs.first) {
				logIds.insert(log.first);
			}

			bool found = false;
			for (auto& logSet : self->logSystem->getLogSystemConfig().tLogs) {
				for (auto& log : logSet.tLogs) {
					if (logIds.count(log.id())) {
						found = true;
						break;
					}
				}
				if (found) {
					break;
				}
			}

			if (!found) {
				TEST(true); // old master attempted to change logsKey
				return Void();
			}

			tr.set(logsKey, self->logSystem->getLogsValue());
			wait(tr.commit());
			return Void();
		} catch (Error& e) {
			wait(tr.onError(e));
		}
	}
}

Future<Void> sendMasterRegistration(MasterData* self,
                                    LogSystemConfig const& logSystemConfig,
                                    vector<CommitProxyInterface> commitProxies,
                                    vector<GrvProxyInterface> grvProxies,
                                    vector<ResolverInterface> resolvers,
                                    DBRecoveryCount recoveryCount,
                                    vector<UID> priorCommittedLogServers) {
	RegisterMasterRequest masterReq;
	masterReq.id = self->myInterface.id();
	masterReq.mi = self->myInterface.locality;
	masterReq.logSystemConfig = logSystemConfig;
	masterReq.commitProxies = commitProxies;
	masterReq.grvProxies = grvProxies;
	masterReq.resolvers = resolvers;
	masterReq.recoveryCount = recoveryCount;
	if (self->hasConfiguration)
		masterReq.configuration = self->configuration;
	masterReq.registrationCount = ++self->registrationCount;
	masterReq.priorCommittedLogServers = priorCommittedLogServers;
	masterReq.recoveryState = self->recoveryState;
	masterReq.recoveryStalled = self->recruitmentStalled->get();
	return brokenPromiseToNever(self->clusterController.registerMaster.getReply(masterReq));
}

ACTOR Future<Void> updateRegistration(Reference<MasterData> self, Reference<ILogSystem> logSystem) {
	state Database cx = openDBOnServer(self->dbInfo, TaskPriority::DefaultEndpoint, true, true);
	state Future<Void> trigger = self->registrationTrigger.onTrigger();
	state Future<Void> updateLogsKey;

	loop {
		wait(trigger);
		wait(delay(.001)); // Coalesce multiple changes

		trigger = self->registrationTrigger.onTrigger();

		auto logSystemConfig = logSystem->getLogSystemConfig();
		TraceEvent("MasterUpdateRegistration", self->dbgid)
		    .detail("RecoveryCount", self->cstate.myDBState.recoveryCount)
		    .detail("OldestBackupEpoch", logSystemConfig.oldestBackupEpoch)
		    .detail("Logs", describe(logSystemConfig.tLogs));

		if (!self->cstateUpdated.isSet()) {
			wait(sendMasterRegistration(self.getPtr(),
			                            logSystemConfig,
			                            self->provisionalCommitProxies,
			                            self->provisionalGrvProxies,
			                            self->resolvers,
			                            self->cstate.myDBState.recoveryCount,
			                            self->cstate.prevDBState.getPriorCommittedLogServers()));
		} else {
			updateLogsKey = updateLogsValue(self, cx);
			wait(sendMasterRegistration(self.getPtr(),
			                            logSystemConfig,
			                            self->commitProxies,
			                            self->grvProxies,
			                            self->resolvers,
			                            self->cstate.myDBState.recoveryCount,
			                            vector<UID>()));
		}
	}
}

ACTOR Future<Standalone<CommitTransactionRef>> provisionalMaster(Reference<MasterData> parent, Future<Void> activate) {
	wait(activate);

	// Register a fake commit proxy (to be provided right here) to make ourselves available to clients
	parent->provisionalCommitProxies = vector<CommitProxyInterface>(1);
	parent->provisionalCommitProxies[0].provisional = true;
	parent->provisionalCommitProxies[0].initEndpoints();
	parent->provisionalGrvProxies = vector<GrvProxyInterface>(1);
	parent->provisionalGrvProxies[0].provisional = true;
	parent->provisionalGrvProxies[0].initEndpoints();
	state Future<Void> waitCommitProxyFailure =
	    waitFailureServer(parent->provisionalCommitProxies[0].waitFailure.getFuture());
	state Future<Void> waitGrvProxyFailure =
	    waitFailureServer(parent->provisionalGrvProxies[0].waitFailure.getFuture());
	parent->registrationTrigger.trigger();

	auto lockedKey = parent->txnStateStore->readValue(databaseLockedKey).get();
	state bool locked = lockedKey.present() && lockedKey.get().size();

	state Optional<Value> metadataVersion = parent->txnStateStore->readValue(metadataVersionKey).get();

	// We respond to a minimal subset of the commit proxy protocol.  Our sole purpose is to receive a single write-only
	// transaction which might repair our configuration, and return it.
	loop choose {
		when(GetReadVersionRequest req =
		         waitNext(parent->provisionalGrvProxies[0].getConsistentReadVersion.getFuture())) {
			if (req.flags & GetReadVersionRequest::FLAG_CAUSAL_READ_RISKY && parent->lastEpochEnd) {
				GetReadVersionReply rep;
				rep.version = parent->lastEpochEnd;
				rep.locked = locked;
				rep.metadataVersion = metadataVersion;
				req.reply.send(rep);
			} else
				req.reply.send(Never()); // We can't perform causally consistent reads without recovering
		}
		when(CommitTransactionRequest req = waitNext(parent->provisionalCommitProxies[0].commit.getFuture())) {
			req.reply.send(Never()); // don't reply (clients always get commit_unknown_result)
			auto t = &req.transaction;
			if (t->read_snapshot == parent->lastEpochEnd && //< So no transactions can fall between the read snapshot
			                                                // and the recovery transaction this (might) be merged with
			                                                // vvv and also the changes we will make in the recovery
			                                                // transaction (most notably to lastEpochEndKey) BEFORE we
			                                                // merge initialConfChanges won't conflict
			    !std::any_of(t->read_conflict_ranges.begin(), t->read_conflict_ranges.end(), [](KeyRangeRef const& r) {
				    return r.contains(lastEpochEndKey);
			    })) {
				for (auto m = t->mutations.begin(); m != t->mutations.end(); ++m) {
					TraceEvent("PM_CTM", parent->dbgid)
					    .detail("MType", m->type)
					    .detail("Param1", m->param1)
					    .detail("Param2", m->param2);
					if (isMetadataMutation(*m)) {
						// We keep the mutations and write conflict ranges from this transaction, but not its read
						// conflict ranges
						Standalone<CommitTransactionRef> out;
						out.read_snapshot = invalidVersion;
						out.mutations.append_deep(out.arena(), t->mutations.begin(), t->mutations.size());
						out.write_conflict_ranges.append_deep(
						    out.arena(), t->write_conflict_ranges.begin(), t->write_conflict_ranges.size());
						return out;
					}
				}
			}
		}
		when(GetKeyServerLocationsRequest req =
		         waitNext(parent->provisionalCommitProxies[0].getKeyServersLocations.getFuture())) {
			req.reply.send(Never());
		}
		when(wait(waitCommitProxyFailure)) { throw worker_removed(); }
		when(wait(waitGrvProxyFailure)) { throw worker_removed(); }
	}
}

ACTOR Future<vector<Standalone<CommitTransactionRef>>> recruitEverything(Reference<MasterData> self,
                                                                         vector<StorageServerInterface>* seedServers,
                                                                         Reference<ILogSystem> oldLogSystem) {
	if (!self->configuration.isValid()) {
		RecoveryStatus::RecoveryStatus status;
		if (self->configuration.initialized) {
			TraceEvent(SevWarn, "MasterRecoveryInvalidConfiguration", self->dbgid)
			    .setMaxEventLength(11000)
			    .setMaxFieldLength(10000)
			    .detail("Conf", self->configuration.toString());
			status = RecoveryStatus::configuration_invalid;
		} else if (!self->cstate.prevDBState.tLogs.size()) {
			status = RecoveryStatus::configuration_never_created;
			self->neverCreated = true;
		} else {
			status = RecoveryStatus::configuration_missing;
		}
		TraceEvent("MasterRecoveryState", self->dbgid)
		    .detail("StatusCode", status)
		    .detail("Status", RecoveryStatus::names[status])
		    .trackLatest("MasterRecoveryState");
		return Never();
	} else
		TraceEvent("MasterRecoveryState", self->dbgid)
		    .detail("StatusCode", RecoveryStatus::recruiting_transaction_servers)
		    .detail("Status", RecoveryStatus::names[RecoveryStatus::recruiting_transaction_servers])
		    .detail("RequiredTLogs", self->configuration.tLogReplicationFactor)
		    .detail("DesiredTLogs", self->configuration.getDesiredLogs())
		    .detail("RequiredCommitProxies", 1)
		    .detail("DesiredCommitProxies", self->configuration.getDesiredCommitProxies())
		    .detail("RequiredGrvProxies", 1)
		    .detail("DesiredGrvProxies", self->configuration.getDesiredGrvProxies())
		    .detail("RequiredResolvers", 1)
		    .detail("DesiredResolvers", self->configuration.getDesiredResolvers())
		    .detail("StoreType", self->configuration.storageServerStoreType)
		    .trackLatest("MasterRecoveryState");

	// FIXME: we only need log routers for the same locality as the master
	int maxLogRouters = self->cstate.prevDBState.logRouterTags;
	for (auto& old : self->cstate.prevDBState.oldTLogData) {
		maxLogRouters = std::max(maxLogRouters, old.logRouterTags);
	}

	state RecruitFromConfigurationReply recruits =
	    wait(brokenPromiseToNever(self->clusterController.recruitFromConfiguration.getReply(
	        RecruitFromConfigurationRequest(self->configuration, self->lastEpochEnd == 0, maxLogRouters))));

	self->primaryDcId.clear();
	self->remoteDcIds.clear();
	if (recruits.dcId.present()) {
		self->primaryDcId.push_back(recruits.dcId);
		if (self->configuration.regions.size() > 1) {
			self->remoteDcIds.push_back(recruits.dcId.get() == self->configuration.regions[0].dcId
			                                ? self->configuration.regions[1].dcId
			                                : self->configuration.regions[0].dcId);
		}
	}
	self->backupWorkers.swap(recruits.backupWorkers);

	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::initializing_transaction_servers)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::initializing_transaction_servers])
	    .detail("CommitProxies", recruits.commitProxies.size())
	    .detail("GrvProxies", recruits.grvProxies.size())
	    .detail("TLogs", recruits.tLogs.size())
	    .detail("Resolvers", recruits.resolvers.size())
	    .detail("SatelliteTLogs", recruits.satelliteTLogs.size())
	    .detail("OldLogRouters", recruits.oldLogRouters.size())
	    .detail("StorageServers", recruits.storageServers.size())
	    .detail("BackupWorkers", self->backupWorkers.size())
	    .trackLatest("MasterRecoveryState");

	// Actually, newSeedServers does both the recruiting and initialization of the seed servers; so if this is a brand
	// new database we are sort of lying that we are past the recruitment phase.  In a perfect world we would split that
	// up so that the recruitment part happens above (in parallel with recruiting the transaction servers?).
	wait(newSeedServers(self, recruits, seedServers));
	state vector<Standalone<CommitTransactionRef>> confChanges;
	wait(newCommitProxies(self, recruits) && newGrvProxies(self, recruits) && newResolvers(self, recruits) &&
	     newTLogServers(self, recruits, oldLogSystem, &confChanges));
	return confChanges;
}

ACTOR Future<Void> updateLocalityForDcId(Optional<Key> dcId,
                                         Reference<ILogSystem> oldLogSystem,
                                         Reference<AsyncVar<PeekTxsInfo>> locality) {
	loop {
		std::pair<int8_t, int8_t> loc = oldLogSystem->getLogSystemConfig().getLocalityForDcId(dcId);
		Version ver = locality->get().knownCommittedVersion;
		if (ver == invalidVersion) {
			ver = oldLogSystem->getKnownCommittedVersion();
		}
		locality->set(PeekTxsInfo(loc.first, loc.second, ver));
		TraceEvent("UpdatedLocalityForDcId")
		    .detail("DcId", dcId)
		    .detail("Locality0", loc.first)
		    .detail("Locality1", loc.second)
		    .detail("Version", ver);
		wait(oldLogSystem->onLogSystemConfigChange() || oldLogSystem->onKnownCommittedVersionChange());
	}
}

ACTOR Future<Void> readTransactionSystemState(Reference<MasterData> self,
                                              Reference<ILogSystem> oldLogSystem,
                                              Version txsPoppedVersion) {
	state Reference<AsyncVar<PeekTxsInfo>> myLocality = Reference<AsyncVar<PeekTxsInfo>>(
	    new AsyncVar<PeekTxsInfo>(PeekTxsInfo(tagLocalityInvalid, tagLocalityInvalid, invalidVersion)));
	state Future<Void> localityUpdater =
	    updateLocalityForDcId(self->myInterface.locality.dcId(), oldLogSystem, myLocality);
	// Peek the txnStateTag in oldLogSystem and recover self->txnStateStore

	// For now, we also obtain the recovery metadata that the log system obtained during the end_epoch process for
	// comparison

	// Sets self->lastEpochEnd and self->recoveryTransactionVersion
	// Sets self->configuration to the configuration (FF/conf/ keys) at self->lastEpochEnd

	// Recover transaction state store
	if (self->txnStateStore)
		self->txnStateStore->close();
	self->txnStateLogAdapter = openDiskQueueAdapter(oldLogSystem, myLocality, txsPoppedVersion);
	self->txnStateStore =
	    keyValueStoreLogSystem(self->txnStateLogAdapter, self->dbgid, self->memoryLimit, false, false, true);

	// Versionstamped operations (particularly those applied from DR) define a minimum commit version
	// that we may recover to, as they embed the version in user-readable data and require that no
	// transactions will be committed at a lower version.
	Optional<Standalone<StringRef>> requiredCommitVersion =
	    wait(self->txnStateStore->readValue(minRequiredCommitVersionKey));
	Version minRequiredCommitVersion = -1;
	if (requiredCommitVersion.present()) {
		minRequiredCommitVersion = BinaryReader::fromStringRef<Version>(requiredCommitVersion.get(), Unversioned());
	}

	// Recover version info
	self->lastEpochEnd = oldLogSystem->getEnd() - 1;
	if (self->lastEpochEnd == 0) {
		self->recoveryTransactionVersion = 1;
	} else {
		if (self->forceRecovery) {
			self->recoveryTransactionVersion = self->lastEpochEnd + SERVER_KNOBS->MAX_VERSIONS_IN_FLIGHT_FORCED;
		} else {
			self->recoveryTransactionVersion = self->lastEpochEnd + SERVER_KNOBS->MAX_VERSIONS_IN_FLIGHT;
		}

		if (BUGGIFY) {
			self->recoveryTransactionVersion +=
			    deterministicRandom()->randomInt64(0, SERVER_KNOBS->MAX_VERSIONS_IN_FLIGHT);
		}
		if (self->recoveryTransactionVersion < minRequiredCommitVersion)
			self->recoveryTransactionVersion = minRequiredCommitVersion;
	}

	TraceEvent("MasterRecovering", self->dbgid)
	    .detail("LastEpochEnd", self->lastEpochEnd)
	    .detail("RecoveryTransactionVersion", self->recoveryTransactionVersion);

	RangeResult rawConf = wait(self->txnStateStore->readRange(configKeys));
	self->configuration.fromKeyValues(rawConf.castTo<VectorRef<KeyValueRef>>());
	self->originalConfiguration = self->configuration;
	self->hasConfiguration = true;

	TraceEvent("MasterRecoveredConfig", self->dbgid)
	    .setMaxEventLength(11000)
	    .setMaxFieldLength(10000)
	    .detail("Conf", self->configuration.toString())
	    .trackLatest("RecoveredConfig");

	RangeResult rawLocalities = wait(self->txnStateStore->readRange(tagLocalityListKeys));
	self->dcId_locality.clear();
	for (auto& kv : rawLocalities) {
		self->dcId_locality[decodeTagLocalityListKey(kv.key)] = decodeTagLocalityListValue(kv.value);
	}

	RangeResult rawTags = wait(self->txnStateStore->readRange(serverTagKeys));
	self->allTags.clear();
	if (self->lastEpochEnd > 0) {
		self->allTags.push_back(cacheTag);
	}

	if (self->forceRecovery) {
		self->safeLocality = oldLogSystem->getLogSystemConfig().tLogs[0].locality;
		for (auto& kv : rawTags) {
			Tag tag = decodeServerTagValue(kv.value);
			if (tag.locality == self->safeLocality) {
				self->allTags.push_back(tag);
			}
		}
	} else {
		for (auto& kv : rawTags) {
			self->allTags.push_back(decodeServerTagValue(kv.value));
		}
	}

	RangeResult rawHistoryTags = wait(self->txnStateStore->readRange(serverTagHistoryKeys));
	for (auto& kv : rawHistoryTags) {
		self->allTags.push_back(decodeServerTagValue(kv.value));
	}

	uniquify(self->allTags);

	// auto kvs = self->txnStateStore->readRange( systemKeys );
	// for( auto & kv : kvs.get() )
	//	TraceEvent("MasterRecoveredTXS", self->dbgid).detail("K", kv.key).detail("V", kv.value);

	self->txnStateLogAdapter->setNextVersion(
	    oldLogSystem->getEnd()); //< FIXME: (1) the log adapter should do this automatically after recovery; (2) if we
	                             // make KeyValueStoreMemory guarantee immediate reads, we should be able to get rid of
	                             // the discardCommit() below and not need a writable log adapter

	TraceEvent("RTSSComplete", self->dbgid);

	return Void();
}

ACTOR Future<Void> sendInitialCommitToResolvers(Reference<MasterData> self) {
	state KeyRange txnKeys = allKeys;
	state Sequence txnSequence = 0;
	ASSERT(self->recoveryTransactionVersion);

	state RangeResult data =
	    self->txnStateStore
	        ->readRange(txnKeys, BUGGIFY ? 3 : SERVER_KNOBS->DESIRED_TOTAL_BYTES, SERVER_KNOBS->DESIRED_TOTAL_BYTES)
	        .get();
	state std::vector<Future<Void>> txnReplies;
	state int64_t dataOutstanding = 0;

	state std::vector<Endpoint> endpoints;
	for (auto& it : self->commitProxies) {
		endpoints.push_back(it.txnState.getEndpoint());
	}

	loop {
		if (!data.size())
			break;
		((KeyRangeRef&)txnKeys) = KeyRangeRef(keyAfter(data.back().key, txnKeys.arena()), txnKeys.end);
		RangeResult nextData =
		    self->txnStateStore
		        ->readRange(txnKeys, BUGGIFY ? 3 : SERVER_KNOBS->DESIRED_TOTAL_BYTES, SERVER_KNOBS->DESIRED_TOTAL_BYTES)
		        .get();

		TxnStateRequest req;
		req.arena = data.arena();
		req.data = data;
		req.sequence = txnSequence;
		req.last = !nextData.size();
		req.broadcastInfo = endpoints;
		txnReplies.push_back(broadcastTxnRequest(req, SERVER_KNOBS->TXN_STATE_SEND_AMOUNT, false));
		dataOutstanding += SERVER_KNOBS->TXN_STATE_SEND_AMOUNT * data.arena().getSize();
		data = nextData;
		txnSequence++;

		if (dataOutstanding > SERVER_KNOBS->MAX_TXS_SEND_MEMORY) {
			wait(waitForAll(txnReplies));
			txnReplies = vector<Future<Void>>();
			dataOutstanding = 0;
		}

		wait(yield());
	}
	wait(waitForAll(txnReplies));

	vector<Future<ResolveTransactionBatchReply>> replies;
	for (auto& r : self->resolvers) {
		ResolveTransactionBatchRequest req;
		req.prevVersion = -1;
		req.version = self->lastEpochEnd;
		req.lastReceivedVersion = -1;

		replies.push_back(brokenPromiseToNever(r.resolve.getReply(req)));
	}

	wait(waitForAll(replies));
	return Void();
}

ACTOR Future<Void> triggerUpdates(Reference<MasterData> self, Reference<ILogSystem> oldLogSystem) {
	loop {
		wait(oldLogSystem->onLogSystemConfigChange() || self->cstate.fullyRecovered.getFuture() ||
		     self->recruitmentStalled->onChange());
		if (self->cstate.fullyRecovered.isSet())
			return Void();

		self->registrationTrigger.trigger();
	}
}

ACTOR Future<Void> discardCommit(IKeyValueStore* store, LogSystemDiskQueueAdapter* adapter) {
	state Future<LogSystemDiskQueueAdapter::CommitMessage> fcm = adapter->getCommitMessage();
	state Future<Void> committed = store->commit();
	LogSystemDiskQueueAdapter::CommitMessage cm = wait(fcm);
	ASSERT(!committed.isReady());
	cm.acknowledge.send(Void());
	ASSERT(committed.isReady());
	return Void();
}

void updateConfigForForcedRecovery(Reference<MasterData> self,
                                   vector<Standalone<CommitTransactionRef>>* initialConfChanges) {
	bool regionsChanged = false;
	for (auto& it : self->configuration.regions) {
		if (it.dcId == self->myInterface.locality.dcId().get() && it.priority < 0) {
			it.priority = 1;
			regionsChanged = true;
		} else if (it.dcId != self->myInterface.locality.dcId().get() && it.priority >= 0) {
			it.priority = -1;
			regionsChanged = true;
		}
	}
	Standalone<CommitTransactionRef> regionCommit;
	regionCommit.mutations.push_back_deep(
	    regionCommit.arena(),
	    MutationRef(MutationRef::SetValue, configKeysPrefix.toString() + "usable_regions", LiteralStringRef("1")));
	self->configuration.applyMutation(regionCommit.mutations.back());
	if (regionsChanged) {
		std::sort(
		    self->configuration.regions.begin(), self->configuration.regions.end(), RegionInfo::sort_by_priority());
		StatusObject regionJSON;
		regionJSON["regions"] = self->configuration.getRegionJSON();
		regionCommit.mutations.push_back_deep(
		    regionCommit.arena(),
		    MutationRef(MutationRef::SetValue,
		                configKeysPrefix.toString() + "regions",
		                BinaryWriter::toValue(regionJSON, IncludeVersion(ProtocolVersion::withRegionConfiguration()))
		                    .toString()));
		self->configuration.applyMutation(
		    regionCommit.mutations.back()); // modifying the configuration directly does not change the configuration
		                                    // when it is re-serialized unless we call applyMutation
		TraceEvent("ForcedRecoveryConfigChange", self->dbgid)
		    .setMaxEventLength(11000)
		    .setMaxFieldLength(10000)
		    .detail("Conf", self->configuration.toString());
	}
	initialConfChanges->push_back(regionCommit);
}

ACTOR Future<Void> recoverFrom(Reference<MasterData> self,
                               Reference<ILogSystem> oldLogSystem,
                               vector<StorageServerInterface>* seedServers,
                               vector<Standalone<CommitTransactionRef>>* initialConfChanges,
                               Future<Version> poppedTxsVersion) {
	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::reading_transaction_system_state)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::reading_transaction_system_state])
	    .trackLatest("MasterRecoveryState");
	self->hasConfiguration = false;

	if (BUGGIFY)
		wait(delay(10.0));

	Version txsPoppedVersion = wait(poppedTxsVersion);
	wait(readTransactionSystemState(self, oldLogSystem, txsPoppedVersion));
	for (auto& itr : *initialConfChanges) {
		for (auto& m : itr.mutations) {
			self->configuration.applyMutation(m);
		}
	}

	if (self->forceRecovery) {
		updateConfigForForcedRecovery(self, initialConfChanges);
	}

	debug_checkMaxRestoredVersion(UID(), self->lastEpochEnd, "DBRecovery");

	// Ordinarily we pass through this loop once and recover.  We go around the loop if recovery stalls for more than a
	// second, a provisional master is initialized, and an "emergency transaction" is submitted that might change the
	// configuration so that we can finish recovery.

	state std::map<Optional<Value>, int8_t> originalLocalityMap = self->dcId_locality;
	state Future<vector<Standalone<CommitTransactionRef>>> recruitments =
	    recruitEverything(self, seedServers, oldLogSystem);
	state double provisionalDelay = SERVER_KNOBS->PROVISIONAL_START_DELAY;
	loop {
		state Future<Standalone<CommitTransactionRef>> provisional = provisionalMaster(self, delay(provisionalDelay));
		provisionalDelay =
		    std::min(SERVER_KNOBS->PROVISIONAL_MAX_DELAY, provisionalDelay * SERVER_KNOBS->PROVISIONAL_DELAY_GROWTH);
		choose {
			when(vector<Standalone<CommitTransactionRef>> confChanges = wait(recruitments)) {
				initialConfChanges->insert(initialConfChanges->end(), confChanges.begin(), confChanges.end());
				provisional.cancel();
				break;
			}
			when(Standalone<CommitTransactionRef> _req = wait(provisional)) {
				state Standalone<CommitTransactionRef> req = _req; // mutable
				TEST(true); // Emergency transaction processing during recovery
				TraceEvent("EmergencyTransaction", self->dbgid);
				for (auto m = req.mutations.begin(); m != req.mutations.end(); ++m)
					TraceEvent("EmergencyTransactionMutation", self->dbgid)
					    .detail("MType", m->type)
					    .detail("P1", m->param1)
					    .detail("P2", m->param2);

				DatabaseConfiguration oldConf = self->configuration;
				self->configuration = self->originalConfiguration;
				for (auto& m : req.mutations)
					self->configuration.applyMutation(m);

				initialConfChanges->clear();
				if (self->originalConfiguration.isValid() &&
				    self->configuration.usableRegions != self->originalConfiguration.usableRegions) {
					TraceEvent(SevWarnAlways, "CannotChangeUsableRegions", self->dbgid);
					self->configuration = self->originalConfiguration;
				} else {
					initialConfChanges->push_back(req);
				}
				if (self->forceRecovery) {
					updateConfigForForcedRecovery(self, initialConfChanges);
				}

				if (self->configuration != oldConf) { // confChange does not trigger when including servers
					self->dcId_locality = originalLocalityMap;
					recruitments = recruitEverything(self, seedServers, oldLogSystem);
				}
			}
		}

		provisional.cancel();
	}

	return Void();
}

ACTOR Future<Void> getVersion(Reference<MasterData> self, GetCommitVersionRequest req) {
	state Span span("M:getVersion"_loc, { req.spanContext });
	state std::map<UID, CommitProxyVersionReplies>::iterator proxyItr =
	    self->lastCommitProxyVersionReplies.find(req.requestingProxy); // lastCommitProxyVersionReplies never changes

	++self->getCommitVersionRequests;

	if (proxyItr == self->lastCommitProxyVersionReplies.end()) {
		// Request from invalid proxy (e.g. from duplicate recruitment request)
		req.reply.send(Never());
		return Void();
	}

	TEST(proxyItr->second.latestRequestNum.get() < req.requestNum - 1); // Commit version request queued up
	wait(proxyItr->second.latestRequestNum.whenAtLeast(req.requestNum - 1));

	auto itr = proxyItr->second.replies.find(req.requestNum);
	if (itr != proxyItr->second.replies.end()) {
		TEST(true); // Duplicate request for sequence
		req.reply.send(itr->second);
	} else if (req.requestNum <= proxyItr->second.latestRequestNum.get()) {
		TEST(true); // Old request for previously acknowledged sequence - may be impossible with current FlowTransport
		ASSERT(req.requestNum <
		       proxyItr->second.latestRequestNum.get()); // The latest request can never be acknowledged
		req.reply.send(Never());
	} else {
		GetCommitVersionReply rep;

		if (self->version == invalidVersion) {
			self->lastVersionTime = now();
			self->version = self->recoveryTransactionVersion;
			rep.prevVersion = self->lastEpochEnd;
		} else {
			double t1 = now();
			if (BUGGIFY) {
				t1 = self->lastVersionTime;
			}
			rep.prevVersion = self->version;
			self->version +=
			    std::max<Version>(1,
			                      std::min<Version>(SERVER_KNOBS->MAX_READ_TRANSACTION_LIFE_VERSIONS,
			                                        SERVER_KNOBS->VERSIONS_PER_SECOND * (t1 - self->lastVersionTime)));

			TEST(self->version - rep.prevVersion == 1); // Minimum possible version gap

			bool maxVersionGap = self->version - rep.prevVersion == SERVER_KNOBS->MAX_READ_TRANSACTION_LIFE_VERSIONS;
			TEST(maxVersionGap); // Maximum possible version gap
			self->lastVersionTime = t1;

			if (self->resolverNeedingChanges.count(req.requestingProxy)) {
				rep.resolverChanges = self->resolverChanges.get();
				rep.resolverChangesVersion = self->resolverChangesVersion;
				self->resolverNeedingChanges.erase(req.requestingProxy);

				if (self->resolverNeedingChanges.empty())
					self->resolverChanges.set(Standalone<VectorRef<ResolverMoveRef>>());
			}
		}

		rep.version = self->version;
		rep.requestNum = req.requestNum;

		proxyItr->second.replies.erase(proxyItr->second.replies.begin(),
		                               proxyItr->second.replies.upper_bound(req.mostRecentProcessedRequestNum));
		proxyItr->second.replies[req.requestNum] = rep;
		ASSERT(rep.prevVersion >= 0);
		req.reply.send(rep);

		ASSERT(proxyItr->second.latestRequestNum.get() == req.requestNum - 1);
		proxyItr->second.latestRequestNum.set(req.requestNum);
	}

	return Void();
}

ACTOR Future<Void> provideVersions(Reference<MasterData> self) {
	state ActorCollection versionActors(false);

	for (auto& p : self->commitProxies)
		self->lastCommitProxyVersionReplies[p.id()] = CommitProxyVersionReplies();

	loop {
		choose {
			when(GetCommitVersionRequest req = waitNext(self->myInterface.getCommitVersion.getFuture())) {
				versionActors.add(getVersion(self, req));
			}
			when(wait(versionActors.getResult())) {}
		}
	}
}

ACTOR Future<Void> serveLiveCommittedVersion(Reference<MasterData> self) {
	loop {
		choose {
			when(GetRawCommittedVersionRequest req = waitNext(self->myInterface.getLiveCommittedVersion.getFuture())) {
				if (req.debugID.present())
					g_traceBatch.addEvent("TransactionDebug",
					                      req.debugID.get().first(),
					                      "MasterServer.serveLiveCommittedVersion.GetRawCommittedVersion");

				if (self->liveCommittedVersion == invalidVersion) {
					self->liveCommittedVersion = self->recoveryTransactionVersion;
				}
				++self->getLiveCommittedVersionRequests;
				GetRawCommittedVersionReply reply;
				reply.version = self->liveCommittedVersion;
				reply.locked = self->databaseLocked;
				reply.metadataVersion = self->proxyMetadataVersion;
				reply.minKnownCommittedVersion = self->minKnownCommittedVersion;
				req.reply.send(reply);
			}
			when(ReportRawCommittedVersionRequest req =
			         waitNext(self->myInterface.reportLiveCommittedVersion.getFuture())) {
				self->minKnownCommittedVersion = std::max(self->minKnownCommittedVersion, req.minKnownCommittedVersion);
				if (req.version > self->liveCommittedVersion) {
					self->liveCommittedVersion = req.version;
					self->databaseLocked = req.locked;
					self->proxyMetadataVersion = req.metadataVersion;
				}
				++self->reportLiveCommittedVersionRequests;
				req.reply.send(Void());
			}
		}
	}
}

std::pair<KeyRangeRef, bool> findRange(CoalescedKeyRangeMap<int>& key_resolver,
                                       Standalone<VectorRef<ResolverMoveRef>>& movedRanges,
                                       int src,
                                       int dest) {
	auto ranges = key_resolver.ranges();
	auto prev = ranges.begin();
	auto it = ranges.begin();
	++it;
	if (it == ranges.end()) {
		if (ranges.begin().value() != src ||
		    std::find(movedRanges.begin(), movedRanges.end(), ResolverMoveRef(ranges.begin()->range(), dest)) !=
		        movedRanges.end())
			throw operation_failed();
		return std::make_pair(ranges.begin().range(), true);
	}

	std::set<int> borders;
	// If possible expand an existing boundary between the two resolvers
	for (; it != ranges.end(); ++it) {
		if (it->value() == src && prev->value() == dest &&
		    std::find(movedRanges.begin(), movedRanges.end(), ResolverMoveRef(it->range(), dest)) ==
		        movedRanges.end()) {
			return std::make_pair(it->range(), true);
		}
		if (it->value() == dest && prev->value() == src &&
		    std::find(movedRanges.begin(), movedRanges.end(), ResolverMoveRef(prev->range(), dest)) ==
		        movedRanges.end()) {
			return std::make_pair(prev->range(), false);
		}
		if (it->value() == dest)
			borders.insert(prev->value());
		if (prev->value() == dest)
			borders.insert(it->value());
		++prev;
	}

	prev = ranges.begin();
	it = ranges.begin();
	++it;
	// If possible create a new boundry which doesn't exist yet
	for (; it != ranges.end(); ++it) {
		if (it->value() == src && !borders.count(prev->value()) &&
		    std::find(movedRanges.begin(), movedRanges.end(), ResolverMoveRef(it->range(), dest)) ==
		        movedRanges.end()) {
			return std::make_pair(it->range(), true);
		}
		if (prev->value() == src && !borders.count(it->value()) &&
		    std::find(movedRanges.begin(), movedRanges.end(), ResolverMoveRef(prev->range(), dest)) ==
		        movedRanges.end()) {
			return std::make_pair(prev->range(), false);
		}
		++prev;
	}

	it = ranges.begin();
	for (; it != ranges.end(); ++it) {
		if (it->value() == src &&
		    std::find(movedRanges.begin(), movedRanges.end(), ResolverMoveRef(it->range(), dest)) ==
		        movedRanges.end()) {
			return std::make_pair(it->range(), true);
		}
	}
	throw operation_failed(); // we are already attempting to move all of the data one resolver is assigned, so do not
	                          // move anything
}

ACTOR Future<Void> resolutionBalancing(Reference<MasterData> self) {
	state CoalescedKeyRangeMap<int> key_resolver;
	key_resolver.insert(allKeys, 0);
	loop {
		wait(delay(SERVER_KNOBS->MIN_BALANCE_TIME, TaskPriority::ResolutionMetrics));
		while (self->resolverChanges.get().size())
			wait(self->resolverChanges.onChange());
		state std::vector<Future<ResolutionMetricsReply>> futures;
		for (auto& p : self->resolvers)
			futures.push_back(
			    brokenPromiseToNever(p.metrics.getReply(ResolutionMetricsRequest(), TaskPriority::ResolutionMetrics)));
		wait(waitForAll(futures));
		state IndexedSet<std::pair<int64_t, int>, NoMetric> metrics;

		int64_t total = 0;
		for (int i = 0; i < futures.size(); i++) {
			total += futures[i].get().value;
			metrics.insert(std::make_pair(futures[i].get().value, i), NoMetric());
			//TraceEvent("ResolverMetric").detail("I", i).detail("Metric", futures[i].get());
		}
		if (metrics.lastItem()->first - metrics.begin()->first > SERVER_KNOBS->MIN_BALANCE_DIFFERENCE) {
			try {
				state int src = metrics.lastItem()->second;
				state int dest = metrics.begin()->second;
				state int64_t amount = std::min(metrics.lastItem()->first - total / self->resolvers.size(),
				                                total / self->resolvers.size() - metrics.begin()->first) /
				                       2;
				state Standalone<VectorRef<ResolverMoveRef>> movedRanges;

				loop {
					state std::pair<KeyRangeRef, bool> range = findRange(key_resolver, movedRanges, src, dest);

					ResolutionSplitRequest req;
					req.front = range.second;
					req.offset = amount;
					req.range = range.first;

					ResolutionSplitReply split =
					    wait(brokenPromiseToNever(self->resolvers[metrics.lastItem()->second].split.getReply(
					        req, TaskPriority::ResolutionMetrics)));
					KeyRangeRef moveRange = range.second ? KeyRangeRef(range.first.begin, split.key)
					                                     : KeyRangeRef(split.key, range.first.end);
					movedRanges.push_back_deep(movedRanges.arena(), ResolverMoveRef(moveRange, dest));
					TraceEvent("MovingResolutionRange")
					    .detail("Src", src)
					    .detail("Dest", dest)
					    .detail("Amount", amount)
					    .detail("StartRange", range.first)
					    .detail("MoveRange", moveRange)
					    .detail("Used", split.used)
					    .detail("KeyResolverRanges", key_resolver.size());
					amount -= split.used;
					if (moveRange != range.first || amount <= 0)
						break;
				}
				for (auto& it : movedRanges)
					key_resolver.insert(it.range, it.dest);
				// for(auto& it : key_resolver.ranges())
				//	TraceEvent("KeyResolver").detail("Range", it.range()).detail("Value", it.value());

				self->resolverChangesVersion = self->version + 1;
				for (auto& p : self->commitProxies)
					self->resolverNeedingChanges.insert(p.id());
				self->resolverChanges.set(movedRanges);
			} catch (Error& e) {
				if (e.code() != error_code_operation_failed)
					throw;
			}
		}
	}
}

static std::set<int> const& normalMasterErrors() {
	static std::set<int> s;
	if (s.empty()) {
		s.insert(error_code_tlog_stopped);
		s.insert(error_code_master_tlog_failed);
		s.insert(error_code_commit_proxy_failed);
		s.insert(error_code_grv_proxy_failed);
		s.insert(error_code_master_resolver_failed);
		s.insert(error_code_master_backup_worker_failed);
		s.insert(error_code_recruitment_failed);
		s.insert(error_code_no_more_servers);
		s.insert(error_code_master_recovery_failed);
		s.insert(error_code_coordinated_state_conflict);
		s.insert(error_code_master_max_versions_in_flight);
		s.insert(error_code_worker_removed);
		s.insert(error_code_new_coordinators_timed_out);
		s.insert(error_code_broken_promise);
	}
	return s;
}

ACTOR Future<Void> changeCoordinators(Reference<MasterData> self) {
	loop {
		ChangeCoordinatorsRequest req = waitNext(self->myInterface.changeCoordinators.getFuture());
		++self->changeCoordinatorsRequests;
		state ChangeCoordinatorsRequest changeCoordinatorsRequest = req;

		while (!self->cstate.previousWrite.isReady()) {
			wait(self->cstate.previousWrite);
			wait(delay(
			    0)); // if a new core state is ready to be written, have that take priority over our finalizing write;
		}

		if (!self->cstate.fullyRecovered.isSet()) {
			wait(self->cstate.write(self->cstate.myDBState, true));
		}

		try {
			wait(self->cstate.move(ClusterConnectionString(changeCoordinatorsRequest.newConnectionString.toString())));
		} catch (Error& e) {
			if (e.code() != error_code_actor_cancelled)
				changeCoordinatorsRequest.reply.sendError(e);

			throw;
		}

		throw internal_error();
	}
}

ACTOR Future<Void> rejoinRequestHandler(Reference<MasterData> self) {
	loop {
		TLogRejoinRequest req = waitNext(self->myInterface.tlogRejoin.getFuture());
		req.reply.send(true);
	}
}

// Keeps the coordinated state (cstate) updated as the set of recruited tlogs change through recovery.
ACTOR Future<Void> trackTlogRecovery(Reference<MasterData> self,
                                     Reference<AsyncVar<Reference<ILogSystem>>> oldLogSystems,
                                     Future<Void> minRecoveryDuration) {
	state Future<Void> rejoinRequests = Never();
	state DBRecoveryCount recoverCount = self->cstate.myDBState.recoveryCount + 1;
	state DatabaseConfiguration configuration =
	    self->configuration; // self-configuration can be changed by configurationMonitor so we need a copy
	loop {
		state DBCoreState newState;
		self->logSystem->toCoreState(newState);
		newState.recoveryCount = recoverCount;
		state Future<Void> changed = self->logSystem->onCoreStateChanged();

		ASSERT(newState.tLogs[0].tLogWriteAntiQuorum == configuration.tLogWriteAntiQuorum &&
		       newState.tLogs[0].tLogReplicationFactor == configuration.tLogReplicationFactor);

		state bool allLogs =
		    newState.tLogs.size() ==
		    configuration.expectedLogSets(self->primaryDcId.size() ? self->primaryDcId[0] : Optional<Key>());
		state bool finalUpdate = !newState.oldTLogData.size() && allLogs;
		wait(self->cstate.write(newState, finalUpdate));
		wait(minRecoveryDuration);
		self->logSystem->coreStateWritten(newState);
		if (self->cstateUpdated.canBeSet()) {
			self->cstateUpdated.send(Void());
		}

		if (finalUpdate) {
			self->recoveryState = RecoveryState::FULLY_RECOVERED;
			TraceEvent("MasterRecoveryState", self->dbgid)
			    .detail("StatusCode", RecoveryStatus::fully_recovered)
			    .detail("Status", RecoveryStatus::names[RecoveryStatus::fully_recovered])
			    .detail("FullyRecoveredAtVersion", self->version)
			    .trackLatest("MasterRecoveryState");

			TraceEvent("MasterRecoveryGenerations", self->dbgid)
			    .detail("ActiveGenerations", 1)
			    .trackLatest("MasterRecoveryGenerations");
		} else if (!newState.oldTLogData.size() && self->recoveryState < RecoveryState::STORAGE_RECOVERED) {
			self->recoveryState = RecoveryState::STORAGE_RECOVERED;
			TraceEvent("MasterRecoveryState", self->dbgid)
			    .detail("StatusCode", RecoveryStatus::storage_recovered)
			    .detail("Status", RecoveryStatus::names[RecoveryStatus::storage_recovered])
			    .trackLatest("MasterRecoveryState");
		} else if (allLogs && self->recoveryState < RecoveryState::ALL_LOGS_RECRUITED) {
			self->recoveryState = RecoveryState::ALL_LOGS_RECRUITED;
			TraceEvent("MasterRecoveryState", self->dbgid)
			    .detail("StatusCode", RecoveryStatus::all_logs_recruited)
			    .detail("Status", RecoveryStatus::names[RecoveryStatus::all_logs_recruited])
			    .trackLatest("MasterRecoveryState");
		}

		if (newState.oldTLogData.size() && configuration.repopulateRegionAntiQuorum > 0 &&
		    self->logSystem->remoteStorageRecovered()) {
			TraceEvent(SevWarnAlways, "RecruitmentStalled_RemoteStorageRecovered", self->dbgid);
			self->recruitmentStalled->set(true);
		}
		self->registrationTrigger.trigger();

		if (finalUpdate) {
			oldLogSystems->get()->stopRejoins();
			rejoinRequests = rejoinRequestHandler(self);
			return Void();
		}

		wait(changed);
	}
}

ACTOR Future<Void> configurationMonitor(Reference<MasterData> self, Database cx) {
	loop {
		state ReadYourWritesTransaction tr(cx);

		loop {
			try {
				tr.setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
				RangeResult results = wait(tr.getRange(configKeys, CLIENT_KNOBS->TOO_MANY));
				ASSERT(!results.more && results.size() < CLIENT_KNOBS->TOO_MANY);

				DatabaseConfiguration conf;
				conf.fromKeyValues((VectorRef<KeyValueRef>)results);
				if (conf != self->configuration) {
					if (self->recoveryState != RecoveryState::ALL_LOGS_RECRUITED &&
					    self->recoveryState != RecoveryState::FULLY_RECOVERED) {
						throw master_recovery_failed();
					}

					self->configuration = conf;
					self->registrationTrigger.trigger();
				}

				state Future<Void> watchFuture = tr.watch(moveKeysLockOwnerKey) ||
				                                 tr.watch(excludedServersVersionKey) ||
				                                 tr.watch(failedServersVersionKey);
				wait(tr.commit());
				wait(watchFuture);
				break;
			} catch (Error& e) {
				wait(tr.onError(e));
			}
		}
	}
}

ACTOR static Future<Optional<Version>> getMinBackupVersion(Reference<MasterData> self, Database cx) {
	loop {
		state ReadYourWritesTransaction tr(cx);

		try {
			tr.setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);
			tr.setOption(FDBTransactionOptions::LOCK_AWARE);
			Optional<Value> value = wait(tr.get(backupStartedKey));
			Optional<Version> minVersion;
			if (value.present()) {
				auto uidVersions = decodeBackupStartedValue(value.get());
				TraceEvent e("GotBackupStartKey", self->dbgid);
				int i = 1;
				for (auto [uid, version] : uidVersions) {
					e.detail(format("BackupID%d", i), uid).detail(format("Version%d", i), version);
					i++;
					minVersion = minVersion.present() ? std::min(version, minVersion.get()) : version;
				}
			} else {
				TraceEvent("EmptyBackupStartKey", self->dbgid);
			}
			return minVersion;

		} catch (Error& e) {
			wait(tr.onError(e));
		}
	}
}

ACTOR static Future<Void> recruitBackupWorkers(Reference<MasterData> self, Database cx) {
	ASSERT(self->backupWorkers.size() > 0);

	// Avoid race between a backup worker's save progress and the reads below.
	wait(delay(SERVER_KNOBS->SECONDS_BEFORE_RECRUIT_BACKUP_WORKER));

	state LogEpoch epoch = self->cstate.myDBState.recoveryCount;
	state Reference<BackupProgress> backupProgress(
	    new BackupProgress(self->dbgid, self->logSystem->getOldEpochTagsVersionsInfo()));
	state Future<Void> gotProgress = getBackupProgress(cx, self->dbgid, backupProgress, /*logging=*/true);
	state std::vector<Future<InitializeBackupReply>> initializationReplies;

	state std::vector<std::pair<UID, Tag>> idsTags; // worker IDs and tags for current epoch
	state int logRouterTags = self->logSystem->getLogRouterTags();
	idsTags.reserve(logRouterTags);
	for (int i = 0; i < logRouterTags; i++) {
		idsTags.emplace_back(deterministicRandom()->randomUniqueID(), Tag(tagLocalityLogRouter, i));
	}

	const Version startVersion = self->logSystem->getBackupStartVersion();
	state int i = 0;
	for (; i < logRouterTags; i++) {
		const auto& worker = self->backupWorkers[i % self->backupWorkers.size()];
		InitializeBackupRequest req(idsTags[i].first);
		req.recruitedEpoch = epoch;
		req.backupEpoch = epoch;
		req.routerTag = idsTags[i].second;
		req.totalTags = logRouterTags;
		req.startVersion = startVersion;
		TraceEvent("BackupRecruitment", self->dbgid)
		    .detail("RequestID", req.reqId)
		    .detail("Tag", req.routerTag.toString())
		    .detail("Epoch", epoch)
		    .detail("BackupEpoch", epoch)
		    .detail("StartVersion", req.startVersion);
		initializationReplies.push_back(
		    transformErrors(throwErrorOr(worker.backup.getReplyUnlessFailedFor(
		                        req, SERVER_KNOBS->BACKUP_TIMEOUT, SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
		                    master_backup_worker_failed()));
	}

	state Future<Optional<Version>> fMinVersion = getMinBackupVersion(self, cx);
	wait(gotProgress && success(fMinVersion));
	TraceEvent("MinBackupVersion", self->dbgid).detail("Version", fMinVersion.get().present() ? fMinVersion.get() : -1);

	std::map<std::tuple<LogEpoch, Version, int>, std::map<Tag, Version>> toRecruit =
	    backupProgress->getUnfinishedBackup();
	for (const auto& [epochVersionTags, tagVersions] : toRecruit) {
		const Version oldEpochEnd = std::get<1>(epochVersionTags);
		if (!fMinVersion.get().present() || fMinVersion.get().get() + 1 >= oldEpochEnd) {
			TraceEvent("SkipBackupRecruitment", self->dbgid)
			    .detail("MinVersion", fMinVersion.get().present() ? fMinVersion.get() : -1)
			    .detail("Epoch", epoch)
			    .detail("OldEpoch", std::get<0>(epochVersionTags))
			    .detail("OldEpochEnd", oldEpochEnd);
			continue;
		}
		for (const auto& [tag, version] : tagVersions) {
			const auto& worker = self->backupWorkers[i % self->backupWorkers.size()];
			i++;
			InitializeBackupRequest req(deterministicRandom()->randomUniqueID());
			req.recruitedEpoch = epoch;
			req.backupEpoch = std::get<0>(epochVersionTags);
			req.routerTag = tag;
			req.totalTags = std::get<2>(epochVersionTags);
			req.startVersion = version; // savedVersion + 1
			req.endVersion = std::get<1>(epochVersionTags) - 1;
			TraceEvent("BackupRecruitment", self->dbgid)
			    .detail("RequestID", req.reqId)
			    .detail("Tag", req.routerTag.toString())
			    .detail("Epoch", epoch)
			    .detail("BackupEpoch", req.backupEpoch)
			    .detail("StartVersion", req.startVersion)
			    .detail("EndVersion", req.endVersion.get());
			initializationReplies.push_back(transformErrors(
			    throwErrorOr(worker.backup.getReplyUnlessFailedFor(
			        req, SERVER_KNOBS->BACKUP_TIMEOUT, SERVER_KNOBS->MASTER_FAILURE_SLOPE_DURING_RECOVERY)),
			    master_backup_worker_failed()));
		}
	}

	std::vector<InitializeBackupReply> newRecruits = wait(getAll(initializationReplies));
	self->logSystem->setBackupWorkers(newRecruits);
	TraceEvent("BackupRecruitmentDone", self->dbgid);
	self->registrationTrigger.trigger();
	return Void();
}

ACTOR Future<Void> masterCore(Reference<MasterData> self) {
	state TraceInterval recoveryInterval("MasterRecovery");
	state double recoverStartTime = now();

	self->addActor.send(waitFailureServer(self->myInterface.waitFailure.getFuture()));

	TraceEvent(recoveryInterval.begin(), self->dbgid);

	self->recoveryState = RecoveryState::READING_CSTATE;
	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::reading_coordinated_state)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::reading_coordinated_state])
	    .trackLatest("MasterRecoveryState");

	wait(self->cstate.read());

	self->recoveryState = RecoveryState::LOCKING_CSTATE;
	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::locking_coordinated_state)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::locking_coordinated_state])
	    .detail("TLogs", self->cstate.prevDBState.tLogs.size())
	    .detail("ActiveGenerations", self->cstate.myDBState.oldTLogData.size() + 1)
	    .detail("MyRecoveryCount", self->cstate.prevDBState.recoveryCount + 2)
	    .detail("ForceRecovery", self->forceRecovery)
	    .trackLatest("MasterRecoveryState");
	// for (const auto& old : self->cstate.prevDBState.oldTLogData) {
	//	TraceEvent("BWReadCoreState", self->dbgid).detail("Epoch", old.epoch).detail("Version", old.epochEnd);
	//}

	TraceEvent("MasterRecoveryGenerations", self->dbgid)
	    .detail("ActiveGenerations", self->cstate.myDBState.oldTLogData.size() + 1)
	    .trackLatest("MasterRecoveryGenerations");

	if (self->cstate.myDBState.oldTLogData.size() > CLIENT_KNOBS->MAX_GENERATIONS_OVERRIDE) {
		if (self->cstate.myDBState.oldTLogData.size() >= CLIENT_KNOBS->MAX_GENERATIONS) {
			TraceEvent(SevError, "RecoveryStoppedTooManyOldGenerations")
			    .detail("OldGenerations", self->cstate.myDBState.oldTLogData.size())
			    .detail("Reason",
			            "Recovery stopped because too many recoveries have happened since the last time the cluster "
			            "was fully_recovered. Set --knob_max_generations_override on your server processes to a value "
			            "larger than OldGenerations to resume recovery once the underlying problem has been fixed.");
			wait(Future<Void>(Never()));
		} else if (self->cstate.myDBState.oldTLogData.size() > CLIENT_KNOBS->RECOVERY_DELAY_START_GENERATION) {
			TraceEvent(SevError, "RecoveryDelayedTooManyOldGenerations")
			    .detail("OldGenerations", self->cstate.myDBState.oldTLogData.size())
			    .detail("Reason",
			            "Recovery is delayed because too many recoveries have happened since the last time the cluster "
			            "was fully_recovered. Set --knob_max_generations_override on your server processes to a value "
			            "larger than OldGenerations to resume recovery once the underlying problem has been fixed.");
			wait(delay(CLIENT_KNOBS->RECOVERY_DELAY_SECONDS_PER_GENERATION *
			           (self->cstate.myDBState.oldTLogData.size() - CLIENT_KNOBS->RECOVERY_DELAY_START_GENERATION)));
		}
		if (g_network->isSimulated() && self->cstate.myDBState.oldTLogData.size() > CLIENT_KNOBS->MAX_GENERATIONS_SIM) {
			g_simulator.connectionFailuresDisableDuration = 1e6;
			g_simulator.speedUpSimulation = true;
			TraceEvent(SevWarnAlways, "DisableConnectionFailures_TooManyGenerations");
		}
	}

	state Reference<AsyncVar<Reference<ILogSystem>>> oldLogSystems(new AsyncVar<Reference<ILogSystem>>);
	state Future<Void> recoverAndEndEpoch = ILogSystem::recoverAndEndEpoch(oldLogSystems,
	                                                                       self->dbgid,
	                                                                       self->cstate.prevDBState,
	                                                                       self->myInterface.tlogRejoin.getFuture(),
	                                                                       self->myInterface.locality,
	                                                                       &self->forceRecovery);

	DBCoreState newState = self->cstate.myDBState;
	newState.recoveryCount++;
	wait(self->cstate.write(newState) || recoverAndEndEpoch);

	self->recoveryState = RecoveryState::RECRUITING;

	state vector<StorageServerInterface> seedServers;
	state vector<Standalone<CommitTransactionRef>> initialConfChanges;
	state Future<Void> logChanges;
	state Future<Void> minRecoveryDuration;
	state Future<Version> poppedTxsVersion;

	loop {
		Reference<ILogSystem> oldLogSystem = oldLogSystems->get();
		if (oldLogSystem) {
			logChanges = triggerUpdates(self, oldLogSystem);
			if (!minRecoveryDuration.isValid()) {
				minRecoveryDuration = delay(SERVER_KNOBS->ENFORCED_MIN_RECOVERY_DURATION);
				poppedTxsVersion = oldLogSystem->getTxsPoppedVersion();
			}
		}

		state Future<Void> reg = oldLogSystem ? updateRegistration(self, oldLogSystem) : Never();
		self->registrationTrigger.trigger();

		choose {
			when(wait(oldLogSystem
			              ? recoverFrom(self, oldLogSystem, &seedServers, &initialConfChanges, poppedTxsVersion)
			              : Never())) {
				reg.cancel();
				break;
			}
			when(wait(oldLogSystems->onChange())) {}
			when(wait(reg)) { throw internal_error(); }
			when(wait(recoverAndEndEpoch)) { throw internal_error(); }
		}
	}

	if (self->neverCreated) {
		recoverStartTime = now();
	}

	recoverAndEndEpoch.cancel();

	ASSERT(self->commitProxies.size() <= self->configuration.getDesiredCommitProxies());
	ASSERT(self->commitProxies.size() >= 1);
	ASSERT(self->grvProxies.size() <= self->configuration.getDesiredGrvProxies());
	ASSERT(self->grvProxies.size() >= 1);
	ASSERT(self->resolvers.size() <= self->configuration.getDesiredResolvers());
	ASSERT(self->resolvers.size() >= 1);

	self->recoveryState = RecoveryState::RECOVERY_TRANSACTION;
	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::recovery_transaction)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::recovery_transaction])
	    .detail("PrimaryLocality", self->primaryLocality)
	    .detail("DcId", self->myInterface.locality.dcId())
	    .trackLatest("MasterRecoveryState");

	// Recovery transaction
	state bool debugResult = debug_checkMinRestoredVersion(UID(), self->lastEpochEnd, "DBRecovery", SevWarn);

	CommitTransactionRequest recoveryCommitRequest;
	recoveryCommitRequest.flags = recoveryCommitRequest.flags | CommitTransactionRequest::FLAG_IS_LOCK_AWARE;
	CommitTransactionRef& tr = recoveryCommitRequest.transaction;
	int mmApplied = 0; // The number of mutations in tr.mutations that have been applied to the txnStateStore so far
	if (self->lastEpochEnd != 0) {
		Optional<Value> snapRecoveryFlag = self->txnStateStore->readValue(writeRecoveryKey).get();
		TraceEvent("MasterRecoverySnapshotCheck")
		    .detail("SnapRecoveryFlag", snapRecoveryFlag.present() ? snapRecoveryFlag.get().toString() : "N/A")
		    .detail("LastEpochEnd", self->lastEpochEnd);
		if (snapRecoveryFlag.present()) {
			TEST(true); // Recovering from snapshot, writing to snapShotEndVersionKey
			BinaryWriter bw(Unversioned());
			tr.set(recoveryCommitRequest.arena, snapshotEndVersionKey, (bw << self->lastEpochEnd).toValue());
			// Pause the backups that got restored in this snapshot to avoid data corruption
			// Requires further operational work to abort the backup
			TraceEvent("MasterRecoveryPauseBackupAgents");
			Key backupPauseKey = FileBackupAgent::getPauseKey();
			tr.set(recoveryCommitRequest.arena, backupPauseKey, StringRef());
			// Clear the key so multiple recoveries will not overwrite the first version recorded
			tr.clear(recoveryCommitRequest.arena, singleKeyRange(writeRecoveryKey));
		}
		if (self->forceRecovery) {
			BinaryWriter bw(Unversioned());
			tr.set(recoveryCommitRequest.arena, killStorageKey, (bw << self->safeLocality).toValue());
		}

		// This transaction sets \xff/lastEpochEnd, which the shard servers can use to roll back speculatively
		//   processed semi-committed transactions from the previous epoch.
		// It also guarantees the shard servers and tlog servers eventually get versions in the new epoch, which
		//   clients might rely on.
		// This transaction is by itself in a batch (has its own version number), which simplifies storage servers
		// slightly (they assume there are no modifications to serverKeys in the same batch) The proxy also expects the
		// lastEpochEndKey mutation to be first in the transaction
		BinaryWriter bw(Unversioned());
		tr.set(recoveryCommitRequest.arena, lastEpochEndKey, (bw << self->lastEpochEnd).toValue());

		if (self->forceRecovery) {
			tr.set(recoveryCommitRequest.arena, rebootWhenDurableKey, StringRef());
			tr.set(recoveryCommitRequest.arena,
			       moveKeysLockOwnerKey,
			       BinaryWriter::toValue(deterministicRandom()->randomUniqueID(), Unversioned()));
		}
	} else {
		// Recruit and seed initial shard servers
		// This transaction must be the very first one in the database (version 1)
		seedShardServers(recoveryCommitRequest.arena, tr, seedServers);
	}
	// initialConfChanges have not been conflict checked against any earlier writes in the recovery transaction, so do
	// this as early as possible in the recovery transaction but see above comments as to why it can't be absolutely
	// first.  Theoretically emergency transactions should conflict check against the lastEpochEndKey.
	for (auto& itr : initialConfChanges) {
		tr.mutations.append_deep(recoveryCommitRequest.arena, itr.mutations.begin(), itr.mutations.size());
		tr.write_conflict_ranges.append_deep(
		    recoveryCommitRequest.arena, itr.write_conflict_ranges.begin(), itr.write_conflict_ranges.size());
	}

	tr.set(
	    recoveryCommitRequest.arena, primaryLocalityKey, BinaryWriter::toValue(self->primaryLocality, Unversioned()));
	tr.set(recoveryCommitRequest.arena, backupVersionKey, backupVersionValue);
	tr.set(recoveryCommitRequest.arena, coordinatorsKey, self->coordinators.ccf->getConnectionString().toString());
	tr.set(recoveryCommitRequest.arena, logsKey, self->logSystem->getLogsValue());
	tr.set(recoveryCommitRequest.arena,
	       primaryDatacenterKey,
	       self->myInterface.locality.dcId().present() ? self->myInterface.locality.dcId().get() : StringRef());

	tr.clear(recoveryCommitRequest.arena, tLogDatacentersKeys);
	for (auto& dc : self->primaryDcId) {
		tr.set(recoveryCommitRequest.arena, tLogDatacentersKeyFor(dc), StringRef());
	}
	if (self->configuration.usableRegions > 1) {
		for (auto& dc : self->remoteDcIds) {
			tr.set(recoveryCommitRequest.arena, tLogDatacentersKeyFor(dc), StringRef());
		}
	}

	applyMetadataMutations(SpanID(),
	                       self->dbgid,
	                       recoveryCommitRequest.arena,
	                       tr.mutations.slice(mmApplied, tr.mutations.size()),
	                       self->txnStateStore);
	mmApplied = tr.mutations.size();

	tr.read_snapshot = self->recoveryTransactionVersion; // lastEpochEnd would make more sense, but isn't in the initial
	                                                     // window of the resolver(s)

	TraceEvent("MasterRecoveryCommit", self->dbgid);
	state Future<ErrorOr<CommitID>> recoveryCommit = self->commitProxies[0].commit.tryGetReply(recoveryCommitRequest);
	self->addActor.send(self->logSystem->onError());
	self->addActor.send(waitResolverFailure(self->resolvers));
	self->addActor.send(waitCommitProxyFailure(self->commitProxies));
	self->addActor.send(waitGrvProxyFailure(self->grvProxies));
	self->addActor.send(provideVersions(self));
	self->addActor.send(serveLiveCommittedVersion(self));
	self->addActor.send(reportErrors(updateRegistration(self, self->logSystem), "UpdateRegistration", self->dbgid));
	self->registrationTrigger.trigger();

	wait(discardCommit(self->txnStateStore, self->txnStateLogAdapter));

	// Wait for the recovery transaction to complete.
	// SOMEDAY: For faster recovery, do this and setDBState asynchronously and don't wait for them
	// unless we want to change TLogs
	wait((success(recoveryCommit) && sendInitialCommitToResolvers(self)));
	if (recoveryCommit.isReady() && recoveryCommit.get().isError()) {
		TEST(true); // Master recovery failed because of the initial commit failed
		throw master_recovery_failed();
	}

	ASSERT(self->recoveryTransactionVersion != 0);

	self->recoveryState = RecoveryState::WRITING_CSTATE;
	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::writing_coordinated_state)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::writing_coordinated_state])
	    .detail("TLogList", self->logSystem->describe())
	    .trackLatest("MasterRecoveryState");

	// Multiple masters prevent conflicts between themselves via CoordinatedState (self->cstate)
	//  1. If SetMaster succeeds, then by CS's contract, these "new" Tlogs are the immediate
	//     successors of the "old" ones we are replacing
	//  2. logSystem->recoverAndEndEpoch ensured that a co-quorum of the "old" tLogs were stopped at
	//     versions <= self->lastEpochEnd, so no versions > self->lastEpochEnd could be (fully) committed to them.
	//  3. No other master will attempt to commit anything to our "new" Tlogs
	//     because it didn't recruit them
	//  4. Therefore, no full commit can come between self->lastEpochEnd and the first commit
	//     we made to the new Tlogs (self->recoveryTransactionVersion), and only our own semi-commits can come between
	//     our first commit and the next new TLogs

	self->addActor.send(trackTlogRecovery(self, oldLogSystems, minRecoveryDuration));
	debug_advanceMaxCommittedVersion(UID(), self->recoveryTransactionVersion);
	wait(self->cstateUpdated.getFuture());
	debug_advanceMinCommittedVersion(UID(), self->recoveryTransactionVersion);

	if (debugResult) {
		TraceEvent(self->forceRecovery ? SevWarn : SevError, "DBRecoveryDurabilityError");
	}

	TraceEvent("MasterCommittedTLogs", self->dbgid)
	    .detail("TLogs", self->logSystem->describe())
	    .detail("RecoveryCount", self->cstate.myDBState.recoveryCount)
	    .detail("RecoveryTransactionVersion", self->recoveryTransactionVersion);

	TraceEvent(recoveryInterval.end(), self->dbgid)
	    .detail("RecoveryTransactionVersion", self->recoveryTransactionVersion);

	self->recoveryState = RecoveryState::ACCEPTING_COMMITS;
	double recoveryDuration = now() - recoverStartTime;

	TraceEvent((recoveryDuration > 4 && !g_network->isSimulated()) ? SevWarnAlways : SevInfo,
	           "MasterRecoveryDuration",
	           self->dbgid)
	    .detail("RecoveryDuration", recoveryDuration)
	    .trackLatest("MasterRecoveryDuration");

	TraceEvent("MasterRecoveryState", self->dbgid)
	    .detail("StatusCode", RecoveryStatus::accepting_commits)
	    .detail("Status", RecoveryStatus::names[RecoveryStatus::accepting_commits])
	    .detail("StoreType", self->configuration.storageServerStoreType)
	    .detail("RecoveryDuration", recoveryDuration)
	    .trackLatest("MasterRecoveryState");

	TraceEvent("MasterRecoveryAvailable", self->dbgid)
	    .detail("AvailableAtVersion", self->version)
	    .trackLatest("MasterRecoveryAvailable");

	if (self->resolvers.size() > 1)
		self->addActor.send(resolutionBalancing(self));

	self->addActor.send(changeCoordinators(self));
	Database cx = openDBOnServer(self->dbInfo, TaskPriority::DefaultEndpoint, true, true);
	self->addActor.send(configurationMonitor(self, cx));
	if (self->configuration.backupWorkerEnabled) {
		self->addActor.send(recruitBackupWorkers(self, cx));
	} else {
		self->logSystem->setOldestBackupEpoch(self->cstate.myDBState.recoveryCount);
	}

	wait(Future<Void>(Never()));
	throw internal_error();
}

ACTOR Future<Void> masterServer(MasterInterface mi,
                                Reference<AsyncVar<ServerDBInfo>> db,
                                Reference<AsyncVar<Optional<ClusterControllerFullInterface>>> ccInterface,
                                ServerCoordinators coordinators,
                                LifetimeToken lifetime,
                                bool forceRecovery) {
	state Future<Void> ccTimeout = delay(SERVER_KNOBS->CC_INTERFACE_TIMEOUT);
	while (!ccInterface->get().present() || db->get().clusterInterface != ccInterface->get().get()) {
		wait(ccInterface->onChange() || db->onChange() || ccTimeout);
		if (ccTimeout.isReady()) {
			TraceEvent("MasterTerminated", mi.id())
			    .detail("Reason", "Timeout")
			    .detail("CCInterface", ccInterface->get().present() ? ccInterface->get().get().id() : UID())
			    .detail("DBInfoInterface", db->get().clusterInterface.id());
			return Void();
		}
	}

	state Future<Void> onDBChange = Void();
	state PromiseStream<Future<Void>> addActor;
	state Reference<MasterData> self(new MasterData(
	    db, mi, coordinators, db->get().clusterInterface, LiteralStringRef(""), addActor, forceRecovery));
	state Future<Void> collection = actorCollection(self->addActor.getFuture());
	self->addActor.send(traceRole(Role::MASTER, mi.id()));

	TEST(!lifetime.isStillValid(db->get().masterLifetime, mi.id() == db->get().master.id())); // Master born doomed
	TraceEvent("MasterLifetime", self->dbgid).detail("LifetimeToken", lifetime.toString());

	try {
		state Future<Void> core = masterCore(self);
		loop choose {
			when(wait(core)) { break; }
			when(wait(onDBChange)) {
				onDBChange = db->onChange();
				if (!lifetime.isStillValid(db->get().masterLifetime, mi.id() == db->get().master.id())) {
					TraceEvent("MasterTerminated", mi.id())
					    .detail("Reason", "LifetimeToken")
					    .detail("MyToken", lifetime.toString())
					    .detail("CurrentToken", db->get().masterLifetime.toString());
					TEST(true); // Master replaced, dying
					if (BUGGIFY)
						wait(delay(5));
					throw worker_removed();
				}
			}
			when(BackupWorkerDoneRequest req = waitNext(mi.notifyBackupWorkerDone.getFuture())) {
				if (self->logSystem.isValid() && self->logSystem->removeBackupWorker(req)) {
					self->registrationTrigger.trigger();
				}
				++self->backupWorkerDoneRequests;
				req.reply.send(Void());
			}
			when(wait(collection)) {
				ASSERT(false);
				throw internal_error();
			}
		}
	} catch (Error& e) {
		state Error err = e;
		if (e.code() != error_code_actor_cancelled) {
			wait(delay(0.0));
		}

		while (!self->addActor.isEmpty()) {
			self->addActor.getFuture().pop();
		}

		TEST(err.code() == error_code_master_tlog_failed); // Master: terminated due to tLog failure
		TEST(err.code() == error_code_commit_proxy_failed); // Master: terminated due to commit proxy failure
		TEST(err.code() == error_code_grv_proxy_failed); // Master: terminated due to GRV proxy failure
		TEST(err.code() == error_code_master_resolver_failed); // Master: terminated due to resolver failure
		TEST(err.code() == error_code_master_backup_worker_failed); // Master: terminated due to backup worker failure

		if (normalMasterErrors().count(err.code())) {
			TraceEvent("MasterTerminated", mi.id()).error(err);
			return Void();
		}
		throw err;
	}
	return Void();
}