foundationdb/fdbserver/IKeyValueStore.h

/*
 * IKeyValueStore.h
 *
 * 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.
 */

#ifndef FDBSERVER_IKEYVALUESTORE_H
#define FDBSERVER_IKEYVALUESTORE_H
#pragma once

#include "fdbclient/FDBTypes.h"
#include "fdbserver/Knobs.h"

class IClosable {
public:
	// IClosable is a base interface for any disk-backed data structure that needs to support asynchronous errors, shutdown and deletion

	virtual Future<Void> getError() = 0;  // asynchronously throws an error if there is an internal error. Never set inside (on the stack of) a call to another API function on this object.
	virtual Future<Void> onClosed() = 0;  // the future is set to Void when this is totally shut down after dispose() or close().  But this function cannot be called after dispose or close!
	virtual void dispose() = 0;   // permanently delete the data AND invalidate this interface
	virtual void close() = 0;     // invalidate this interface, but do not delete the data.  Outstanding operations may or may not take effect in the background.
};

class IKeyValueStore : public IClosable {
public:
	virtual KeyValueStoreType getType() = 0;
	virtual void set( KeyValueRef keyValue, const Arena* arena = NULL ) = 0;
	virtual void clear( KeyRangeRef range, const Arena* arena = NULL ) = 0;
	virtual Future<Void> commit(bool sequential = false) = 0;  // returns when prior sets and clears are (atomically) durable

	virtual Future<Optional<Value>> readValue( KeyRef key, Optional<UID> debugID = Optional<UID>() ) = 0;

	// Like readValue(), but returns only the first maxLength bytes of the value if it is longer
	virtual Future<Optional<Value>> readValuePrefix( KeyRef key, int maxLength, Optional<UID> debugID = Optional<UID>() ) = 0;

	// If rowLimit>=0, reads first rows sorted ascending, otherwise reads last rows sorted descending
	// The total size of the returned value (less the last entry) will be less than byteLimit
	virtual Future<Standalone<VectorRef<KeyValueRef>>> readRange( KeyRangeRef keys, int rowLimit = 1<<30, int byteLimit = 1<<30 ) = 0;

	//Returns the amount of free and total space for this store, in bytes
	virtual StorageBytes getStorageBytes() = 0;

	virtual void resyncLog() {}

	virtual void enableSnapshot() {}
	/*
	Concurrency contract
		Causal consistency:
			A read which begins after a commit ends sees the effects of the commit.
			A read which ends before a commit begins does not see the effects of the commit.

		Thus, a read returns a version as of a call to commit which began before the read ends such that no subsequent commit ended before the read begins:

			commit()		// can't be this version (subsequent commit ends before read begins)
				endcommit()
			commit()		// could be this or any later version (no subsequent commit ends before read begins)
				endcommit()
			commit()
			read()
	*/
	virtual Future<Void> init() {
		return Void();
	}
protected:
	virtual ~IKeyValueStore() {}
};

extern IKeyValueStore* keyValueStoreSQLite( std::string const& filename, UID logID, KeyValueStoreType storeType, bool checkChecksums=false, bool checkIntegrity=false );
extern IKeyValueStore* keyValueStoreRedwoodV1( std::string const& filename, UID logID);
extern IKeyValueStore* keyValueStoreMemory( std::string const& basename, UID logID, int64_t memoryLimit, std::string ext = "fdq");
extern IKeyValueStore* keyValueStoreLogSystem( class IDiskQueue* queue, UID logID, int64_t memoryLimit, bool disableSnapshot, bool replaceContent, bool exactRecovery );

inline IKeyValueStore* openKVStore( KeyValueStoreType storeType, std::string const& filename, UID logID, int64_t memoryLimit, bool checkChecksums=false, bool checkIntegrity=false ) {
	switch( storeType ) {
	case KeyValueStoreType::SSD_BTREE_V1:
		return keyValueStoreSQLite(filename, logID, KeyValueStoreType::SSD_BTREE_V1, false, checkIntegrity);
	case KeyValueStoreType::SSD_BTREE_V2:
		return keyValueStoreSQLite(filename, logID, KeyValueStoreType::SSD_BTREE_V2, checkChecksums, checkIntegrity);
	case KeyValueStoreType::MEMORY:
		return keyValueStoreMemory( filename, logID, memoryLimit );
	case KeyValueStoreType::SSD_REDWOOD_V1:
		return keyValueStoreRedwoodV1( filename, logID );
	default:
		UNREACHABLE();
	}
	UNREACHABLE(); // FIXME: is this right?
}

void GenerateIOLogChecksumFile(std::string filename);
Future<Void> KVFileCheck(std::string const & filename, bool const &integrity);

#endif