98 lines
4.0 KiB
C++
98 lines
4.0 KiB
C++
/*
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* LogSystemDiskQueueAdapter.h
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef FDBSERVER_LOGSYSTEMDISKQUEUEADAPTER_H
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#define FDBSERVER_LOGSYSTEMDISKQUEUEADAPTER_H
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#pragma once
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#include "fdbclient/FDBTypes.h"
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#include "IDiskQueue.h"
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class LogSystemDiskQueueAdapter : public IDiskQueue {
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public:
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// This adapter is designed to let KeyValueStoreMemory use ILogSystem
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// as a backing store, so that the transaction subsystem can in
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// turn use KeyValueStoreMemory to track configuration information as of
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// the database version and recover it from the logging subsystem as necessary.
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// Because the transaction subsystem will need to control the actual pushing of
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// committed information to the ILogSystem, commit() in this interface doesn't directly
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// call ILogSystem::push(). Instead it makes a commit message available through
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// getCommitMessage(), and doesn't return until its acknowledge promise is set.
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// The caller is responsible for calling ILogSystem::push() and ILogSystem::pop() with the results.
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// It does, however, peek the specified tag directly at recovery time.
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LogSystemDiskQueueAdapter( Reference<ILogSystem> logSystem, Tag tag, bool recover=true ) : logSystem(logSystem), tag(tag), enableRecovery(recover), recoveryLoc(1), recoveryQueueLoc(1), poppedUpTo(0), nextCommit(1), recoveryQueueDataSize(0) {
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if (enableRecovery)
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cursor = logSystem->peek( 0, tag, true );
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}
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struct CommitMessage {
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Standalone<VectorRef<VectorRef<uint8_t>>> messages; // push this into the logSystem with `tag`
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Version popTo; // pop this from the logSystem with `tag`
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Promise<Void> acknowledge; // then send Void to this, so commit() can return
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};
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// Set the version of the next push or commit (or a lower version)
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// If lower, locations returned by the IDiskQueue interface will be conservative, so things that could be popped might not be
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void setNextVersion( Version next ) { nextCommit = next; }
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// Return the next commit message resulting from a call to commit().
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Future<CommitMessage> getCommitMessage();
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// IClosable interface
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virtual Future<Void> getError();
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virtual Future<Void> onClosed();
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virtual void dispose();
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virtual void close();
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// IDiskQueue interface
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virtual Future<Standalone<StringRef>> readNext( int bytes );
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virtual IDiskQueue::location getNextReadLocation();
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virtual IDiskQueue::location push( StringRef contents );
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virtual void pop( IDiskQueue::location upTo );
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virtual Future<Void> commit();
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virtual StorageBytes getStorageBytes() { ASSERT(false); throw internal_error(); }
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virtual int getCommitOverhead() { return 0; } //SOMEDAY: could this be more accurate?
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private:
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Reference<ILogSystem::IPeekCursor> cursor;
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Tag tag;
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// Recovery state (used while readNext() is being called repeatedly)
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bool enableRecovery;
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Reference<ILogSystem> logSystem;
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Version recoveryLoc, recoveryQueueLoc;
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std::vector<Standalone<StringRef>> recoveryQueue;
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int recoveryQueueDataSize;
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// State for next commit() call
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Standalone<VectorRef<VectorRef<uint8_t>>> pushedData; // SOMEDAY: better representation?
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Version poppedUpTo;
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std::deque< Promise<CommitMessage> > commitMessages;
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Version nextCommit;
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friend class LogSystemDiskQueueAdapterImpl;
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};
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LogSystemDiskQueueAdapter* openDiskQueueAdapter( Reference<ILogSystem> logSystem, Tag tag );
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#endif |