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/*
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/base/disallow_copying.h"
#include "mongo/db/service_context.h"
#include "mongo/db/storage/snapshot_manager.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/thread.h"
namespace mongo {
namespace repl {
/**
* The thread that makes storage snapshots periodically to enable majority committed reads.
*
* Currently the implementation must live in oplog.cpp because it uses newOpMutex.
* TODO find a better home for this.
*/
class SnapshotThread {
MONGO_DISALLOW_COPYING(SnapshotThread);
public:
/**
* Starts a thread to take periodic snapshots if supported by the storageEngine.
*
* If the current storage engine doesn't support snapshots, a null pointer will be returned.
*/
static std::unique_ptr<SnapshotThread> start(ServiceContext* service);
/**
* Signals the thread to stop and waits for it to finish.
* This must be called exactly once before exitCleanly() takes the global X lock.
*/
void shutdown();
/**
* Forces a new snapshot to be taken even if the global timestamp hasn't changed.
*
* Does not wait for the snapshot to be taken.
*/
void forceSnapshot();
private:
explicit SnapshotThread(SnapshotManager* manager);
void run();
bool shouldSleepMore(int numSleepsDone, size_t numUncommittedSnapshots);
SnapshotManager* const _manager;
bool _hitSnapshotLimit = false;
AtomicWord<bool> _inShutdown{false}; // writes guarded by newOpMutex in oplog.cpp.
AtomicWord<bool> _forcedSnapshotPending{false}; // writes guarded by newOpMutex in oplog.cpp.
stdx::thread _thread;
};
} // namespace repl
} // namespace mongo
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