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/**
* Copyright (C) 2012 10gen 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 <memory>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/status_with.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/repl/data_replicator_external_state.h"
#include "mongo/db/repl/oplog_buffer.h"
#include "mongo/db/repl/oplog_fetcher.h"
#include "mongo/db/repl/optime.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/net/hostandport.h"
namespace mongo {
class DBClientBase;
class OperationContext;
namespace repl {
class ReplicationCoordinator;
class ReplicationCoordinatorExternalState;
class BackgroundSync {
MONGO_DISALLOW_COPYING(BackgroundSync);
public:
BackgroundSync(ReplicationCoordinatorExternalState* replicationCoordinatorExternalState,
std::unique_ptr<OplogBuffer> oplogBuffer);
// stop syncing (when this node becomes a primary, e.g.)
void stop();
/**
* Starts oplog buffer, task executor and producer thread, in that order.
*/
void startup(OperationContext* txn);
/**
* Signals producer thread to stop.
*/
void shutdown(OperationContext* txn);
/**
* Waits for producer thread to stop before shutting down the task executor and oplog buffer.
*/
void join(OperationContext* txn);
/**
* Returns true if shutdown() has been called.
* Once this returns true, nothing more will be added to the queue and consumers must shutdown.
*/
bool inShutdown() const;
bool isStopped() const;
// starts the sync target notifying thread
void notifierThread();
HostAndPort getSyncTarget() const;
// Interface implementation
bool peek(OperationContext* txn, BSONObj* op);
void consume(OperationContext* txn);
void clearSyncTarget();
void waitForMore();
// For monitoring
BSONObj getCounters();
// Clears any fetched and buffered oplog entries.
void clearBuffer(OperationContext* txn);
/**
* Cancel existing find/getMore commands on the sync source's oplog collection.
*/
void cancelFetcher();
/**
* Returns true if any of the following is true:
* 1) We are shutting down;
* 2) We are primary;
* 3) We are in drain mode; or
* 4) We are stopped.
*/
bool shouldStopFetching() const;
// Testing related stuff
void pushTestOpToBuffer(OperationContext* txn, const BSONObj& op);
private:
bool _inShutdown_inlock() const;
/**
* Starts the producer thread which runs until shutdown. Upon resolving the current sync source
* the producer thread uses the OplogFetcher (which requires the replication coordinator
* external state at construction) to fetch oplog entries from the source's oplog via a long
* running find query.
*/
void _run();
// Production thread inner loop.
void _runProducer();
void _produce(OperationContext* txn);
/**
* Signals to the applier that we have no new data,
* and are in sync with the applier at this point.
*
* NOTE: Used after rollback and during draining to transition to Primary role;
*/
void _signalNoNewDataForApplier(OperationContext* txn);
/**
* Checks current background sync state before pushing operations into blocking queue and
* updating metrics. If the queue is full, might block.
*/
void _enqueueDocuments(Fetcher::Documents::const_iterator begin,
Fetcher::Documents::const_iterator end,
const OplogFetcher::DocumentsInfo& info);
/**
* Executes a rollback.
* 'getConnection' returns a connection to the sync source.
*/
void _rollback(OperationContext* txn,
const HostAndPort& source,
stdx::function<DBClientBase*()> getConnection);
// restart syncing
void start(OperationContext* txn);
long long _readLastAppliedHash(OperationContext* txn);
// Production thread
std::unique_ptr<OplogBuffer> _oplogBuffer;
// A pointer to the replication coordinator running the show.
ReplicationCoordinator* _replCoord;
// A pointer to the replication coordinator external state.
ReplicationCoordinatorExternalState* _replicationCoordinatorExternalState;
// _mutex protects all of the class variables declared below.
mutable stdx::mutex _mutex;
OpTime _lastOpTimeFetched;
// lastFetchedHash is used to match ops to determine if we need to rollback, when
// a secondary.
long long _lastFetchedHash = 0LL;
// Thread running producerThread().
std::unique_ptr<stdx::thread> _producerThread;
// Set to true if shutdown() has been called.
bool _inShutdown = false;
// if producer thread should not be running
bool _stopped = true;
HostAndPort _syncSourceHost;
// Current oplog fetcher tailing the oplog on the sync source.
// Owned by us.
std::unique_ptr<OplogFetcher> _oplogFetcher;
};
} // namespace repl
} // namespace mongo
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