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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 <boost/thread/mutex.hpp>
#include "mongo/util/queue.h"
#include "mongo/db/repl/oplogreader.h"
#include "mongo/db/jsobj.h"
namespace mongo {
namespace repl {
class Member;
class ReplicationCoordinator;
// This interface exists to facilitate easier testing;
// the test infrastructure implements these functions with stubs.
class BackgroundSyncInterface {
public:
virtual ~BackgroundSyncInterface();
// Gets the head of the buffer, but does not remove it.
// Returns true if an element was present at the head;
// false if the queue was empty.
virtual bool peek(BSONObj* op) = 0;
// Deletes objects in the queue;
// called by sync thread after it has applied an op
virtual void consume() = 0;
// wait up to 1 second for more ops to appear
virtual void waitForMore() = 0;
};
/**
* Lock order:
* 1. rslock
* 2. rwlock
* 3. BackgroundSync::_mutex
*/
class BackgroundSync : public BackgroundSyncInterface {
public:
// Allow index prefetching to be turned on/off
enum IndexPrefetchConfig { PREFETCH_NONE = 0, PREFETCH_ID_ONLY = 1, PREFETCH_ALL = 2 };
static BackgroundSync* get();
// stop syncing (when this node becomes a primary, e.g.)
void stop();
void shutdown();
void notify(OperationContext* txn);
// Blocks until _pause becomes true from a call to stop() or shutdown()
void waitUntilPaused();
virtual ~BackgroundSync() {}
// starts the producer thread
void producerThread();
// starts the sync target notifying thread
void notifierThread();
HostAndPort getSyncTarget();
// Interface implementation
virtual bool peek(BSONObj* op);
virtual void consume();
virtual void clearSyncTarget();
virtual void waitForMore();
// For monitoring
BSONObj getCounters();
long long getLastAppliedHash() const;
void setLastAppliedHash(long long oldH);
void loadLastAppliedHash(OperationContext* txn);
// Clears any fetched and buffered oplog entries.
void clearBuffer();
bool getInitialSyncRequestedFlag();
void setInitialSyncRequestedFlag(bool value);
void setIndexPrefetchConfig(const IndexPrefetchConfig cfg) {
_indexPrefetchConfig = cfg;
}
IndexPrefetchConfig getIndexPrefetchConfig() {
return _indexPrefetchConfig;
}
// Testing related stuff
void pushTestOpToBuffer(const BSONObj& op);
private:
static BackgroundSync* s_instance;
// protects creation of s_instance
static boost::mutex s_mutex;
// Production thread
BlockingQueue<BSONObj> _buffer;
OplogReader _syncSourceReader;
// _mutex protects all of the class variables except _syncSourceReader and _buffer
mutable boost::mutex _mutex;
OpTime _lastOpTimeFetched;
// lastAppliedHash is used to generate a new hash for the following op, when primary.
long long _lastAppliedHash;
// lastFetchedHash is used to match ops to determine if we need to rollback, when
// a secondary.
long long _lastFetchedHash;
// if produce thread should be running
bool _pause;
boost::condition _pausedCondition;
bool _appliedBuffer;
boost::condition _appliedBufferCondition;
HostAndPort _syncSourceHost;
BackgroundSync();
BackgroundSync(const BackgroundSync& s);
BackgroundSync operator=(const BackgroundSync& s);
// Production thread
void _producerThread();
// Adds elements to the list, up to maxSize.
void produce(OperationContext* txn);
// Checks the criteria for rolling back and executes a rollback if warranted.
bool _rollbackIfNeeded(OperationContext* txn, OplogReader& r);
// Evaluate if the current sync target is still good
bool shouldChangeSyncSource();
// restart syncing
void start(OperationContext* txn);
long long _readLastAppliedHash(OperationContext* txn);
// A pointer to the replication coordinator running the show.
ReplicationCoordinator* _replCoord;
// bool for indicating resync need on this node and the mutex that protects it
// The resync command sets this flag; the Applier thread observes and clears it.
bool _initialSyncRequestedFlag;
boost::mutex _initialSyncMutex;
// This setting affects the Applier prefetcher behavior.
IndexPrefetchConfig _indexPrefetchConfig;
};
} // namespace repl
} // namespace mongo
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