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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/>.
*/
#pragma once
#include <boost/thread/mutex.hpp>
#include "mongo/util/queue.h"
#include "mongo/db/repl/oplogreader.h"
#include "mongo/db/repl/rs.h"
#include "mongo/db/jsobj.h"
namespace mongo {
namespace replset {
// 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;
// Returns the member we're currently syncing from (or NULL)
virtual const Member* getSyncTarget() = 0;
// wait up to 1 second for more ops to appear
virtual void waitForMore() = 0;
};
/**
* notifierThread() uses lastOpTimeWritten to inform the sync target where this member is
* currently synced to.
*
* Lock order:
* 1. rslock
* 2. rwlock
* 3. BackgroundSync::_mutex
*/
class BackgroundSync : public BackgroundSyncInterface {
static BackgroundSync *s_instance;
// protects creation of s_instance
static boost::mutex s_mutex;
// _mutex protects all of the class variables
boost::mutex _mutex;
// Production thread
BlockingQueue<BSONObj> _buffer;
OpTime _lastOpTimeFetched;
long long _lastH;
// if produce thread should be running
bool _pause;
bool _appliedBuffer;
bool _assumingPrimary;
boost::condition _condvar;
const Member* _currentSyncTarget;
// Notifier thread
// used to wait until another op has been replicated
boost::condition_variable _lastOpCond;
boost::mutex _lastOpMutex;
const Member* _oplogMarkerTarget;
OpTime _consumedOpTime; // not locked, only used by notifier thread
BackgroundSync();
BackgroundSync(const BackgroundSync& s);
BackgroundSync operator=(const BackgroundSync& s);
// Production thread
void _producerThread();
// Adds elements to the list, up to maxSize.
void produce();
// Check if rollback is necessary
bool isRollbackRequired(OplogReader& r);
void getOplogReader(OplogReader& r);
// Evaluate if the current sync target is still good
bool shouldChangeSyncTarget();
// check lastOpTimeWritten against the remote's earliest op, filling in remoteOldestOp.
bool isStale(OplogReader& r, BSONObj& remoteOldestOp);
// stop syncing when this becomes a primary
void stop();
// restart syncing
void start();
// Tracker thread
// tells the sync target where this member is synced to
void markOplog();
bool hasCursor();
// Sets _oplogMarkerTarget and calls connect();
// used for both the notifier command and the older OplogReader style notifier
bool connectOplogNotifier();
bool isAssumingPrimary();
public:
static BackgroundSync* get();
static void shutdown();
static void notify();
virtual ~BackgroundSync() {}
// starts the producer thread
void producerThread();
// starts the sync target notifying thread
void notifierThread();
// Interface implementation
virtual bool peek(BSONObj* op);
virtual void consume();
virtual const Member* getSyncTarget();
virtual void waitForMore();
// For monitoring
BSONObj getCounters();
// Wait for replication to finish and buffer to be applied so that the member can become
// primary.
void stopReplicationAndFlushBuffer();
};
} // namespace replset
} // namespace mongo
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