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// @file d_writeback.h
/**
* Copyright (C) 2010 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 "../pch.h"
#include "../util/queue.h"
#include "../util/background.h"
namespace mongo {
/*
* The WriteBackManager keeps one queue of pending operations per mongos. The operations get here
* if they were directed to a chunk that is no longer in this mongod server. The operations are
* "written back" to the mongos server per its request (command 'writebacklisten').
*
* The class is thread safe.
*/
class WriteBackManager {
public:
class QueueInfo : boost::noncopyable {
public:
QueueInfo(){}
BlockingQueue<BSONObj> queue;
long long lastCall; // this is ellapsed millis since startup
};
// a map from mongos's serverIDs to queues of "rejected" operations
// an operation is rejected if it targets data that does not live on this shard anymore
typedef map<string,shared_ptr<QueueInfo> > WriteBackQueuesMap;
public:
WriteBackManager();
~WriteBackManager();
/*
* @param remote server ID this operation came from
* @param op the operation itself
*
* Enqueues opeartion 'op' in server 'remote's queue. The operation will be written back to
* remote at a later stager.
*/
void queueWriteBack( const string& remote , const BSONObj& op );
/*
* @param remote server ID
* @return the queue for operations that came from 'remote'
*
* Gets access to server 'remote's queue, which is synchronized.
*/
shared_ptr<QueueInfo> getWritebackQueue( const string& remote );
/*
* @return true if there is no operation queued for write back
*/
bool queuesEmpty() const;
/**
* appends a number of statistics
*/
void appendStats( BSONObjBuilder& b ) const;
/**
* removes queues that have been idle
* @return if something was removed
*/
bool cleanupOldQueues();
private:
// '_writebackQueueLock' protects only the map itself, since each queue is syncrhonized.
mutable mongo::mutex _writebackQueueLock;
WriteBackQueuesMap _writebackQueues;
class Cleaner : public PeriodicTask {
public:
virtual string taskName() const { return "WriteBackManager::cleaner"; }
virtual void taskDoWork();
};
Cleaner _cleaner;
};
// TODO collect global state in a central place and init during startup
extern WriteBackManager writeBackManager;
} // namespace mongo
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