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diff --git a/src/mongo/s/d_writeback.h b/src/mongo/s/d_writeback.h
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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 "mongo/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