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// @file writeback_listener.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
* 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 <>.
#pragma once
#include "../pch.h"
#include "../client/connpool.h"
#include "../util/background.h"
#include "../db/client.h"
namespace mongo {
* The writeback listener takes back write attempts that were made against a wrong shard.
* (Wrong here in the sense that the target chunk moved before this mongos had a chance to
* learn so.) It is responsible for reapplying these writes to the correct shard.
* Runs (instantiated) on mongos.
* Currently, there is one writebacklistener per shard.
class WriteBackListener : public BackgroundJob {
class ConnectionIdent {
ConnectionIdent( const string& ii , ConnectionId id )
: instanceIdent( ii ) , connectionId( id ) {
bool operator<(const ConnectionIdent& other) const {
if ( instanceIdent == other.instanceIdent )
return connectionId < other.connectionId;
return instanceIdent < other.instanceIdent;
string toString() const { return str::stream() << instanceIdent << ":" << connectionId; }
string instanceIdent;
ConnectionId connectionId;
static void init( DBClientBase& conn );
static void init( const string& host );
static BSONObj waitFor( const ConnectionIdent& ident, const OID& oid );
WriteBackListener( const string& addr );
string name() const { return "WriteBackListener"; }
void run();
string _addr;
static mongo::mutex _cacheLock; // protects _cache
static map<string,WriteBackListener*> _cache; // server to listener
static set<string> _seenSets; // cache of set urls we've seen - note this is ever expanding for order, case, changes
struct WBStatus {
OID id;
BSONObj gle;
static mongo::mutex _seenWritebacksLock; // protects _seenWritbacks
static map<ConnectionIdent,WBStatus> _seenWritebacks; // connectionId -> last write back GLE
void waitForWriteback( const OID& oid );
} // namespace mongo