mirror of
https://github.com/mongodb/mongo.git
synced 2024-12-01 09:32:32 +01:00
289 lines
9.9 KiB
C++
289 lines
9.9 KiB
C++
// @file distlock.h
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/* Copyright 2009 10gen Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "pch.h"
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#include "boost/thread/once.hpp"
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#include "dbclient.h"
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#include "distlock.h"
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namespace mongo {
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string lockPingNS = "config.lockpings";
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ThreadLocalValue<string> distLockIds("");
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/* ==================
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* Module initialization
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*/
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boost::once_flag _init = BOOST_ONCE_INIT;
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static string* _cachedProcessString = NULL;
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static void initModule() {
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// cache process string
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stringstream ss;
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ss << getHostName() << ":" << time(0) << ":" << rand();
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_cachedProcessString = new string( ss.str() );
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}
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/* =================== */
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string getDistLockProcess(){
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boost::call_once( initModule, _init );
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assert( _cachedProcessString );
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return *_cachedProcessString;
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}
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string getDistLockId(){
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string s = distLockIds.get();
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if ( s.empty() ){
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stringstream ss;
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ss << getDistLockProcess() << ":" << getThreadName() << ":" << rand();
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s = ss.str();
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distLockIds.set( s );
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}
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return s;
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}
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void distLockPingThread( ConnectionString addr ){
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setThreadName( "LockPinger" );
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static int loops = 0;
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while( ! inShutdown() ){
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string process = getDistLockProcess();
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log(4) << "dist_lock about to ping for: " << process << endl;
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try {
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ScopedDbConnection conn( addr );
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// refresh the entry corresponding to this process in the lockpings collection
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conn->update( lockPingNS ,
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BSON( "_id" << process ) ,
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BSON( "$set" << BSON( "ping" << DATENOW ) ) ,
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true );
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string err = conn->getLastError();
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if ( ! err.empty() ){
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log( LL_WARNING ) << "dist_lock process: " << process << " pinging: " << addr << " failed: "
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<< err << endl;
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conn.done();
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sleepsecs(30);
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continue;
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}
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// remove really old entries from the lockpings collection
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BSONObjBuilder f;
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f.appendDate( "$lt" , jsTime() - ( 4 * 86400 * 1000 ) ); // 4 days
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BSONObj r = BSON( "ping" << f.obj() );
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conn->remove( lockPingNS , r );
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err = conn->getLastError();
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if ( ! err.empty() ){
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log ( LL_WARNING ) << "dist_lock cleanup request from process: " << process << " to: " << addr
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<< " failed: " << err << endl;
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conn.done();
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sleepsecs(30);
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continue;
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}
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// create index so remove is fast even with a lot of servers
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if ( loops++ == 0 ){
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conn->ensureIndex( lockPingNS , BSON( "ping" << 1 ) );
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}
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conn.done();
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}
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catch ( std::exception& e ){
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log( LL_WARNING ) << "dist_lock exception during ping: " << e.what() << endl;
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}
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log(4) << "dist_lock pinged successfully for: " << process << endl;
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sleepsecs(30);
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}
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}
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class DistributedLockPinger {
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public:
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DistributedLockPinger()
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: _mutex( "DistributedLockPinger" ){
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}
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void got( const ConnectionString& conn ){
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string s = conn.toString();
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scoped_lock lk( _mutex );
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if ( _seen.count( s ) > 0 )
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return;
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boost::thread t( boost::bind( &distLockPingThread , conn ) );
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_seen.insert( s );
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}
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set<string> _seen;
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mongo::mutex _mutex;
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} distLockPinger;
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DistributedLock::DistributedLock( const ConnectionString& conn , const string& name , unsigned takeoverMinutes )
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: _conn(conn),_name(name),_takeoverMinutes(takeoverMinutes){
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_id = BSON( "_id" << name );
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_ns = "config.locks";
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distLockPinger.got( conn );
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}
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bool DistributedLock::lock_try( string why , BSONObj * other ){
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// write to dummy if 'other' is null
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BSONObj dummyOther;
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if ( other == NULL )
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other = &dummyOther;
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ScopedDbConnection conn( _conn );
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BSONObjBuilder queryBuilder;
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queryBuilder.appendElements( _id );
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queryBuilder.append( "state" , 0 );
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{ // make sure its there so we can use simple update logic below
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BSONObj o = conn->findOne( _ns , _id );
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if ( o.isEmpty() ){
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try {
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log(4) << "dist_lock inserting initial doc in " << _ns << " for lock " << _name << endl;
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conn->insert( _ns , BSON( "_id" << _name << "state" << 0 << "who" << "" ) );
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}
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catch ( UserException& e ){
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log() << "dist_lock could not insert initial doc: " << e << endl;
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}
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}
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else if ( o["state"].numberInt() > 0 ){
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BSONObj lastPing = conn->findOne( lockPingNS , o["process"].wrap( "_id" ) );
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if ( lastPing.isEmpty() ){
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// TODO: maybe this should clear, not sure yet
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log() << "config.locks: " << _name << " lastPing is empty! this could be bad: " << o << endl;
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conn.done();
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return false;
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}
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unsigned long long elapsed = jsTime() - lastPing["ping"].Date(); // in ms
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elapsed = elapsed / ( 1000 * 60 ); // convert to minutes
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if ( elapsed <= _takeoverMinutes ){
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log(1) << "dist_lock lock failed because taken by: " << o << " elapsed minutes: " << elapsed << endl;
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*other = o;
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other->getOwned();
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conn.done();
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return false;
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}
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log() << "dist_lock forcefully taking over from: " << o << " elapsed minutes: " << elapsed << endl;
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conn->update( _ns , _id , BSON( "$set" << BSON( "state" << 0 ) ) );
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}
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else if ( o["ts"].type() ){
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queryBuilder.append( o["ts"] );
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}
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}
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OID ts;
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ts.init();
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bool gotLock = false;
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BSONObj now;
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BSONObj lockDetails = BSON( "state" << 1 << "who" << getDistLockId() << "process" << getDistLockProcess() <<
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"when" << DATENOW << "why" << why << "ts" << ts );
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BSONObj whatIWant = BSON( "$set" << lockDetails );
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try {
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log(4) << "dist_lock about to aquire lock: " << lockDetails << endl;
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conn->update( _ns , queryBuilder.obj() , whatIWant );
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BSONObj o = conn->getLastErrorDetailed();
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now = conn->findOne( _ns , _id );
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if ( o["n"].numberInt() == 0 ){
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*other = now;
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other->getOwned();
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log() << "dist_lock error trying to aquire lock: " << lockDetails << " error: " << o << endl;
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gotLock = false;
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}
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else {
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gotLock = true;
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}
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}
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catch ( UpdateNotTheSame& up ){
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// this means our update got through on some, but not others
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log(4) << "dist_lock lock did not propagate properly" << endl;
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for ( unsigned i=0; i<up.size(); i++ ){
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ScopedDbConnection temp( up[i].first );
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BSONObj temp2 = temp->findOne( _ns , _id );
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if ( now.isEmpty() || now["ts"] < temp2["ts"] ){
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now = temp2.getOwned();
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}
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temp.done();
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}
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if ( now["ts"].OID() == ts ){
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log(4) << "dist_lock completed lock propagation" << endl;
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gotLock = true;
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conn->update( _ns , _id , whatIWant );
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}
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else {
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log() << "dist_lock error trying to complete propagation" << endl;
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gotLock = false;
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}
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}
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conn.done();
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log(2) << "dist_lock lock gotLock: " << gotLock << " now: " << now << endl;
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return gotLock;
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}
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void DistributedLock::unlock(){
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const int maxAttempts = 3;
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int attempted = 0;
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while ( ++attempted <= maxAttempts ) {
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try {
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ScopedDbConnection conn( _conn );
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conn->update( _ns , _id, BSON( "$set" << BSON( "state" << 0 ) ) );
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log(2) << "dist_lock unlock: " << conn->findOne( _ns , _id ) << endl;
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conn.done();
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return;
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} catch ( std::exception& e) {
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log( LL_WARNING ) << "dist_lock " << _name << " failed to contact config server in unlock attempt "
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<< attempted << ": " << e.what() << endl;
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sleepsecs(1 << attempted);
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}
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}
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log( LL_WARNING ) << "dist_lock couldn't consumate unlock request. " << "Lock " << _name
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<< " will be taken over after " << _takeoverMinutes << " minutes timeout" << endl;
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}
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}
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