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// @file distlock.h
/* Copyright 2009 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "pch.h"
#include "dbclient.h"
#include "distlock.h"
namespace mongo {
bool DistributedLock::lock_try( string why , BSONObj * other ){
// recursive
if ( getState() > 0 )
return true;
ScopedDbConnection conn( _conn );
BSONObjBuilder queryBuilder;
queryBuilder.appendElements( _id );
queryBuilder.append( "state" , 0 );
{ // make sure its there so we can use simple update logic below
BSONObj o = conn->findOne( _ns , _id );
if ( o.isEmpty() ){
try {
conn->insert( _ns , BSON( "_id" << _name << "state" << 0 << "who" << "" ) );
}
catch ( UserException& ){
}
}
else if ( o["state"].numberInt() > 0 ){
return false;
}
else if ( o["ts"].type() ){
queryBuilder.append( o["ts"] );
}
}
OID ts;
ts.init();
bool gotLock = false;
BSONObj now;
BSONObj whatIWant = BSON( "$set" << BSON( "state" << 1 << "who" << myid() <<
"when" << DATENOW << "why" << why << "ts" << ts ) );
try {
conn->update( _ns , queryBuilder.obj() , whatIWant );
BSONObj o = conn->getLastErrorDetailed();
now = conn->findOne( _ns , _id );
if ( o["n"].numberInt() == 0 ){
if ( other )
*other = now;
gotLock = false;
}
else {
gotLock = true;
}
}
catch ( UpdateNotTheSame& up ){
// this means our update got through on some, but not others
for ( unsigned i=0; i<up.size(); i++ ){
ScopedDbConnection temp( up[i].first );
BSONObj temp2 = temp->findOne( _ns , _id );
if ( now.isEmpty() || now["ts"] < temp2["ts"] ){
now = temp2.getOwned();
}
temp.done();
}
if ( now["ts"].OID() == ts ){
gotLock = true;
conn->update( _ns , _id , whatIWant );
}
else {
gotLock = false;
}
}
conn.done();
log(1) << "dist_lock lock gotLock: " << gotLock << " now: " << now << endl;
if ( ! gotLock )
return false;
_state.set( 1 );
return true;
}
void DistributedLock::unlock(){
ScopedDbConnection conn( _conn );
conn->update( _ns , _id, BSON( "$set" << BSON( "state" << 0 ) ) );
log(1) << "dist_lock unlock: " << conn->findOne( _ns , _id ) << endl;
conn.done();
_state.set( 0 );
}
}
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