121 lines
3.5 KiB
C++
121 lines
3.5 KiB
C++
// 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 "dbclient.h"
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#include "distlock.h"
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namespace mongo {
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bool DistributedLock::lock_try( string why , BSONObj * other ){
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// recursive
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if ( getState() > 0 )
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return true;
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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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conn->insert( _ns , BSON( "_id" << _name << "state" << 0 << "who" << "" ) );
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}
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catch ( UserException& ){
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}
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}
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else if ( o["state"].numberInt() > 0 ){
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return false;
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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 whatIWant = BSON( "$set" << BSON( "state" << 1 << "who" << myid() <<
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"when" << DATENOW << "why" << why << "ts" << ts ) );
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try {
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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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if ( other )
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*other = now;
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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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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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gotLock = true;
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conn->update( _ns , _id , whatIWant );
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}
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else {
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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(1) << "dist_lock lock gotLock: " << gotLock << " now: " << now << endl;
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if ( ! gotLock )
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return false;
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_state.set( 1 );
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return true;
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}
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void DistributedLock::unlock(){
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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(1) << "dist_lock unlock: " << conn->findOne( _ns , _id ) << endl;
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conn.done();
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_state.set( 0 );
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}
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}
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