ad01e102a8
Retries unlock when process is still up but config server has gone down, in case of errors during locking and unlocking. Also allows testing of locks already held.
971 lines
42 KiB
C++
971 lines
42 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 "dbclient.h"
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#include "distlock.h"
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namespace mongo {
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LabeledLevel DistributedLock::logLvl( 1 );
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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() << ":" << cmdLine.port << ":" << 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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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 _distLockPingThread( ConnectionString addr, string process, unsigned long long sleepTime ) {
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setThreadName( "LockPinger" );
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string pingId = pingThreadId( addr, process );
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log( DistributedLock::logLvl - 1 ) << "creating distributed lock ping thread for " << addr
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<< " and process " << process
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<< " (sleeping for " << sleepTime << "ms)" << endl;
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static int loops = 0;
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while( ! inShutdown() && ! shouldKill( addr, process ) ) {
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log( DistributedLock::logLvl + 2 ) << "distributed lock pinger '" << pingId << "' about to ping." << endl;
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Date_t pingTime;
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try {
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ScopedDbConnection conn( addr );
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pingTime = jsTime();
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// refresh the entry corresponding to this process in the lockpings collection
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conn->update( DistributedLock::lockPingNS ,
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BSON( "_id" << process ) ,
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BSON( "$set" << BSON( "ping" << pingTime ) ) ,
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true );
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string err = conn->getLastError();
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if ( ! err.empty() ) {
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warning() << "pinging failed for distributed lock pinger '" << pingId << "'."
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<< causedBy( err ) << endl;
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conn.done();
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// Sleep for normal ping time
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sleepmillis(sleepTime);
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continue;
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}
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// remove really old entries from the lockpings collection if they're not holding a lock
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// (this may happen if an instance of a process was taken down and no new instance came up to
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// replace it for a quite a while)
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// if the lock is taken, the take-over mechanism should handle the situation
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auto_ptr<DBClientCursor> c = conn->query( DistributedLock::locksNS , BSONObj() );
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vector<string> pids;
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while ( c->more() ) {
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BSONObj lock = c->next();
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if ( ! lock["process"].eoo() ) {
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pids.push_back( lock["process"].valuestrsafe() );
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}
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}
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Date_t fourDays = pingTime - ( 4 * 86400 * 1000 ); // 4 days
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conn->remove( DistributedLock::lockPingNS , BSON( "_id" << BSON( "$nin" << pids ) << "ping" << LT << fourDays ) );
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err = conn->getLastError();
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if ( ! err.empty() ) {
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warning() << "ping cleanup for distributed lock pinger '" << pingId << " failed."
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<< causedBy( err ) << endl;
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conn.done();
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// Sleep for normal ping time
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sleepmillis(sleepTime);
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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( DistributedLock::lockPingNS , BSON( "ping" << 1 ) );
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}
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log( DistributedLock::logLvl - ( loops % 10 == 0 ? 1 : 0 ) ) << "cluster " << addr << " pinged successfully at " << pingTime
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<< " by distributed lock pinger '" << pingId
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<< "', sleeping for " << sleepTime << "ms" << endl;
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// Remove old locks, if possible
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// Make sure no one else is adding to this list at the same time
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scoped_lock lk( _mutex );
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int numOldLocks = _oldLockOIDs.size();
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if( numOldLocks > 0 )
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log( DistributedLock::logLvl - 1 ) << "trying to delete " << _oldLockOIDs.size() << " old lock entries for process " << process << endl;
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bool removed = false;
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for( list<OID>::iterator i = _oldLockOIDs.begin(); i != _oldLockOIDs.end();
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i = ( removed ? _oldLockOIDs.erase( i ) : ++i ) ) {
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removed = false;
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try {
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// Got OID from lock with id, so we don't need to specify id again
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conn->update( DistributedLock::locksNS ,
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BSON( "ts" << *i ),
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BSON( "$set" << BSON( "state" << 0 ) ) );
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// Either the update went through or it didn't, either way we're done trying to
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// unlock
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log( DistributedLock::logLvl - 1 ) << "handled late remove of old distributed lock with ts " << *i << endl;
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removed = true;
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}
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catch( UpdateNotTheSame& ) {
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log( DistributedLock::logLvl - 1 ) << "partially removed old distributed lock with ts " << *i << endl;
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removed = true;
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}
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catch ( std::exception& e) {
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warning() << "could not remove old distributed lock with ts " << *i
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<< causedBy( e ) << endl;
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}
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}
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if( numOldLocks > 0 && _oldLockOIDs.size() > 0 ){
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log( DistributedLock::logLvl - 1 ) << "not all old lock entries could be removed for process " << process << endl;
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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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warning() << "distributed lock pinger '" << pingId << "' detected an exception while pinging."
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<< causedBy( e ) << endl;
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}
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sleepmillis(sleepTime);
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}
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warning() << "removing distributed lock ping thread '" << pingId << "'" << endl;
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if( shouldKill( addr, process ) )
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finishKill( addr, process );
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}
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void distLockPingThread( ConnectionString addr, long long clockSkew, string processId, unsigned long long sleepTime ) {
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try {
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jsTimeVirtualThreadSkew( clockSkew );
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_distLockPingThread( addr, processId, sleepTime );
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}
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catch ( std::exception& e ) {
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error() << "unexpected error while running distributed lock pinger for " << addr << ", process " << processId << causedBy( e ) << endl;
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}
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catch ( ... ) {
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error() << "unknown error while running distributed lock pinger for " << addr << ", process " << processId << endl;
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}
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}
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string pingThreadId( const ConnectionString& conn, const string& processId ) {
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return conn.toString() + "/" + processId;
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}
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string got( DistributedLock& lock, unsigned long long sleepTime ) {
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// Make sure we don't start multiple threads for a process id
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scoped_lock lk( _mutex );
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const ConnectionString& conn = lock.getRemoteConnection();
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const string& processId = lock.getProcessId();
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string s = pingThreadId( conn, processId );
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// Ignore if we already have a pinging thread for this process.
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if ( _seen.count( s ) > 0 ) return "";
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// Check our clock skew
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try {
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if( lock.isRemoteTimeSkewed() ) {
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throw LockException( str::stream() << "clock skew of the cluster " << conn.toString() << " is too far out of bounds to allow distributed locking." , 13650 );
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}
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}
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catch( LockException& e) {
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throw LockException( str::stream() << "error checking clock skew of cluster " << conn.toString() << causedBy( e ) , 13651);
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}
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boost::thread t( boost::bind( &DistributedLockPinger::distLockPingThread, this, conn, getJSTimeVirtualThreadSkew(), processId, sleepTime) );
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_seen.insert( s );
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return s;
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}
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void addUnlockOID( OID oid ) {
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// Modifying the lock from some other thread
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scoped_lock lk( _mutex );
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_oldLockOIDs.push_back( oid );
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}
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bool willUnlockOID( OID oid ) {
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scoped_lock lk( _mutex );
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return find( _oldLockOIDs.begin(), _oldLockOIDs.end(), oid ) != _oldLockOIDs.end();
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}
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void kill( ConnectionString& conn, string& processId ) {
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// Make sure we're in a consistent state before other threads can see us
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scoped_lock lk( _mutex );
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string pingId = pingThreadId( conn, processId );
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assert( _seen.count( pingId ) > 0 );
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_kill.insert( pingId );
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}
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bool shouldKill( ConnectionString& conn, string& processId ) {
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return _kill.count( pingThreadId( conn, processId ) ) > 0;
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}
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void finishKill( ConnectionString& conn, string& processId ) {
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// Make sure we're in a consistent state before other threads can see us
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scoped_lock lk( _mutex );
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string pingId = pingThreadId( conn, processId );
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_kill.erase( pingId );
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_seen.erase( pingId );
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}
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set<string> _kill;
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set<string> _seen;
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mongo::mutex _mutex;
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list<OID> _oldLockOIDs;
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} distLockPinger;
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const string DistributedLock::lockPingNS = "config.lockpings";
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const string DistributedLock::locksNS = "config.locks";
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/**
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* Create a new distributed lock, potentially with a custom sleep and takeover time. If a custom sleep time is
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* specified (time between pings)
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*/
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DistributedLock::DistributedLock( const ConnectionString& conn , const string& name , unsigned long long lockTimeout, bool asProcess, bool legacy)
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: _conn(conn) , _name(name) , _lockTimeout(lockTimeout), _takeoverMinutes(0), _lastPingCheck(string(""), (mongo::Date_t) 0, (mongo::Date_t) 0) {
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_id = BSON( "_id" << name );
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_ns = locksNS;
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_maxClockSkew = 0;
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_maxNetSkew = 0;
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_lockPing = 0;
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// If this is a legacy lock, set our takeover minutes for local time comparisons
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if(legacy) {
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_takeoverMinutes = (unsigned) _lockTimeout;
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if(_takeoverMinutes == 0) _takeoverMinutes = 15;
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_lockTimeout = 0;
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_lockPing = _maxClockSkew = _maxNetSkew = (_takeoverMinutes * 60 * 1000) / LOCK_SKEW_FACTOR;
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}
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else {
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if(lockTimeout == 0) _lockTimeout = lockTimeout = LOCK_TIMEOUT;
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//if(lockPing == 0) lockPing = LOCK_PING;
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_lockPing = _maxClockSkew = _maxNetSkew = _lockTimeout / LOCK_SKEW_FACTOR;
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}
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// If we're emulating a new process for this lock, generate a processId
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if(asProcess) _processId = getDistLockId();
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else _processId = getDistLockProcess();
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log( logLvl - 1 ) << "created new distributed lock for " << name << " on " << conn
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<< " ( lock timeout : " << _lockTimeout << ", legacy timeout : " << _takeoverMinutes
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<< ", ping interval : " << _lockPing << ", process : " << asProcess
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<< ", legacy : " << legacy << " )" << endl;
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}
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Date_t DistributedLock::getRemoteTime() {
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return DistributedLock::remoteTime( _conn, _maxNetSkew );
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}
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bool DistributedLock::isRemoteTimeSkewed() {
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return !DistributedLock::checkSkew( _conn, NUM_LOCK_SKEW_CHECKS, _maxClockSkew, _maxNetSkew );
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}
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const ConnectionString& DistributedLock::getRemoteConnection() {
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return _conn;
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}
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const string& DistributedLock::getProcessId() {
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return _processId;
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}
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/**
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* Returns the remote time as reported by the cluster or server. The maximum difference between the reported time
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* and the actual time on the remote server (at the completion of the function) is the maxNetSkew
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*/
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Date_t DistributedLock::remoteTime( const ConnectionString& cluster, unsigned long long maxNetSkew ) {
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ConnectionString server( *cluster.getServers().begin() );
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ScopedDbConnection conn( server );
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BSONObj result;
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long long delay;
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try {
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Date_t then = jsTime();
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bool success = conn->runCommand( string("admin"), BSON( "serverStatus" << 1 ), result );
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delay = jsTime() - then;
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if( !success )
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throw TimeNotFoundException( str::stream() << "could not get status from server "
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<< server.toString() << " in cluster " << cluster.toString()
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<< " to check time", 13647 );
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// Make sure that our delay is not more than 2x our maximum network skew, since this is the max our remote
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// time value can be off by if we assume a response in the middle of the delay.
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if( delay > (long long) (maxNetSkew * 2) )
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throw TimeNotFoundException( str::stream() << "server " << server.toString()
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<< " in cluster " << cluster.toString()
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<< " did not respond within max network delay of "
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<< maxNetSkew << "ms", 13648 );
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}
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catch(...) {
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conn.done();
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throw;
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}
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conn.done();
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return result["localTime"].Date() - (delay / 2);
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}
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bool DistributedLock::checkSkew( const ConnectionString& cluster, unsigned skewChecks, unsigned long long maxClockSkew, unsigned long long maxNetSkew ) {
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vector<HostAndPort> servers = cluster.getServers();
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if(servers.size() < 1) return true;
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vector<long long> avgSkews;
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for(unsigned i = 0; i < skewChecks; i++) {
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// Find the average skew for each server
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unsigned s = 0;
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for(vector<HostAndPort>::iterator si = servers.begin(); si != servers.end(); ++si,s++) {
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if(i == 0) avgSkews.push_back(0);
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// Could check if this is self, but shouldn't matter since local network connection should be fast.
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ConnectionString server( *si );
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vector<long long> skew;
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BSONObj result;
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Date_t remote = remoteTime( server, maxNetSkew );
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Date_t local = jsTime();
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// Remote time can be delayed by at most MAX_NET_SKEW
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// Skew is how much time we'd have to add to local to get to remote
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avgSkews[s] += (long long) (remote - local);
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log( logLvl + 1 ) << "skew from remote server " << server << " found: " << (long long) (remote - local) << endl;
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}
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}
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// Analyze skews
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long long serverMaxSkew = 0;
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long long serverMinSkew = 0;
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for(unsigned s = 0; s < avgSkews.size(); s++) {
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long long avgSkew = (avgSkews[s] /= skewChecks);
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// Keep track of max and min skews
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if(s == 0) {
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serverMaxSkew = avgSkew;
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serverMinSkew = avgSkew;
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}
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else {
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if(avgSkew > serverMaxSkew)
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serverMaxSkew = avgSkew;
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if(avgSkew < serverMinSkew)
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serverMinSkew = avgSkew;
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}
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}
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long long totalSkew = serverMaxSkew - serverMinSkew;
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// Make sure our max skew is not more than our pre-set limit
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if(totalSkew > (long long) maxClockSkew) {
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log( logLvl + 1 ) << "total clock skew of " << totalSkew << "ms for servers " << cluster << " is out of " << maxClockSkew << "ms bounds." << endl;
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return false;
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}
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log( logLvl + 1 ) << "total clock skew of " << totalSkew << "ms for servers " << cluster << " is in " << maxClockSkew << "ms bounds." << endl;
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return true;
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}
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// For use in testing, ping thread should run indefinitely in practice.
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bool DistributedLock::killPinger( DistributedLock& lock ) {
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if( lock._threadId == "") return false;
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distLockPinger.kill( lock._conn, lock._processId );
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return true;
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}
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// Semantics of this method are basically that if the lock cannot be acquired, returns false, can be retried.
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// If the lock should not be tried again (some unexpected error) a LockException is thrown.
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// If we are only trying to re-enter a currently held lock, reenter should be true.
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// Note: reenter doesn't actually make this lock re-entrant in the normal sense, since it can still only
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// be unlocked once, instead it is used to verify that the lock is already held.
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bool DistributedLock::lock_try( string why , bool reenter, BSONObj * other ) {
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// TODO: Start pinging only when we actually get the lock?
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// If we don't have a thread pinger, make sure we shouldn't have one
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if( _threadId == "" )
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_threadId = distLockPinger.got( *this, _lockPing );
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// This should always be true, if not, we are using the lock incorrectly.
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assert( _name != "" );
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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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{
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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 ).getOwned();
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// Case 1: No locks
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if ( o.isEmpty() ) {
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try {
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log( logLvl ) << "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 ) {
|
|
warning() << "could not insert initial doc for distributed lock " << _name << causedBy( e ) << endl;
|
|
}
|
|
}
|
|
|
|
// Case 2: A set lock that we might be able to force
|
|
else if ( o["state"].numberInt() > 0 ) {
|
|
|
|
string lockName = o["_id"].String() + string("/") + o["process"].String();
|
|
|
|
bool canReenter = reenter && o["process"].String() == _processId && ! distLockPinger.willUnlockOID( o["ts"].OID() ) && o["state"].numberInt() == 2;
|
|
if( reenter && ! canReenter ) {
|
|
log( logLvl ) << "not re-entering distributed lock " << lockName;
|
|
if( o["process"].String() != _processId ) log( logLvl ) << ", different process " << _processId << endl;
|
|
else if( o["state"].numberInt() == 2 ) log( logLvl ) << ", state not finalized" << endl;
|
|
else log( logLvl ) << ", ts " << o["ts"].OID() << " scheduled for late unlock" << endl;
|
|
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
|
|
BSONObj lastPing = conn->findOne( lockPingNS , o["process"].wrap( "_id" ) );
|
|
if ( lastPing.isEmpty() ) {
|
|
if(_lockTimeout > 0) {
|
|
log( logLvl ) << "empty ping found for process in lock '" << lockName << "'" << endl;
|
|
// TODO: Using 0 as a "no time found" value Will fail if dates roll over, but then, so will a lot.
|
|
lastPing = BSON( "_id" << o["process"].String() << "ping" << (Date_t) 0 );
|
|
}
|
|
else {
|
|
// LEGACY
|
|
|
|
// if a lock is taken but there's no ping for it, we're in an inconsistent situation
|
|
// if the lock holder (mongos or d) does not exist anymore, the lock could safely be removed
|
|
// but we'd require analysis of the situation before a manual intervention
|
|
warning() << "config.locks: " << _name << " lock is taken by old process? "
|
|
<< "remove the following lock if the process is not active anymore: " << o << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
}
|
|
|
|
unsigned long long elapsed = 0;
|
|
unsigned long long takeover = ( _lockTimeout > 0 ? _lockTimeout : _takeoverMinutes);
|
|
if( _lockTimeout > 0 ) {
|
|
|
|
log( logLvl ) << "checking last ping for lock '" << lockName << "'" << " against process " << _lastPingCheck.get<0>() << " and ping " << _lastPingCheck.get<1>() << endl;
|
|
|
|
try {
|
|
|
|
Date_t remote = remoteTime( _conn );
|
|
|
|
// Timeout the elapsed time using comparisons of remote clock
|
|
// For non-finalized locks, timeout 15 minutes since last seen (ts)
|
|
// For finalized locks, timeout 15 minutes since last ping
|
|
bool recPingChange = o["state"].numberInt() == 2 && ( _lastPingCheck.get<0>() != lastPing["_id"].String() || _lastPingCheck.get<1>() != lastPing["ping"].Date() );
|
|
bool recTSChange = o["state"].numberInt() == 1 && _lastPingCheck.get<3>() != o["ts"].OID();
|
|
|
|
if( recPingChange || recTSChange ) {
|
|
// If the ping has changed since we last checked, mark the current date and time
|
|
_lastPingCheck = make_tuple(lastPing["_id"].String(), lastPing["ping"].Date(), remote, o["ts"].OID() );
|
|
}
|
|
else {
|
|
|
|
// GOTCHA! Due to network issues, it is possible that the current time
|
|
// is less than the remote time. We *have* to check this here, otherwise
|
|
// we overflow and our lock breaks.
|
|
if(_lastPingCheck.get<2>() >= remote)
|
|
elapsed = 0;
|
|
else
|
|
elapsed = remote - _lastPingCheck.get<2>();
|
|
}
|
|
|
|
}
|
|
catch( LockException& e ) {
|
|
|
|
// Remote server cannot be found / is not responsive
|
|
warning() << "Could not get remote time from " << _conn << causedBy( e );
|
|
|
|
}
|
|
|
|
}
|
|
else {
|
|
// LEGACY
|
|
|
|
// GOTCHA! If jsTime() (current time) is less than the remote time,
|
|
// we should definitely not break the lock. However, if we don't check
|
|
// this here, we get an invalid unsigned elapsed, which is ginormous and
|
|
// causes the lock to be forced.
|
|
if(lastPing["ping"].Date() > jsTime())
|
|
elapsed = 0;
|
|
else
|
|
elapsed = jsTime() - lastPing["ping"].Date(); // in ms
|
|
|
|
elapsed = elapsed / ( 1000 * 60 ); // convert to minutes
|
|
}
|
|
|
|
if ( elapsed <= takeover && ! canReenter ) {
|
|
log( logLvl ) << "could not force lock '" << lockName << "' because elapsed time " << elapsed << " <= takeover time " << takeover << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
else if( elapsed > takeover && canReenter ) {
|
|
log( logLvl ) << "not re-entering distributed lock " << lockName << "' because elapsed time " << elapsed << " > takeover time " << takeover << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
|
|
log( logLvl - 1 ) << ( canReenter ? "re-entering" : "forcing" ) << " lock '" << lockName << "' because "
|
|
<< ( canReenter ? "re-entering is allowed, " : "" )
|
|
<< "elapsed time " << elapsed << " > takeover time " << takeover << endl;
|
|
|
|
if( elapsed > takeover ) {
|
|
|
|
try {
|
|
|
|
// Check the clock skew again. If we check this before we get a lock
|
|
// and after the lock times out, we can be pretty sure the time is
|
|
// increasing at the same rate on all servers and therefore our
|
|
// timeout is accurate
|
|
uassert( 14023, str::stream() << "remote time in cluster " << _conn.toString() << " is now skewed, cannot force lock.", !isRemoteTimeSkewed() );
|
|
|
|
// Make sure we break the lock with the correct "ts" (OID) value, otherwise
|
|
// we can overwrite a new lock inserted in the meantime.
|
|
conn->update( _ns , BSON( "_id" << _id["_id"].String() << "state" << o["state"].numberInt() << "ts" << o["ts"] ),
|
|
BSON( "$set" << BSON( "state" << 0 ) ) );
|
|
|
|
BSONObj err = conn->getLastErrorDetailed();
|
|
string errMsg = DBClientWithCommands::getLastErrorString(err);
|
|
|
|
// TODO: Clean up all the extra code to exit this method, probably with a refactor
|
|
if ( !errMsg.empty() || !err["n"].type() || err["n"].numberInt() < 1 ) {
|
|
( errMsg.empty() ? log( logLvl - 1 ) : warning() ) << "Could not force lock '" << lockName << "' "
|
|
<< ( !errMsg.empty() ? causedBy(errMsg) : string("(another force won)") ) << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
|
|
}
|
|
catch( UpdateNotTheSame& ) {
|
|
// Ok to continue since we know we forced at least one lock document, and all lock docs
|
|
// are required for a lock to be held.
|
|
warning() << "lock forcing " << lockName << " inconsistent" << endl;
|
|
}
|
|
catch( std::exception& e ) {
|
|
conn.done();
|
|
throw LockException( str::stream() << "exception forcing distributed lock "
|
|
<< lockName << causedBy( e ), 13660);
|
|
}
|
|
|
|
}
|
|
else {
|
|
|
|
assert( canReenter );
|
|
|
|
// Test that the lock is held by trying to update the finalized state of the lock to the same state
|
|
// if it does not update or does not update on all servers, we can't re-enter.
|
|
try {
|
|
|
|
// Test the lock with the correct "ts" (OID) value
|
|
conn->update( _ns , BSON( "_id" << _id["_id"].String() << "state" << 2 << "ts" << o["ts"] ),
|
|
BSON( "$set" << BSON( "state" << 2 ) ) );
|
|
|
|
BSONObj err = conn->getLastErrorDetailed();
|
|
string errMsg = DBClientWithCommands::getLastErrorString(err);
|
|
|
|
// TODO: Clean up all the extra code to exit this method, probably with a refactor
|
|
if ( ! errMsg.empty() || ! err["n"].type() || err["n"].numberInt() < 1 ) {
|
|
( errMsg.empty() ? log( logLvl - 1 ) : warning() ) << "Could not re-enter lock '" << lockName << "' "
|
|
<< ( !errMsg.empty() ? causedBy(errMsg) : string("(not sure lock is held)") ) << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
|
|
}
|
|
catch( UpdateNotTheSame& ) {
|
|
// NOT ok to continue since our lock isn't held by all servers, so isn't valid.
|
|
warning() << "inconsistent state re-entering lock, lock " << lockName << " not held" << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return false;
|
|
}
|
|
catch( std::exception& e ) {
|
|
conn.done();
|
|
throw LockException( str::stream() << "exception re-entering distributed lock "
|
|
<< lockName << causedBy( e ), 13660);
|
|
}
|
|
|
|
log( logLvl - 1 ) << "re-entered distributed lock '" << lockName << "'" << endl;
|
|
*other = o; other->getOwned(); conn.done();
|
|
return true;
|
|
|
|
}
|
|
|
|
// Lock forced, reset our timer
|
|
if(_lockTimeout > 0)
|
|
_lastPingCheck = make_tuple(string(""), 0, 0, OID());
|
|
|
|
log( logLvl - 1 ) << "lock '" << lockName << "' successfully forced" << endl;
|
|
|
|
// We don't need the ts value in the query, since we will only ever replace locks with state=0.
|
|
}
|
|
// Case 3: We have an expired lock
|
|
else if ( o["ts"].type() ) {
|
|
queryBuilder.append( o["ts"] );
|
|
}
|
|
}
|
|
|
|
bool gotLock = false;
|
|
BSONObj currLock;
|
|
|
|
BSONObj lockDetails = BSON( "state" << 1 << "who" << getDistLockId() << "process" << _processId <<
|
|
"when" << jsTime() << "why" << why << "ts" << OID::gen() );
|
|
BSONObj whatIWant = BSON( "$set" << lockDetails );
|
|
|
|
BSONObj query = queryBuilder.obj();
|
|
|
|
string lockName = _name + string("/") + _processId;
|
|
|
|
try {
|
|
|
|
// Main codepath to acquire lock
|
|
|
|
log( logLvl ) << "about to acquire distributed lock '" << lockName << ":\n"
|
|
<< lockDetails.jsonString(Strict, true) << "\n"
|
|
<< query.jsonString(Strict, true) << endl;
|
|
|
|
conn->update( _ns , query , whatIWant );
|
|
|
|
BSONObj err = conn->getLastErrorDetailed();
|
|
string errMsg = DBClientWithCommands::getLastErrorString(err);
|
|
|
|
currLock = conn->findOne( _ns , _id );
|
|
|
|
if ( !errMsg.empty() || !err["n"].type() || err["n"].numberInt() < 1 ) {
|
|
( errMsg.empty() ? log( logLvl - 1 ) : warning() ) << "could not acquire lock '" << lockName << "' "
|
|
<< ( !errMsg.empty() ? causedBy( errMsg ) : string("(another update won)") ) << endl;
|
|
*other = currLock;
|
|
other->getOwned();
|
|
gotLock = false;
|
|
}
|
|
else {
|
|
gotLock = true;
|
|
}
|
|
|
|
}
|
|
catch ( UpdateNotTheSame& up ) {
|
|
|
|
// this means our update got through on some, but not others
|
|
warning() << "distributed lock '" << lockName << " did not propagate properly." << causedBy( up ) << endl;
|
|
|
|
// Overall protection derives from:
|
|
// All unlocking updates use the ts value when setting state to 0
|
|
// This ensures that during locking, we can override all smaller ts locks with
|
|
// our own safe ts value and not be unlocked afterward.
|
|
for ( unsigned i = 0; i < up.size(); i++ ) {
|
|
|
|
ScopedDbConnection indDB( up[i].first );
|
|
BSONObj indUpdate;
|
|
|
|
try {
|
|
|
|
indUpdate = indDB->findOne( _ns , _id );
|
|
|
|
// If we override this lock in any way, grab and protect it.
|
|
// We assume/ensure that if a process does not have all lock documents, it is no longer
|
|
// holding the lock.
|
|
// Note - finalized locks may compete too, but we know they've won already if competing
|
|
// in this round. Cleanup of crashes during finalizing may take a few tries.
|
|
if( indUpdate["ts"] < lockDetails["ts"] || indUpdate["state"].numberInt() == 0 ) {
|
|
|
|
BSONObj grabQuery = BSON( "_id" << _id["_id"].String() << "ts" << indUpdate["ts"].OID() );
|
|
|
|
// Change ts so we won't be forced, state so we won't be relocked
|
|
BSONObj grabChanges = BSON( "ts" << lockDetails["ts"].OID() << "state" << 1 );
|
|
|
|
// Either our update will succeed, and we'll grab the lock, or it will fail b/c some other
|
|
// process grabbed the lock (which will change the ts), but the lock will be set until forcing
|
|
indDB->update( _ns, grabQuery, BSON( "$set" << grabChanges ) );
|
|
|
|
indUpdate = indDB->findOne( _ns, _id );
|
|
|
|
// Our lock should now be set until forcing.
|
|
assert( indUpdate["state"].numberInt() == 1 );
|
|
|
|
}
|
|
// else our lock is the same, in which case we're safe, or it's a bigger lock,
|
|
// in which case we won't need to protect anything since we won't have the lock.
|
|
|
|
}
|
|
catch( std::exception& e ) {
|
|
conn.done();
|
|
throw LockException( str::stream() << "distributed lock " << lockName
|
|
<< " had errors communicating with individual server "
|
|
<< up[1].first << causedBy( e ), 13661 );
|
|
}
|
|
|
|
assert( !indUpdate.isEmpty() );
|
|
|
|
// Find max TS value
|
|
if ( currLock.isEmpty() || currLock["ts"] < indUpdate["ts"] ) {
|
|
currLock = indUpdate.getOwned();
|
|
}
|
|
|
|
indDB.done();
|
|
|
|
}
|
|
|
|
// Locks on all servers are now set and safe until forcing
|
|
|
|
if ( currLock["ts"] == lockDetails["ts"] ) {
|
|
log( logLvl - 1 ) << "lock update won, completing lock propagation for '" << lockName << "'" << endl;
|
|
gotLock = true;
|
|
}
|
|
else {
|
|
log( logLvl - 1 ) << "lock update lost, lock '" << lockName << "' not propagated." << endl;
|
|
|
|
// Register the lock for deletion, to speed up failover
|
|
// Not strictly necessary, but helpful
|
|
distLockPinger.addUnlockOID( lockDetails["ts"].OID() );
|
|
|
|
gotLock = false;
|
|
}
|
|
}
|
|
catch( std::exception& e ) {
|
|
conn.done();
|
|
throw LockException( str::stream() << "exception creating distributed lock "
|
|
<< lockName << causedBy( e ), 13663 );
|
|
}
|
|
|
|
// Complete lock propagation
|
|
if( gotLock ) {
|
|
|
|
// This is now safe, since we know that no new locks will be placed on top of the ones we've checked for at
|
|
// least 15 minutes. Sets the state = 2, so that future clients can determine that the lock is truly set.
|
|
// The invariant for rollbacks is that we will never force locks with state = 2 and active pings, since that
|
|
// indicates the lock is active, but this means the process creating/destroying them must explicitly poll
|
|
// when something goes wrong.
|
|
try {
|
|
|
|
BSONObjBuilder finalLockDetails;
|
|
BSONObjIterator bi( lockDetails );
|
|
while( bi.more() ) {
|
|
BSONElement el = bi.next();
|
|
if( (string) ( el.fieldName() ) == "state" )
|
|
finalLockDetails.append( "state", 2 );
|
|
else finalLockDetails.append( el );
|
|
}
|
|
|
|
conn->update( _ns , _id , BSON( "$set" << finalLockDetails.obj() ) );
|
|
|
|
BSONObj err = conn->getLastErrorDetailed();
|
|
string errMsg = DBClientWithCommands::getLastErrorString(err);
|
|
|
|
currLock = conn->findOne( _ns , _id );
|
|
|
|
if ( !errMsg.empty() || !err["n"].type() || err["n"].numberInt() < 1 ) {
|
|
warning() << "could not finalize winning lock " << lockName
|
|
<< ( !errMsg.empty() ? causedBy( errMsg ) : " (did not update lock) " ) << endl;
|
|
gotLock = false;
|
|
}
|
|
else {
|
|
// SUCCESS!
|
|
gotLock = true;
|
|
}
|
|
|
|
}
|
|
catch( std::exception& e ) {
|
|
conn.done();
|
|
|
|
// Register the bad final lock for deletion, in case it exists
|
|
distLockPinger.addUnlockOID( lockDetails["ts"].OID() );
|
|
|
|
throw LockException( str::stream() << "exception finalizing winning lock"
|
|
<< causedBy( e ), 13662 );
|
|
}
|
|
|
|
}
|
|
|
|
*other = currLock;
|
|
other->getOwned();
|
|
|
|
// Log our lock results
|
|
if(gotLock)
|
|
log( logLvl - 1 ) << "distributed lock '" << lockName << "' acquired, now : " << currLock << endl;
|
|
else
|
|
log( logLvl - 1 ) << "distributed lock '" << lockName << "' was not acquired." << endl;
|
|
|
|
conn.done();
|
|
|
|
return gotLock;
|
|
}
|
|
|
|
// Unlock now takes an optional pointer to the lock, so you can be specific about which
|
|
// particular lock you want to unlock. This is required when the config server is down,
|
|
// and so cannot tell you what lock ts you should try later.
|
|
void DistributedLock::unlock( BSONObj* oldLockPtr ) {
|
|
|
|
assert( _name != "" );
|
|
|
|
string lockName = _name + string("/") + _processId;
|
|
|
|
const int maxAttempts = 3;
|
|
int attempted = 0;
|
|
|
|
BSONObj oldLock;
|
|
if( oldLockPtr ) oldLock = *oldLockPtr;
|
|
|
|
while ( ++attempted <= maxAttempts ) {
|
|
|
|
ScopedDbConnection conn( _conn );
|
|
|
|
try {
|
|
|
|
if( oldLock.isEmpty() )
|
|
oldLock = conn->findOne( _ns, _id );
|
|
|
|
if( oldLock["state"].eoo() || oldLock["state"].numberInt() != 2 || oldLock["ts"].eoo() ) {
|
|
warning() << "cannot unlock invalid distributed lock " << oldLock << endl;
|
|
conn.done();
|
|
break;
|
|
}
|
|
|
|
// Use ts when updating lock, so that new locks can be sure they won't get trampled.
|
|
conn->update( _ns ,
|
|
BSON( "_id" << _id["_id"].String() << "ts" << oldLock["ts"].OID() ),
|
|
BSON( "$set" << BSON( "state" << 0 ) ) );
|
|
|
|
log( logLvl - 1 ) << "distributed lock '" << lockName << "' unlocked. " << endl;
|
|
conn.done();
|
|
return;
|
|
}
|
|
catch( UpdateNotTheSame& ) {
|
|
log( logLvl - 1 ) << "distributed lock '" << lockName << "' unlocked (messily). " << endl;
|
|
conn.done();
|
|
break;
|
|
}
|
|
catch ( std::exception& e) {
|
|
warning() << "distributed lock '" << lockName << "' failed unlock attempt."
|
|
<< causedBy( e ) << endl;
|
|
|
|
conn.done();
|
|
// TODO: If our lock timeout is small, sleeping this long may be unsafe.
|
|
if( attempted != maxAttempts) sleepsecs(1 << attempted);
|
|
}
|
|
}
|
|
|
|
if( attempted > maxAttempts && ! oldLock.isEmpty() && ! oldLock["ts"].eoo() ) {
|
|
|
|
log( logLvl - 1 ) << "could not unlock distributed lock with ts " << oldLock["ts"].OID()
|
|
<< ", will attempt again later" << endl;
|
|
|
|
// We couldn't unlock the lock at all, so try again later in the pinging thread...
|
|
distLockPinger.addUnlockOID( oldLock["ts"].OID() );
|
|
}
|
|
else if( attempted > maxAttempts ) {
|
|
warning() << "could not unlock untracked distributed lock, a manual force may be required" << endl;
|
|
}
|
|
|
|
warning() << "distributed lock '" << lockName << "' couldn't consummate unlock request. "
|
|
<< "lock may be taken over after "
|
|
<< (_lockTimeout > 0 ? _lockTimeout / (60 * 1000) : _takeoverMinutes)
|
|
<< " minutes timeout." << endl;
|
|
}
|
|
|
|
|
|
|
|
}
|