includes/jobqueue/JobRunner.php

   1 <?php
   2 /**
   3  * Job queue runner utility methods
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup JobQueue
  22  */
  23
  24 use MediaWiki\MediaWikiServices;
  25 use MediaWiki\Logger\LoggerFactory;
  26 use Liuggio\StatsdClient\Factory\StatsdDataFactory;
  27 use Psr\Log\LoggerAwareInterface;
  28 use Psr\Log\LoggerInterface;
  29 use Wikimedia\ScopedCallback;
  30 use Wikimedia\Rdbms\LBFactory;
  31
  32 /**
  33  * Job queue runner utility methods
  34  *
  35  * @ingroup JobQueue
  36  * @since 1.24
  37  */
  38 class JobRunner implements LoggerAwareInterface {
  39         /** @var callable|null Debug output handler */
  40         protected $debug;
  41
  42         /**
  43          * @var LoggerInterface $logger
  44          */
  45         protected $logger;
  46
  47         const MAX_ALLOWED_LAG = 3; // abort if more than this much DB lag is present
  48         const LAG_CHECK_PERIOD = 1.0; // check replica DB lag this many seconds
  49         const ERROR_BACKOFF_TTL = 1; // seconds to back off a queue due to errors
  50         const READONLY_BACKOFF_TTL = 30; // seconds to back off a queue due to read-only errors
  51
  52         /**
  53          * @param callable $debug Optional debug output handler
  54          */
  55         public function setDebugHandler( $debug ) {
  56                 $this->debug = $debug;
  57         }
  58
  59         /**
  60          * @param LoggerInterface $logger
  61          * @return void
  62          */
  63         public function setLogger( LoggerInterface $logger ) {
  64                 $this->logger = $logger;
  65         }
  66
  67         /**
  68          * @param LoggerInterface $logger
  69          */
  70         public function __construct( LoggerInterface $logger = null ) {
  71                 if ( $logger === null ) {
  72                         $logger = LoggerFactory::getInstance( 'runJobs' );
  73                 }
  74                 $this->setLogger( $logger );
  75         }
  76
  77         /**
  78          * Run jobs of the specified number/type for the specified time
  79          *
  80          * The response map has a 'job' field that lists status of each job, including:
  81          *   - type   : the job type
  82          *   - status : ok/failed
  83          *   - error  : any error message string
  84          *   - time   : the job run time in ms
  85          * The response map also has:
  86          *   - backoffs : the (job type => seconds) map of backoff times
  87          *   - elapsed  : the total time spent running tasks in ms
  88          *   - reached  : the reason the script finished, one of (none-ready, job-limit, time-limit,
  89          *  memory-limit)
  90          *
  91          * This method outputs status information only if a debug handler was set.
  92          * Any exceptions are caught and logged, but are not reported as output.
  93          *
  94          * @param array $options Map of parameters:
  95          *    - type     : the job type (or false for the default types)
  96          *    - maxJobs  : maximum number of jobs to run
  97          *    - maxTime  : maximum time in seconds before stopping
  98          *    - throttle : whether to respect job backoff configuration
  99          * @return array Summary response that can easily be JSON serialized
 100          */
 101         public function run( array $options ) {
 102                 global $wgJobClasses, $wgTrxProfilerLimits;
 103
 104                 $response = [ 'jobs' => [], 'reached' => 'none-ready' ];
 105
 106                 $type = isset( $options['type'] ) ? $options['type'] : false;
 107                 $maxJobs = isset( $options['maxJobs'] ) ? $options['maxJobs'] : false;
 108                 $maxTime = isset( $options['maxTime'] ) ? $options['maxTime'] : false;
 109                 $noThrottle = isset( $options['throttle'] ) && !$options['throttle'];
 110
 111                 // Bail if job type is invalid
 112                 if ( $type !== false && !isset( $wgJobClasses[$type] ) ) {
 113                         $response['reached'] = 'none-possible';
 114                         return $response;
 115                 }
 116                 // Bail out if DB is in read-only mode
 117                 if ( wfReadOnly() ) {
 118                         $response['reached'] = 'read-only';
 119                         return $response;
 120                 }
 121
 122                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 123                 // Bail out if there is too much DB lag.
 124                 // This check should not block as we want to try other wiki queues.
 125                 list( , $maxLag ) = $lbFactory->getMainLB( wfWikiID() )->getMaxLag();
 126                 if ( $maxLag >= self::MAX_ALLOWED_LAG ) {
 127                         $response['reached'] = 'replica-lag-limit';
 128                         return $response;
 129                 }
 130
 131                 // Flush any pending DB writes for sanity
 132                 $lbFactory->commitAll( __METHOD__ );
 133
 134                 // Catch huge single updates that lead to replica DB lag
 135                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
 136                 $trxProfiler->setLogger( LoggerFactory::getInstance( 'DBPerformance' ) );
 137                 $trxProfiler->setExpectations( $wgTrxProfilerLimits['JobRunner'], __METHOD__ );
 138
 139                 // Some jobs types should not run until a certain timestamp
 140                 $backoffs = []; // map of (type => UNIX expiry)
 141                 $backoffDeltas = []; // map of (type => seconds)
 142                 $wait = 'wait'; // block to read backoffs the first time
 143
 144                 $group = JobQueueGroup::singleton();
 145                 $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
 146                 $jobsPopped = 0;
 147                 $timeMsTotal = 0;
 148                 $startTime = microtime( true ); // time since jobs started running
 149                 $lastCheckTime = 1; // timestamp of last replica DB check
 150                 do {
 151                         // Sync the persistent backoffs with concurrent runners
 152                         $backoffs = $this->syncBackoffDeltas( $backoffs, $backoffDeltas, $wait );
 153                         $blacklist = $noThrottle ? [] : array_keys( $backoffs );
 154                         $wait = 'nowait'; // less important now
 155
 156                         if ( $type === false ) {
 157                                 $job = $group->pop(
 158                                         JobQueueGroup::TYPE_DEFAULT,
 159                                         JobQueueGroup::USE_CACHE,
 160                                         $blacklist
 161                                 );
 162                         } elseif ( in_array( $type, $blacklist ) ) {
 163                                 $job = false; // requested queue in backoff state
 164                         } else {
 165                                 $job = $group->pop( $type ); // job from a single queue
 166                         }
 167                         $lbFactory->commitMasterChanges( __METHOD__ ); // flush any JobQueueDB writes
 168
 169                         if ( $job ) { // found a job
 170                                 ++$jobsPopped;
 171                                 $popTime = time();
 172                                 $jType = $job->getType();
 173
 174                                 WebRequest::overrideRequestId( $job->getRequestId() );
 175
 176                                 // Back off of certain jobs for a while (for throttling and for errors)
 177                                 $ttw = $this->getBackoffTimeToWait( $job );
 178                                 if ( $ttw > 0 ) {
 179                                         // Always add the delta for other runners in case the time running the
 180                                         // job negated the backoff for each individually but not collectively.
 181                                         $backoffDeltas[$jType] = isset( $backoffDeltas[$jType] )
 182                                                 ? $backoffDeltas[$jType] + $ttw
 183                                                 : $ttw;
 184                                         $backoffs = $this->syncBackoffDeltas( $backoffs, $backoffDeltas, $wait );
 185                                 }
 186
 187                                 $info = $this->executeJob( $job, $lbFactory, $stats, $popTime );
 188                                 if ( $info['status'] !== false || !$job->allowRetries() ) {
 189                                         $group->ack( $job ); // succeeded or job cannot be retried
 190                                         $lbFactory->commitMasterChanges( __METHOD__ ); // flush any JobQueueDB writes
 191                                 }
 192
 193                                 // Back off of certain jobs for a while (for throttling and for errors)
 194                                 if ( $info['status'] === false && mt_rand( 0, 49 ) == 0 ) {
 195                                         $ttw = max( $ttw, $this->getErrorBackoffTTL( $info['error'] ) );
 196                                         $backoffDeltas[$jType] = isset( $backoffDeltas[$jType] )
 197                                                 ? $backoffDeltas[$jType] + $ttw
 198                                                 : $ttw;
 199                                 }
 200
 201                                 $response['jobs'][] = [
 202                                         'type'   => $jType,
 203                                         'status' => ( $info['status'] === false ) ? 'failed' : 'ok',
 204                                         'error'  => $info['error'],
 205                                         'time'   => $info['timeMs']
 206                                 ];
 207                                 $timeMsTotal += $info['timeMs'];
 208
 209                                 // Break out if we hit the job count or wall time limits...
 210                                 if ( $maxJobs && $jobsPopped >= $maxJobs ) {
 211                                         $response['reached'] = 'job-limit';
 212                                         break;
 213                                 } elseif ( $maxTime && ( microtime( true ) - $startTime ) > $maxTime ) {
 214                                         $response['reached'] = 'time-limit';
 215                                         break;
 216                                 }
 217
 218                                 // Don't let any of the main DB replica DBs get backed up.
 219                                 // This only waits for so long before exiting and letting
 220                                 // other wikis in the farm (on different masters) get a chance.
 221                                 $timePassed = microtime( true ) - $lastCheckTime;
 222                                 if ( $timePassed >= self::LAG_CHECK_PERIOD || $timePassed < 0 ) {
 223                                         try {
 224                                                 $lbFactory->waitForReplication( [
 225                                                         'ifWritesSince' => $lastCheckTime,
 226                                                         'timeout' => self::MAX_ALLOWED_LAG
 227                                                 ] );
 228                                         } catch ( DBReplicationWaitError $e ) {
 229                                                 $response['reached'] = 'replica-lag-limit';
 230                                                 break;
 231                                         }
 232                                         $lastCheckTime = microtime( true );
 233                                 }
 234                                 // Don't let any queue replica DBs/backups fall behind
 235                                 if ( $jobsPopped > 0 && ( $jobsPopped % 100 ) == 0 ) {
 236                                         $group->waitForBackups();
 237                                 }
 238
 239                                 // Bail if near-OOM instead of in a job
 240                                 if ( !$this->checkMemoryOK() ) {
 241                                         $response['reached'] = 'memory-limit';
 242                                         break;
 243                                 }
 244                         }
 245                 } while ( $job ); // stop when there are no jobs
 246
 247                 // Sync the persistent backoffs for the next runJobs.php pass
 248                 if ( $backoffDeltas ) {
 249                         $this->syncBackoffDeltas( $backoffs, $backoffDeltas, 'wait' );
 250                 }
 251
 252                 $response['backoffs'] = $backoffs;
 253                 $response['elapsed'] = $timeMsTotal;
 254
 255                 return $response;
 256         }
 257
 258         /**
 259          * @param string $error
 260          * @return int TTL in seconds
 261          */
 262         private function getErrorBackoffTTL( $error ) {
 263                 return strpos( $error, 'DBReadOnlyError' ) !== false
 264                         ? self::READONLY_BACKOFF_TTL
 265                         : self::ERROR_BACKOFF_TTL;
 266         }
 267
 268         /**
 269          * @param Job $job
 270          * @param LBFactory $lbFactory
 271          * @param StatsdDataFactory $stats
 272          * @param float $popTime
 273          * @return array Map of status/error/timeMs
 274          */
 275         private function executeJob( Job $job, LBFactory $lbFactory, $stats, $popTime ) {
 276                 $jType = $job->getType();
 277                 $msg = $job->toString() . " STARTING";
 278                 $this->logger->debug( $msg );
 279                 $this->debugCallback( $msg );
 280
 281                 // Run the job...
 282                 $rssStart = $this->getMaxRssKb();
 283                 $jobStartTime = microtime( true );
 284                 try {
 285                         $fnameTrxOwner = get_class( $job ) . '::run'; // give run() outer scope
 286                         $lbFactory->beginMasterChanges( $fnameTrxOwner );
 287                         $status = $job->run();
 288                         $error = $job->getLastError();
 289                         $this->commitMasterChanges( $lbFactory, $job, $fnameTrxOwner );
 290                         // Run any deferred update tasks; doUpdates() manages transactions itself
 291                         DeferredUpdates::doUpdates();
 292                 } catch ( Exception $e ) {
 293                         MWExceptionHandler::rollbackMasterChangesAndLog( $e );
 294                         $status = false;
 295                         $error = get_class( $e ) . ': ' . $e->getMessage();
 296                 }
 297                 // Always attempt to call teardown() even if Job throws exception.
 298                 try {
 299                         $job->teardown( $status );
 300                 } catch ( Exception $e ) {
 301                         MWExceptionHandler::logException( $e );
 302                 }
 303
 304                 // Commit all outstanding connections that are in a transaction
 305                 // to get a fresh repeatable read snapshot on every connection.
 306                 // Note that jobs are still responsible for handling replica DB lag.
 307                 $lbFactory->flushReplicaSnapshots( __METHOD__ );
 308                 // Clear out title cache data from prior snapshots
 309                 MediaWikiServices::getInstance()->getLinkCache()->clear();
 310                 $timeMs = intval( ( microtime( true ) - $jobStartTime ) * 1000 );
 311                 $rssEnd = $this->getMaxRssKb();
 312
 313                 // Record how long jobs wait before getting popped
 314                 $readyTs = $job->getReadyTimestamp();
 315                 if ( $readyTs ) {
 316                         $pickupDelay = max( 0, $popTime - $readyTs );
 317                         $stats->timing( 'jobqueue.pickup_delay.all', 1000 * $pickupDelay );
 318                         $stats->timing( "jobqueue.pickup_delay.$jType", 1000 * $pickupDelay );
 319                 }
 320                 // Record root job age for jobs being run
 321                 $rootTimestamp = $job->getRootJobParams()['rootJobTimestamp'];
 322                 if ( $rootTimestamp ) {
 323                         $age = max( 0, $popTime - wfTimestamp( TS_UNIX, $rootTimestamp ) );
 324                         $stats->timing( "jobqueue.pickup_root_age.$jType", 1000 * $age );
 325                 }
 326                 // Track the execution time for jobs
 327                 $stats->timing( "jobqueue.run.$jType", $timeMs );
 328                 // Track RSS increases for jobs (in case of memory leaks)
 329                 if ( $rssStart && $rssEnd ) {
 330                         $stats->updateCount( "jobqueue.rss_delta.$jType", $rssEnd - $rssStart );
 331                 }
 332
 333                 if ( $status === false ) {
 334                         $msg = $job->toString() . " t=$timeMs error={$error}";
 335                         $this->logger->error( $msg );
 336                         $this->debugCallback( $msg );
 337                 } else {
 338                         $msg = $job->toString() . " t=$timeMs good";
 339                         $this->logger->info( $msg );
 340                         $this->debugCallback( $msg );
 341                 }
 342
 343                 return [ 'status' => $status, 'error' => $error, 'timeMs' => $timeMs ];
 344         }
 345
 346         /**
 347          * @return int|null Max memory RSS in kilobytes
 348          */
 349         private function getMaxRssKb() {
 350                 $info = wfGetRusage() ?: [];
 351                 // see https://linux.die.net/man/2/getrusage
 352                 return isset( $info['ru_maxrss'] ) ? (int)$info['ru_maxrss'] : null;
 353         }
 354
 355         /**
 356          * @param Job $job
 357          * @return int Seconds for this runner to avoid doing more jobs of this type
 358          * @see $wgJobBackoffThrottling
 359          */
 360         private function getBackoffTimeToWait( Job $job ) {
 361                 global $wgJobBackoffThrottling;
 362
 363                 if ( !isset( $wgJobBackoffThrottling[$job->getType()] ) ||
 364                         $job instanceof DuplicateJob // no work was done
 365                 ) {
 366                         return 0; // not throttled
 367                 }
 368
 369                 $itemsPerSecond = $wgJobBackoffThrottling[$job->getType()];
 370                 if ( $itemsPerSecond <= 0 ) {
 371                         return 0; // not throttled
 372                 }
 373
 374                 $seconds = 0;
 375                 if ( $job->workItemCount() > 0 ) {
 376                         $exactSeconds = $job->workItemCount() / $itemsPerSecond;
 377                         // use randomized rounding
 378                         $seconds = floor( $exactSeconds );
 379                         $remainder = $exactSeconds - $seconds;
 380                         $seconds += ( mt_rand() / mt_getrandmax() < $remainder ) ? 1 : 0;
 381                 }
 382
 383                 return (int)$seconds;
 384         }
 385
 386         /**
 387          * Get the previous backoff expiries from persistent storage
 388          * On I/O or lock acquisition failure this returns the original $backoffs.
 389          *
 390          * @param array $backoffs Map of (job type => UNIX timestamp)
 391          * @param string $mode Lock wait mode - "wait" or "nowait"
 392          * @return array Map of (job type => backoff expiry timestamp)
 393          */
 394         private function loadBackoffs( array $backoffs, $mode = 'wait' ) {
 395                 $file = wfTempDir() . '/mw-runJobs-backoffs.json';
 396                 if ( is_file( $file ) ) {
 397                         $noblock = ( $mode === 'nowait' ) ? LOCK_NB : 0;
 398                         $handle = fopen( $file, 'rb' );
 399                         if ( !flock( $handle, LOCK_SH | $noblock ) ) {
 400                                 fclose( $handle );
 401                                 return $backoffs; // don't wait on lock
 402                         }
 403                         $content = stream_get_contents( $handle );
 404                         flock( $handle, LOCK_UN );
 405                         fclose( $handle );
 406                         $ctime = microtime( true );
 407                         $cBackoffs = json_decode( $content, true ) ?: [];
 408                         foreach ( $cBackoffs as $type => $timestamp ) {
 409                                 if ( $timestamp < $ctime ) {
 410                                         unset( $cBackoffs[$type] );
 411                                 }
 412                         }
 413                 } else {
 414                         $cBackoffs = [];
 415                 }
 416
 417                 return $cBackoffs;
 418         }
 419
 420         /**
 421          * Merge the current backoff expiries from persistent storage
 422          *
 423          * The $deltas map is set to an empty array on success.
 424          * On I/O or lock acquisition failure this returns the original $backoffs.
 425          *
 426          * @param array $backoffs Map of (job type => UNIX timestamp)
 427          * @param array $deltas Map of (job type => seconds)
 428          * @param string $mode Lock wait mode - "wait" or "nowait"
 429          * @return array The new backoffs account for $backoffs and the latest file data
 430          */
 431         private function syncBackoffDeltas( array $backoffs, array &$deltas, $mode = 'wait' ) {
 432                 if ( !$deltas ) {
 433                         return $this->loadBackoffs( $backoffs, $mode );
 434                 }
 435
 436                 $noblock = ( $mode === 'nowait' ) ? LOCK_NB : 0;
 437                 $file = wfTempDir() . '/mw-runJobs-backoffs.json';
 438                 $handle = fopen( $file, 'wb+' );
 439                 if ( !flock( $handle, LOCK_EX | $noblock ) ) {
 440                         fclose( $handle );
 441                         return $backoffs; // don't wait on lock
 442                 }
 443                 $ctime = microtime( true );
 444                 $content = stream_get_contents( $handle );
 445                 $cBackoffs = json_decode( $content, true ) ?: [];
 446                 foreach ( $deltas as $type => $seconds ) {
 447                         $cBackoffs[$type] = isset( $cBackoffs[$type] ) && $cBackoffs[$type] >= $ctime
 448                                 ? $cBackoffs[$type] + $seconds
 449                                 : $ctime + $seconds;
 450                 }
 451                 foreach ( $cBackoffs as $type => $timestamp ) {
 452                         if ( $timestamp < $ctime ) {
 453                                 unset( $cBackoffs[$type] );
 454                         }
 455                 }
 456                 ftruncate( $handle, 0 );
 457                 fwrite( $handle, json_encode( $cBackoffs ) );
 458                 flock( $handle, LOCK_UN );
 459                 fclose( $handle );
 460
 461                 $deltas = [];
 462
 463                 return $cBackoffs;
 464         }
 465
 466         /**
 467          * Make sure that this script is not too close to the memory usage limit.
 468          * It is better to die in between jobs than OOM right in the middle of one.
 469          * @return bool
 470          */
 471         private function checkMemoryOK() {
 472                 static $maxBytes = null;
 473                 if ( $maxBytes === null ) {
 474                         $m = [];
 475                         if ( preg_match( '!^(\d+)(k|m|g|)$!i', ini_get( 'memory_limit' ), $m ) ) {
 476                                 list( , $num, $unit ) = $m;
 477                                 $conv = [ 'g' => 1073741824, 'm' => 1048576, 'k' => 1024, '' => 1 ];
 478                                 $maxBytes = $num * $conv[strtolower( $unit )];
 479                         } else {
 480                                 $maxBytes = 0;
 481                         }
 482                 }
 483                 $usedBytes = memory_get_usage();
 484                 if ( $maxBytes && $usedBytes >= 0.95 * $maxBytes ) {
 485                         $msg = "Detected excessive memory usage ($usedBytes/$maxBytes).";
 486                         $this->debugCallback( $msg );
 487                         $this->logger->error( $msg );
 488
 489                         return false;
 490                 }
 491
 492                 return true;
 493         }
 494
 495         /**
 496          * Log the job message
 497          * @param string $msg The message to log
 498          */
 499         private function debugCallback( $msg ) {
 500                 if ( $this->debug ) {
 501                         call_user_func_array( $this->debug, [ wfTimestamp( TS_DB ) . " $msg\n" ] );
 502                 }
 503         }
 504
 505         /**
 506          * Issue a commit on all masters who are currently in a transaction and have
 507          * made changes to the database. It also supports sometimes waiting for the
 508          * local wiki's replica DBs to catch up. See the documentation for
 509          * $wgJobSerialCommitThreshold for more.
 510          *
 511          * @param LBFactory $lbFactory
 512          * @param Job $job
 513          * @param string $fnameTrxOwner
 514          * @throws DBError
 515          */
 516         private function commitMasterChanges( LBFactory $lbFactory, Job $job, $fnameTrxOwner ) {
 517                 global $wgJobSerialCommitThreshold;
 518
 519                 $time = false;
 520                 $lb = $lbFactory->getMainLB( wfWikiID() );
 521                 if ( $wgJobSerialCommitThreshold !== false && $lb->getServerCount() > 1 ) {
 522                         // Generally, there is one master connection to the local DB
 523                         $dbwSerial = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
 524                         // We need natively blocking fast locks
 525                         if ( $dbwSerial && $dbwSerial->namedLocksEnqueue() ) {
 526                                 $time = $dbwSerial->pendingWriteQueryDuration( $dbwSerial::ESTIMATE_DB_APPLY );
 527                                 if ( $time < $wgJobSerialCommitThreshold ) {
 528                                         $dbwSerial = false;
 529                                 }
 530                         } else {
 531                                 $dbwSerial = false;
 532                         }
 533                 } else {
 534                         // There are no replica DBs or writes are all to foreign DB (we don't handle that)
 535                         $dbwSerial = false;
 536                 }
 537
 538                 if ( !$dbwSerial ) {
 539                         $lbFactory->commitMasterChanges( $fnameTrxOwner );
 540                         return;
 541                 }
 542
 543                 $ms = intval( 1000 * $time );
 544                 $msg = $job->toString() . " COMMIT ENQUEUED [{$ms}ms of writes]";
 545                 $this->logger->info( $msg );
 546                 $this->debugCallback( $msg );
 547
 548                 // Wait for an exclusive lock to commit
 549                 if ( !$dbwSerial->lock( 'jobrunner-serial-commit', __METHOD__, 30 ) ) {
 550                         // This will trigger a rollback in the main loop
 551                         throw new DBError( $dbwSerial, "Timed out waiting on commit queue." );
 552                 }
 553                 $unlocker = new ScopedCallback( function () use ( $dbwSerial ) {
 554                         $dbwSerial->unlock( 'jobrunner-serial-commit', __METHOD__ );
 555                 } );
 556
 557                 // Wait for the replica DBs to catch up
 558                 $pos = $lb->getMasterPos();
 559                 if ( $pos ) {
 560                         $lb->waitForAll( $pos );
 561                 }
 562
 563                 // Actually commit the DB master changes
 564                 $lbFactory->commitMasterChanges( $fnameTrxOwner );
 565                 ScopedCallback::consume( $unlocker );
 566         }
 567 }