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 use Wikimedia\Rdbms\DBError;
  32 use Wikimedia\Rdbms\DBReplicationWaitError;
  33
  34 /**
  35  * Job queue runner utility methods
  36  *
  37  * @ingroup JobQueue
  38  * @since 1.24
  39  */
  40 class JobRunner implements LoggerAwareInterface {
  41         /** @var callable|null Debug output handler */
  42         protected $debug;
  43
  44         /**
  45          * @var LoggerInterface $logger
  46          */
  47         protected $logger;
  48
  49         const MAX_ALLOWED_LAG = 3; // abort if more than this much DB lag is present
  50         const LAG_CHECK_PERIOD = 1.0; // check replica DB lag this many seconds
  51         const ERROR_BACKOFF_TTL = 1; // seconds to back off a queue due to errors
  52         const READONLY_BACKOFF_TTL = 30; // seconds to back off a queue due to read-only errors
  53
  54         /**
  55          * @param callable $debug Optional debug output handler
  56          */
  57         public function setDebugHandler( $debug ) {
  58                 $this->debug = $debug;
  59         }
  60
  61         /**
  62          * @param LoggerInterface $logger
  63          * @return void
  64          */
  65         public function setLogger( LoggerInterface $logger ) {
  66                 $this->logger = $logger;
  67         }
  68
  69         /**
  70          * @param LoggerInterface $logger
  71          */
  72         public function __construct( LoggerInterface $logger = null ) {
  73                 if ( $logger === null ) {
  74                         $logger = LoggerFactory::getInstance( 'runJobs' );
  75                 }
  76                 $this->setLogger( $logger );
  77         }
  78
  79         /**
  80          * Run jobs of the specified number/type for the specified time
  81          *
  82          * The response map has a 'job' field that lists status of each job, including:
  83          *   - type   : the job type
  84          *   - status : ok/failed
  85          *   - error  : any error message string
  86          *   - time   : the job run time in ms
  87          * The response map also has:
  88          *   - backoffs : the (job type => seconds) map of backoff times
  89          *   - elapsed  : the total time spent running tasks in ms
  90          *   - reached  : the reason the script finished, one of (none-ready, job-limit, time-limit,
  91          *  memory-limit)
  92          *
  93          * This method outputs status information only if a debug handler was set.
  94          * Any exceptions are caught and logged, but are not reported as output.
  95          *
  96          * @param array $options Map of parameters:
  97          *    - type     : the job type (or false for the default types)
  98          *    - maxJobs  : maximum number of jobs to run
  99          *    - maxTime  : maximum time in seconds before stopping
 100          *    - throttle : whether to respect job backoff configuration
 101          * @return array Summary response that can easily be JSON serialized
 102          */
 103         public function run( array $options ) {
 104                 global $wgJobClasses, $wgTrxProfilerLimits;
 105
 106                 $response = [ 'jobs' => [], 'reached' => 'none-ready' ];
 107
 108                 $type = isset( $options['type'] ) ? $options['type'] : false;
 109                 $maxJobs = isset( $options['maxJobs'] ) ? $options['maxJobs'] : false;
 110                 $maxTime = isset( $options['maxTime'] ) ? $options['maxTime'] : false;
 111                 $noThrottle = isset( $options['throttle'] ) && !$options['throttle'];
 112
 113                 // Bail if job type is invalid
 114                 if ( $type !== false && !isset( $wgJobClasses[$type] ) ) {
 115                         $response['reached'] = 'none-possible';
 116                         return $response;
 117                 }
 118                 // Bail out if DB is in read-only mode
 119                 if ( wfReadOnly() ) {
 120                         $response['reached'] = 'read-only';
 121                         return $response;
 122                 }
 123
 124                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 125                 // Bail out if there is too much DB lag.
 126                 // This check should not block as we want to try other wiki queues.
 127                 list( , $maxLag ) = $lbFactory->getMainLB( wfWikiID() )->getMaxLag();
 128                 if ( $maxLag >= self::MAX_ALLOWED_LAG ) {
 129                         $response['reached'] = 'replica-lag-limit';
 130                         return $response;
 131                 }
 132
 133                 // Flush any pending DB writes for sanity
 134                 $lbFactory->commitAll( __METHOD__ );
 135
 136                 // Catch huge single updates that lead to replica DB lag
 137                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
 138                 $trxProfiler->setLogger( LoggerFactory::getInstance( 'DBPerformance' ) );
 139                 $trxProfiler->setExpectations( $wgTrxProfilerLimits['JobRunner'], __METHOD__ );
 140
 141                 // Some jobs types should not run until a certain timestamp
 142                 $backoffs = []; // map of (type => UNIX expiry)
 143                 $backoffDeltas = []; // map of (type => seconds)
 144                 $wait = 'wait'; // block to read backoffs the first time
 145
 146                 $group = JobQueueGroup::singleton();
 147                 $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
 148                 $jobsPopped = 0;
 149                 $timeMsTotal = 0;
 150                 $startTime = microtime( true ); // time since jobs started running
 151                 $lastCheckTime = 1; // timestamp of last replica DB check
 152                 do {
 153                         // Sync the persistent backoffs with concurrent runners
 154                         $backoffs = $this->syncBackoffDeltas( $backoffs, $backoffDeltas, $wait );
 155                         $blacklist = $noThrottle ? [] : array_keys( $backoffs );
 156                         $wait = 'nowait'; // less important now
 157
 158                         if ( $type === false ) {
 159                                 $job = $group->pop(
 160                                         JobQueueGroup::TYPE_DEFAULT,
 161                                         JobQueueGroup::USE_CACHE,
 162                                         $blacklist
 163                                 );
 164                         } elseif ( in_array( $type, $blacklist ) ) {
 165                                 $job = false; // requested queue in backoff state
 166                         } else {
 167                                 $job = $group->pop( $type ); // job from a single queue
 168                         }
 169                         $lbFactory->commitMasterChanges( __METHOD__ ); // flush any JobQueueDB writes
 170
 171                         if ( $job ) { // found a job
 172                                 ++$jobsPopped;
 173                                 $popTime = time();
 174                                 $jType = $job->getType();
 175
 176                                 WebRequest::overrideRequestId( $job->getRequestId() );
 177
 178                                 // Back off of certain jobs for a while (for throttling and for errors)
 179                                 $ttw = $this->getBackoffTimeToWait( $job );
 180                                 if ( $ttw > 0 ) {
 181                                         // Always add the delta for other runners in case the time running the
 182                                         // job negated the backoff for each individually but not collectively.
 183                                         $backoffDeltas[$jType] = isset( $backoffDeltas[$jType] )
 184                                                 ? $backoffDeltas[$jType] + $ttw
 185                                                 : $ttw;
 186                                         $backoffs = $this->syncBackoffDeltas( $backoffs, $backoffDeltas, $wait );
 187                                 }
 188
 189                                 $info = $this->executeJob( $job, $lbFactory, $stats, $popTime );
 190                                 if ( $info['status'] !== false || !$job->allowRetries() ) {
 191                                         $group->ack( $job ); // succeeded or job cannot be retried
 192                                         $lbFactory->commitMasterChanges( __METHOD__ ); // flush any JobQueueDB writes
 193                                 }
 194
 195                                 // Back off of certain jobs for a while (for throttling and for errors)
 196                                 if ( $info['status'] === false && mt_rand( 0, 49 ) == 0 ) {
 197                                         $ttw = max( $ttw, $this->getErrorBackoffTTL( $info['error'] ) );
 198                                         $backoffDeltas[$jType] = isset( $backoffDeltas[$jType] )
 199                                                 ? $backoffDeltas[$jType] + $ttw
 200                                                 : $ttw;
 201                                 }
 202
 203                                 $response['jobs'][] = [
 204                                         'type'   => $jType,
 205                                         'status' => ( $info['status'] === false ) ? 'failed' : 'ok',
 206                                         'error'  => $info['error'],
 207                                         'time'   => $info['timeMs']
 208                                 ];
 209                                 $timeMsTotal += $info['timeMs'];
 210
 211                                 // Break out if we hit the job count or wall time limits...
 212                                 if ( $maxJobs && $jobsPopped >= $maxJobs ) {
 213                                         $response['reached'] = 'job-limit';
 214                                         break;
 215                                 } elseif ( $maxTime && ( microtime( true ) - $startTime ) > $maxTime ) {
 216                                         $response['reached'] = 'time-limit';
 217                                         break;
 218                                 }
 219
 220                                 // Don't let any of the main DB replica DBs get backed up.
 221                                 // This only waits for so long before exiting and letting
 222                                 // other wikis in the farm (on different masters) get a chance.
 223                                 $timePassed = microtime( true ) - $lastCheckTime;
 224                                 if ( $timePassed >= self::LAG_CHECK_PERIOD || $timePassed < 0 ) {
 225                                         try {
 226                                                 $lbFactory->waitForReplication( [
 227                                                         'ifWritesSince' => $lastCheckTime,
 228                                                         'timeout' => self::MAX_ALLOWED_LAG
 229                                                 ] );
 230                                         } catch ( DBReplicationWaitError $e ) {
 231                                                 $response['reached'] = 'replica-lag-limit';
 232                                                 break;
 233                                         }
 234                                         $lastCheckTime = microtime( true );
 235                                 }
 236                                 // Don't let any queue replica DBs/backups fall behind
 237                                 if ( $jobsPopped > 0 && ( $jobsPopped % 100 ) == 0 ) {
 238                                         $group->waitForBackups();
 239                                 }
 240
 241                                 // Bail if near-OOM instead of in a job
 242                                 if ( !$this->checkMemoryOK() ) {
 243                                         $response['reached'] = 'memory-limit';
 244                                         break;
 245                                 }
 246                         }
 247                 } while ( $job ); // stop when there are no jobs
 248
 249                 // Sync the persistent backoffs for the next runJobs.php pass
 250                 if ( $backoffDeltas ) {
 251                         $this->syncBackoffDeltas( $backoffs, $backoffDeltas, 'wait' );
 252                 }
 253
 254                 $response['backoffs'] = $backoffs;
 255                 $response['elapsed'] = $timeMsTotal;
 256
 257                 return $response;
 258         }
 259
 260         /**
 261          * @param string $error
 262          * @return int TTL in seconds
 263          */
 264         private function getErrorBackoffTTL( $error ) {
 265                 return strpos( $error, 'DBReadOnlyError' ) !== false
 266                         ? self::READONLY_BACKOFF_TTL
 267                         : self::ERROR_BACKOFF_TTL;
 268         }
 269
 270         /**
 271          * @param Job $job
 272          * @param LBFactory $lbFactory
 273          * @param StatsdDataFactory $stats
 274          * @param float $popTime
 275          * @return array Map of status/error/timeMs
 276          */
 277         private function executeJob( Job $job, LBFactory $lbFactory, $stats, $popTime ) {
 278                 $jType = $job->getType();
 279                 $msg = $job->toString() . " STARTING";
 280                 $this->logger->debug( $msg );
 281                 $this->debugCallback( $msg );
 282
 283                 // Run the job...
 284                 $rssStart = $this->getMaxRssKb();
 285                 $jobStartTime = microtime( true );
 286                 try {
 287                         $fnameTrxOwner = get_class( $job ) . '::run'; // give run() outer scope
 288                         $lbFactory->beginMasterChanges( $fnameTrxOwner );
 289                         $status = $job->run();
 290                         $error = $job->getLastError();
 291                         $this->commitMasterChanges( $lbFactory, $job, $fnameTrxOwner );
 292                         // Run any deferred update tasks; doUpdates() manages transactions itself
 293                         DeferredUpdates::doUpdates();
 294                 } catch ( Exception $e ) {
 295                         MWExceptionHandler::rollbackMasterChangesAndLog( $e );
 296                         $status = false;
 297                         $error = get_class( $e ) . ': ' . $e->getMessage();
 298                 }
 299                 // Always attempt to call teardown() even if Job throws exception.
 300                 try {
 301                         $job->teardown( $status );
 302                 } catch ( Exception $e ) {
 303                         MWExceptionHandler::logException( $e );
 304                 }
 305
 306                 // Commit all outstanding connections that are in a transaction
 307                 // to get a fresh repeatable read snapshot on every connection.
 308                 // Note that jobs are still responsible for handling replica DB lag.
 309                 $lbFactory->flushReplicaSnapshots( __METHOD__ );
 310                 // Clear out title cache data from prior snapshots
 311                 MediaWikiServices::getInstance()->getLinkCache()->clear();
 312                 $timeMs = intval( ( microtime( true ) - $jobStartTime ) * 1000 );
 313                 $rssEnd = $this->getMaxRssKb();
 314
 315                 // Record how long jobs wait before getting popped
 316                 $readyTs = $job->getReadyTimestamp();
 317                 if ( $readyTs ) {
 318                         $pickupDelay = max( 0, $popTime - $readyTs );
 319                         $stats->timing( 'jobqueue.pickup_delay.all', 1000 * $pickupDelay );
 320                         $stats->timing( "jobqueue.pickup_delay.$jType", 1000 * $pickupDelay );
 321                 }
 322                 // Record root job age for jobs being run
 323                 $rootTimestamp = $job->getRootJobParams()['rootJobTimestamp'];
 324                 if ( $rootTimestamp ) {
 325                         $age = max( 0, $popTime - wfTimestamp( TS_UNIX, $rootTimestamp ) );
 326                         $stats->timing( "jobqueue.pickup_root_age.$jType", 1000 * $age );
 327                 }
 328                 // Track the execution time for jobs
 329                 $stats->timing( "jobqueue.run.$jType", $timeMs );
 330                 // Track RSS increases for jobs (in case of memory leaks)
 331                 if ( $rssStart && $rssEnd ) {
 332                         $stats->updateCount( "jobqueue.rss_delta.$jType", $rssEnd - $rssStart );
 333                 }
 334
 335                 if ( $status === false ) {
 336                         $msg = $job->toString() . " t=$timeMs error={$error}";
 337                         $this->logger->error( $msg );
 338                         $this->debugCallback( $msg );
 339                 } else {
 340                         $msg = $job->toString() . " t=$timeMs good";
 341                         $this->logger->info( $msg );
 342                         $this->debugCallback( $msg );
 343                 }
 344
 345                 return [ 'status' => $status, 'error' => $error, 'timeMs' => $timeMs ];
 346         }
 347
 348         /**
 349          * @return int|null Max memory RSS in kilobytes
 350          */
 351         private function getMaxRssKb() {
 352                 $info = wfGetRusage() ?: [];
 353                 // see https://linux.die.net/man/2/getrusage
 354                 return isset( $info['ru_maxrss'] ) ? (int)$info['ru_maxrss'] : null;
 355         }
 356
 357         /**
 358          * @param Job $job
 359          * @return int Seconds for this runner to avoid doing more jobs of this type
 360          * @see $wgJobBackoffThrottling
 361          */
 362         private function getBackoffTimeToWait( Job $job ) {
 363                 global $wgJobBackoffThrottling;
 364
 365                 if ( !isset( $wgJobBackoffThrottling[$job->getType()] ) ||
 366                         $job instanceof DuplicateJob // no work was done
 367                 ) {
 368                         return 0; // not throttled
 369                 }
 370
 371                 $itemsPerSecond = $wgJobBackoffThrottling[$job->getType()];
 372                 if ( $itemsPerSecond <= 0 ) {
 373                         return 0; // not throttled
 374                 }
 375
 376                 $seconds = 0;
 377                 if ( $job->workItemCount() > 0 ) {
 378                         $exactSeconds = $job->workItemCount() / $itemsPerSecond;
 379                         // use randomized rounding
 380                         $seconds = floor( $exactSeconds );
 381                         $remainder = $exactSeconds - $seconds;
 382                         $seconds += ( mt_rand() / mt_getrandmax() < $remainder ) ? 1 : 0;
 383                 }
 384
 385                 return (int)$seconds;
 386         }
 387
 388         /**
 389          * Get the previous backoff expiries from persistent storage
 390          * On I/O or lock acquisition failure this returns the original $backoffs.
 391          *
 392          * @param array $backoffs Map of (job type => UNIX timestamp)
 393          * @param string $mode Lock wait mode - "wait" or "nowait"
 394          * @return array Map of (job type => backoff expiry timestamp)
 395          */
 396         private function loadBackoffs( array $backoffs, $mode = 'wait' ) {
 397                 $file = wfTempDir() . '/mw-runJobs-backoffs.json';
 398                 if ( is_file( $file ) ) {
 399                         $noblock = ( $mode === 'nowait' ) ? LOCK_NB : 0;
 400                         $handle = fopen( $file, 'rb' );
 401                         if ( !flock( $handle, LOCK_SH | $noblock ) ) {
 402                                 fclose( $handle );
 403                                 return $backoffs; // don't wait on lock
 404                         }
 405                         $content = stream_get_contents( $handle );
 406                         flock( $handle, LOCK_UN );
 407                         fclose( $handle );
 408                         $ctime = microtime( true );
 409                         $cBackoffs = json_decode( $content, true ) ?: [];
 410                         foreach ( $cBackoffs as $type => $timestamp ) {
 411                                 if ( $timestamp < $ctime ) {
 412                                         unset( $cBackoffs[$type] );
 413                                 }
 414                         }
 415                 } else {
 416                         $cBackoffs = [];
 417                 }
 418
 419                 return $cBackoffs;
 420         }
 421
 422         /**
 423          * Merge the current backoff expiries from persistent storage
 424          *
 425          * The $deltas map is set to an empty array on success.
 426          * On I/O or lock acquisition failure this returns the original $backoffs.
 427          *
 428          * @param array $backoffs Map of (job type => UNIX timestamp)
 429          * @param array $deltas Map of (job type => seconds)
 430          * @param string $mode Lock wait mode - "wait" or "nowait"
 431          * @return array The new backoffs account for $backoffs and the latest file data
 432          */
 433         private function syncBackoffDeltas( array $backoffs, array &$deltas, $mode = 'wait' ) {
 434                 if ( !$deltas ) {
 435                         return $this->loadBackoffs( $backoffs, $mode );
 436                 }
 437
 438                 $noblock = ( $mode === 'nowait' ) ? LOCK_NB : 0;
 439                 $file = wfTempDir() . '/mw-runJobs-backoffs.json';
 440                 $handle = fopen( $file, 'wb+' );
 441                 if ( !flock( $handle, LOCK_EX | $noblock ) ) {
 442                         fclose( $handle );
 443                         return $backoffs; // don't wait on lock
 444                 }
 445                 $ctime = microtime( true );
 446                 $content = stream_get_contents( $handle );
 447                 $cBackoffs = json_decode( $content, true ) ?: [];
 448                 foreach ( $deltas as $type => $seconds ) {
 449                         $cBackoffs[$type] = isset( $cBackoffs[$type] ) && $cBackoffs[$type] >= $ctime
 450                                 ? $cBackoffs[$type] + $seconds
 451                                 : $ctime + $seconds;
 452                 }
 453                 foreach ( $cBackoffs as $type => $timestamp ) {
 454                         if ( $timestamp < $ctime ) {
 455                                 unset( $cBackoffs[$type] );
 456                         }
 457                 }
 458                 ftruncate( $handle, 0 );
 459                 fwrite( $handle, json_encode( $cBackoffs ) );
 460                 flock( $handle, LOCK_UN );
 461                 fclose( $handle );
 462
 463                 $deltas = [];
 464
 465                 return $cBackoffs;
 466         }
 467
 468         /**
 469          * Make sure that this script is not too close to the memory usage limit.
 470          * It is better to die in between jobs than OOM right in the middle of one.
 471          * @return bool
 472          */
 473         private function checkMemoryOK() {
 474                 static $maxBytes = null;
 475                 if ( $maxBytes === null ) {
 476                         $m = [];
 477                         if ( preg_match( '!^(\d+)(k|m|g|)$!i', ini_get( 'memory_limit' ), $m ) ) {
 478                                 list( , $num, $unit ) = $m;
 479                                 $conv = [ 'g' => 1073741824, 'm' => 1048576, 'k' => 1024, '' => 1 ];
 480                                 $maxBytes = $num * $conv[strtolower( $unit )];
 481                         } else {
 482                                 $maxBytes = 0;
 483                         }
 484                 }
 485                 $usedBytes = memory_get_usage();
 486                 if ( $maxBytes && $usedBytes >= 0.95 * $maxBytes ) {
 487                         $msg = "Detected excessive memory usage ($usedBytes/$maxBytes).";
 488                         $this->debugCallback( $msg );
 489                         $this->logger->error( $msg );
 490
 491                         return false;
 492                 }
 493
 494                 return true;
 495         }
 496
 497         /**
 498          * Log the job message
 499          * @param string $msg The message to log
 500          */
 501         private function debugCallback( $msg ) {
 502                 if ( $this->debug ) {
 503                         call_user_func_array( $this->debug, [ wfTimestamp( TS_DB ) . " $msg\n" ] );
 504                 }
 505         }
 506
 507         /**
 508          * Issue a commit on all masters who are currently in a transaction and have
 509          * made changes to the database. It also supports sometimes waiting for the
 510          * local wiki's replica DBs to catch up. See the documentation for
 511          * $wgJobSerialCommitThreshold for more.
 512          *
 513          * @param LBFactory $lbFactory
 514          * @param Job $job
 515          * @param string $fnameTrxOwner
 516          * @throws DBError
 517          */
 518         private function commitMasterChanges( LBFactory $lbFactory, Job $job, $fnameTrxOwner ) {
 519                 global $wgJobSerialCommitThreshold;
 520
 521                 $time = false;
 522                 $lb = $lbFactory->getMainLB( wfWikiID() );
 523                 if ( $wgJobSerialCommitThreshold !== false && $lb->getServerCount() > 1 ) {
 524                         // Generally, there is one master connection to the local DB
 525                         $dbwSerial = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
 526                         // We need natively blocking fast locks
 527                         if ( $dbwSerial && $dbwSerial->namedLocksEnqueue() ) {
 528                                 $time = $dbwSerial->pendingWriteQueryDuration( $dbwSerial::ESTIMATE_DB_APPLY );
 529                                 if ( $time < $wgJobSerialCommitThreshold ) {
 530                                         $dbwSerial = false;
 531                                 }
 532                         } else {
 533                                 $dbwSerial = false;
 534                         }
 535                 } else {
 536                         // There are no replica DBs or writes are all to foreign DB (we don't handle that)
 537                         $dbwSerial = false;
 538                 }
 539
 540                 if ( !$dbwSerial ) {
 541                         $lbFactory->commitMasterChanges( $fnameTrxOwner );
 542                         return;
 543                 }
 544
 545                 $ms = intval( 1000 * $time );
 546                 $msg = $job->toString() . " COMMIT ENQUEUED [{$ms}ms of writes]";
 547                 $this->logger->info( $msg );
 548                 $this->debugCallback( $msg );
 549
 550                 // Wait for an exclusive lock to commit
 551                 if ( !$dbwSerial->lock( 'jobrunner-serial-commit', __METHOD__, 30 ) ) {
 552                         // This will trigger a rollback in the main loop
 553                         throw new DBError( $dbwSerial, "Timed out waiting on commit queue." );
 554                 }
 555                 $unlocker = new ScopedCallback( function () use ( $dbwSerial ) {
 556                         $dbwSerial->unlock( 'jobrunner-serial-commit', __METHOD__ );
 557                 } );
 558
 559                 // Wait for the replica DBs to catch up
 560                 $pos = $lb->getMasterPos();
 561                 if ( $pos ) {
 562                         $lb->waitForAll( $pos );
 563                 }
 564
 565                 // Actually commit the DB master changes
 566                 $lbFactory->commitMasterChanges( $fnameTrxOwner );
 567                 ScopedCallback::consume( $unlocker );
 568         }
 569 }