includes/jobqueue/JobQueueDB.php

   1 <?php
   2 /**
   3  * Database-backed job queue code.
   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  * @author Aaron Schulz
  22  */
  23 use MediaWiki\MediaWikiServices;
  24 use Wikimedia\ScopedCallback;
  25
  26 /**
  27  * Class to handle job queues stored in the DB
  28  *
  29  * @ingroup JobQueue
  30  * @since 1.21
  31  */
  32 class JobQueueDB extends JobQueue {
  33         const CACHE_TTL_SHORT = 30; // integer; seconds to cache info without re-validating
  34         const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed
  35         const MAX_JOB_RANDOM = 2147483647; // integer; 2^31 - 1, used for job_random
  36         const MAX_OFFSET = 255; // integer; maximum number of rows to skip
  37
  38         /** @var WANObjectCache */
  39         protected $cache;
  40
  41         /** @var bool|string Name of an external DB cluster. False if not set */
  42         protected $cluster = false;
  43
  44         /**
  45          * Additional parameters include:
  46          *   - cluster : The name of an external cluster registered via LBFactory.
  47          *               If not specified, the primary DB cluster for the wiki will be used.
  48          *               This can be overridden with a custom cluster so that DB handles will
  49          *               be retrieved via LBFactory::getExternalLB() and getConnection().
  50          * @param array $params
  51          */
  52         protected function __construct( array $params ) {
  53                 parent::__construct( $params );
  54
  55                 $this->cluster = isset( $params['cluster'] ) ? $params['cluster'] : false;
  56                 $this->cache = ObjectCache::getMainWANInstance();
  57         }
  58
  59         protected function supportedOrders() {
  60                 return [ 'random', 'timestamp', 'fifo' ];
  61         }
  62
  63         protected function optimalOrder() {
  64                 return 'random';
  65         }
  66
  67         /**
  68          * @see JobQueue::doIsEmpty()
  69          * @return bool
  70          */
  71         protected function doIsEmpty() {
  72                 $dbr = $this->getReplicaDB();
  73                 try {
  74                         $found = $dbr->selectField( // unclaimed job
  75                                 'job', '1', [ 'job_cmd' => $this->type, 'job_token' => '' ], __METHOD__
  76                         );
  77                 } catch ( DBError $e ) {
  78                         $this->throwDBException( $e );
  79                 }
  80
  81                 return !$found;
  82         }
  83
  84         /**
  85          * @see JobQueue::doGetSize()
  86          * @return int
  87          */
  88         protected function doGetSize() {
  89                 $key = $this->getCacheKey( 'size' );
  90
  91                 $size = $this->cache->get( $key );
  92                 if ( is_int( $size ) ) {
  93                         return $size;
  94                 }
  95
  96                 try {
  97                         $dbr = $this->getReplicaDB();
  98                         $size = (int)$dbr->selectField( 'job', 'COUNT(*)',
  99                                 [ 'job_cmd' => $this->type, 'job_token' => '' ],
 100                                 __METHOD__
 101                         );
 102                 } catch ( DBError $e ) {
 103                         $this->throwDBException( $e );
 104                 }
 105                 $this->cache->set( $key, $size, self::CACHE_TTL_SHORT );
 106
 107                 return $size;
 108         }
 109
 110         /**
 111          * @see JobQueue::doGetAcquiredCount()
 112          * @return int
 113          */
 114         protected function doGetAcquiredCount() {
 115                 if ( $this->claimTTL <= 0 ) {
 116                         return 0; // no acknowledgements
 117                 }
 118
 119                 $key = $this->getCacheKey( 'acquiredcount' );
 120
 121                 $count = $this->cache->get( $key );
 122                 if ( is_int( $count ) ) {
 123                         return $count;
 124                 }
 125
 126                 $dbr = $this->getReplicaDB();
 127                 try {
 128                         $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
 129                                 [ 'job_cmd' => $this->type, "job_token != {$dbr->addQuotes( '' )}" ],
 130                                 __METHOD__
 131                         );
 132                 } catch ( DBError $e ) {
 133                         $this->throwDBException( $e );
 134                 }
 135                 $this->cache->set( $key, $count, self::CACHE_TTL_SHORT );
 136
 137                 return $count;
 138         }
 139
 140         /**
 141          * @see JobQueue::doGetAbandonedCount()
 142          * @return int
 143          * @throws MWException
 144          */
 145         protected function doGetAbandonedCount() {
 146                 if ( $this->claimTTL <= 0 ) {
 147                         return 0; // no acknowledgements
 148                 }
 149
 150                 $key = $this->getCacheKey( 'abandonedcount' );
 151
 152                 $count = $this->cache->get( $key );
 153                 if ( is_int( $count ) ) {
 154                         return $count;
 155                 }
 156
 157                 $dbr = $this->getReplicaDB();
 158                 try {
 159                         $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
 160                                 [
 161                                         'job_cmd' => $this->type,
 162                                         "job_token != {$dbr->addQuotes( '' )}",
 163                                         "job_attempts >= " . $dbr->addQuotes( $this->maxTries )
 164                                 ],
 165                                 __METHOD__
 166                         );
 167                 } catch ( DBError $e ) {
 168                         $this->throwDBException( $e );
 169                 }
 170
 171                 $this->cache->set( $key, $count, self::CACHE_TTL_SHORT );
 172
 173                 return $count;
 174         }
 175
 176         /**
 177          * @see JobQueue::doBatchPush()
 178          * @param IJobSpecification[] $jobs
 179          * @param int $flags
 180          * @throws DBError|Exception
 181          * @return void
 182          */
 183         protected function doBatchPush( array $jobs, $flags ) {
 184                 $dbw = $this->getMasterDB();
 185
 186                 $method = __METHOD__;
 187                 $dbw->onTransactionIdle(
 188                         function () use ( $dbw, $jobs, $flags, $method ) {
 189                                 $this->doBatchPushInternal( $dbw, $jobs, $flags, $method );
 190                         },
 191                         __METHOD__
 192                 );
 193         }
 194
 195         /**
 196          * This function should *not* be called outside of JobQueueDB
 197          *
 198          * @param IDatabase $dbw
 199          * @param IJobSpecification[] $jobs
 200          * @param int $flags
 201          * @param string $method
 202          * @throws DBError
 203          * @return void
 204          */
 205         public function doBatchPushInternal( IDatabase $dbw, array $jobs, $flags, $method ) {
 206                 if ( !count( $jobs ) ) {
 207                         return;
 208                 }
 209
 210                 $rowSet = []; // (sha1 => job) map for jobs that are de-duplicated
 211                 $rowList = []; // list of jobs for jobs that are not de-duplicated
 212                 foreach ( $jobs as $job ) {
 213                         $row = $this->insertFields( $job );
 214                         if ( $job->ignoreDuplicates() ) {
 215                                 $rowSet[$row['job_sha1']] = $row;
 216                         } else {
 217                                 $rowList[] = $row;
 218                         }
 219                 }
 220
 221                 if ( $flags & self::QOS_ATOMIC ) {
 222                         $dbw->startAtomic( $method ); // wrap all the job additions in one transaction
 223                 }
 224                 try {
 225                         // Strip out any duplicate jobs that are already in the queue...
 226                         if ( count( $rowSet ) ) {
 227                                 $res = $dbw->select( 'job', 'job_sha1',
 228                                         [
 229                                                 // No job_type condition since it's part of the job_sha1 hash
 230                                                 'job_sha1' => array_keys( $rowSet ),
 231                                                 'job_token' => '' // unclaimed
 232                                         ],
 233                                         $method
 234                                 );
 235                                 foreach ( $res as $row ) {
 236                                         wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate.\n" );
 237                                         unset( $rowSet[$row->job_sha1] ); // already enqueued
 238                                 }
 239                         }
 240                         // Build the full list of job rows to insert
 241                         $rows = array_merge( $rowList, array_values( $rowSet ) );
 242                         // Insert the job rows in chunks to avoid replica DB lag...
 243                         foreach ( array_chunk( $rows, 50 ) as $rowBatch ) {
 244                                 $dbw->insert( 'job', $rowBatch, $method );
 245                         }
 246                         JobQueue::incrStats( 'inserts', $this->type, count( $rows ) );
 247                         JobQueue::incrStats( 'dupe_inserts', $this->type,
 248                                 count( $rowSet ) + count( $rowList ) - count( $rows )
 249                         );
 250                 } catch ( DBError $e ) {
 251                         $this->throwDBException( $e );
 252                 }
 253                 if ( $flags & self::QOS_ATOMIC ) {
 254                         $dbw->endAtomic( $method );
 255                 }
 256
 257                 return;
 258         }
 259
 260         /**
 261          * @see JobQueue::doPop()
 262          * @return Job|bool
 263          */
 264         protected function doPop() {
 265                 $dbw = $this->getMasterDB();
 266                 try {
 267                         $autoTrx = $dbw->getFlag( DBO_TRX ); // get current setting
 268                         $dbw->clearFlag( DBO_TRX ); // make each query its own transaction
 269                         $scopedReset = new ScopedCallback( function () use ( $dbw, $autoTrx ) {
 270                                 $dbw->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore old setting
 271                         } );
 272
 273                         $uuid = wfRandomString( 32 ); // pop attempt
 274                         $job = false; // job popped off
 275                         do { // retry when our row is invalid or deleted as a duplicate
 276                                 // Try to reserve a row in the DB...
 277                                 if ( in_array( $this->order, [ 'fifo', 'timestamp' ] ) ) {
 278                                         $row = $this->claimOldest( $uuid );
 279                                 } else { // random first
 280                                         $rand = mt_rand( 0, self::MAX_JOB_RANDOM ); // encourage concurrent UPDATEs
 281                                         $gte = (bool)mt_rand( 0, 1 ); // find rows with rand before/after $rand
 282                                         $row = $this->claimRandom( $uuid, $rand, $gte );
 283                                 }
 284                                 // Check if we found a row to reserve...
 285                                 if ( !$row ) {
 286                                         break; // nothing to do
 287                                 }
 288                                 JobQueue::incrStats( 'pops', $this->type );
 289                                 // Get the job object from the row...
 290                                 $title = Title::makeTitle( $row->job_namespace, $row->job_title );
 291                                 $job = Job::factory( $row->job_cmd, $title,
 292                                         self::extractBlob( $row->job_params ), $row->job_id );
 293                                 $job->metadata['id'] = $row->job_id;
 294                                 $job->metadata['timestamp'] = $row->job_timestamp;
 295                                 break; // done
 296                         } while ( true );
 297
 298                         if ( !$job || mt_rand( 0, 9 ) == 0 ) {
 299                                 // Handled jobs that need to be recycled/deleted;
 300                                 // any recycled jobs will be picked up next attempt
 301                                 $this->recycleAndDeleteStaleJobs();
 302                         }
 303                 } catch ( DBError $e ) {
 304                         $this->throwDBException( $e );
 305                 }
 306
 307                 return $job;
 308         }
 309
 310         /**
 311          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 312          *
 313          * @param string $uuid 32 char hex string
 314          * @param int $rand Random unsigned integer (31 bits)
 315          * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
 316          * @return stdClass|bool Row|false
 317          */
 318         protected function claimRandom( $uuid, $rand, $gte ) {
 319                 $dbw = $this->getMasterDB();
 320                 // Check cache to see if the queue has <= OFFSET items
 321                 $tinyQueue = $this->cache->get( $this->getCacheKey( 'small' ) );
 322
 323                 $row = false; // the row acquired
 324                 $invertedDirection = false; // whether one job_random direction was already scanned
 325                 // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
 326                 // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
 327                 // not replication safe. Due to https://bugs.mysql.com/bug.php?id=6980, subqueries cannot
 328                 // be used here with MySQL.
 329                 do {
 330                         if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
 331                                 // For small queues, using OFFSET will overshoot and return no rows more often.
 332                                 // Instead, this uses job_random to pick a row (possibly checking both directions).
 333                                 $ineq = $gte ? '>=' : '<=';
 334                                 $dir = $gte ? 'ASC' : 'DESC';
 335                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 336                                         [
 337                                                 'job_cmd' => $this->type,
 338                                                 'job_token' => '', // unclaimed
 339                                                 "job_random {$ineq} {$dbw->addQuotes( $rand )}" ],
 340                                         __METHOD__,
 341                                         [ 'ORDER BY' => "job_random {$dir}" ]
 342                                 );
 343                                 if ( !$row && !$invertedDirection ) {
 344                                         $gte = !$gte;
 345                                         $invertedDirection = true;
 346                                         continue; // try the other direction
 347                                 }
 348                         } else { // table *may* have >= MAX_OFFSET rows
 349                                 // T44614: "ORDER BY job_random" with a job_random inequality causes high CPU
 350                                 // in MySQL if there are many rows for some reason. This uses a small OFFSET
 351                                 // instead of job_random for reducing excess claim retries.
 352                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 353                                         [
 354                                                 'job_cmd' => $this->type,
 355                                                 'job_token' => '', // unclaimed
 356                                         ],
 357                                         __METHOD__,
 358                                         [ 'OFFSET' => mt_rand( 0, self::MAX_OFFSET ) ]
 359                                 );
 360                                 if ( !$row ) {
 361                                         $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
 362                                         $this->cache->set( $this->getCacheKey( 'small' ), 1, 30 );
 363                                         continue; // use job_random
 364                                 }
 365                         }
 366
 367                         if ( $row ) { // claim the job
 368                                 $dbw->update( 'job', // update by PK
 369                                         [
 370                                                 'job_token' => $uuid,
 371                                                 'job_token_timestamp' => $dbw->timestamp(),
 372                                                 'job_attempts = job_attempts+1' ],
 373                                         [ 'job_cmd' => $this->type, 'job_id' => $row->job_id, 'job_token' => '' ],
 374                                         __METHOD__
 375                                 );
 376                                 // This might get raced out by another runner when claiming the previously
 377                                 // selected row. The use of job_random should minimize this problem, however.
 378                                 if ( !$dbw->affectedRows() ) {
 379                                         $row = false; // raced out
 380                                 }
 381                         } else {
 382                                 break; // nothing to do
 383                         }
 384                 } while ( !$row );
 385
 386                 return $row;
 387         }
 388
 389         /**
 390          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 391          *
 392          * @param string $uuid 32 char hex string
 393          * @return stdClass|bool Row|false
 394          */
 395         protected function claimOldest( $uuid ) {
 396                 $dbw = $this->getMasterDB();
 397
 398                 $row = false; // the row acquired
 399                 do {
 400                         if ( $dbw->getType() === 'mysql' ) {
 401                                 // Per https://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
 402                                 // same table being changed in an UPDATE query in MySQL (gives Error: 1093).
 403                                 // Oracle and Postgre have no such limitation. However, MySQL offers an
 404                                 // alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
 405                                 $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
 406                                         "SET " .
 407                                                 "job_token = {$dbw->addQuotes( $uuid ) }, " .
 408                                                 "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
 409                                                 "job_attempts = job_attempts+1 " .
 410                                         "WHERE ( " .
 411                                                 "job_cmd = {$dbw->addQuotes( $this->type )} " .
 412                                                 "AND job_token = {$dbw->addQuotes( '' )} " .
 413                                         ") ORDER BY job_id ASC LIMIT 1",
 414                                         __METHOD__
 415                                 );
 416                         } else {
 417                                 // Use a subquery to find the job, within an UPDATE to claim it.
 418                                 // This uses as much of the DB wrapper functions as possible.
 419                                 $dbw->update( 'job',
 420                                         [
 421                                                 'job_token' => $uuid,
 422                                                 'job_token_timestamp' => $dbw->timestamp(),
 423                                                 'job_attempts = job_attempts+1' ],
 424                                         [ 'job_id = (' .
 425                                                 $dbw->selectSQLText( 'job', 'job_id',
 426                                                         [ 'job_cmd' => $this->type, 'job_token' => '' ],
 427                                                         __METHOD__,
 428                                                         [ 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ] ) .
 429                                                 ')'
 430                                         ],
 431                                         __METHOD__
 432                                 );
 433                         }
 434                         // Fetch any row that we just reserved...
 435                         if ( $dbw->affectedRows() ) {
 436                                 $row = $dbw->selectRow( 'job', self::selectFields(),
 437                                         [ 'job_cmd' => $this->type, 'job_token' => $uuid ], __METHOD__
 438                                 );
 439                                 if ( !$row ) { // raced out by duplicate job removal
 440                                         wfDebug( "Row deleted as duplicate by another process.\n" );
 441                                 }
 442                         } else {
 443                                 break; // nothing to do
 444                         }
 445                 } while ( !$row );
 446
 447                 return $row;
 448         }
 449
 450         /**
 451          * @see JobQueue::doAck()
 452          * @param Job $job
 453          * @throws MWException
 454          */
 455         protected function doAck( Job $job ) {
 456                 if ( !isset( $job->metadata['id'] ) ) {
 457                         throw new MWException( "Job of type '{$job->getType()}' has no ID." );
 458                 }
 459
 460                 $dbw = $this->getMasterDB();
 461                 try {
 462                         $autoTrx = $dbw->getFlag( DBO_TRX ); // get current setting
 463                         $dbw->clearFlag( DBO_TRX ); // make each query its own transaction
 464                         $scopedReset = new ScopedCallback( function () use ( $dbw, $autoTrx ) {
 465                                 $dbw->setFlag( $autoTrx ? DBO_TRX : 0 ); // restore old setting
 466                         } );
 467
 468                         // Delete a row with a single DELETE without holding row locks over RTTs...
 469                         $dbw->delete( 'job',
 470                                 [ 'job_cmd' => $this->type, 'job_id' => $job->metadata['id'] ], __METHOD__ );
 471
 472                         JobQueue::incrStats( 'acks', $this->type );
 473                 } catch ( DBError $e ) {
 474                         $this->throwDBException( $e );
 475                 }
 476         }
 477
 478         /**
 479          * @see JobQueue::doDeduplicateRootJob()
 480          * @param IJobSpecification $job
 481          * @throws MWException
 482          * @return bool
 483          */
 484         protected function doDeduplicateRootJob( IJobSpecification $job ) {
 485                 $params = $job->getParams();
 486                 if ( !isset( $params['rootJobSignature'] ) ) {
 487                         throw new MWException( "Cannot register root job; missing 'rootJobSignature'." );
 488                 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
 489                         throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." );
 490                 }
 491                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 492                 // Callers should call batchInsert() and then this function so that if the insert
 493                 // fails, the de-duplication registration will be aborted. Since the insert is
 494                 // deferred till "transaction idle", do the same here, so that the ordering is
 495                 // maintained. Having only the de-duplication registration succeed would cause
 496                 // jobs to become no-ops without any actual jobs that made them redundant.
 497                 $dbw = $this->getMasterDB();
 498                 $cache = $this->dupCache;
 499                 $dbw->onTransactionIdle(
 500                         function () use ( $cache, $params, $key, $dbw ) {
 501                                 $timestamp = $cache->get( $key ); // current last timestamp of this job
 502                                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 503                                         return true; // a newer version of this root job was enqueued
 504                                 }
 505
 506                                 // Update the timestamp of the last root job started at the location...
 507                                 return $cache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 508                         },
 509                         __METHOD__
 510                 );
 511
 512                 return true;
 513         }
 514
 515         /**
 516          * @see JobQueue::doDelete()
 517          * @return bool
 518          */
 519         protected function doDelete() {
 520                 $dbw = $this->getMasterDB();
 521                 try {
 522                         $dbw->delete( 'job', [ 'job_cmd' => $this->type ] );
 523                 } catch ( DBError $e ) {
 524                         $this->throwDBException( $e );
 525                 }
 526
 527                 return true;
 528         }
 529
 530         /**
 531          * @see JobQueue::doWaitForBackups()
 532          * @return void
 533          */
 534         protected function doWaitForBackups() {
 535                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 536                 $lbFactory->waitForReplication( [ 'wiki' => $this->wiki, 'cluster' => $this->cluster ] );
 537         }
 538
 539         /**
 540          * @return void
 541          */
 542         protected function doFlushCaches() {
 543                 foreach ( [ 'size', 'acquiredcount' ] as $type ) {
 544                         $this->cache->delete( $this->getCacheKey( $type ) );
 545                 }
 546         }
 547
 548         /**
 549          * @see JobQueue::getAllQueuedJobs()
 550          * @return Iterator
 551          */
 552         public function getAllQueuedJobs() {
 553                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), 'job_token' => '' ] );
 554         }
 555
 556         /**
 557          * @see JobQueue::getAllAcquiredJobs()
 558          * @return Iterator
 559          */
 560         public function getAllAcquiredJobs() {
 561                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), "job_token > ''" ] );
 562         }
 563
 564         /**
 565          * @param array $conds Query conditions
 566          * @return Iterator
 567          */
 568         protected function getJobIterator( array $conds ) {
 569                 $dbr = $this->getReplicaDB();
 570                 try {
 571                         return new MappedIterator(
 572                                 $dbr->select( 'job', self::selectFields(), $conds ),
 573                                 function ( $row ) {
 574                                         $job = Job::factory(
 575                                                 $row->job_cmd,
 576                                                 Title::makeTitle( $row->job_namespace, $row->job_title ),
 577                                                 strlen( $row->job_params ) ? unserialize( $row->job_params ) : []
 578                                         );
 579                                         $job->metadata['id'] = $row->job_id;
 580                                         $job->metadata['timestamp'] = $row->job_timestamp;
 581
 582                                         return $job;
 583                                 }
 584                         );
 585                 } catch ( DBError $e ) {
 586                         $this->throwDBException( $e );
 587                 }
 588         }
 589
 590         public function getCoalesceLocationInternal() {
 591                 return $this->cluster
 592                         ? "DBCluster:{$this->cluster}:{$this->wiki}"
 593                         : "LBFactory:{$this->wiki}";
 594         }
 595
 596         protected function doGetSiblingQueuesWithJobs( array $types ) {
 597                 $dbr = $this->getReplicaDB();
 598                 // @note: this does not check whether the jobs are claimed or not.
 599                 // This is useful so JobQueueGroup::pop() also sees queues that only
 600                 // have stale jobs. This lets recycleAndDeleteStaleJobs() re-enqueue
 601                 // failed jobs so that they can be popped again for that edge case.
 602                 $res = $dbr->select( 'job', 'DISTINCT job_cmd',
 603                         [ 'job_cmd' => $types ], __METHOD__ );
 604
 605                 $types = [];
 606                 foreach ( $res as $row ) {
 607                         $types[] = $row->job_cmd;
 608                 }
 609
 610                 return $types;
 611         }
 612
 613         protected function doGetSiblingQueueSizes( array $types ) {
 614                 $dbr = $this->getReplicaDB();
 615                 $res = $dbr->select( 'job', [ 'job_cmd', 'COUNT(*) AS count' ],
 616                         [ 'job_cmd' => $types ], __METHOD__, [ 'GROUP BY' => 'job_cmd' ] );
 617
 618                 $sizes = [];
 619                 foreach ( $res as $row ) {
 620                         $sizes[$row->job_cmd] = (int)$row->count;
 621                 }
 622
 623                 return $sizes;
 624         }
 625
 626         /**
 627          * Recycle or destroy any jobs that have been claimed for too long
 628          *
 629          * @return int Number of jobs recycled/deleted
 630          */
 631         public function recycleAndDeleteStaleJobs() {
 632                 $now = time();
 633                 $count = 0; // affected rows
 634                 $dbw = $this->getMasterDB();
 635
 636                 try {
 637                         if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__, 1 ) ) {
 638                                 return $count; // already in progress
 639                         }
 640
 641                         // Remove claims on jobs acquired for too long if enabled...
 642                         if ( $this->claimTTL > 0 ) {
 643                                 $claimCutoff = $dbw->timestamp( $now - $this->claimTTL );
 644                                 // Get the IDs of jobs that have be claimed but not finished after too long.
 645                                 // These jobs can be recycled into the queue by expiring the claim. Selecting
 646                                 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 647                                 $res = $dbw->select( 'job', 'job_id',
 648                                         [
 649                                                 'job_cmd' => $this->type,
 650                                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 651                                                 "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
 652                                                 "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ], // retries left
 653                                         __METHOD__
 654                                 );
 655                                 $ids = array_map(
 656                                         function ( $o ) {
 657                                                 return $o->job_id;
 658                                         }, iterator_to_array( $res )
 659                                 );
 660                                 if ( count( $ids ) ) {
 661                                         // Reset job_token for these jobs so that other runners will pick them up.
 662                                         // Set the timestamp to the current time, as it is useful to now that the job
 663                                         // was already tried before (the timestamp becomes the "released" time).
 664                                         $dbw->update( 'job',
 665                                                 [
 666                                                         'job_token' => '',
 667                                                         'job_token_timestamp' => $dbw->timestamp( $now ) ], // time of release
 668                                                 [
 669                                                         'job_id' => $ids ],
 670                                                 __METHOD__
 671                                         );
 672                                         $affected = $dbw->affectedRows();
 673                                         $count += $affected;
 674                                         JobQueue::incrStats( 'recycles', $this->type, $affected );
 675                                         $this->aggr->notifyQueueNonEmpty( $this->wiki, $this->type );
 676                                 }
 677                         }
 678
 679                         // Just destroy any stale jobs...
 680                         $pruneCutoff = $dbw->timestamp( $now - self::MAX_AGE_PRUNE );
 681                         $conds = [
 682                                 'job_cmd' => $this->type,
 683                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 684                                 "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
 685                         ];
 686                         if ( $this->claimTTL > 0 ) { // only prune jobs attempted too many times...
 687                                 $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
 688                         }
 689                         // Get the IDs of jobs that are considered stale and should be removed. Selecting
 690                         // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 691                         $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__ );
 692                         $ids = array_map(
 693                                 function ( $o ) {
 694                                         return $o->job_id;
 695                                 }, iterator_to_array( $res )
 696                         );
 697                         if ( count( $ids ) ) {
 698                                 $dbw->delete( 'job', [ 'job_id' => $ids ], __METHOD__ );
 699                                 $affected = $dbw->affectedRows();
 700                                 $count += $affected;
 701                                 JobQueue::incrStats( 'abandons', $this->type, $affected );
 702                         }
 703
 704                         $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__ );
 705                 } catch ( DBError $e ) {
 706                         $this->throwDBException( $e );
 707                 }
 708
 709                 return $count;
 710         }
 711
 712         /**
 713          * @param IJobSpecification $job
 714          * @return array
 715          */
 716         protected function insertFields( IJobSpecification $job ) {
 717                 $dbw = $this->getMasterDB();
 718
 719                 return [
 720                         // Fields that describe the nature of the job
 721                         'job_cmd' => $job->getType(),
 722                         'job_namespace' => $job->getTitle()->getNamespace(),
 723                         'job_title' => $job->getTitle()->getDBkey(),
 724                         'job_params' => self::makeBlob( $job->getParams() ),
 725                         // Additional job metadata
 726                         'job_id' => $dbw->nextSequenceValue( 'job_job_id_seq' ),
 727                         'job_timestamp' => $dbw->timestamp(),
 728                         'job_sha1' => Wikimedia\base_convert(
 729                                 sha1( serialize( $job->getDeduplicationInfo() ) ),
 730                                 16, 36, 31
 731                         ),
 732                         'job_random' => mt_rand( 0, self::MAX_JOB_RANDOM )
 733                 ];
 734         }
 735
 736         /**
 737          * @throws JobQueueConnectionError
 738          * @return DBConnRef
 739          */
 740         protected function getReplicaDB() {
 741                 try {
 742                         return $this->getDB( DB_REPLICA );
 743                 } catch ( DBConnectionError $e ) {
 744                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 745                 }
 746         }
 747
 748         /**
 749          * @throws JobQueueConnectionError
 750          * @return DBConnRef
 751          */
 752         protected function getMasterDB() {
 753                 try {
 754                         return $this->getDB( DB_MASTER );
 755                 } catch ( DBConnectionError $e ) {
 756                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 757                 }
 758         }
 759
 760         /**
 761          * @param int $index (DB_REPLICA/DB_MASTER)
 762          * @return DBConnRef
 763          */
 764         protected function getDB( $index ) {
 765                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 766                 $lb = ( $this->cluster !== false )
 767                         ? $lbFactory->getExternalLB( $this->cluster, $this->wiki )
 768                         : $lbFactory->getMainLB( $this->wiki );
 769
 770                 return $lb->getConnectionRef( $index, [], $this->wiki );
 771         }
 772
 773         /**
 774          * @param string $property
 775          * @return string
 776          */
 777         private function getCacheKey( $property ) {
 778                 list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
 779                 $cluster = is_string( $this->cluster ) ? $this->cluster : 'main';
 780
 781                 return wfForeignMemcKey( $db, $prefix, 'jobqueue', $cluster, $this->type, $property );
 782         }
 783
 784         /**
 785          * @param array|bool $params
 786          * @return string
 787          */
 788         protected static function makeBlob( $params ) {
 789                 if ( $params !== false ) {
 790                         return serialize( $params );
 791                 } else {
 792                         return '';
 793                 }
 794         }
 795
 796         /**
 797          * @param string $blob
 798          * @return bool|mixed
 799          */
 800         protected static function extractBlob( $blob ) {
 801                 if ( (string)$blob !== '' ) {
 802                         return unserialize( $blob );
 803                 } else {
 804                         return false;
 805                 }
 806         }
 807
 808         /**
 809          * @param DBError $e
 810          * @throws JobQueueError
 811          */
 812         protected function throwDBException( DBError $e ) {
 813                 throw new JobQueueError( get_class( $e ) . ": " . $e->getMessage() );
 814         }
 815
 816         /**
 817          * Return the list of job fields that should be selected.
 818          * @since 1.23
 819          * @return array
 820          */
 821         public static function selectFields() {
 822                 return [
 823                         'job_id',
 824                         'job_cmd',
 825                         'job_namespace',
 826                         'job_title',
 827                         'job_timestamp',
 828                         'job_params',
 829                         'job_random',
 830                         'job_attempts',
 831                         'job_token',
 832                         'job_token_timestamp',
 833                         'job_sha1',
 834                 ];
 835         }
 836 }