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  */
  22 use Wikimedia\Rdbms\IDatabase;
  23 use Wikimedia\Rdbms\Database;
  24 use Wikimedia\Rdbms\DBConnectionError;
  25 use Wikimedia\Rdbms\DBError;
  26 use MediaWiki\MediaWikiServices;
  27 use Wikimedia\Rdbms\IMaintainableDatabase;
  28 use Wikimedia\ScopedCallback;
  29
  30 /**
  31  * Class to handle job queues stored in the DB
  32  *
  33  * @ingroup JobQueue
  34  * @since 1.21
  35  */
  36 class JobQueueDB extends JobQueue {
  37         const CACHE_TTL_SHORT = 30; // integer; seconds to cache info without re-validating
  38         const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed
  39         const MAX_JOB_RANDOM = 2147483647; // integer; 2^31 - 1, used for job_random
  40         const MAX_OFFSET = 255; // integer; maximum number of rows to skip
  41
  42         /** @var IMaintainableDatabase|DBError|null */
  43         protected $conn;
  44
  45         /** @var array|null Server configuration array */
  46         protected $server;
  47         /** @var string|null Name of an external DB cluster or null for the local DB cluster */
  48         protected $cluster;
  49
  50         /**
  51          * Additional parameters include:
  52          *   - server  : Server configuration array for Database::factory. Overrides "cluster".
  53          *   - cluster : The name of an external cluster registered via LBFactory.
  54          *               If not specified, the primary DB cluster for the wiki will be used.
  55          *               This can be overridden with a custom cluster so that DB handles will
  56          *               be retrieved via LBFactory::getExternalLB() and getConnection().
  57          * @param array $params
  58          */
  59         protected function __construct( array $params ) {
  60                 parent::__construct( $params );
  61
  62                 if ( isset( $params['server'] ) ) {
  63                         $this->server = $params['server'];
  64                 } elseif ( isset( $params['cluster'] ) && is_string( $params['cluster'] ) ) {
  65                         $this->cluster = $params['cluster'];
  66                 }
  67         }
  68
  69         protected function supportedOrders() {
  70                 return [ 'random', 'timestamp', 'fifo' ];
  71         }
  72
  73         protected function optimalOrder() {
  74                 return 'random';
  75         }
  76
  77         /**
  78          * @see JobQueue::doIsEmpty()
  79          * @return bool
  80          */
  81         protected function doIsEmpty() {
  82                 $dbr = $this->getReplicaDB();
  83                 /** @noinspection PhpUnusedLocalVariableInspection */
  84                 $scope = $this->getScopedNoTrxFlag( $dbr );
  85                 try {
  86                         $found = $dbr->selectField( // unclaimed job
  87                                 'job', '1', [ 'job_cmd' => $this->type, 'job_token' => '' ], __METHOD__
  88                         );
  89                 } catch ( DBError $e ) {
  90                         throw $this->getDBException( $e );
  91                 }
  92
  93                 return !$found;
  94         }
  95
  96         /**
  97          * @see JobQueue::doGetSize()
  98          * @return int
  99          */
 100         protected function doGetSize() {
 101                 $key = $this->getCacheKey( 'size' );
 102
 103                 $size = $this->wanCache->get( $key );
 104                 if ( is_int( $size ) ) {
 105                         return $size;
 106                 }
 107
 108                 $dbr = $this->getReplicaDB();
 109                 /** @noinspection PhpUnusedLocalVariableInspection */
 110                 $scope = $this->getScopedNoTrxFlag( $dbr );
 111                 try {
 112                         $size = (int)$dbr->selectField( 'job', 'COUNT(*)',
 113                                 [ 'job_cmd' => $this->type, 'job_token' => '' ],
 114                                 __METHOD__
 115                         );
 116                 } catch ( DBError $e ) {
 117                         throw $this->getDBException( $e );
 118                 }
 119                 $this->wanCache->set( $key, $size, self::CACHE_TTL_SHORT );
 120
 121                 return $size;
 122         }
 123
 124         /**
 125          * @see JobQueue::doGetAcquiredCount()
 126          * @return int
 127          */
 128         protected function doGetAcquiredCount() {
 129                 if ( $this->claimTTL <= 0 ) {
 130                         return 0; // no acknowledgements
 131                 }
 132
 133                 $key = $this->getCacheKey( 'acquiredcount' );
 134
 135                 $count = $this->wanCache->get( $key );
 136                 if ( is_int( $count ) ) {
 137                         return $count;
 138                 }
 139
 140                 $dbr = $this->getReplicaDB();
 141                 /** @noinspection PhpUnusedLocalVariableInspection */
 142                 $scope = $this->getScopedNoTrxFlag( $dbr );
 143                 try {
 144                         $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
 145                                 [ 'job_cmd' => $this->type, "job_token != {$dbr->addQuotes( '' )}" ],
 146                                 __METHOD__
 147                         );
 148                 } catch ( DBError $e ) {
 149                         throw $this->getDBException( $e );
 150                 }
 151                 $this->wanCache->set( $key, $count, self::CACHE_TTL_SHORT );
 152
 153                 return $count;
 154         }
 155
 156         /**
 157          * @see JobQueue::doGetAbandonedCount()
 158          * @return int
 159          * @throws MWException
 160          */
 161         protected function doGetAbandonedCount() {
 162                 if ( $this->claimTTL <= 0 ) {
 163                         return 0; // no acknowledgements
 164                 }
 165
 166                 $key = $this->getCacheKey( 'abandonedcount' );
 167
 168                 $count = $this->wanCache->get( $key );
 169                 if ( is_int( $count ) ) {
 170                         return $count;
 171                 }
 172
 173                 $dbr = $this->getReplicaDB();
 174                 /** @noinspection PhpUnusedLocalVariableInspection */
 175                 $scope = $this->getScopedNoTrxFlag( $dbr );
 176                 try {
 177                         $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
 178                                 [
 179                                         'job_cmd' => $this->type,
 180                                         "job_token != {$dbr->addQuotes( '' )}",
 181                                         "job_attempts >= " . $dbr->addQuotes( $this->maxTries )
 182                                 ],
 183                                 __METHOD__
 184                         );
 185                 } catch ( DBError $e ) {
 186                         throw $this->getDBException( $e );
 187                 }
 188
 189                 $this->wanCache->set( $key, $count, self::CACHE_TTL_SHORT );
 190
 191                 return $count;
 192         }
 193
 194         /**
 195          * @see JobQueue::doBatchPush()
 196          * @param IJobSpecification[] $jobs
 197          * @param int $flags
 198          * @throws DBError|Exception
 199          * @return void
 200          */
 201         protected function doBatchPush( array $jobs, $flags ) {
 202                 $dbw = $this->getMasterDB();
 203                 /** @noinspection PhpUnusedLocalVariableInspection */
 204                 $scope = $this->getScopedNoTrxFlag( $dbw );
 205                 // In general, there will be two cases here:
 206                 // a) sqlite; DB connection is probably a regular round-aware handle.
 207                 // If the connection is busy with a transaction, then defer the job writes
 208                 // until right before the main round commit step. Any errors that bubble
 209                 // up will rollback the main commit round.
 210                 // b) mysql/postgres; DB connection is generally a separate CONN_TRX_AUTOCOMMIT handle.
 211                 // No transaction is active nor will be started by writes, so enqueue the jobs
 212                 // now so that any errors will show up immediately as the interface expects. Any
 213                 // errors that bubble up will rollback the main commit round.
 214                 $fname = __METHOD__;
 215                 $dbw->onTransactionPreCommitOrIdle(
 216                         function ( IDatabase $dbw ) use ( $jobs, $flags, $fname ) {
 217                                 $this->doBatchPushInternal( $dbw, $jobs, $flags, $fname );
 218                         },
 219                         $fname
 220                 );
 221         }
 222
 223         /**
 224          * This function should *not* be called outside of JobQueueDB
 225          *
 226          * @suppress SecurityCheck-SQLInjection Bug in phan-taint-check handling bulk inserts
 227          * @param IDatabase $dbw
 228          * @param IJobSpecification[] $jobs
 229          * @param int $flags
 230          * @param string $method
 231          * @throws DBError
 232          * @return void
 233          */
 234         public function doBatchPushInternal( IDatabase $dbw, array $jobs, $flags, $method ) {
 235                 if ( $jobs === [] ) {
 236                         return;
 237                 }
 238
 239                 $rowSet = []; // (sha1 => job) map for jobs that are de-duplicated
 240                 $rowList = []; // list of jobs for jobs that are not de-duplicated
 241                 foreach ( $jobs as $job ) {
 242                         $row = $this->insertFields( $job, $dbw );
 243                         if ( $job->ignoreDuplicates() ) {
 244                                 $rowSet[$row['job_sha1']] = $row;
 245                         } else {
 246                                 $rowList[] = $row;
 247                         }
 248                 }
 249
 250                 if ( $flags & self::QOS_ATOMIC ) {
 251                         $dbw->startAtomic( $method ); // wrap all the job additions in one transaction
 252                 }
 253                 try {
 254                         // Strip out any duplicate jobs that are already in the queue...
 255                         if ( count( $rowSet ) ) {
 256                                 $res = $dbw->select( 'job', 'job_sha1',
 257                                         [
 258                                                 // No job_type condition since it's part of the job_sha1 hash
 259                                                 'job_sha1' => array_keys( $rowSet ),
 260                                                 'job_token' => '' // unclaimed
 261                                         ],
 262                                         $method
 263                                 );
 264                                 foreach ( $res as $row ) {
 265                                         wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate.\n" );
 266                                         unset( $rowSet[$row->job_sha1] ); // already enqueued
 267                                 }
 268                         }
 269                         // Build the full list of job rows to insert
 270                         $rows = array_merge( $rowList, array_values( $rowSet ) );
 271                         // Insert the job rows in chunks to avoid replica DB lag...
 272                         foreach ( array_chunk( $rows, 50 ) as $rowBatch ) {
 273                                 $dbw->insert( 'job', $rowBatch, $method );
 274                         }
 275                         $this->incrStats( 'inserts', $this->type, count( $rows ) );
 276                         $this->incrStats( 'dupe_inserts', $this->type,
 277                                 count( $rowSet ) + count( $rowList ) - count( $rows )
 278                         );
 279                 } catch ( DBError $e ) {
 280                         throw $this->getDBException( $e );
 281                 }
 282                 if ( $flags & self::QOS_ATOMIC ) {
 283                         $dbw->endAtomic( $method );
 284                 }
 285         }
 286
 287         /**
 288          * @see JobQueue::doPop()
 289          * @return RunnableJob|bool
 290          */
 291         protected function doPop() {
 292                 $dbw = $this->getMasterDB();
 293                 /** @noinspection PhpUnusedLocalVariableInspection */
 294                 $scope = $this->getScopedNoTrxFlag( $dbw );
 295
 296                 $job = false; // job popped off
 297                 try {
 298                         $uuid = wfRandomString( 32 ); // pop attempt
 299                         do { // retry when our row is invalid or deleted as a duplicate
 300                                 // Try to reserve a row in the DB...
 301                                 if ( in_array( $this->order, [ 'fifo', 'timestamp' ] ) ) {
 302                                         $row = $this->claimOldest( $uuid );
 303                                 } else { // random first
 304                                         $rand = mt_rand( 0, self::MAX_JOB_RANDOM ); // encourage concurrent UPDATEs
 305                                         $gte = (bool)mt_rand( 0, 1 ); // find rows with rand before/after $rand
 306                                         $row = $this->claimRandom( $uuid, $rand, $gte );
 307                                 }
 308                                 // Check if we found a row to reserve...
 309                                 if ( !$row ) {
 310                                         break; // nothing to do
 311                                 }
 312                                 $this->incrStats( 'pops', $this->type );
 313
 314                                 // Get the job object from the row...
 315                                 $job = $this->jobFromRow( $row );
 316                                 break; // done
 317                         } while ( true );
 318
 319                         if ( !$job || mt_rand( 0, 9 ) == 0 ) {
 320                                 // Handled jobs that need to be recycled/deleted;
 321                                 // any recycled jobs will be picked up next attempt
 322                                 $this->recycleAndDeleteStaleJobs();
 323                         }
 324                 } catch ( DBError $e ) {
 325                         throw $this->getDBException( $e );
 326                 }
 327
 328                 return $job;
 329         }
 330
 331         /**
 332          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 333          *
 334          * @param string $uuid 32 char hex string
 335          * @param int $rand Random unsigned integer (31 bits)
 336          * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
 337          * @return stdClass|bool Row|false
 338          */
 339         protected function claimRandom( $uuid, $rand, $gte ) {
 340                 $dbw = $this->getMasterDB();
 341                 /** @noinspection PhpUnusedLocalVariableInspection */
 342                 $scope = $this->getScopedNoTrxFlag( $dbw );
 343                 // Check cache to see if the queue has <= OFFSET items
 344                 $tinyQueue = $this->wanCache->get( $this->getCacheKey( 'small' ) );
 345
 346                 $invertedDirection = false; // whether one job_random direction was already scanned
 347                 // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
 348                 // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
 349                 // not replication safe. Due to https://bugs.mysql.com/bug.php?id=6980, subqueries cannot
 350                 // be used here with MySQL.
 351                 do {
 352                         if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
 353                                 // For small queues, using OFFSET will overshoot and return no rows more often.
 354                                 // Instead, this uses job_random to pick a row (possibly checking both directions).
 355                                 $ineq = $gte ? '>=' : '<=';
 356                                 $dir = $gte ? 'ASC' : 'DESC';
 357                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 358                                         [
 359                                                 'job_cmd' => $this->type,
 360                                                 'job_token' => '', // unclaimed
 361                                                 "job_random {$ineq} {$dbw->addQuotes( $rand )}" ],
 362                                         __METHOD__,
 363                                         [ 'ORDER BY' => "job_random {$dir}" ]
 364                                 );
 365                                 if ( !$row && !$invertedDirection ) {
 366                                         $gte = !$gte;
 367                                         $invertedDirection = true;
 368                                         continue; // try the other direction
 369                                 }
 370                         } else { // table *may* have >= MAX_OFFSET rows
 371                                 // T44614: "ORDER BY job_random" with a job_random inequality causes high CPU
 372                                 // in MySQL if there are many rows for some reason. This uses a small OFFSET
 373                                 // instead of job_random for reducing excess claim retries.
 374                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 375                                         [
 376                                                 'job_cmd' => $this->type,
 377                                                 'job_token' => '', // unclaimed
 378                                         ],
 379                                         __METHOD__,
 380                                         [ 'OFFSET' => mt_rand( 0, self::MAX_OFFSET ) ]
 381                                 );
 382                                 if ( !$row ) {
 383                                         $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
 384                                         $this->wanCache->set( $this->getCacheKey( 'small' ), 1, 30 );
 385                                         continue; // use job_random
 386                                 }
 387                         }
 388
 389                         if ( $row ) { // claim the job
 390                                 $dbw->update( 'job', // update by PK
 391                                         [
 392                                                 'job_token' => $uuid,
 393                                                 'job_token_timestamp' => $dbw->timestamp(),
 394                                                 'job_attempts = job_attempts+1' ],
 395                                         [ 'job_cmd' => $this->type, 'job_id' => $row->job_id, 'job_token' => '' ],
 396                                         __METHOD__
 397                                 );
 398                                 // This might get raced out by another runner when claiming the previously
 399                                 // selected row. The use of job_random should minimize this problem, however.
 400                                 if ( !$dbw->affectedRows() ) {
 401                                         $row = false; // raced out
 402                                 }
 403                         } else {
 404                                 break; // nothing to do
 405                         }
 406                 } while ( !$row );
 407
 408                 return $row;
 409         }
 410
 411         /**
 412          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 413          *
 414          * @param string $uuid 32 char hex string
 415          * @return stdClass|bool Row|false
 416          */
 417         protected function claimOldest( $uuid ) {
 418                 $dbw = $this->getMasterDB();
 419                 /** @noinspection PhpUnusedLocalVariableInspection */
 420                 $scope = $this->getScopedNoTrxFlag( $dbw );
 421
 422                 $row = false; // the row acquired
 423                 do {
 424                         if ( $dbw->getType() === 'mysql' ) {
 425                                 // Per https://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
 426                                 // same table being changed in an UPDATE query in MySQL (gives Error: 1093).
 427                                 // Oracle and Postgre have no such limitation. However, MySQL offers an
 428                                 // alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
 429                                 $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
 430                                         "SET " .
 431                                                 "job_token = {$dbw->addQuotes( $uuid ) }, " .
 432                                                 "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
 433                                                 "job_attempts = job_attempts+1 " .
 434                                         "WHERE ( " .
 435                                                 "job_cmd = {$dbw->addQuotes( $this->type )} " .
 436                                                 "AND job_token = {$dbw->addQuotes( '' )} " .
 437                                         ") ORDER BY job_id ASC LIMIT 1",
 438                                         __METHOD__
 439                                 );
 440                         } else {
 441                                 // Use a subquery to find the job, within an UPDATE to claim it.
 442                                 // This uses as much of the DB wrapper functions as possible.
 443                                 $dbw->update( 'job',
 444                                         [
 445                                                 'job_token' => $uuid,
 446                                                 'job_token_timestamp' => $dbw->timestamp(),
 447                                                 'job_attempts = job_attempts+1' ],
 448                                         [ 'job_id = (' .
 449                                                 $dbw->selectSQLText( 'job', 'job_id',
 450                                                         [ 'job_cmd' => $this->type, 'job_token' => '' ],
 451                                                         __METHOD__,
 452                                                         [ 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ] ) .
 453                                                 ')'
 454                                         ],
 455                                         __METHOD__
 456                                 );
 457                         }
 458                         // Fetch any row that we just reserved...
 459                         if ( $dbw->affectedRows() ) {
 460                                 $row = $dbw->selectRow( 'job', self::selectFields(),
 461                                         [ 'job_cmd' => $this->type, 'job_token' => $uuid ], __METHOD__
 462                                 );
 463                                 if ( !$row ) { // raced out by duplicate job removal
 464                                         wfDebug( "Row deleted as duplicate by another process.\n" );
 465                                 }
 466                         } else {
 467                                 break; // nothing to do
 468                         }
 469                 } while ( !$row );
 470
 471                 return $row;
 472         }
 473
 474         /**
 475          * @see JobQueue::doAck()
 476          * @param RunnableJob $job
 477          * @throws MWException
 478          */
 479         protected function doAck( RunnableJob $job ) {
 480                 $id = $job->getMetadata( 'id' );
 481                 if ( $id === null ) {
 482                         throw new MWException( "Job of type '{$job->getType()}' has no ID." );
 483                 }
 484
 485                 $dbw = $this->getMasterDB();
 486                 /** @noinspection PhpUnusedLocalVariableInspection */
 487                 $scope = $this->getScopedNoTrxFlag( $dbw );
 488                 try {
 489                         // Delete a row with a single DELETE without holding row locks over RTTs...
 490                         $dbw->delete(
 491                                 'job',
 492                                 [ 'job_cmd' => $this->type, 'job_id' => $id ],
 493                                 __METHOD__
 494                         );
 495
 496                         $this->incrStats( 'acks', $this->type );
 497                 } catch ( DBError $e ) {
 498                         throw $this->getDBException( $e );
 499                 }
 500         }
 501
 502         /**
 503          * @see JobQueue::doDeduplicateRootJob()
 504          * @param IJobSpecification $job
 505          * @throws MWException
 506          * @return bool
 507          */
 508         protected function doDeduplicateRootJob( IJobSpecification $job ) {
 509                 // Callers should call JobQueueGroup::push() before this method so that if the
 510                 // insert fails, the de-duplication registration will be aborted. Since the insert
 511                 // is deferred till "transaction idle", do the same here, so that the ordering is
 512                 // maintained. Having only the de-duplication registration succeed would cause
 513                 // jobs to become no-ops without any actual jobs that made them redundant.
 514                 $dbw = $this->getMasterDB();
 515                 /** @noinspection PhpUnusedLocalVariableInspection */
 516                 $scope = $this->getScopedNoTrxFlag( $dbw );
 517                 $dbw->onTransactionCommitOrIdle(
 518                         function () use ( $job ) {
 519                                 parent::doDeduplicateRootJob( $job );
 520                         },
 521                         __METHOD__
 522                 );
 523
 524                 return true;
 525         }
 526
 527         /**
 528          * @see JobQueue::doDelete()
 529          * @return bool
 530          */
 531         protected function doDelete() {
 532                 $dbw = $this->getMasterDB();
 533                 /** @noinspection PhpUnusedLocalVariableInspection */
 534                 $scope = $this->getScopedNoTrxFlag( $dbw );
 535                 try {
 536                         $dbw->delete( 'job', [ 'job_cmd' => $this->type ] );
 537                 } catch ( DBError $e ) {
 538                         throw $this->getDBException( $e );
 539                 }
 540
 541                 return true;
 542         }
 543
 544         /**
 545          * @see JobQueue::doWaitForBackups()
 546          * @return void
 547          */
 548         protected function doWaitForBackups() {
 549                 if ( $this->server ) {
 550                         return; // not using LBFactory instance
 551                 }
 552
 553                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 554                 $lbFactory->waitForReplication( [
 555                         'domain' => $this->domain,
 556                         'cluster' => is_string( $this->cluster ) ? $this->cluster : false
 557                 ] );
 558         }
 559
 560         /**
 561          * @return void
 562          */
 563         protected function doFlushCaches() {
 564                 foreach ( [ 'size', 'acquiredcount' ] as $type ) {
 565                         $this->wanCache->delete( $this->getCacheKey( $type ) );
 566                 }
 567         }
 568
 569         /**
 570          * @see JobQueue::getAllQueuedJobs()
 571          * @return Iterator
 572          */
 573         public function getAllQueuedJobs() {
 574                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), 'job_token' => '' ] );
 575         }
 576
 577         /**
 578          * @see JobQueue::getAllAcquiredJobs()
 579          * @return Iterator
 580          */
 581         public function getAllAcquiredJobs() {
 582                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), "job_token > ''" ] );
 583         }
 584
 585         /**
 586          * @param array $conds Query conditions
 587          * @return Iterator
 588          */
 589         protected function getJobIterator( array $conds ) {
 590                 $dbr = $this->getReplicaDB();
 591                 /** @noinspection PhpUnusedLocalVariableInspection */
 592                 $scope = $this->getScopedNoTrxFlag( $dbr );
 593                 try {
 594                         return new MappedIterator(
 595                                 $dbr->select( 'job', self::selectFields(), $conds ),
 596                                 function ( $row ) {
 597                                         return $this->jobFromRow( $row );
 598                                 }
 599                         );
 600                 } catch ( DBError $e ) {
 601                         throw $this->getDBException( $e );
 602                 }
 603         }
 604
 605         public function getCoalesceLocationInternal() {
 606                 if ( $this->server ) {
 607                         return null; // not using the LBFactory instance
 608                 }
 609
 610                 return is_string( $this->cluster )
 611                         ? "DBCluster:{$this->cluster}:{$this->domain}"
 612                         : "LBFactory:{$this->domain}";
 613         }
 614
 615         protected function doGetSiblingQueuesWithJobs( array $types ) {
 616                 $dbr = $this->getReplicaDB();
 617                 /** @noinspection PhpUnusedLocalVariableInspection */
 618                 $scope = $this->getScopedNoTrxFlag( $dbr );
 619                 // @note: this does not check whether the jobs are claimed or not.
 620                 // This is useful so JobQueueGroup::pop() also sees queues that only
 621                 // have stale jobs. This lets recycleAndDeleteStaleJobs() re-enqueue
 622                 // failed jobs so that they can be popped again for that edge case.
 623                 $res = $dbr->select( 'job', 'DISTINCT job_cmd',
 624                         [ 'job_cmd' => $types ], __METHOD__ );
 625
 626                 $types = [];
 627                 foreach ( $res as $row ) {
 628                         $types[] = $row->job_cmd;
 629                 }
 630
 631                 return $types;
 632         }
 633
 634         protected function doGetSiblingQueueSizes( array $types ) {
 635                 $dbr = $this->getReplicaDB();
 636                 /** @noinspection PhpUnusedLocalVariableInspection */
 637                 $scope = $this->getScopedNoTrxFlag( $dbr );
 638
 639                 $res = $dbr->select( 'job', [ 'job_cmd', 'COUNT(*) AS count' ],
 640                         [ 'job_cmd' => $types ], __METHOD__, [ 'GROUP BY' => 'job_cmd' ] );
 641
 642                 $sizes = [];
 643                 foreach ( $res as $row ) {
 644                         $sizes[$row->job_cmd] = (int)$row->count;
 645                 }
 646
 647                 return $sizes;
 648         }
 649
 650         /**
 651          * Recycle or destroy any jobs that have been claimed for too long
 652          *
 653          * @return int Number of jobs recycled/deleted
 654          */
 655         public function recycleAndDeleteStaleJobs() {
 656                 $now = time();
 657                 $count = 0; // affected rows
 658                 $dbw = $this->getMasterDB();
 659                 /** @noinspection PhpUnusedLocalVariableInspection */
 660                 $scope = $this->getScopedNoTrxFlag( $dbw );
 661
 662                 try {
 663                         if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__, 1 ) ) {
 664                                 return $count; // already in progress
 665                         }
 666
 667                         // Remove claims on jobs acquired for too long if enabled...
 668                         if ( $this->claimTTL > 0 ) {
 669                                 $claimCutoff = $dbw->timestamp( $now - $this->claimTTL );
 670                                 // Get the IDs of jobs that have be claimed but not finished after too long.
 671                                 // These jobs can be recycled into the queue by expiring the claim. Selecting
 672                                 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 673                                 $res = $dbw->select( 'job', 'job_id',
 674                                         [
 675                                                 'job_cmd' => $this->type,
 676                                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 677                                                 "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
 678                                                 "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ], // retries left
 679                                         __METHOD__
 680                                 );
 681                                 $ids = array_map(
 682                                         function ( $o ) {
 683                                                 return $o->job_id;
 684                                         }, iterator_to_array( $res )
 685                                 );
 686                                 if ( count( $ids ) ) {
 687                                         // Reset job_token for these jobs so that other runners will pick them up.
 688                                         // Set the timestamp to the current time, as it is useful to now that the job
 689                                         // was already tried before (the timestamp becomes the "released" time).
 690                                         $dbw->update( 'job',
 691                                                 [
 692                                                         'job_token' => '',
 693                                                         'job_token_timestamp' => $dbw->timestamp( $now ) ], // time of release
 694                                                 [
 695                                                         'job_id' => $ids ],
 696                                                 __METHOD__
 697                                         );
 698                                         $affected = $dbw->affectedRows();
 699                                         $count += $affected;
 700                                         $this->incrStats( 'recycles', $this->type, $affected );
 701                                 }
 702                         }
 703
 704                         // Just destroy any stale jobs...
 705                         $pruneCutoff = $dbw->timestamp( $now - self::MAX_AGE_PRUNE );
 706                         $conds = [
 707                                 'job_cmd' => $this->type,
 708                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 709                                 "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
 710                         ];
 711                         if ( $this->claimTTL > 0 ) { // only prune jobs attempted too many times...
 712                                 $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
 713                         }
 714                         // Get the IDs of jobs that are considered stale and should be removed. Selecting
 715                         // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 716                         $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__ );
 717                         $ids = array_map(
 718                                 function ( $o ) {
 719                                         return $o->job_id;
 720                                 }, iterator_to_array( $res )
 721                         );
 722                         if ( count( $ids ) ) {
 723                                 $dbw->delete( 'job', [ 'job_id' => $ids ], __METHOD__ );
 724                                 $affected = $dbw->affectedRows();
 725                                 $count += $affected;
 726                                 $this->incrStats( 'abandons', $this->type, $affected );
 727                         }
 728
 729                         $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__ );
 730                 } catch ( DBError $e ) {
 731                         throw $this->getDBException( $e );
 732                 }
 733
 734                 return $count;
 735         }
 736
 737         /**
 738          * @param IJobSpecification $job
 739          * @param IDatabase $db
 740          * @return array
 741          */
 742         protected function insertFields( IJobSpecification $job, IDatabase $db ) {
 743                 return [
 744                         // Fields that describe the nature of the job
 745                         'job_cmd' => $job->getType(),
 746                         'job_namespace' => $job->getParams()['namespace'] ?? NS_SPECIAL,
 747                         'job_title' => $job->getParams()['title'] ?? '',
 748                         'job_params' => self::makeBlob( $job->getParams() ),
 749                         // Additional job metadata
 750                         'job_timestamp' => $db->timestamp(),
 751                         'job_sha1' => Wikimedia\base_convert(
 752                                 sha1( serialize( $job->getDeduplicationInfo() ) ),
 753                                 16, 36, 31
 754                         ),
 755                         'job_random' => mt_rand( 0, self::MAX_JOB_RANDOM )
 756                 ];
 757         }
 758
 759         /**
 760          * @throws JobQueueConnectionError
 761          * @return IDatabase
 762          */
 763         protected function getReplicaDB() {
 764                 try {
 765                         return $this->getDB( DB_REPLICA );
 766                 } catch ( DBConnectionError $e ) {
 767                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 768                 }
 769         }
 770
 771         /**
 772          * @throws JobQueueConnectionError
 773          * @return IMaintainableDatabase
 774          */
 775         protected function getMasterDB() {
 776                 try {
 777                         return $this->getDB( DB_MASTER );
 778                 } catch ( DBConnectionError $e ) {
 779                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 780                 }
 781         }
 782
 783         /**
 784          * @param int $index (DB_REPLICA/DB_MASTER)
 785          * @return IMaintainableDatabase
 786          */
 787         protected function getDB( $index ) {
 788                 if ( $this->server ) {
 789                         if ( $this->conn instanceof IDatabase ) {
 790                                 return $this->conn;
 791                         } elseif ( $this->conn instanceof DBError ) {
 792                                 throw $this->conn;
 793                         }
 794
 795                         try {
 796                                 $this->conn = Database::factory( $this->server['type'], $this->server );
 797                         } catch ( DBError $e ) {
 798                                 $this->conn = $e;
 799                                 throw $e;
 800                         }
 801
 802                         return $this->conn;
 803                 } else {
 804                         $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 805                         $lb = is_string( $this->cluster )
 806                                 ? $lbFactory->getExternalLB( $this->cluster )
 807                                 : $lbFactory->getMainLB( $this->domain );
 808
 809                         if ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' ) {
 810                                 // Keep a separate connection to avoid contention and deadlocks;
 811                                 // However, SQLite has the opposite behavior due to DB-level locking.
 812                                 $flags = $lb::CONN_TRX_AUTOCOMMIT;
 813                         } else {
 814                                 // Jobs insertion will be defered until the PRESEND stage to reduce contention.
 815                                 $flags = 0;
 816                         }
 817
 818                         return $lb->getMaintenanceConnectionRef( $index, [], $this->domain, $flags );
 819                 }
 820         }
 821
 822         /**
 823          * @param IDatabase $db
 824          * @return ScopedCallback
 825          */
 826         private function getScopedNoTrxFlag( IDatabase $db ) {
 827                 $autoTrx = $db->getFlag( DBO_TRX ); // get current setting
 828                 $db->clearFlag( DBO_TRX ); // make each query its own transaction
 829
 830                 return new ScopedCallback( function () use ( $db, $autoTrx ) {
 831                         if ( $autoTrx ) {
 832                                 $db->setFlag( DBO_TRX ); // restore old setting
 833                         }
 834                 } );
 835         }
 836
 837         /**
 838          * @param string $property
 839          * @return string
 840          */
 841         private function getCacheKey( $property ) {
 842                 $cluster = is_string( $this->cluster ) ? $this->cluster : 'main';
 843
 844                 return $this->wanCache->makeGlobalKey(
 845                         'jobqueue',
 846                         $this->domain,
 847                         $cluster,
 848                         $this->type,
 849                         $property
 850                 );
 851         }
 852
 853         /**
 854          * @param array|bool $params
 855          * @return string
 856          */
 857         protected static function makeBlob( $params ) {
 858                 if ( $params !== false ) {
 859                         return serialize( $params );
 860                 } else {
 861                         return '';
 862                 }
 863         }
 864
 865         /**
 866          * @param stdClass $row
 867          * @return RunnableJob|null
 868          */
 869         protected function jobFromRow( $row ) {
 870                 $params = ( (string)$row->job_params !== '' ) ? unserialize( $row->job_params ) : [];
 871                 if ( !is_array( $params ) ) { // this shouldn't happen
 872                         throw new UnexpectedValueException(
 873                                 "Could not unserialize job with ID '{$row->job_id}'." );
 874                 }
 875
 876                 $params += [ 'namespace' => $row->job_namespace, 'title' => $row->job_title ];
 877                 $job = $this->factoryJob( $row->job_cmd, $params );
 878                 $job->setMetadata( 'id', $row->job_id );
 879                 $job->setMetadata( 'timestamp', $row->job_timestamp );
 880
 881                 return $job;
 882         }
 883
 884         /**
 885          * @param DBError $e
 886          * @return JobQueueError
 887          */
 888         protected function getDBException( DBError $e ) {
 889                 return new JobQueueError( get_class( $e ) . ": " . $e->getMessage() );
 890         }
 891
 892         /**
 893          * Return the list of job fields that should be selected.
 894          * @since 1.23
 895          * @return array
 896          */
 897         public static function selectFields() {
 898                 return [
 899                         'job_id',
 900                         'job_cmd',
 901                         'job_namespace',
 902                         'job_title',
 903                         'job_timestamp',
 904                         'job_params',
 905                         'job_random',
 906                         'job_attempts',
 907                         'job_token',
 908                         'job_token_timestamp',
 909                         'job_sha1',
 910                 ];
 911         }
 912 }