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\ScopedCallback;
  28
  29 /**
  30  * Class to handle job queues stored in the DB
  31  *
  32  * @ingroup JobQueue
  33  * @since 1.21
  34  */
  35 class JobQueueDB extends JobQueue {
  36         const CACHE_TTL_SHORT = 30; // integer; seconds to cache info without re-validating
  37         const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed
  38         const MAX_JOB_RANDOM = 2147483647; // integer; 2^31 - 1, used for job_random
  39         const MAX_OFFSET = 255; // integer; maximum number of rows to skip
  40
  41         /** @var WANObjectCache */
  42         protected $cache;
  43         /** @var IDatabase|DBError|null */
  44         protected $conn;
  45
  46         /** @var array|null Server configuration array */
  47         protected $server;
  48         /** @var string|null Name of an external DB cluster or null for the local DB cluster */
  49         protected $cluster;
  50
  51         /**
  52          * Additional parameters include:
  53          *   - server  : Server configuration array for Database::factory. Overrides "cluster".
  54          *   - cluster : The name of an external cluster registered via LBFactory.
  55          *               If not specified, the primary DB cluster for the wiki will be used.
  56          *               This can be overridden with a custom cluster so that DB handles will
  57          *               be retrieved via LBFactory::getExternalLB() and getConnection().
  58          *   - wanCache : An instance of WANObjectCache to use for caching.
  59          * @param array $params
  60          */
  61         protected function __construct( array $params ) {
  62                 parent::__construct( $params );
  63
  64                 if ( isset( $params['server'] ) ) {
  65                         $this->server = $params['server'];
  66                 } elseif ( isset( $params['cluster'] ) && is_string( $params['cluster'] ) ) {
  67                         $this->cluster = $params['cluster'];
  68                 }
  69
  70                 $this->cache = $params['wanCache'] ?? WANObjectCache::newEmpty();
  71         }
  72
  73         protected function supportedOrders() {
  74                 return [ 'random', 'timestamp', 'fifo' ];
  75         }
  76
  77         protected function optimalOrder() {
  78                 return 'random';
  79         }
  80
  81         /**
  82          * @see JobQueue::doIsEmpty()
  83          * @return bool
  84          */
  85         protected function doIsEmpty() {
  86                 $dbr = $this->getReplicaDB();
  87                 /** @noinspection PhpUnusedLocalVariableInspection */
  88                 $scope = $this->getScopedNoTrxFlag( $dbr );
  89                 try {
  90                         $found = $dbr->selectField( // unclaimed job
  91                                 'job', '1', [ 'job_cmd' => $this->type, 'job_token' => '' ], __METHOD__
  92                         );
  93                 } catch ( DBError $e ) {
  94                         $this->throwDBException( $e );
  95                 }
  96
  97                 return !$found;
  98         }
  99
 100         /**
 101          * @see JobQueue::doGetSize()
 102          * @return int
 103          */
 104         protected function doGetSize() {
 105                 $key = $this->getCacheKey( 'size' );
 106
 107                 $size = $this->cache->get( $key );
 108                 if ( is_int( $size ) ) {
 109                         return $size;
 110                 }
 111
 112                 $dbr = $this->getReplicaDB();
 113                 /** @noinspection PhpUnusedLocalVariableInspection */
 114                 $scope = $this->getScopedNoTrxFlag( $dbr );
 115                 try {
 116                         $size = (int)$dbr->selectField( 'job', 'COUNT(*)',
 117                                 [ 'job_cmd' => $this->type, 'job_token' => '' ],
 118                                 __METHOD__
 119                         );
 120                 } catch ( DBError $e ) {
 121                         $this->throwDBException( $e );
 122                 }
 123                 $this->cache->set( $key, $size, self::CACHE_TTL_SHORT );
 124
 125                 return $size;
 126         }
 127
 128         /**
 129          * @see JobQueue::doGetAcquiredCount()
 130          * @return int
 131          */
 132         protected function doGetAcquiredCount() {
 133                 if ( $this->claimTTL <= 0 ) {
 134                         return 0; // no acknowledgements
 135                 }
 136
 137                 $key = $this->getCacheKey( 'acquiredcount' );
 138
 139                 $count = $this->cache->get( $key );
 140                 if ( is_int( $count ) ) {
 141                         return $count;
 142                 }
 143
 144                 $dbr = $this->getReplicaDB();
 145                 /** @noinspection PhpUnusedLocalVariableInspection */
 146                 $scope = $this->getScopedNoTrxFlag( $dbr );
 147                 try {
 148                         $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
 149                                 [ 'job_cmd' => $this->type, "job_token != {$dbr->addQuotes( '' )}" ],
 150                                 __METHOD__
 151                         );
 152                 } catch ( DBError $e ) {
 153                         $this->throwDBException( $e );
 154                 }
 155                 $this->cache->set( $key, $count, self::CACHE_TTL_SHORT );
 156
 157                 return $count;
 158         }
 159
 160         /**
 161          * @see JobQueue::doGetAbandonedCount()
 162          * @return int
 163          * @throws MWException
 164          */
 165         protected function doGetAbandonedCount() {
 166                 if ( $this->claimTTL <= 0 ) {
 167                         return 0; // no acknowledgements
 168                 }
 169
 170                 $key = $this->getCacheKey( 'abandonedcount' );
 171
 172                 $count = $this->cache->get( $key );
 173                 if ( is_int( $count ) ) {
 174                         return $count;
 175                 }
 176
 177                 $dbr = $this->getReplicaDB();
 178                 /** @noinspection PhpUnusedLocalVariableInspection */
 179                 $scope = $this->getScopedNoTrxFlag( $dbr );
 180                 try {
 181                         $count = (int)$dbr->selectField( 'job', 'COUNT(*)',
 182                                 [
 183                                         'job_cmd' => $this->type,
 184                                         "job_token != {$dbr->addQuotes( '' )}",
 185                                         "job_attempts >= " . $dbr->addQuotes( $this->maxTries )
 186                                 ],
 187                                 __METHOD__
 188                         );
 189                 } catch ( DBError $e ) {
 190                         $this->throwDBException( $e );
 191                 }
 192
 193                 $this->cache->set( $key, $count, self::CACHE_TTL_SHORT );
 194
 195                 return $count;
 196         }
 197
 198         /**
 199          * @see JobQueue::doBatchPush()
 200          * @param IJobSpecification[] $jobs
 201          * @param int $flags
 202          * @throws DBError|Exception
 203          * @return void
 204          */
 205         protected function doBatchPush( array $jobs, $flags ) {
 206                 $dbw = $this->getMasterDB();
 207                 /** @noinspection PhpUnusedLocalVariableInspection */
 208                 $scope = $this->getScopedNoTrxFlag( $dbw );
 209                 // In general, there will be two cases here:
 210                 // a) sqlite; DB connection is probably a regular round-aware handle.
 211                 // If the connection is busy with a transaction, then defer the job writes
 212                 // until right before the main round commit step. Any errors that bubble
 213                 // up will rollback the main commit round.
 214                 // b) mysql/postgres; DB connection is generally a separate CONN_TRX_AUTOCOMMIT handle.
 215                 // No transaction is active nor will be started by writes, so enqueue the jobs
 216                 // now so that any errors will show up immediately as the interface expects. Any
 217                 // errors that bubble up will rollback the main commit round.
 218                 $fname = __METHOD__;
 219                 $dbw->onTransactionPreCommitOrIdle(
 220                         function ( IDatabase $dbw ) use ( $jobs, $flags, $fname ) {
 221                                 $this->doBatchPushInternal( $dbw, $jobs, $flags, $fname );
 222                         },
 223                         $fname
 224                 );
 225         }
 226
 227         /**
 228          * This function should *not* be called outside of JobQueueDB
 229          *
 230          * @suppress SecurityCheck-SQLInjection Bug in phan-taint-check handling bulk inserts
 231          * @param IDatabase $dbw
 232          * @param IJobSpecification[] $jobs
 233          * @param int $flags
 234          * @param string $method
 235          * @throws DBError
 236          * @return void
 237          */
 238         public function doBatchPushInternal( IDatabase $dbw, array $jobs, $flags, $method ) {
 239                 if ( $jobs === [] ) {
 240                         return;
 241                 }
 242
 243                 $rowSet = []; // (sha1 => job) map for jobs that are de-duplicated
 244                 $rowList = []; // list of jobs for jobs that are not de-duplicated
 245                 foreach ( $jobs as $job ) {
 246                         $row = $this->insertFields( $job, $dbw );
 247                         if ( $job->ignoreDuplicates() ) {
 248                                 $rowSet[$row['job_sha1']] = $row;
 249                         } else {
 250                                 $rowList[] = $row;
 251                         }
 252                 }
 253
 254                 if ( $flags & self::QOS_ATOMIC ) {
 255                         $dbw->startAtomic( $method ); // wrap all the job additions in one transaction
 256                 }
 257                 try {
 258                         // Strip out any duplicate jobs that are already in the queue...
 259                         if ( count( $rowSet ) ) {
 260                                 $res = $dbw->select( 'job', 'job_sha1',
 261                                         [
 262                                                 // No job_type condition since it's part of the job_sha1 hash
 263                                                 'job_sha1' => array_keys( $rowSet ),
 264                                                 'job_token' => '' // unclaimed
 265                                         ],
 266                                         $method
 267                                 );
 268                                 foreach ( $res as $row ) {
 269                                         wfDebug( "Job with hash '{$row->job_sha1}' is a duplicate.\n" );
 270                                         unset( $rowSet[$row->job_sha1] ); // already enqueued
 271                                 }
 272                         }
 273                         // Build the full list of job rows to insert
 274                         $rows = array_merge( $rowList, array_values( $rowSet ) );
 275                         // Insert the job rows in chunks to avoid replica DB lag...
 276                         foreach ( array_chunk( $rows, 50 ) as $rowBatch ) {
 277                                 $dbw->insert( 'job', $rowBatch, $method );
 278                         }
 279                         $this->incrStats( 'inserts', $this->type, count( $rows ) );
 280                         $this->incrStats( 'dupe_inserts', $this->type,
 281                                 count( $rowSet ) + count( $rowList ) - count( $rows )
 282                         );
 283                 } catch ( DBError $e ) {
 284                         $this->throwDBException( $e );
 285                 }
 286                 if ( $flags & self::QOS_ATOMIC ) {
 287                         $dbw->endAtomic( $method );
 288                 }
 289         }
 290
 291         /**
 292          * @see JobQueue::doPop()
 293          * @return RunnableJob|bool
 294          */
 295         protected function doPop() {
 296                 $dbw = $this->getMasterDB();
 297                 /** @noinspection PhpUnusedLocalVariableInspection */
 298                 $scope = $this->getScopedNoTrxFlag( $dbw );
 299
 300                 $job = false; // job popped off
 301                 try {
 302                         $uuid = wfRandomString( 32 ); // pop attempt
 303                         do { // retry when our row is invalid or deleted as a duplicate
 304                                 // Try to reserve a row in the DB...
 305                                 if ( in_array( $this->order, [ 'fifo', 'timestamp' ] ) ) {
 306                                         $row = $this->claimOldest( $uuid );
 307                                 } else { // random first
 308                                         $rand = mt_rand( 0, self::MAX_JOB_RANDOM ); // encourage concurrent UPDATEs
 309                                         $gte = (bool)mt_rand( 0, 1 ); // find rows with rand before/after $rand
 310                                         $row = $this->claimRandom( $uuid, $rand, $gte );
 311                                 }
 312                                 // Check if we found a row to reserve...
 313                                 if ( !$row ) {
 314                                         break; // nothing to do
 315                                 }
 316                                 $this->incrStats( 'pops', $this->type );
 317
 318                                 // Get the job object from the row...
 319                                 $params = self::extractBlob( $row->job_params );
 320                                 $params = is_array( $params ) ? $params : []; // sanity
 321                                 $params += [ 'namespace' => $row->job_namespace, 'title' => $row->job_title ];
 322                                 $job = $this->factoryJob( $row->job_cmd, $params );
 323                                 $job->setMetadata( 'id', $row->job_id );
 324                                 $job->setMetadata( 'timestamp', $row->job_timestamp );
 325                                 break; // done
 326                         } while ( true );
 327
 328                         if ( !$job || mt_rand( 0, 9 ) == 0 ) {
 329                                 // Handled jobs that need to be recycled/deleted;
 330                                 // any recycled jobs will be picked up next attempt
 331                                 $this->recycleAndDeleteStaleJobs();
 332                         }
 333                 } catch ( DBError $e ) {
 334                         $this->throwDBException( $e );
 335                 }
 336
 337                 return $job;
 338         }
 339
 340         /**
 341          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 342          *
 343          * @param string $uuid 32 char hex string
 344          * @param int $rand Random unsigned integer (31 bits)
 345          * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
 346          * @return stdClass|bool Row|false
 347          */
 348         protected function claimRandom( $uuid, $rand, $gte ) {
 349                 $dbw = $this->getMasterDB();
 350                 /** @noinspection PhpUnusedLocalVariableInspection */
 351                 $scope = $this->getScopedNoTrxFlag( $dbw );
 352                 // Check cache to see if the queue has <= OFFSET items
 353                 $tinyQueue = $this->cache->get( $this->getCacheKey( 'small' ) );
 354
 355                 $row = false; // the row acquired
 356                 $invertedDirection = false; // whether one job_random direction was already scanned
 357                 // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
 358                 // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
 359                 // not replication safe. Due to https://bugs.mysql.com/bug.php?id=6980, subqueries cannot
 360                 // be used here with MySQL.
 361                 do {
 362                         if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
 363                                 // For small queues, using OFFSET will overshoot and return no rows more often.
 364                                 // Instead, this uses job_random to pick a row (possibly checking both directions).
 365                                 $ineq = $gte ? '>=' : '<=';
 366                                 $dir = $gte ? 'ASC' : 'DESC';
 367                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 368                                         [
 369                                                 'job_cmd' => $this->type,
 370                                                 'job_token' => '', // unclaimed
 371                                                 "job_random {$ineq} {$dbw->addQuotes( $rand )}" ],
 372                                         __METHOD__,
 373                                         [ 'ORDER BY' => "job_random {$dir}" ]
 374                                 );
 375                                 if ( !$row && !$invertedDirection ) {
 376                                         $gte = !$gte;
 377                                         $invertedDirection = true;
 378                                         continue; // try the other direction
 379                                 }
 380                         } else { // table *may* have >= MAX_OFFSET rows
 381                                 // T44614: "ORDER BY job_random" with a job_random inequality causes high CPU
 382                                 // in MySQL if there are many rows for some reason. This uses a small OFFSET
 383                                 // instead of job_random for reducing excess claim retries.
 384                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 385                                         [
 386                                                 'job_cmd' => $this->type,
 387                                                 'job_token' => '', // unclaimed
 388                                         ],
 389                                         __METHOD__,
 390                                         [ 'OFFSET' => mt_rand( 0, self::MAX_OFFSET ) ]
 391                                 );
 392                                 if ( !$row ) {
 393                                         $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
 394                                         $this->cache->set( $this->getCacheKey( 'small' ), 1, 30 );
 395                                         continue; // use job_random
 396                                 }
 397                         }
 398
 399                         if ( $row ) { // claim the job
 400                                 $dbw->update( 'job', // update by PK
 401                                         [
 402                                                 'job_token' => $uuid,
 403                                                 'job_token_timestamp' => $dbw->timestamp(),
 404                                                 'job_attempts = job_attempts+1' ],
 405                                         [ 'job_cmd' => $this->type, 'job_id' => $row->job_id, 'job_token' => '' ],
 406                                         __METHOD__
 407                                 );
 408                                 // This might get raced out by another runner when claiming the previously
 409                                 // selected row. The use of job_random should minimize this problem, however.
 410                                 if ( !$dbw->affectedRows() ) {
 411                                         $row = false; // raced out
 412                                 }
 413                         } else {
 414                                 break; // nothing to do
 415                         }
 416                 } while ( !$row );
 417
 418                 return $row;
 419         }
 420
 421         /**
 422          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 423          *
 424          * @param string $uuid 32 char hex string
 425          * @return stdClass|bool Row|false
 426          */
 427         protected function claimOldest( $uuid ) {
 428                 $dbw = $this->getMasterDB();
 429                 /** @noinspection PhpUnusedLocalVariableInspection */
 430                 $scope = $this->getScopedNoTrxFlag( $dbw );
 431
 432                 $row = false; // the row acquired
 433                 do {
 434                         if ( $dbw->getType() === 'mysql' ) {
 435                                 // Per https://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
 436                                 // same table being changed in an UPDATE query in MySQL (gives Error: 1093).
 437                                 // Oracle and Postgre have no such limitation. However, MySQL offers an
 438                                 // alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
 439                                 $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
 440                                         "SET " .
 441                                                 "job_token = {$dbw->addQuotes( $uuid ) }, " .
 442                                                 "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
 443                                                 "job_attempts = job_attempts+1 " .
 444                                         "WHERE ( " .
 445                                                 "job_cmd = {$dbw->addQuotes( $this->type )} " .
 446                                                 "AND job_token = {$dbw->addQuotes( '' )} " .
 447                                         ") ORDER BY job_id ASC LIMIT 1",
 448                                         __METHOD__
 449                                 );
 450                         } else {
 451                                 // Use a subquery to find the job, within an UPDATE to claim it.
 452                                 // This uses as much of the DB wrapper functions as possible.
 453                                 $dbw->update( 'job',
 454                                         [
 455                                                 'job_token' => $uuid,
 456                                                 'job_token_timestamp' => $dbw->timestamp(),
 457                                                 'job_attempts = job_attempts+1' ],
 458                                         [ 'job_id = (' .
 459                                                 $dbw->selectSQLText( 'job', 'job_id',
 460                                                         [ 'job_cmd' => $this->type, 'job_token' => '' ],
 461                                                         __METHOD__,
 462                                                         [ 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ] ) .
 463                                                 ')'
 464                                         ],
 465                                         __METHOD__
 466                                 );
 467                         }
 468                         // Fetch any row that we just reserved...
 469                         if ( $dbw->affectedRows() ) {
 470                                 $row = $dbw->selectRow( 'job', self::selectFields(),
 471                                         [ 'job_cmd' => $this->type, 'job_token' => $uuid ], __METHOD__
 472                                 );
 473                                 if ( !$row ) { // raced out by duplicate job removal
 474                                         wfDebug( "Row deleted as duplicate by another process.\n" );
 475                                 }
 476                         } else {
 477                                 break; // nothing to do
 478                         }
 479                 } while ( !$row );
 480
 481                 return $row;
 482         }
 483
 484         /**
 485          * @see JobQueue::doAck()
 486          * @param RunnableJob $job
 487          * @throws MWException
 488          */
 489         protected function doAck( RunnableJob $job ) {
 490                 $id = $job->getMetadata( 'id' );
 491                 if ( $id === null ) {
 492                         throw new MWException( "Job of type '{$job->getType()}' has no ID." );
 493                 }
 494
 495                 $dbw = $this->getMasterDB();
 496                 /** @noinspection PhpUnusedLocalVariableInspection */
 497                 $scope = $this->getScopedNoTrxFlag( $dbw );
 498                 try {
 499                         // Delete a row with a single DELETE without holding row locks over RTTs...
 500                         $dbw->delete(
 501                                 'job',
 502                                 [ 'job_cmd' => $this->type, 'job_id' => $id ],
 503                                 __METHOD__
 504                         );
 505
 506                         $this->incrStats( 'acks', $this->type );
 507                 } catch ( DBError $e ) {
 508                         $this->throwDBException( $e );
 509                 }
 510         }
 511
 512         /**
 513          * @see JobQueue::doDeduplicateRootJob()
 514          * @param IJobSpecification $job
 515          * @throws MWException
 516          * @return bool
 517          */
 518         protected function doDeduplicateRootJob( IJobSpecification $job ) {
 519                 $params = $job->getParams();
 520                 if ( !isset( $params['rootJobSignature'] ) ) {
 521                         throw new MWException( "Cannot register root job; missing 'rootJobSignature'." );
 522                 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
 523                         throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." );
 524                 }
 525                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 526                 // Callers should call JobQueueGroup::push() before this method so that if the insert
 527                 // fails, the de-duplication registration will be aborted. Since the insert is
 528                 // deferred till "transaction idle", do the same here, so that the ordering is
 529                 // maintained. Having only the de-duplication registration succeed would cause
 530                 // jobs to become no-ops without any actual jobs that made them redundant.
 531                 $dbw = $this->getMasterDB();
 532                 /** @noinspection PhpUnusedLocalVariableInspection */
 533                 $scope = $this->getScopedNoTrxFlag( $dbw );
 534
 535                 $cache = $this->dupCache;
 536                 $dbw->onTransactionCommitOrIdle(
 537                         function () use ( $cache, $params, $key ) {
 538                                 $timestamp = $cache->get( $key ); // current last timestamp of this job
 539                                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 540                                         return true; // a newer version of this root job was enqueued
 541                                 }
 542
 543                                 // Update the timestamp of the last root job started at the location...
 544                                 return $cache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 545                         },
 546                         __METHOD__
 547                 );
 548
 549                 return true;
 550         }
 551
 552         /**
 553          * @see JobQueue::doDelete()
 554          * @return bool
 555          */
 556         protected function doDelete() {
 557                 $dbw = $this->getMasterDB();
 558                 /** @noinspection PhpUnusedLocalVariableInspection */
 559                 $scope = $this->getScopedNoTrxFlag( $dbw );
 560                 try {
 561                         $dbw->delete( 'job', [ 'job_cmd' => $this->type ] );
 562                 } catch ( DBError $e ) {
 563                         $this->throwDBException( $e );
 564                 }
 565
 566                 return true;
 567         }
 568
 569         /**
 570          * @see JobQueue::doWaitForBackups()
 571          * @return void
 572          */
 573         protected function doWaitForBackups() {
 574                 if ( $this->server ) {
 575                         return; // not using LBFactory instance
 576                 }
 577
 578                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 579                 $lbFactory->waitForReplication( [
 580                         'domain' => $this->domain,
 581                         'cluster' => is_string( $this->cluster ) ? $this->cluster : false
 582                 ] );
 583         }
 584
 585         /**
 586          * @return void
 587          */
 588         protected function doFlushCaches() {
 589                 foreach ( [ 'size', 'acquiredcount' ] as $type ) {
 590                         $this->cache->delete( $this->getCacheKey( $type ) );
 591                 }
 592         }
 593
 594         /**
 595          * @see JobQueue::getAllQueuedJobs()
 596          * @return Iterator
 597          */
 598         public function getAllQueuedJobs() {
 599                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), 'job_token' => '' ] );
 600         }
 601
 602         /**
 603          * @see JobQueue::getAllAcquiredJobs()
 604          * @return Iterator
 605          */
 606         public function getAllAcquiredJobs() {
 607                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), "job_token > ''" ] );
 608         }
 609
 610         /**
 611          * @param array $conds Query conditions
 612          * @return Iterator
 613          */
 614         protected function getJobIterator( array $conds ) {
 615                 $dbr = $this->getReplicaDB();
 616                 /** @noinspection PhpUnusedLocalVariableInspection */
 617                 $scope = $this->getScopedNoTrxFlag( $dbr );
 618                 try {
 619                         return new MappedIterator(
 620                                 $dbr->select( 'job', self::selectFields(), $conds ),
 621                                 function ( $row ) {
 622                                         $params = strlen( $row->job_params ) ? unserialize( $row->job_params ) : [];
 623                                         $params = is_array( $params ) ? $params : []; // sanity
 624                                         $params += [
 625                                                 'namespace' => $row->job_namespace,
 626                                                 'title' => $row->job_title
 627                                         ];
 628
 629                                         $job = $this->factoryJob( $row->job_cmd, $params );
 630                                         $job->setMetadata( 'id', $row->job_id );
 631                                         $job->setMetadata( 'timestamp', $row->job_timestamp );
 632
 633                                         return $job;
 634                                 }
 635                         );
 636                 } catch ( DBError $e ) {
 637                         $this->throwDBException( $e );
 638                 }
 639         }
 640
 641         public function getCoalesceLocationInternal() {
 642                 if ( $this->server ) {
 643                         return null; // not using the LBFactory instance
 644                 }
 645
 646                 return is_string( $this->cluster )
 647                         ? "DBCluster:{$this->cluster}:{$this->domain}"
 648                         : "LBFactory:{$this->domain}";
 649         }
 650
 651         protected function doGetSiblingQueuesWithJobs( array $types ) {
 652                 $dbr = $this->getReplicaDB();
 653                 /** @noinspection PhpUnusedLocalVariableInspection */
 654                 $scope = $this->getScopedNoTrxFlag( $dbr );
 655                 // @note: this does not check whether the jobs are claimed or not.
 656                 // This is useful so JobQueueGroup::pop() also sees queues that only
 657                 // have stale jobs. This lets recycleAndDeleteStaleJobs() re-enqueue
 658                 // failed jobs so that they can be popped again for that edge case.
 659                 $res = $dbr->select( 'job', 'DISTINCT job_cmd',
 660                         [ 'job_cmd' => $types ], __METHOD__ );
 661
 662                 $types = [];
 663                 foreach ( $res as $row ) {
 664                         $types[] = $row->job_cmd;
 665                 }
 666
 667                 return $types;
 668         }
 669
 670         protected function doGetSiblingQueueSizes( array $types ) {
 671                 $dbr = $this->getReplicaDB();
 672                 /** @noinspection PhpUnusedLocalVariableInspection */
 673                 $scope = $this->getScopedNoTrxFlag( $dbr );
 674
 675                 $res = $dbr->select( 'job', [ 'job_cmd', 'COUNT(*) AS count' ],
 676                         [ 'job_cmd' => $types ], __METHOD__, [ 'GROUP BY' => 'job_cmd' ] );
 677
 678                 $sizes = [];
 679                 foreach ( $res as $row ) {
 680                         $sizes[$row->job_cmd] = (int)$row->count;
 681                 }
 682
 683                 return $sizes;
 684         }
 685
 686         /**
 687          * Recycle or destroy any jobs that have been claimed for too long
 688          *
 689          * @return int Number of jobs recycled/deleted
 690          */
 691         public function recycleAndDeleteStaleJobs() {
 692                 $now = time();
 693                 $count = 0; // affected rows
 694                 $dbw = $this->getMasterDB();
 695                 /** @noinspection PhpUnusedLocalVariableInspection */
 696                 $scope = $this->getScopedNoTrxFlag( $dbw );
 697
 698                 try {
 699                         if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__, 1 ) ) {
 700                                 return $count; // already in progress
 701                         }
 702
 703                         // Remove claims on jobs acquired for too long if enabled...
 704                         if ( $this->claimTTL > 0 ) {
 705                                 $claimCutoff = $dbw->timestamp( $now - $this->claimTTL );
 706                                 // Get the IDs of jobs that have be claimed but not finished after too long.
 707                                 // These jobs can be recycled into the queue by expiring the claim. Selecting
 708                                 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 709                                 $res = $dbw->select( 'job', 'job_id',
 710                                         [
 711                                                 'job_cmd' => $this->type,
 712                                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 713                                                 "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
 714                                                 "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ], // retries left
 715                                         __METHOD__
 716                                 );
 717                                 $ids = array_map(
 718                                         function ( $o ) {
 719                                                 return $o->job_id;
 720                                         }, iterator_to_array( $res )
 721                                 );
 722                                 if ( count( $ids ) ) {
 723                                         // Reset job_token for these jobs so that other runners will pick them up.
 724                                         // Set the timestamp to the current time, as it is useful to now that the job
 725                                         // was already tried before (the timestamp becomes the "released" time).
 726                                         $dbw->update( 'job',
 727                                                 [
 728                                                         'job_token' => '',
 729                                                         'job_token_timestamp' => $dbw->timestamp( $now ) ], // time of release
 730                                                 [
 731                                                         'job_id' => $ids ],
 732                                                 __METHOD__
 733                                         );
 734                                         $affected = $dbw->affectedRows();
 735                                         $count += $affected;
 736                                         $this->incrStats( 'recycles', $this->type, $affected );
 737                                 }
 738                         }
 739
 740                         // Just destroy any stale jobs...
 741                         $pruneCutoff = $dbw->timestamp( $now - self::MAX_AGE_PRUNE );
 742                         $conds = [
 743                                 'job_cmd' => $this->type,
 744                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 745                                 "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
 746                         ];
 747                         if ( $this->claimTTL > 0 ) { // only prune jobs attempted too many times...
 748                                 $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
 749                         }
 750                         // Get the IDs of jobs that are considered stale and should be removed. Selecting
 751                         // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 752                         $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__ );
 753                         $ids = array_map(
 754                                 function ( $o ) {
 755                                         return $o->job_id;
 756                                 }, iterator_to_array( $res )
 757                         );
 758                         if ( count( $ids ) ) {
 759                                 $dbw->delete( 'job', [ 'job_id' => $ids ], __METHOD__ );
 760                                 $affected = $dbw->affectedRows();
 761                                 $count += $affected;
 762                                 $this->incrStats( 'abandons', $this->type, $affected );
 763                         }
 764
 765                         $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__ );
 766                 } catch ( DBError $e ) {
 767                         $this->throwDBException( $e );
 768                 }
 769
 770                 return $count;
 771         }
 772
 773         /**
 774          * @param IJobSpecification $job
 775          * @param IDatabase $db
 776          * @return array
 777          */
 778         protected function insertFields( IJobSpecification $job, IDatabase $db ) {
 779                 return [
 780                         // Fields that describe the nature of the job
 781                         'job_cmd' => $job->getType(),
 782                         'job_namespace' => $job->getParams()['namespace'] ?? NS_SPECIAL,
 783                         'job_title' => $job->getParams()['title'] ?? '',
 784                         'job_params' => self::makeBlob( $job->getParams() ),
 785                         // Additional job metadata
 786                         'job_timestamp' => $db->timestamp(),
 787                         'job_sha1' => Wikimedia\base_convert(
 788                                 sha1( serialize( $job->getDeduplicationInfo() ) ),
 789                                 16, 36, 31
 790                         ),
 791                         'job_random' => mt_rand( 0, self::MAX_JOB_RANDOM )
 792                 ];
 793         }
 794
 795         /**
 796          * @throws JobQueueConnectionError
 797          * @return IDatabase
 798          */
 799         protected function getReplicaDB() {
 800                 try {
 801                         return $this->getDB( DB_REPLICA );
 802                 } catch ( DBConnectionError $e ) {
 803                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 804                 }
 805         }
 806
 807         /**
 808          * @throws JobQueueConnectionError
 809          * @return IDatabase
 810          */
 811         protected function getMasterDB() {
 812                 try {
 813                         return $this->getDB( DB_MASTER );
 814                 } catch ( DBConnectionError $e ) {
 815                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 816                 }
 817         }
 818
 819         /**
 820          * @param int $index (DB_REPLICA/DB_MASTER)
 821          * @return IDatabase
 822          */
 823         protected function getDB( $index ) {
 824                 if ( $this->server ) {
 825                         if ( $this->conn instanceof IDatabase ) {
 826                                 return $this->conn;
 827                         } elseif ( $this->conn instanceof DBError ) {
 828                                 throw $this->conn;
 829                         }
 830
 831                         try {
 832                                 $this->conn = Database::factory( $this->server['type'], $this->server );
 833                         } catch ( DBError $e ) {
 834                                 $this->conn = $e;
 835                                 throw $e;
 836                         }
 837
 838                         return $this->conn;
 839                 } else {
 840                         $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 841                         $lb = is_string( $this->cluster )
 842                                 ? $lbFactory->getExternalLB( $this->cluster )
 843                                 : $lbFactory->getMainLB( $this->domain );
 844
 845                         return ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' )
 846                                 // Keep a separate connection to avoid contention and deadlocks;
 847                                 // However, SQLite has the opposite behavior due to DB-level locking.
 848                                 ? $lb->getConnectionRef( $index, [], $this->domain, $lb::CONN_TRX_AUTOCOMMIT )
 849                                 // Jobs insertion will be defered until the PRESEND stage to reduce contention.
 850                                 : $lb->getConnectionRef( $index, [], $this->domain );
 851                 }
 852         }
 853
 854         /**
 855          * @param IDatabase $db
 856          * @return ScopedCallback
 857          */
 858         private function getScopedNoTrxFlag( IDatabase $db ) {
 859                 $autoTrx = $db->getFlag( DBO_TRX ); // get current setting
 860                 $db->clearFlag( DBO_TRX ); // make each query its own transaction
 861
 862                 return new ScopedCallback( function () use ( $db, $autoTrx ) {
 863                         if ( $autoTrx ) {
 864                                 $db->setFlag( DBO_TRX ); // restore old setting
 865                         }
 866                 } );
 867         }
 868
 869         /**
 870          * @param string $property
 871          * @return string
 872          */
 873         private function getCacheKey( $property ) {
 874                 $cluster = is_string( $this->cluster ) ? $this->cluster : 'main';
 875
 876                 return $this->cache->makeGlobalKey(
 877                         'jobqueue',
 878                         $this->domain,
 879                         $cluster,
 880                         $this->type,
 881                         $property
 882                 );
 883         }
 884
 885         /**
 886          * @param array|bool $params
 887          * @return string
 888          */
 889         protected static function makeBlob( $params ) {
 890                 if ( $params !== false ) {
 891                         return serialize( $params );
 892                 } else {
 893                         return '';
 894                 }
 895         }
 896
 897         /**
 898          * @param string $blob
 899          * @return bool|mixed
 900          */
 901         protected static function extractBlob( $blob ) {
 902                 if ( (string)$blob !== '' ) {
 903                         return unserialize( $blob );
 904                 } else {
 905                         return false;
 906                 }
 907         }
 908
 909         /**
 910          * @param DBError $e
 911          * @throws JobQueueError
 912          */
 913         protected function throwDBException( DBError $e ) {
 914                 throw new JobQueueError( get_class( $e ) . ": " . $e->getMessage() );
 915         }
 916
 917         /**
 918          * Return the list of job fields that should be selected.
 919          * @since 1.23
 920          * @return array
 921          */
 922         public static function selectFields() {
 923                 return [
 924                         'job_id',
 925                         'job_cmd',
 926                         'job_namespace',
 927                         'job_title',
 928                         'job_timestamp',
 929                         'job_params',
 930                         'job_random',
 931                         'job_attempts',
 932                         'job_token',
 933                         'job_token_timestamp',
 934                         'job_sha1',
 935                 ];
 936         }
 937 }