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 Job|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                                 // Get the job object from the row...
 318                                 $title = Title::makeTitle( $row->job_namespace, $row->job_title );
 319                                 $job = Job::factory( $row->job_cmd, $title,
 320                                         self::extractBlob( $row->job_params ) );
 321                                 $job->setMetadata( 'id', $row->job_id );
 322                                 $job->setMetadata( 'timestamp', $row->job_timestamp );
 323                                 break; // done
 324                         } while ( true );
 325
 326                         if ( !$job || mt_rand( 0, 9 ) == 0 ) {
 327                                 // Handled jobs that need to be recycled/deleted;
 328                                 // any recycled jobs will be picked up next attempt
 329                                 $this->recycleAndDeleteStaleJobs();
 330                         }
 331                 } catch ( DBError $e ) {
 332                         $this->throwDBException( $e );
 333                 }
 334
 335                 return $job;
 336         }
 337
 338         /**
 339          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 340          *
 341          * @param string $uuid 32 char hex string
 342          * @param int $rand Random unsigned integer (31 bits)
 343          * @param bool $gte Search for job_random >= $random (otherwise job_random <= $random)
 344          * @return stdClass|bool Row|false
 345          */
 346         protected function claimRandom( $uuid, $rand, $gte ) {
 347                 $dbw = $this->getMasterDB();
 348                 /** @noinspection PhpUnusedLocalVariableInspection */
 349                 $scope = $this->getScopedNoTrxFlag( $dbw );
 350                 // Check cache to see if the queue has <= OFFSET items
 351                 $tinyQueue = $this->cache->get( $this->getCacheKey( 'small' ) );
 352
 353                 $row = false; // the row acquired
 354                 $invertedDirection = false; // whether one job_random direction was already scanned
 355                 // This uses a replication safe method for acquiring jobs. One could use UPDATE+LIMIT
 356                 // instead, but that either uses ORDER BY (in which case it deadlocks in MySQL) or is
 357                 // not replication safe. Due to https://bugs.mysql.com/bug.php?id=6980, subqueries cannot
 358                 // be used here with MySQL.
 359                 do {
 360                         if ( $tinyQueue ) { // queue has <= MAX_OFFSET rows
 361                                 // For small queues, using OFFSET will overshoot and return no rows more often.
 362                                 // Instead, this uses job_random to pick a row (possibly checking both directions).
 363                                 $ineq = $gte ? '>=' : '<=';
 364                                 $dir = $gte ? 'ASC' : 'DESC';
 365                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 366                                         [
 367                                                 'job_cmd' => $this->type,
 368                                                 'job_token' => '', // unclaimed
 369                                                 "job_random {$ineq} {$dbw->addQuotes( $rand )}" ],
 370                                         __METHOD__,
 371                                         [ 'ORDER BY' => "job_random {$dir}" ]
 372                                 );
 373                                 if ( !$row && !$invertedDirection ) {
 374                                         $gte = !$gte;
 375                                         $invertedDirection = true;
 376                                         continue; // try the other direction
 377                                 }
 378                         } else { // table *may* have >= MAX_OFFSET rows
 379                                 // T44614: "ORDER BY job_random" with a job_random inequality causes high CPU
 380                                 // in MySQL if there are many rows for some reason. This uses a small OFFSET
 381                                 // instead of job_random for reducing excess claim retries.
 382                                 $row = $dbw->selectRow( 'job', self::selectFields(), // find a random job
 383                                         [
 384                                                 'job_cmd' => $this->type,
 385                                                 'job_token' => '', // unclaimed
 386                                         ],
 387                                         __METHOD__,
 388                                         [ 'OFFSET' => mt_rand( 0, self::MAX_OFFSET ) ]
 389                                 );
 390                                 if ( !$row ) {
 391                                         $tinyQueue = true; // we know the queue must have <= MAX_OFFSET rows
 392                                         $this->cache->set( $this->getCacheKey( 'small' ), 1, 30 );
 393                                         continue; // use job_random
 394                                 }
 395                         }
 396
 397                         if ( $row ) { // claim the job
 398                                 $dbw->update( 'job', // update by PK
 399                                         [
 400                                                 'job_token' => $uuid,
 401                                                 'job_token_timestamp' => $dbw->timestamp(),
 402                                                 'job_attempts = job_attempts+1' ],
 403                                         [ 'job_cmd' => $this->type, 'job_id' => $row->job_id, 'job_token' => '' ],
 404                                         __METHOD__
 405                                 );
 406                                 // This might get raced out by another runner when claiming the previously
 407                                 // selected row. The use of job_random should minimize this problem, however.
 408                                 if ( !$dbw->affectedRows() ) {
 409                                         $row = false; // raced out
 410                                 }
 411                         } else {
 412                                 break; // nothing to do
 413                         }
 414                 } while ( !$row );
 415
 416                 return $row;
 417         }
 418
 419         /**
 420          * Reserve a row with a single UPDATE without holding row locks over RTTs...
 421          *
 422          * @param string $uuid 32 char hex string
 423          * @return stdClass|bool Row|false
 424          */
 425         protected function claimOldest( $uuid ) {
 426                 $dbw = $this->getMasterDB();
 427                 /** @noinspection PhpUnusedLocalVariableInspection */
 428                 $scope = $this->getScopedNoTrxFlag( $dbw );
 429
 430                 $row = false; // the row acquired
 431                 do {
 432                         if ( $dbw->getType() === 'mysql' ) {
 433                                 // Per https://bugs.mysql.com/bug.php?id=6980, we can't use subqueries on the
 434                                 // same table being changed in an UPDATE query in MySQL (gives Error: 1093).
 435                                 // Oracle and Postgre have no such limitation. However, MySQL offers an
 436                                 // alternative here by supporting ORDER BY + LIMIT for UPDATE queries.
 437                                 $dbw->query( "UPDATE {$dbw->tableName( 'job' )} " .
 438                                         "SET " .
 439                                                 "job_token = {$dbw->addQuotes( $uuid ) }, " .
 440                                                 "job_token_timestamp = {$dbw->addQuotes( $dbw->timestamp() )}, " .
 441                                                 "job_attempts = job_attempts+1 " .
 442                                         "WHERE ( " .
 443                                                 "job_cmd = {$dbw->addQuotes( $this->type )} " .
 444                                                 "AND job_token = {$dbw->addQuotes( '' )} " .
 445                                         ") ORDER BY job_id ASC LIMIT 1",
 446                                         __METHOD__
 447                                 );
 448                         } else {
 449                                 // Use a subquery to find the job, within an UPDATE to claim it.
 450                                 // This uses as much of the DB wrapper functions as possible.
 451                                 $dbw->update( 'job',
 452                                         [
 453                                                 'job_token' => $uuid,
 454                                                 'job_token_timestamp' => $dbw->timestamp(),
 455                                                 'job_attempts = job_attempts+1' ],
 456                                         [ 'job_id = (' .
 457                                                 $dbw->selectSQLText( 'job', 'job_id',
 458                                                         [ 'job_cmd' => $this->type, 'job_token' => '' ],
 459                                                         __METHOD__,
 460                                                         [ 'ORDER BY' => 'job_id ASC', 'LIMIT' => 1 ] ) .
 461                                                 ')'
 462                                         ],
 463                                         __METHOD__
 464                                 );
 465                         }
 466                         // Fetch any row that we just reserved...
 467                         if ( $dbw->affectedRows() ) {
 468                                 $row = $dbw->selectRow( 'job', self::selectFields(),
 469                                         [ 'job_cmd' => $this->type, 'job_token' => $uuid ], __METHOD__
 470                                 );
 471                                 if ( !$row ) { // raced out by duplicate job removal
 472                                         wfDebug( "Row deleted as duplicate by another process.\n" );
 473                                 }
 474                         } else {
 475                                 break; // nothing to do
 476                         }
 477                 } while ( !$row );
 478
 479                 return $row;
 480         }
 481
 482         /**
 483          * @see JobQueue::doAck()
 484          * @param Job $job
 485          * @throws MWException
 486          */
 487         protected function doAck( Job $job ) {
 488                 $id = $job->getMetadata( 'id' );
 489                 if ( $id === null ) {
 490                         throw new MWException( "Job of type '{$job->getType()}' has no ID." );
 491                 }
 492
 493                 $dbw = $this->getMasterDB();
 494                 /** @noinspection PhpUnusedLocalVariableInspection */
 495                 $scope = $this->getScopedNoTrxFlag( $dbw );
 496                 try {
 497                         // Delete a row with a single DELETE without holding row locks over RTTs...
 498                         $dbw->delete(
 499                                 'job',
 500                                 [ 'job_cmd' => $this->type, 'job_id' => $id ],
 501                                 __METHOD__
 502                         );
 503
 504                         $this->incrStats( 'acks', $this->type );
 505                 } catch ( DBError $e ) {
 506                         $this->throwDBException( $e );
 507                 }
 508         }
 509
 510         /**
 511          * @see JobQueue::doDeduplicateRootJob()
 512          * @param IJobSpecification $job
 513          * @throws MWException
 514          * @return bool
 515          */
 516         protected function doDeduplicateRootJob( IJobSpecification $job ) {
 517                 $params = $job->getParams();
 518                 if ( !isset( $params['rootJobSignature'] ) ) {
 519                         throw new MWException( "Cannot register root job; missing 'rootJobSignature'." );
 520                 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
 521                         throw new MWException( "Cannot register root job; missing 'rootJobTimestamp'." );
 522                 }
 523                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 524                 // Callers should call JobQueueGroup::push() before this method so that if the insert
 525                 // fails, the de-duplication registration will be aborted. Since the insert is
 526                 // deferred till "transaction idle", do the same here, so that the ordering is
 527                 // maintained. Having only the de-duplication registration succeed would cause
 528                 // jobs to become no-ops without any actual jobs that made them redundant.
 529                 $dbw = $this->getMasterDB();
 530                 /** @noinspection PhpUnusedLocalVariableInspection */
 531                 $scope = $this->getScopedNoTrxFlag( $dbw );
 532
 533                 $cache = $this->dupCache;
 534                 $dbw->onTransactionCommitOrIdle(
 535                         function () use ( $cache, $params, $key ) {
 536                                 $timestamp = $cache->get( $key ); // current last timestamp of this job
 537                                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 538                                         return true; // a newer version of this root job was enqueued
 539                                 }
 540
 541                                 // Update the timestamp of the last root job started at the location...
 542                                 return $cache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 543                         },
 544                         __METHOD__
 545                 );
 546
 547                 return true;
 548         }
 549
 550         /**
 551          * @see JobQueue::doDelete()
 552          * @return bool
 553          */
 554         protected function doDelete() {
 555                 $dbw = $this->getMasterDB();
 556                 /** @noinspection PhpUnusedLocalVariableInspection */
 557                 $scope = $this->getScopedNoTrxFlag( $dbw );
 558                 try {
 559                         $dbw->delete( 'job', [ 'job_cmd' => $this->type ] );
 560                 } catch ( DBError $e ) {
 561                         $this->throwDBException( $e );
 562                 }
 563
 564                 return true;
 565         }
 566
 567         /**
 568          * @see JobQueue::doWaitForBackups()
 569          * @return void
 570          */
 571         protected function doWaitForBackups() {
 572                 if ( $this->server ) {
 573                         return; // not using LBFactory instance
 574                 }
 575
 576                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 577                 $lbFactory->waitForReplication( [
 578                         'domain' => $this->domain,
 579                         'cluster' => is_string( $this->cluster ) ? $this->cluster : false
 580                 ] );
 581         }
 582
 583         /**
 584          * @return void
 585          */
 586         protected function doFlushCaches() {
 587                 foreach ( [ 'size', 'acquiredcount' ] as $type ) {
 588                         $this->cache->delete( $this->getCacheKey( $type ) );
 589                 }
 590         }
 591
 592         /**
 593          * @see JobQueue::getAllQueuedJobs()
 594          * @return Iterator
 595          */
 596         public function getAllQueuedJobs() {
 597                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), 'job_token' => '' ] );
 598         }
 599
 600         /**
 601          * @see JobQueue::getAllAcquiredJobs()
 602          * @return Iterator
 603          */
 604         public function getAllAcquiredJobs() {
 605                 return $this->getJobIterator( [ 'job_cmd' => $this->getType(), "job_token > ''" ] );
 606         }
 607
 608         /**
 609          * @param array $conds Query conditions
 610          * @return Iterator
 611          */
 612         protected function getJobIterator( array $conds ) {
 613                 $dbr = $this->getReplicaDB();
 614                 /** @noinspection PhpUnusedLocalVariableInspection */
 615                 $scope = $this->getScopedNoTrxFlag( $dbr );
 616                 try {
 617                         return new MappedIterator(
 618                                 $dbr->select( 'job', self::selectFields(), $conds ),
 619                                 function ( $row ) {
 620                                         $job = Job::factory(
 621                                                 $row->job_cmd,
 622                                                 Title::makeTitle( $row->job_namespace, $row->job_title ),
 623                                                 strlen( $row->job_params ) ? unserialize( $row->job_params ) : []
 624                                         );
 625                                         $job->setMetadata( 'id', $row->job_id );
 626                                         $job->setMetadata( 'timestamp', $row->job_timestamp );
 627
 628                                         return $job;
 629                                 }
 630                         );
 631                 } catch ( DBError $e ) {
 632                         $this->throwDBException( $e );
 633                 }
 634         }
 635
 636         public function getCoalesceLocationInternal() {
 637                 if ( $this->server ) {
 638                         return null; // not using the LBFactory instance
 639                 }
 640
 641                 return is_string( $this->cluster )
 642                         ? "DBCluster:{$this->cluster}:{$this->domain}"
 643                         : "LBFactory:{$this->domain}";
 644         }
 645
 646         protected function doGetSiblingQueuesWithJobs( array $types ) {
 647                 $dbr = $this->getReplicaDB();
 648                 /** @noinspection PhpUnusedLocalVariableInspection */
 649                 $scope = $this->getScopedNoTrxFlag( $dbr );
 650                 // @note: this does not check whether the jobs are claimed or not.
 651                 // This is useful so JobQueueGroup::pop() also sees queues that only
 652                 // have stale jobs. This lets recycleAndDeleteStaleJobs() re-enqueue
 653                 // failed jobs so that they can be popped again for that edge case.
 654                 $res = $dbr->select( 'job', 'DISTINCT job_cmd',
 655                         [ 'job_cmd' => $types ], __METHOD__ );
 656
 657                 $types = [];
 658                 foreach ( $res as $row ) {
 659                         $types[] = $row->job_cmd;
 660                 }
 661
 662                 return $types;
 663         }
 664
 665         protected function doGetSiblingQueueSizes( array $types ) {
 666                 $dbr = $this->getReplicaDB();
 667                 /** @noinspection PhpUnusedLocalVariableInspection */
 668                 $scope = $this->getScopedNoTrxFlag( $dbr );
 669
 670                 $res = $dbr->select( 'job', [ 'job_cmd', 'COUNT(*) AS count' ],
 671                         [ 'job_cmd' => $types ], __METHOD__, [ 'GROUP BY' => 'job_cmd' ] );
 672
 673                 $sizes = [];
 674                 foreach ( $res as $row ) {
 675                         $sizes[$row->job_cmd] = (int)$row->count;
 676                 }
 677
 678                 return $sizes;
 679         }
 680
 681         /**
 682          * Recycle or destroy any jobs that have been claimed for too long
 683          *
 684          * @return int Number of jobs recycled/deleted
 685          */
 686         public function recycleAndDeleteStaleJobs() {
 687                 $now = time();
 688                 $count = 0; // affected rows
 689                 $dbw = $this->getMasterDB();
 690                 /** @noinspection PhpUnusedLocalVariableInspection */
 691                 $scope = $this->getScopedNoTrxFlag( $dbw );
 692
 693                 try {
 694                         if ( !$dbw->lock( "jobqueue-recycle-{$this->type}", __METHOD__, 1 ) ) {
 695                                 return $count; // already in progress
 696                         }
 697
 698                         // Remove claims on jobs acquired for too long if enabled...
 699                         if ( $this->claimTTL > 0 ) {
 700                                 $claimCutoff = $dbw->timestamp( $now - $this->claimTTL );
 701                                 // Get the IDs of jobs that have be claimed but not finished after too long.
 702                                 // These jobs can be recycled into the queue by expiring the claim. Selecting
 703                                 // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 704                                 $res = $dbw->select( 'job', 'job_id',
 705                                         [
 706                                                 'job_cmd' => $this->type,
 707                                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 708                                                 "job_token_timestamp < {$dbw->addQuotes( $claimCutoff )}", // stale
 709                                                 "job_attempts < {$dbw->addQuotes( $this->maxTries )}" ], // retries left
 710                                         __METHOD__
 711                                 );
 712                                 $ids = array_map(
 713                                         function ( $o ) {
 714                                                 return $o->job_id;
 715                                         }, iterator_to_array( $res )
 716                                 );
 717                                 if ( count( $ids ) ) {
 718                                         // Reset job_token for these jobs so that other runners will pick them up.
 719                                         // Set the timestamp to the current time, as it is useful to now that the job
 720                                         // was already tried before (the timestamp becomes the "released" time).
 721                                         $dbw->update( 'job',
 722                                                 [
 723                                                         'job_token' => '',
 724                                                         'job_token_timestamp' => $dbw->timestamp( $now ) ], // time of release
 725                                                 [
 726                                                         'job_id' => $ids ],
 727                                                 __METHOD__
 728                                         );
 729                                         $affected = $dbw->affectedRows();
 730                                         $count += $affected;
 731                                         $this->incrStats( 'recycles', $this->type, $affected );
 732                                 }
 733                         }
 734
 735                         // Just destroy any stale jobs...
 736                         $pruneCutoff = $dbw->timestamp( $now - self::MAX_AGE_PRUNE );
 737                         $conds = [
 738                                 'job_cmd' => $this->type,
 739                                 "job_token != {$dbw->addQuotes( '' )}", // was acquired
 740                                 "job_token_timestamp < {$dbw->addQuotes( $pruneCutoff )}" // stale
 741                         ];
 742                         if ( $this->claimTTL > 0 ) { // only prune jobs attempted too many times...
 743                                 $conds[] = "job_attempts >= {$dbw->addQuotes( $this->maxTries )}";
 744                         }
 745                         // Get the IDs of jobs that are considered stale and should be removed. Selecting
 746                         // the IDs first means that the UPDATE can be done by primary key (less deadlocks).
 747                         $res = $dbw->select( 'job', 'job_id', $conds, __METHOD__ );
 748                         $ids = array_map(
 749                                 function ( $o ) {
 750                                         return $o->job_id;
 751                                 }, iterator_to_array( $res )
 752                         );
 753                         if ( count( $ids ) ) {
 754                                 $dbw->delete( 'job', [ 'job_id' => $ids ], __METHOD__ );
 755                                 $affected = $dbw->affectedRows();
 756                                 $count += $affected;
 757                                 $this->incrStats( 'abandons', $this->type, $affected );
 758                         }
 759
 760                         $dbw->unlock( "jobqueue-recycle-{$this->type}", __METHOD__ );
 761                 } catch ( DBError $e ) {
 762                         $this->throwDBException( $e );
 763                 }
 764
 765                 return $count;
 766         }
 767
 768         /**
 769          * @param IJobSpecification $job
 770          * @param IDatabase $db
 771          * @return array
 772          */
 773         protected function insertFields( IJobSpecification $job, IDatabase $db ) {
 774                 return [
 775                         // Fields that describe the nature of the job
 776                         'job_cmd' => $job->getType(),
 777                         'job_namespace' => $job->getTitle()->getNamespace(),
 778                         'job_title' => $job->getTitle()->getDBkey(),
 779                         'job_params' => self::makeBlob( $job->getParams() ),
 780                         // Additional job metadata
 781                         'job_timestamp' => $db->timestamp(),
 782                         'job_sha1' => Wikimedia\base_convert(
 783                                 sha1( serialize( $job->getDeduplicationInfo() ) ),
 784                                 16, 36, 31
 785                         ),
 786                         'job_random' => mt_rand( 0, self::MAX_JOB_RANDOM )
 787                 ];
 788         }
 789
 790         /**
 791          * @throws JobQueueConnectionError
 792          * @return IDatabase
 793          */
 794         protected function getReplicaDB() {
 795                 try {
 796                         return $this->getDB( DB_REPLICA );
 797                 } catch ( DBConnectionError $e ) {
 798                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 799                 }
 800         }
 801
 802         /**
 803          * @throws JobQueueConnectionError
 804          * @return IDatabase
 805          */
 806         protected function getMasterDB() {
 807                 try {
 808                         return $this->getDB( DB_MASTER );
 809                 } catch ( DBConnectionError $e ) {
 810                         throw new JobQueueConnectionError( "DBConnectionError:" . $e->getMessage() );
 811                 }
 812         }
 813
 814         /**
 815          * @param int $index (DB_REPLICA/DB_MASTER)
 816          * @return IDatabase
 817          */
 818         protected function getDB( $index ) {
 819                 if ( $this->server ) {
 820                         if ( $this->conn instanceof IDatabase ) {
 821                                 return $this->conn;
 822                         } elseif ( $this->conn instanceof DBError ) {
 823                                 throw $this->conn;
 824                         }
 825
 826                         try {
 827                                 $this->conn = Database::factory( $this->server['type'], $this->server );
 828                         } catch ( DBError $e ) {
 829                                 $this->conn = $e;
 830                                 throw $e;
 831                         }
 832
 833                         return $this->conn;
 834                 } else {
 835                         $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 836                         $lb = is_string( $this->cluster )
 837                                 ? $lbFactory->getExternalLB( $this->cluster )
 838                                 : $lbFactory->getMainLB( $this->domain );
 839
 840                         return ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' )
 841                                 // Keep a separate connection to avoid contention and deadlocks;
 842                                 // However, SQLite has the opposite behavior due to DB-level locking.
 843                                 ? $lb->getConnectionRef( $index, [], $this->domain, $lb::CONN_TRX_AUTOCOMMIT )
 844                                 // Jobs insertion will be defered until the PRESEND stage to reduce contention.
 845                                 : $lb->getConnectionRef( $index, [], $this->domain );
 846                 }
 847         }
 848
 849         /**
 850          * @param IDatabase $db
 851          * @return ScopedCallback
 852          */
 853         private function getScopedNoTrxFlag( IDatabase $db ) {
 854                 $autoTrx = $db->getFlag( DBO_TRX ); // get current setting
 855                 $db->clearFlag( DBO_TRX ); // make each query its own transaction
 856
 857                 return new ScopedCallback( function () use ( $db, $autoTrx ) {
 858                         if ( $autoTrx ) {
 859                                 $db->setFlag( DBO_TRX ); // restore old setting
 860                         }
 861                 } );
 862         }
 863
 864         /**
 865          * @param string $property
 866          * @return string
 867          */
 868         private function getCacheKey( $property ) {
 869                 $cluster = is_string( $this->cluster ) ? $this->cluster : 'main';
 870
 871                 return $this->cache->makeGlobalKey(
 872                         'jobqueue',
 873                         $this->domain,
 874                         $cluster,
 875                         $this->type,
 876                         $property
 877                 );
 878         }
 879
 880         /**
 881          * @param array|bool $params
 882          * @return string
 883          */
 884         protected static function makeBlob( $params ) {
 885                 if ( $params !== false ) {
 886                         return serialize( $params );
 887                 } else {
 888                         return '';
 889                 }
 890         }
 891
 892         /**
 893          * @param string $blob
 894          * @return bool|mixed
 895          */
 896         protected static function extractBlob( $blob ) {
 897                 if ( (string)$blob !== '' ) {
 898                         return unserialize( $blob );
 899                 } else {
 900                         return false;
 901                 }
 902         }
 903
 904         /**
 905          * @param DBError $e
 906          * @throws JobQueueError
 907          */
 908         protected function throwDBException( DBError $e ) {
 909                 throw new JobQueueError( get_class( $e ) . ": " . $e->getMessage() );
 910         }
 911
 912         /**
 913          * Return the list of job fields that should be selected.
 914          * @since 1.23
 915          * @return array
 916          */
 917         public static function selectFields() {
 918                 return [
 919                         'job_id',
 920                         'job_cmd',
 921                         'job_namespace',
 922                         'job_title',
 923                         'job_timestamp',
 924                         'job_params',
 925                         'job_random',
 926                         'job_attempts',
 927                         'job_token',
 928                         'job_token_timestamp',
 929                         'job_sha1',
 930                 ];
 931         }
 932 }