includes/jobqueue/JobQueue.php

   1 <?php
   2 /**
   3  * Job queue base 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  * @defgroup JobQueue JobQueue
  22  */
  23 use MediaWiki\MediaWikiServices;
  24
  25 /**
  26  * Class to handle enqueueing and running of background jobs
  27  *
  28  * @ingroup JobQueue
  29  * @since 1.21
  30  */
  31 abstract class JobQueue {
  32         /** @var string Wiki ID */
  33         protected $wiki;
  34         /** @var string Job type */
  35         protected $type;
  36         /** @var string Job priority for pop() */
  37         protected $order;
  38         /** @var int Time to live in seconds */
  39         protected $claimTTL;
  40         /** @var int Maximum number of times to try a job */
  41         protected $maxTries;
  42         /** @var string|bool Read only rationale (or false if r/w) */
  43         protected $readOnlyReason;
  44
  45         /** @var BagOStuff */
  46         protected $dupCache;
  47         /** @var JobQueueAggregator */
  48         protected $aggr;
  49
  50         const QOS_ATOMIC = 1; // integer; "all-or-nothing" job insertions
  51
  52         const ROOTJOB_TTL = 2419200; // integer; seconds to remember root jobs (28 days)
  53
  54         /**
  55          * @param array $params
  56          * @throws MWException
  57          */
  58         protected function __construct( array $params ) {
  59                 $this->wiki = $params['wiki'];
  60                 $this->type = $params['type'];
  61                 $this->claimTTL = $params['claimTTL'] ?? 0;
  62                 $this->maxTries = $params['maxTries'] ?? 3;
  63                 if ( isset( $params['order'] ) && $params['order'] !== 'any' ) {
  64                         $this->order = $params['order'];
  65                 } else {
  66                         $this->order = $this->optimalOrder();
  67                 }
  68                 if ( !in_array( $this->order, $this->supportedOrders() ) ) {
  69                         throw new MWException( __CLASS__ . " does not support '{$this->order}' order." );
  70                 }
  71                 $this->dupCache = wfGetCache( CACHE_ANYTHING );
  72                 $this->aggr = $params['aggregator'] ?? new JobQueueAggregatorNull( [] );
  73                 $this->readOnlyReason = $params['readOnlyReason'] ?? false;
  74         }
  75
  76         /**
  77          * Get a job queue object of the specified type.
  78          * $params includes:
  79          *   - class      : What job class to use (determines job type)
  80          *   - wiki       : wiki ID of the wiki the jobs are for (defaults to current wiki)
  81          *   - type       : The name of the job types this queue handles
  82          *   - order      : Order that pop() selects jobs, one of "fifo", "timestamp" or "random".
  83          *                  If "fifo" is used, the queue will effectively be FIFO. Note that job
  84          *                  completion will not appear to be exactly FIFO if there are multiple
  85          *                  job runners since jobs can take different times to finish once popped.
  86          *                  If "timestamp" is used, the queue will at least be loosely ordered
  87          *                  by timestamp, allowing for some jobs to be popped off out of order.
  88          *                  If "random" is used, pop() will pick jobs in random order.
  89          *                  Note that it may only be weakly random (e.g. a lottery of the oldest X).
  90          *                  If "any" is choosen, the queue will use whatever order is the fastest.
  91          *                  This might be useful for improving concurrency for job acquisition.
  92          *   - claimTTL   : If supported, the queue will recycle jobs that have been popped
  93          *                  but not acknowledged as completed after this many seconds. Recycling
  94          *                  of jobs simply means re-inserting them into the queue. Jobs can be
  95          *                  attempted up to three times before being discarded.
  96          *   - readOnlyReason : Set this to a string to make the queue read-only.
  97          *
  98          * Queue classes should throw an exception if they do not support the options given.
  99          *
 100          * @param array $params
 101          * @return JobQueue
 102          * @throws MWException
 103          */
 104         final public static function factory( array $params ) {
 105                 $class = $params['class'];
 106                 if ( !class_exists( $class ) ) {
 107                         throw new MWException( "Invalid job queue class '$class'." );
 108                 }
 109                 $obj = new $class( $params );
 110                 if ( !( $obj instanceof self ) ) {
 111                         throw new MWException( "Class '$class' is not a " . __CLASS__ . " class." );
 112                 }
 113
 114                 return $obj;
 115         }
 116
 117         /**
 118          * @return string Wiki ID
 119          */
 120         final public function getWiki() {
 121                 return $this->wiki;
 122         }
 123
 124         /**
 125          * @return string Job type that this queue handles
 126          */
 127         final public function getType() {
 128                 return $this->type;
 129         }
 130
 131         /**
 132          * @return string One of (random, timestamp, fifo, undefined)
 133          */
 134         final public function getOrder() {
 135                 return $this->order;
 136         }
 137
 138         /**
 139          * Get the allowed queue orders for configuration validation
 140          *
 141          * @return array Subset of (random, timestamp, fifo, undefined)
 142          */
 143         abstract protected function supportedOrders();
 144
 145         /**
 146          * Get the default queue order to use if configuration does not specify one
 147          *
 148          * @return string One of (random, timestamp, fifo, undefined)
 149          */
 150         abstract protected function optimalOrder();
 151
 152         /**
 153          * Find out if delayed jobs are supported for configuration validation
 154          *
 155          * @return bool Whether delayed jobs are supported
 156          */
 157         protected function supportsDelayedJobs() {
 158                 return false; // not implemented
 159         }
 160
 161         /**
 162          * @return bool Whether delayed jobs are enabled
 163          * @since 1.22
 164          */
 165         final public function delayedJobsEnabled() {
 166                 return $this->supportsDelayedJobs();
 167         }
 168
 169         /**
 170          * @return string|bool Read-only rational or false if r/w
 171          * @since 1.27
 172          */
 173         public function getReadOnlyReason() {
 174                 return $this->readOnlyReason;
 175         }
 176
 177         /**
 178          * Quickly check if the queue has no available (unacquired, non-delayed) jobs.
 179          * Queue classes should use caching if they are any slower without memcached.
 180          *
 181          * If caching is used, this might return false when there are actually no jobs.
 182          * If pop() is called and returns false then it should correct the cache. Also,
 183          * calling flushCaches() first prevents this. However, this affect is typically
 184          * not distinguishable from the race condition between isEmpty() and pop().
 185          *
 186          * @return bool
 187          * @throws JobQueueError
 188          */
 189         final public function isEmpty() {
 190                 $res = $this->doIsEmpty();
 191
 192                 return $res;
 193         }
 194
 195         /**
 196          * @see JobQueue::isEmpty()
 197          * @return bool
 198          */
 199         abstract protected function doIsEmpty();
 200
 201         /**
 202          * Get the number of available (unacquired, non-delayed) jobs in the queue.
 203          * Queue classes should use caching if they are any slower without memcached.
 204          *
 205          * If caching is used, this number might be out of date for a minute.
 206          *
 207          * @return int
 208          * @throws JobQueueError
 209          */
 210         final public function getSize() {
 211                 $res = $this->doGetSize();
 212
 213                 return $res;
 214         }
 215
 216         /**
 217          * @see JobQueue::getSize()
 218          * @return int
 219          */
 220         abstract protected function doGetSize();
 221
 222         /**
 223          * Get the number of acquired jobs (these are temporarily out of the queue).
 224          * Queue classes should use caching if they are any slower without memcached.
 225          *
 226          * If caching is used, this number might be out of date for a minute.
 227          *
 228          * @return int
 229          * @throws JobQueueError
 230          */
 231         final public function getAcquiredCount() {
 232                 $res = $this->doGetAcquiredCount();
 233
 234                 return $res;
 235         }
 236
 237         /**
 238          * @see JobQueue::getAcquiredCount()
 239          * @return int
 240          */
 241         abstract protected function doGetAcquiredCount();
 242
 243         /**
 244          * Get the number of delayed jobs (these are temporarily out of the queue).
 245          * Queue classes should use caching if they are any slower without memcached.
 246          *
 247          * If caching is used, this number might be out of date for a minute.
 248          *
 249          * @return int
 250          * @throws JobQueueError
 251          * @since 1.22
 252          */
 253         final public function getDelayedCount() {
 254                 $res = $this->doGetDelayedCount();
 255
 256                 return $res;
 257         }
 258
 259         /**
 260          * @see JobQueue::getDelayedCount()
 261          * @return int
 262          */
 263         protected function doGetDelayedCount() {
 264                 return 0; // not implemented
 265         }
 266
 267         /**
 268          * Get the number of acquired jobs that can no longer be attempted.
 269          * Queue classes should use caching if they are any slower without memcached.
 270          *
 271          * If caching is used, this number might be out of date for a minute.
 272          *
 273          * @return int
 274          * @throws JobQueueError
 275          */
 276         final public function getAbandonedCount() {
 277                 $res = $this->doGetAbandonedCount();
 278
 279                 return $res;
 280         }
 281
 282         /**
 283          * @see JobQueue::getAbandonedCount()
 284          * @return int
 285          */
 286         protected function doGetAbandonedCount() {
 287                 return 0; // not implemented
 288         }
 289
 290         /**
 291          * Push one or more jobs into the queue.
 292          * This does not require $wgJobClasses to be set for the given job type.
 293          * Outside callers should use JobQueueGroup::push() instead of this function.
 294          *
 295          * @param IJobSpecification|IJobSpecification[] $jobs
 296          * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
 297          * @return void
 298          * @throws JobQueueError
 299          */
 300         final public function push( $jobs, $flags = 0 ) {
 301                 $jobs = is_array( $jobs ) ? $jobs : [ $jobs ];
 302                 $this->batchPush( $jobs, $flags );
 303         }
 304
 305         /**
 306          * Push a batch of jobs into the queue.
 307          * This does not require $wgJobClasses to be set for the given job type.
 308          * Outside callers should use JobQueueGroup::push() instead of this function.
 309          *
 310          * @param IJobSpecification[] $jobs
 311          * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
 312          * @return void
 313          * @throws MWException
 314          */
 315         final public function batchPush( array $jobs, $flags = 0 ) {
 316                 $this->assertNotReadOnly();
 317
 318                 if ( !count( $jobs ) ) {
 319                         return; // nothing to do
 320                 }
 321
 322                 foreach ( $jobs as $job ) {
 323                         if ( $job->getType() !== $this->type ) {
 324                                 throw new MWException(
 325                                         "Got '{$job->getType()}' job; expected a '{$this->type}' job." );
 326                         } elseif ( $job->getReleaseTimestamp() && !$this->supportsDelayedJobs() ) {
 327                                 throw new MWException(
 328                                         "Got delayed '{$job->getType()}' job; delays are not supported." );
 329                         }
 330                 }
 331
 332                 $this->doBatchPush( $jobs, $flags );
 333                 $this->aggr->notifyQueueNonEmpty( $this->wiki, $this->type );
 334
 335                 foreach ( $jobs as $job ) {
 336                         if ( $job->isRootJob() ) {
 337                                 $this->deduplicateRootJob( $job );
 338                         }
 339                 }
 340         }
 341
 342         /**
 343          * @see JobQueue::batchPush()
 344          * @param IJobSpecification[] $jobs
 345          * @param int $flags
 346          */
 347         abstract protected function doBatchPush( array $jobs, $flags );
 348
 349         /**
 350          * Pop a job off of the queue.
 351          * This requires $wgJobClasses to be set for the given job type.
 352          * Outside callers should use JobQueueGroup::pop() instead of this function.
 353          *
 354          * @throws MWException
 355          * @return Job|bool Returns false if there are no jobs
 356          */
 357         final public function pop() {
 358                 global $wgJobClasses;
 359
 360                 $this->assertNotReadOnly();
 361                 if ( $this->wiki !== wfWikiID() ) {
 362                         throw new MWException( "Cannot pop '{$this->type}' job off foreign wiki queue." );
 363                 } elseif ( !isset( $wgJobClasses[$this->type] ) ) {
 364                         // Do not pop jobs if there is no class for the queue type
 365                         throw new MWException( "Unrecognized job type '{$this->type}'." );
 366                 }
 367
 368                 $job = $this->doPop();
 369
 370                 if ( !$job ) {
 371                         $this->aggr->notifyQueueEmpty( $this->wiki, $this->type );
 372                 }
 373
 374                 // Flag this job as an old duplicate based on its "root" job...
 375                 try {
 376                         if ( $job && $this->isRootJobOldDuplicate( $job ) ) {
 377                                 self::incrStats( 'dupe_pops', $this->type );
 378                                 $job = DuplicateJob::newFromJob( $job ); // convert to a no-op
 379                         }
 380                 } catch ( Exception $e ) {
 381                         // don't lose jobs over this
 382                 }
 383
 384                 return $job;
 385         }
 386
 387         /**
 388          * @see JobQueue::pop()
 389          * @return Job|bool
 390          */
 391         abstract protected function doPop();
 392
 393         /**
 394          * Acknowledge that a job was completed.
 395          *
 396          * This does nothing for certain queue classes or if "claimTTL" is not set.
 397          * Outside callers should use JobQueueGroup::ack() instead of this function.
 398          *
 399          * @param Job $job
 400          * @return void
 401          * @throws MWException
 402          */
 403         final public function ack( Job $job ) {
 404                 $this->assertNotReadOnly();
 405                 if ( $job->getType() !== $this->type ) {
 406                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 407                 }
 408
 409                 $this->doAck( $job );
 410         }
 411
 412         /**
 413          * @see JobQueue::ack()
 414          * @param Job $job
 415          */
 416         abstract protected function doAck( Job $job );
 417
 418         /**
 419          * Register the "root job" of a given job into the queue for de-duplication.
 420          * This should only be called right *after* all the new jobs have been inserted.
 421          * This is used to turn older, duplicate, job entries into no-ops. The root job
 422          * information will remain in the registry until it simply falls out of cache.
 423          *
 424          * This requires that $job has two special fields in the "params" array:
 425          *   - rootJobSignature : hash (e.g. SHA1) that identifies the task
 426          *   - rootJobTimestamp : TS_MW timestamp of this instance of the task
 427          *
 428          * A "root job" is a conceptual job that consist of potentially many smaller jobs
 429          * that are actually inserted into the queue. For example, "refreshLinks" jobs are
 430          * spawned when a template is edited. One can think of the task as "update links
 431          * of pages that use template X" and an instance of that task as a "root job".
 432          * However, what actually goes into the queue are range and leaf job subtypes.
 433          * Since these jobs include things like page ID ranges and DB master positions,
 434          * and can morph into smaller jobs recursively, simple duplicate detection
 435          * for individual jobs being identical (like that of job_sha1) is not useful.
 436          *
 437          * In the case of "refreshLinks", if these jobs are still in the queue when the template
 438          * is edited again, we want all of these old refreshLinks jobs for that template to become
 439          * no-ops. This can greatly reduce server load, since refreshLinks jobs involves parsing.
 440          * Essentially, the new batch of jobs belong to a new "root job" and the older ones to a
 441          * previous "root job" for the same task of "update links of pages that use template X".
 442          *
 443          * This does nothing for certain queue classes.
 444          *
 445          * @param IJobSpecification $job
 446          * @throws MWException
 447          * @return bool
 448          */
 449         final public function deduplicateRootJob( IJobSpecification $job ) {
 450                 $this->assertNotReadOnly();
 451                 if ( $job->getType() !== $this->type ) {
 452                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 453                 }
 454
 455                 return $this->doDeduplicateRootJob( $job );
 456         }
 457
 458         /**
 459          * @see JobQueue::deduplicateRootJob()
 460          * @param IJobSpecification $job
 461          * @throws MWException
 462          * @return bool
 463          */
 464         protected function doDeduplicateRootJob( IJobSpecification $job ) {
 465                 if ( !$job->hasRootJobParams() ) {
 466                         throw new MWException( "Cannot register root job; missing parameters." );
 467                 }
 468                 $params = $job->getRootJobParams();
 469
 470                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 471                 // Callers should call JobQueueGroup::push() before this method so that if the insert
 472                 // fails, the de-duplication registration will be aborted. Since the insert is
 473                 // deferred till "transaction idle", do the same here, so that the ordering is
 474                 // maintained. Having only the de-duplication registration succeed would cause
 475                 // jobs to become no-ops without any actual jobs that made them redundant.
 476                 $timestamp = $this->dupCache->get( $key ); // current last timestamp of this job
 477                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 478                         return true; // a newer version of this root job was enqueued
 479                 }
 480
 481                 // Update the timestamp of the last root job started at the location...
 482                 return $this->dupCache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 483         }
 484
 485         /**
 486          * Check if the "root" job of a given job has been superseded by a newer one
 487          *
 488          * @param Job $job
 489          * @throws MWException
 490          * @return bool
 491          */
 492         final protected function isRootJobOldDuplicate( Job $job ) {
 493                 if ( $job->getType() !== $this->type ) {
 494                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 495                 }
 496                 $isDuplicate = $this->doIsRootJobOldDuplicate( $job );
 497
 498                 return $isDuplicate;
 499         }
 500
 501         /**
 502          * @see JobQueue::isRootJobOldDuplicate()
 503          * @param Job $job
 504          * @return bool
 505          */
 506         protected function doIsRootJobOldDuplicate( Job $job ) {
 507                 if ( !$job->hasRootJobParams() ) {
 508                         return false; // job has no de-deplication info
 509                 }
 510                 $params = $job->getRootJobParams();
 511
 512                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 513                 // Get the last time this root job was enqueued
 514                 $timestamp = $this->dupCache->get( $key );
 515
 516                 // Check if a new root job was started at the location after this one's...
 517                 return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
 518         }
 519
 520         /**
 521          * @param string $signature Hash identifier of the root job
 522          * @return string
 523          */
 524         protected function getRootJobCacheKey( $signature ) {
 525                 list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
 526
 527                 return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, 'rootjob', $signature );
 528         }
 529
 530         /**
 531          * Deleted all unclaimed and delayed jobs from the queue
 532          *
 533          * @throws JobQueueError
 534          * @since 1.22
 535          * @return void
 536          */
 537         final public function delete() {
 538                 $this->assertNotReadOnly();
 539
 540                 $this->doDelete();
 541         }
 542
 543         /**
 544          * @see JobQueue::delete()
 545          * @throws MWException
 546          */
 547         protected function doDelete() {
 548                 throw new MWException( "This method is not implemented." );
 549         }
 550
 551         /**
 552          * Wait for any replica DBs or backup servers to catch up.
 553          *
 554          * This does nothing for certain queue classes.
 555          *
 556          * @return void
 557          * @throws JobQueueError
 558          */
 559         final public function waitForBackups() {
 560                 $this->doWaitForBackups();
 561         }
 562
 563         /**
 564          * @see JobQueue::waitForBackups()
 565          * @return void
 566          */
 567         protected function doWaitForBackups() {
 568         }
 569
 570         /**
 571          * Clear any process and persistent caches
 572          *
 573          * @return void
 574          */
 575         final public function flushCaches() {
 576                 $this->doFlushCaches();
 577         }
 578
 579         /**
 580          * @see JobQueue::flushCaches()
 581          * @return void
 582          */
 583         protected function doFlushCaches() {
 584         }
 585
 586         /**
 587          * Get an iterator to traverse over all available jobs in this queue.
 588          * This does not include jobs that are currently acquired or delayed.
 589          * Note: results may be stale if the queue is concurrently modified.
 590          *
 591          * @return Iterator
 592          * @throws JobQueueError
 593          */
 594         abstract public function getAllQueuedJobs();
 595
 596         /**
 597          * Get an iterator to traverse over all delayed jobs in this queue.
 598          * Note: results may be stale if the queue is concurrently modified.
 599          *
 600          * @return Iterator
 601          * @throws JobQueueError
 602          * @since 1.22
 603          */
 604         public function getAllDelayedJobs() {
 605                 return new ArrayIterator( [] ); // not implemented
 606         }
 607
 608         /**
 609          * Get an iterator to traverse over all claimed jobs in this queue
 610          *
 611          * Callers should be quick to iterator over it or few results
 612          * will be returned due to jobs being acknowledged and deleted
 613          *
 614          * @return Iterator
 615          * @throws JobQueueError
 616          * @since 1.26
 617          */
 618         public function getAllAcquiredJobs() {
 619                 return new ArrayIterator( [] ); // not implemented
 620         }
 621
 622         /**
 623          * Get an iterator to traverse over all abandoned jobs in this queue
 624          *
 625          * @return Iterator
 626          * @throws JobQueueError
 627          * @since 1.25
 628          */
 629         public function getAllAbandonedJobs() {
 630                 return new ArrayIterator( [] ); // not implemented
 631         }
 632
 633         /**
 634          * Do not use this function outside of JobQueue/JobQueueGroup
 635          *
 636          * @return string
 637          * @since 1.22
 638          */
 639         public function getCoalesceLocationInternal() {
 640                 return null;
 641         }
 642
 643         /**
 644          * Check whether each of the given queues are empty.
 645          * This is used for batching checks for queues stored at the same place.
 646          *
 647          * @param array $types List of queues types
 648          * @return array|null (list of non-empty queue types) or null if unsupported
 649          * @throws MWException
 650          * @since 1.22
 651          */
 652         final public function getSiblingQueuesWithJobs( array $types ) {
 653                 return $this->doGetSiblingQueuesWithJobs( $types );
 654         }
 655
 656         /**
 657          * @see JobQueue::getSiblingQueuesWithJobs()
 658          * @param array $types List of queues types
 659          * @return array|null (list of queue types) or null if unsupported
 660          */
 661         protected function doGetSiblingQueuesWithJobs( array $types ) {
 662                 return null; // not supported
 663         }
 664
 665         /**
 666          * Check the size of each of the given queues.
 667          * For queues not served by the same store as this one, 0 is returned.
 668          * This is used for batching checks for queues stored at the same place.
 669          *
 670          * @param array $types List of queues types
 671          * @return array|null (job type => whether queue is empty) or null if unsupported
 672          * @throws MWException
 673          * @since 1.22
 674          */
 675         final public function getSiblingQueueSizes( array $types ) {
 676                 return $this->doGetSiblingQueueSizes( $types );
 677         }
 678
 679         /**
 680          * @see JobQueue::getSiblingQueuesSize()
 681          * @param array $types List of queues types
 682          * @return array|null (list of queue types) or null if unsupported
 683          */
 684         protected function doGetSiblingQueueSizes( array $types ) {
 685                 return null; // not supported
 686         }
 687
 688         /**
 689          * @throws JobQueueReadOnlyError
 690          */
 691         protected function assertNotReadOnly() {
 692                 if ( $this->readOnlyReason !== false ) {
 693                         throw new JobQueueReadOnlyError( "Job queue is read-only: {$this->readOnlyReason}" );
 694                 }
 695         }
 696
 697         /**
 698          * Call wfIncrStats() for the queue overall and for the queue type
 699          *
 700          * @param string $key Event type
 701          * @param string $type Job type
 702          * @param int $delta
 703          * @since 1.22
 704          */
 705         public static function incrStats( $key, $type, $delta = 1 ) {
 706                 static $stats;
 707                 if ( !$stats ) {
 708                         $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
 709                 }
 710                 $stats->updateCount( "jobqueue.{$key}.all", $delta );
 711                 $stats->updateCount( "jobqueue.{$key}.{$type}", $delta );
 712         }
 713 }
 714
 715 /**
 716  * @ingroup JobQueue
 717  * @since 1.22
 718  */
 719 class JobQueueError extends MWException {
 720 }
 721
 722 class JobQueueConnectionError extends JobQueueError {
 723 }
 724
 725 class JobQueueReadOnlyError extends JobQueueError {
 726
 727 }