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 $domain;
  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->domain = $params['domain'] ?? $params['wiki']; // b/c
  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 getDomain() {
 121                 return $this->domain;
 122         }
 123
 124         /**
 125          * @return string Wiki ID
 126          * @deprecated 1.33
 127          */
 128         final public function getWiki() {
 129                 return $this->domain;
 130         }
 131
 132         /**
 133          * @return string Job type that this queue handles
 134          */
 135         final public function getType() {
 136                 return $this->type;
 137         }
 138
 139         /**
 140          * @return string One of (random, timestamp, fifo, undefined)
 141          */
 142         final public function getOrder() {
 143                 return $this->order;
 144         }
 145
 146         /**
 147          * Get the allowed queue orders for configuration validation
 148          *
 149          * @return array Subset of (random, timestamp, fifo, undefined)
 150          */
 151         abstract protected function supportedOrders();
 152
 153         /**
 154          * Get the default queue order to use if configuration does not specify one
 155          *
 156          * @return string One of (random, timestamp, fifo, undefined)
 157          */
 158         abstract protected function optimalOrder();
 159
 160         /**
 161          * Find out if delayed jobs are supported for configuration validation
 162          *
 163          * @return bool Whether delayed jobs are supported
 164          */
 165         protected function supportsDelayedJobs() {
 166                 return false; // not implemented
 167         }
 168
 169         /**
 170          * @return bool Whether delayed jobs are enabled
 171          * @since 1.22
 172          */
 173         final public function delayedJobsEnabled() {
 174                 return $this->supportsDelayedJobs();
 175         }
 176
 177         /**
 178          * @return string|bool Read-only rational or false if r/w
 179          * @since 1.27
 180          */
 181         public function getReadOnlyReason() {
 182                 return $this->readOnlyReason;
 183         }
 184
 185         /**
 186          * Quickly check if the queue has no available (unacquired, non-delayed) jobs.
 187          * Queue classes should use caching if they are any slower without memcached.
 188          *
 189          * If caching is used, this might return false when there are actually no jobs.
 190          * If pop() is called and returns false then it should correct the cache. Also,
 191          * calling flushCaches() first prevents this. However, this affect is typically
 192          * not distinguishable from the race condition between isEmpty() and pop().
 193          *
 194          * @return bool
 195          * @throws JobQueueError
 196          */
 197         final public function isEmpty() {
 198                 $res = $this->doIsEmpty();
 199
 200                 return $res;
 201         }
 202
 203         /**
 204          * @see JobQueue::isEmpty()
 205          * @return bool
 206          */
 207         abstract protected function doIsEmpty();
 208
 209         /**
 210          * Get the number of available (unacquired, non-delayed) jobs in the queue.
 211          * Queue classes should use caching if they are any slower without memcached.
 212          *
 213          * If caching is used, this number might be out of date for a minute.
 214          *
 215          * @return int
 216          * @throws JobQueueError
 217          */
 218         final public function getSize() {
 219                 $res = $this->doGetSize();
 220
 221                 return $res;
 222         }
 223
 224         /**
 225          * @see JobQueue::getSize()
 226          * @return int
 227          */
 228         abstract protected function doGetSize();
 229
 230         /**
 231          * Get the number of acquired jobs (these are temporarily out of the queue).
 232          * Queue classes should use caching if they are any slower without memcached.
 233          *
 234          * If caching is used, this number might be out of date for a minute.
 235          *
 236          * @return int
 237          * @throws JobQueueError
 238          */
 239         final public function getAcquiredCount() {
 240                 $res = $this->doGetAcquiredCount();
 241
 242                 return $res;
 243         }
 244
 245         /**
 246          * @see JobQueue::getAcquiredCount()
 247          * @return int
 248          */
 249         abstract protected function doGetAcquiredCount();
 250
 251         /**
 252          * Get the number of delayed jobs (these are temporarily out of the queue).
 253          * Queue classes should use caching if they are any slower without memcached.
 254          *
 255          * If caching is used, this number might be out of date for a minute.
 256          *
 257          * @return int
 258          * @throws JobQueueError
 259          * @since 1.22
 260          */
 261         final public function getDelayedCount() {
 262                 $res = $this->doGetDelayedCount();
 263
 264                 return $res;
 265         }
 266
 267         /**
 268          * @see JobQueue::getDelayedCount()
 269          * @return int
 270          */
 271         protected function doGetDelayedCount() {
 272                 return 0; // not implemented
 273         }
 274
 275         /**
 276          * Get the number of acquired jobs that can no longer be attempted.
 277          * Queue classes should use caching if they are any slower without memcached.
 278          *
 279          * If caching is used, this number might be out of date for a minute.
 280          *
 281          * @return int
 282          * @throws JobQueueError
 283          */
 284         final public function getAbandonedCount() {
 285                 $res = $this->doGetAbandonedCount();
 286
 287                 return $res;
 288         }
 289
 290         /**
 291          * @see JobQueue::getAbandonedCount()
 292          * @return int
 293          */
 294         protected function doGetAbandonedCount() {
 295                 return 0; // not implemented
 296         }
 297
 298         /**
 299          * Push one or more jobs into the queue.
 300          * This does not require $wgJobClasses to be set for the given job type.
 301          * Outside callers should use JobQueueGroup::push() instead of this function.
 302          *
 303          * @param IJobSpecification|IJobSpecification[] $jobs
 304          * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
 305          * @return void
 306          * @throws JobQueueError
 307          */
 308         final public function push( $jobs, $flags = 0 ) {
 309                 $jobs = is_array( $jobs ) ? $jobs : [ $jobs ];
 310                 $this->batchPush( $jobs, $flags );
 311         }
 312
 313         /**
 314          * Push a batch of jobs into the queue.
 315          * This does not require $wgJobClasses to be set for the given job type.
 316          * Outside callers should use JobQueueGroup::push() instead of this function.
 317          *
 318          * @param IJobSpecification[] $jobs
 319          * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
 320          * @return void
 321          * @throws MWException
 322          */
 323         final public function batchPush( array $jobs, $flags = 0 ) {
 324                 $this->assertNotReadOnly();
 325
 326                 if ( $jobs === [] ) {
 327                         return; // nothing to do
 328                 }
 329
 330                 foreach ( $jobs as $job ) {
 331                         if ( $job->getType() !== $this->type ) {
 332                                 throw new MWException(
 333                                         "Got '{$job->getType()}' job; expected a '{$this->type}' job." );
 334                         } elseif ( $job->getReleaseTimestamp() && !$this->supportsDelayedJobs() ) {
 335                                 throw new MWException(
 336                                         "Got delayed '{$job->getType()}' job; delays are not supported." );
 337                         }
 338                 }
 339
 340                 $this->doBatchPush( $jobs, $flags );
 341                 $this->aggr->notifyQueueNonEmpty( $this->domain, $this->type );
 342
 343                 foreach ( $jobs as $job ) {
 344                         if ( $job->isRootJob() ) {
 345                                 $this->deduplicateRootJob( $job );
 346                         }
 347                 }
 348         }
 349
 350         /**
 351          * @see JobQueue::batchPush()
 352          * @param IJobSpecification[] $jobs
 353          * @param int $flags
 354          */
 355         abstract protected function doBatchPush( array $jobs, $flags );
 356
 357         /**
 358          * Pop a job off of the queue.
 359          * This requires $wgJobClasses to be set for the given job type.
 360          * Outside callers should use JobQueueGroup::pop() instead of this function.
 361          *
 362          * @throws MWException
 363          * @return Job|bool Returns false if there are no jobs
 364          */
 365         final public function pop() {
 366                 global $wgJobClasses;
 367
 368                 $this->assertNotReadOnly();
 369                 if ( !WikiMap::isCurrentWikiDbDomain( $this->domain ) ) {
 370                         throw new MWException(
 371                                 "Cannot pop '{$this->type}' job off foreign '{$this->domain}' wiki queue." );
 372                 } elseif ( !isset( $wgJobClasses[$this->type] ) ) {
 373                         // Do not pop jobs if there is no class for the queue type
 374                         throw new MWException( "Unrecognized job type '{$this->type}'." );
 375                 }
 376
 377                 $job = $this->doPop();
 378
 379                 if ( !$job ) {
 380                         $this->aggr->notifyQueueEmpty( $this->domain, $this->type );
 381                 }
 382
 383                 // Flag this job as an old duplicate based on its "root" job...
 384                 try {
 385                         if ( $job && $this->isRootJobOldDuplicate( $job ) ) {
 386                                 self::incrStats( 'dupe_pops', $this->type );
 387                                 $job = DuplicateJob::newFromJob( $job ); // convert to a no-op
 388                         }
 389                 } catch ( Exception $e ) {
 390                         // don't lose jobs over this
 391                 }
 392
 393                 return $job;
 394         }
 395
 396         /**
 397          * @see JobQueue::pop()
 398          * @return Job|bool
 399          */
 400         abstract protected function doPop();
 401
 402         /**
 403          * Acknowledge that a job was completed.
 404          *
 405          * This does nothing for certain queue classes or if "claimTTL" is not set.
 406          * Outside callers should use JobQueueGroup::ack() instead of this function.
 407          *
 408          * @param Job $job
 409          * @return void
 410          * @throws MWException
 411          */
 412         final public function ack( Job $job ) {
 413                 $this->assertNotReadOnly();
 414                 if ( $job->getType() !== $this->type ) {
 415                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 416                 }
 417
 418                 $this->doAck( $job );
 419         }
 420
 421         /**
 422          * @see JobQueue::ack()
 423          * @param Job $job
 424          */
 425         abstract protected function doAck( Job $job );
 426
 427         /**
 428          * Register the "root job" of a given job into the queue for de-duplication.
 429          * This should only be called right *after* all the new jobs have been inserted.
 430          * This is used to turn older, duplicate, job entries into no-ops. The root job
 431          * information will remain in the registry until it simply falls out of cache.
 432          *
 433          * This requires that $job has two special fields in the "params" array:
 434          *   - rootJobSignature : hash (e.g. SHA1) that identifies the task
 435          *   - rootJobTimestamp : TS_MW timestamp of this instance of the task
 436          *
 437          * A "root job" is a conceptual job that consist of potentially many smaller jobs
 438          * that are actually inserted into the queue. For example, "refreshLinks" jobs are
 439          * spawned when a template is edited. One can think of the task as "update links
 440          * of pages that use template X" and an instance of that task as a "root job".
 441          * However, what actually goes into the queue are range and leaf job subtypes.
 442          * Since these jobs include things like page ID ranges and DB master positions,
 443          * and can morph into smaller jobs recursively, simple duplicate detection
 444          * for individual jobs being identical (like that of job_sha1) is not useful.
 445          *
 446          * In the case of "refreshLinks", if these jobs are still in the queue when the template
 447          * is edited again, we want all of these old refreshLinks jobs for that template to become
 448          * no-ops. This can greatly reduce server load, since refreshLinks jobs involves parsing.
 449          * Essentially, the new batch of jobs belong to a new "root job" and the older ones to a
 450          * previous "root job" for the same task of "update links of pages that use template X".
 451          *
 452          * This does nothing for certain queue classes.
 453          *
 454          * @param IJobSpecification $job
 455          * @throws MWException
 456          * @return bool
 457          */
 458         final public function deduplicateRootJob( IJobSpecification $job ) {
 459                 $this->assertNotReadOnly();
 460                 if ( $job->getType() !== $this->type ) {
 461                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 462                 }
 463
 464                 return $this->doDeduplicateRootJob( $job );
 465         }
 466
 467         /**
 468          * @see JobQueue::deduplicateRootJob()
 469          * @param IJobSpecification $job
 470          * @throws MWException
 471          * @return bool
 472          */
 473         protected function doDeduplicateRootJob( IJobSpecification $job ) {
 474                 if ( !$job->hasRootJobParams() ) {
 475                         throw new MWException( "Cannot register root job; missing parameters." );
 476                 }
 477                 $params = $job->getRootJobParams();
 478
 479                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 480                 // Callers should call JobQueueGroup::push() before this method so that if the insert
 481                 // fails, the de-duplication registration will be aborted. Since the insert is
 482                 // deferred till "transaction idle", do the same here, so that the ordering is
 483                 // maintained. Having only the de-duplication registration succeed would cause
 484                 // jobs to become no-ops without any actual jobs that made them redundant.
 485                 $timestamp = $this->dupCache->get( $key ); // current last timestamp of this job
 486                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 487                         return true; // a newer version of this root job was enqueued
 488                 }
 489
 490                 // Update the timestamp of the last root job started at the location...
 491                 return $this->dupCache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 492         }
 493
 494         /**
 495          * Check if the "root" job of a given job has been superseded by a newer one
 496          *
 497          * @param Job $job
 498          * @throws MWException
 499          * @return bool
 500          */
 501         final protected function isRootJobOldDuplicate( Job $job ) {
 502                 if ( $job->getType() !== $this->type ) {
 503                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 504                 }
 505                 $isDuplicate = $this->doIsRootJobOldDuplicate( $job );
 506
 507                 return $isDuplicate;
 508         }
 509
 510         /**
 511          * @see JobQueue::isRootJobOldDuplicate()
 512          * @param Job $job
 513          * @return bool
 514          */
 515         protected function doIsRootJobOldDuplicate( Job $job ) {
 516                 if ( !$job->hasRootJobParams() ) {
 517                         return false; // job has no de-deplication info
 518                 }
 519                 $params = $job->getRootJobParams();
 520
 521                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 522                 // Get the last time this root job was enqueued
 523                 $timestamp = $this->dupCache->get( $key );
 524
 525                 // Check if a new root job was started at the location after this one's...
 526                 return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
 527         }
 528
 529         /**
 530          * @param string $signature Hash identifier of the root job
 531          * @return string
 532          */
 533         protected function getRootJobCacheKey( $signature ) {
 534                 return $this->dupCache->makeGlobalKey(
 535                         'jobqueue',
 536                         $this->domain,
 537                         $this->type,
 538                         'rootjob',
 539                         $signature
 540                 );
 541         }
 542
 543         /**
 544          * Deleted all unclaimed and delayed jobs from the queue
 545          *
 546          * @throws JobQueueError
 547          * @since 1.22
 548          * @return void
 549          */
 550         final public function delete() {
 551                 $this->assertNotReadOnly();
 552
 553                 $this->doDelete();
 554         }
 555
 556         /**
 557          * @see JobQueue::delete()
 558          * @throws MWException
 559          */
 560         protected function doDelete() {
 561                 throw new MWException( "This method is not implemented." );
 562         }
 563
 564         /**
 565          * Wait for any replica DBs or backup servers to catch up.
 566          *
 567          * This does nothing for certain queue classes.
 568          *
 569          * @return void
 570          * @throws JobQueueError
 571          */
 572         final public function waitForBackups() {
 573                 $this->doWaitForBackups();
 574         }
 575
 576         /**
 577          * @see JobQueue::waitForBackups()
 578          * @return void
 579          */
 580         protected function doWaitForBackups() {
 581         }
 582
 583         /**
 584          * Clear any process and persistent caches
 585          *
 586          * @return void
 587          */
 588         final public function flushCaches() {
 589                 $this->doFlushCaches();
 590         }
 591
 592         /**
 593          * @see JobQueue::flushCaches()
 594          * @return void
 595          */
 596         protected function doFlushCaches() {
 597         }
 598
 599         /**
 600          * Get an iterator to traverse over all available jobs in this queue.
 601          * This does not include jobs that are currently acquired or delayed.
 602          * Note: results may be stale if the queue is concurrently modified.
 603          *
 604          * @return Iterator
 605          * @throws JobQueueError
 606          */
 607         abstract public function getAllQueuedJobs();
 608
 609         /**
 610          * Get an iterator to traverse over all delayed jobs in this queue.
 611          * Note: results may be stale if the queue is concurrently modified.
 612          *
 613          * @return Iterator
 614          * @throws JobQueueError
 615          * @since 1.22
 616          */
 617         public function getAllDelayedJobs() {
 618                 return new ArrayIterator( [] ); // not implemented
 619         }
 620
 621         /**
 622          * Get an iterator to traverse over all claimed jobs in this queue
 623          *
 624          * Callers should be quick to iterator over it or few results
 625          * will be returned due to jobs being acknowledged and deleted
 626          *
 627          * @return Iterator
 628          * @throws JobQueueError
 629          * @since 1.26
 630          */
 631         public function getAllAcquiredJobs() {
 632                 return new ArrayIterator( [] ); // not implemented
 633         }
 634
 635         /**
 636          * Get an iterator to traverse over all abandoned jobs in this queue
 637          *
 638          * @return Iterator
 639          * @throws JobQueueError
 640          * @since 1.25
 641          */
 642         public function getAllAbandonedJobs() {
 643                 return new ArrayIterator( [] ); // not implemented
 644         }
 645
 646         /**
 647          * Do not use this function outside of JobQueue/JobQueueGroup
 648          *
 649          * @return string
 650          * @since 1.22
 651          */
 652         public function getCoalesceLocationInternal() {
 653                 return null;
 654         }
 655
 656         /**
 657          * Check whether each of the given queues are empty.
 658          * This is used for batching checks for queues stored at the same place.
 659          *
 660          * @param array $types List of queues types
 661          * @return array|null (list of non-empty queue types) or null if unsupported
 662          * @throws MWException
 663          * @since 1.22
 664          */
 665         final public function getSiblingQueuesWithJobs( array $types ) {
 666                 return $this->doGetSiblingQueuesWithJobs( $types );
 667         }
 668
 669         /**
 670          * @see JobQueue::getSiblingQueuesWithJobs()
 671          * @param array $types List of queues types
 672          * @return array|null (list of queue types) or null if unsupported
 673          */
 674         protected function doGetSiblingQueuesWithJobs( array $types ) {
 675                 return null; // not supported
 676         }
 677
 678         /**
 679          * Check the size of each of the given queues.
 680          * For queues not served by the same store as this one, 0 is returned.
 681          * This is used for batching checks for queues stored at the same place.
 682          *
 683          * @param array $types List of queues types
 684          * @return array|null (job type => whether queue is empty) or null if unsupported
 685          * @throws MWException
 686          * @since 1.22
 687          */
 688         final public function getSiblingQueueSizes( array $types ) {
 689                 return $this->doGetSiblingQueueSizes( $types );
 690         }
 691
 692         /**
 693          * @see JobQueue::getSiblingQueuesSize()
 694          * @param array $types List of queues types
 695          * @return array|null (list of queue types) or null if unsupported
 696          */
 697         protected function doGetSiblingQueueSizes( array $types ) {
 698                 return null; // not supported
 699         }
 700
 701         /**
 702          * @throws JobQueueReadOnlyError
 703          */
 704         protected function assertNotReadOnly() {
 705                 if ( $this->readOnlyReason !== false ) {
 706                         throw new JobQueueReadOnlyError( "Job queue is read-only: {$this->readOnlyReason}" );
 707                 }
 708         }
 709
 710         /**
 711          * Call wfIncrStats() for the queue overall and for the queue type
 712          *
 713          * @param string $key Event type
 714          * @param string $type Job type
 715          * @param int $delta
 716          * @since 1.22
 717          */
 718         public static function incrStats( $key, $type, $delta = 1 ) {
 719                 static $stats;
 720                 if ( !$stats ) {
 721                         $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
 722                 }
 723                 $stats->updateCount( "jobqueue.{$key}.all", $delta );
 724                 $stats->updateCount( "jobqueue.{$key}.{$type}", $delta );
 725         }
 726 }
 727
 728 /**
 729  * @ingroup JobQueue
 730  * @since 1.22
 731  */
 732 class JobQueueError extends MWException {
 733 }
 734
 735 class JobQueueConnectionError extends JobQueueError {
 736 }
 737
 738 class JobQueueReadOnlyError extends JobQueueError {
 739
 740 }