includes/job/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  * @author Aaron Schulz
  23  */
  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
  35         /** @var string Job type */
  36         protected $type;
  37
  38         /** @var string Job priority for pop() */
  39         protected $order;
  40
  41         /** @var int Time to live in seconds */
  42         protected $claimTTL;
  43
  44         /** @var int Maximum number of times to try a job */
  45         protected $maxTries;
  46
  47         /** @var bool Allow delayed jobs */
  48         protected $checkDelay;
  49
  50         /** @var BagOStuff */
  51         protected $dupCache;
  52
  53         const QOS_ATOMIC = 1; // integer; "all-or-nothing" job insertions
  54
  55         const ROOTJOB_TTL = 2419200; // integer; seconds to remember root jobs (28 days)
  56
  57         /**
  58          * @param array $params
  59          * @throws MWException
  60          */
  61         protected function __construct( array $params ) {
  62                 $this->wiki = $params['wiki'];
  63                 $this->type = $params['type'];
  64                 $this->claimTTL = isset( $params['claimTTL'] ) ? $params['claimTTL'] : 0;
  65                 $this->maxTries = isset( $params['maxTries'] ) ? $params['maxTries'] : 3;
  66                 if ( isset( $params['order'] ) && $params['order'] !== 'any' ) {
  67                         $this->order = $params['order'];
  68                 } else {
  69                         $this->order = $this->optimalOrder();
  70                 }
  71                 if ( !in_array( $this->order, $this->supportedOrders() ) ) {
  72                         throw new MWException( __CLASS__ . " does not support '{$this->order}' order." );
  73                 }
  74                 $this->checkDelay = !empty( $params['checkDelay'] );
  75                 if ( $this->checkDelay && !$this->supportsDelayedJobs() ) {
  76                         throw new MWException( __CLASS__ . " does not support delayed jobs." );
  77                 }
  78                 $this->dupCache = wfGetCache( CACHE_ANYTHING );
  79         }
  80
  81         /**
  82          * Get a job queue object of the specified type.
  83          * $params includes:
  84          *   - class      : What job class to use (determines job type)
  85          *   - wiki       : wiki ID of the wiki the jobs are for (defaults to current wiki)
  86          *   - type       : The name of the job types this queue handles
  87          *   - order      : Order that pop() selects jobs, one of "fifo", "timestamp" or "random".
  88          *                  If "fifo" is used, the queue will effectively be FIFO. Note that job
  89          *                  completion will not appear to be exactly FIFO if there are multiple
  90          *                  job runners since jobs can take different times to finish once popped.
  91          *                  If "timestamp" is used, the queue will at least be loosely ordered
  92          *                  by timestamp, allowing for some jobs to be popped off out of order.
  93          *                  If "random" is used, pop() will pick jobs in random order.
  94          *                  Note that it may only be weakly random (e.g. a lottery of the oldest X).
  95          *                  If "any" is choosen, the queue will use whatever order is the fastest.
  96          *                  This might be useful for improving concurrency for job acquisition.
  97          *   - claimTTL   : If supported, the queue will recycle jobs that have been popped
  98          *                  but not acknowledged as completed after this many seconds. Recycling
  99          *                  of jobs simple means re-inserting them into the queue. Jobs can be
 100          *                  attempted up to three times before being discarded.
 101          *   - checkDelay : If supported, respect Job::getReleaseTimestamp() in the push functions.
 102          *                  This lets delayed jobs wait in a staging area until a given timestamp is
 103          *                  reached, at which point they will enter the queue. If this is not enabled
 104          *                  or not supported, an exception will be thrown on delayed job insertion.
 105          *
 106          * Queue classes should throw an exception if they do not support the options given.
 107          *
 108          * @param array $params
 109          * @return JobQueue
 110          * @throws MWException
 111          */
 112         final public static function factory( array $params ) {
 113                 $class = $params['class'];
 114                 if ( !class_exists( $class ) ) {
 115                         throw new MWException( "Invalid job queue class '$class'." );
 116                 }
 117                 $obj = new $class( $params );
 118                 if ( !( $obj instanceof self ) ) {
 119                         throw new MWException( "Class '$class' is not a " . __CLASS__ . " class." );
 120                 }
 121
 122                 return $obj;
 123         }
 124
 125         /**
 126          * @return string Wiki ID
 127          */
 128         final public function getWiki() {
 129                 return $this->wiki;
 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          * @return bool Whether delayed jobs are enabled
 148          * @since 1.22
 149          */
 150         final public function delayedJobsEnabled() {
 151                 return $this->checkDelay;
 152         }
 153
 154         /**
 155          * Get the allowed queue orders for configuration validation
 156          *
 157          * @return array Subset of (random, timestamp, fifo, undefined)
 158          */
 159         abstract protected function supportedOrders();
 160
 161         /**
 162          * Get the default queue order to use if configuration does not specify one
 163          *
 164          * @return string One of (random, timestamp, fifo, undefined)
 165          */
 166         abstract protected function optimalOrder();
 167
 168         /**
 169          * Find out if delayed jobs are supported for configuration validation
 170          *
 171          * @return bool Whether delayed jobs are supported
 172          */
 173         protected function supportsDelayedJobs() {
 174                 return false; // not implemented
 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                 wfProfileIn( __METHOD__ );
 191                 $res = $this->doIsEmpty();
 192                 wfProfileOut( __METHOD__ );
 193
 194                 return $res;
 195         }
 196
 197         /**
 198          * @see JobQueue::isEmpty()
 199          * @return bool
 200          */
 201         abstract protected function doIsEmpty();
 202
 203         /**
 204          * Get the number of available (unacquired, non-delayed) jobs in the queue.
 205          * Queue classes should use caching if they are any slower without memcached.
 206          *
 207          * If caching is used, this number might be out of date for a minute.
 208          *
 209          * @return int
 210          * @throws JobQueueError
 211          */
 212         final public function getSize() {
 213                 wfProfileIn( __METHOD__ );
 214                 $res = $this->doGetSize();
 215                 wfProfileOut( __METHOD__ );
 216
 217                 return $res;
 218         }
 219
 220         /**
 221          * @see JobQueue::getSize()
 222          * @return int
 223          */
 224         abstract protected function doGetSize();
 225
 226         /**
 227          * Get the number of acquired jobs (these are temporarily out of the queue).
 228          * Queue classes should use caching if they are any slower without memcached.
 229          *
 230          * If caching is used, this number might be out of date for a minute.
 231          *
 232          * @return int
 233          * @throws JobQueueError
 234          */
 235         final public function getAcquiredCount() {
 236                 wfProfileIn( __METHOD__ );
 237                 $res = $this->doGetAcquiredCount();
 238                 wfProfileOut( __METHOD__ );
 239
 240                 return $res;
 241         }
 242
 243         /**
 244          * @see JobQueue::getAcquiredCount()
 245          * @return int
 246          */
 247         abstract protected function doGetAcquiredCount();
 248
 249         /**
 250          * Get the number of delayed jobs (these are temporarily out of the queue).
 251          * Queue classes should use caching if they are any slower without memcached.
 252          *
 253          * If caching is used, this number might be out of date for a minute.
 254          *
 255          * @return int
 256          * @throws JobQueueError
 257          * @since 1.22
 258          */
 259         final public function getDelayedCount() {
 260                 wfProfileIn( __METHOD__ );
 261                 $res = $this->doGetDelayedCount();
 262                 wfProfileOut( __METHOD__ );
 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                 wfProfileIn( __METHOD__ );
 286                 $res = $this->doGetAbandonedCount();
 287                 wfProfileOut( __METHOD__ );
 288
 289                 return $res;
 290         }
 291
 292         /**
 293          * @see JobQueue::getAbandonedCount()
 294          * @return int
 295          */
 296         protected function doGetAbandonedCount() {
 297                 return 0; // not implemented
 298         }
 299
 300         /**
 301          * Push a single jobs into the queue.
 302          * This does not require $wgJobClasses to be set for the given job type.
 303          * Outside callers should use JobQueueGroup::push() instead of this function.
 304          *
 305          * @param Job|array $jobs A single job or an array of Jobs
 306          * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
 307          * @return bool Returns false on failure
 308          * @throws JobQueueError
 309          */
 310         final public function push( $jobs, $flags = 0 ) {
 311                 return $this->batchPush( is_array( $jobs ) ? $jobs : array( $jobs ), $flags );
 312         }
 313
 314         /**
 315          * Push a batch of jobs into the queue.
 316          * This does not require $wgJobClasses to be set for the given job type.
 317          * Outside callers should use JobQueueGroup::push() instead of this function.
 318          *
 319          * @param array $jobs List of Jobs
 320          * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
 321          * @throws MWException
 322          * @return bool Returns false on failure
 323          */
 324         final public function batchPush( array $jobs, $flags = 0 ) {
 325                 if ( !count( $jobs ) ) {
 326                         return true; // nothing to do
 327                 }
 328
 329                 foreach ( $jobs as $job ) {
 330                         if ( $job->getType() !== $this->type ) {
 331                                 throw new MWException(
 332                                         "Got '{$job->getType()}' job; expected a '{$this->type}' job." );
 333                         } elseif ( $job->getReleaseTimestamp() && !$this->checkDelay ) {
 334                                 throw new MWException(
 335                                         "Got delayed '{$job->getType()}' job; delays are not supported." );
 336                         }
 337                 }
 338
 339                 wfProfileIn( __METHOD__ );
 340                 $ok = $this->doBatchPush( $jobs, $flags );
 341                 wfProfileOut( __METHOD__ );
 342
 343                 return $ok;
 344         }
 345
 346         /**
 347          * @see JobQueue::batchPush()
 348          * @param array $jobs
 349          * @param $flags
 350          * @return bool
 351          */
 352         abstract protected function doBatchPush( array $jobs, $flags );
 353
 354         /**
 355          * Pop a job off of the queue.
 356          * This requires $wgJobClasses to be set for the given job type.
 357          * Outside callers should use JobQueueGroup::pop() instead of this function.
 358          *
 359          * @throws MWException
 360          * @return Job|bool Returns false if there are no jobs
 361          */
 362         final public function pop() {
 363                 global $wgJobClasses;
 364
 365                 if ( $this->wiki !== wfWikiID() ) {
 366                         throw new MWException( "Cannot pop '{$this->type}' job off foreign wiki queue." );
 367                 } elseif ( !isset( $wgJobClasses[$this->type] ) ) {
 368                         // Do not pop jobs if there is no class for the queue type
 369                         throw new MWException( "Unrecognized job type '{$this->type}'." );
 370                 }
 371
 372                 wfProfileIn( __METHOD__ );
 373                 $job = $this->doPop();
 374                 wfProfileOut( __METHOD__ );
 375
 376                 // Flag this job as an old duplicate based on its "root" job...
 377                 try {
 378                         if ( $job && $this->isRootJobOldDuplicate( $job ) ) {
 379                                 JobQueue::incrStats( 'job-pop-duplicate', $this->type );
 380                                 $job = DuplicateJob::newFromJob( $job ); // convert to a no-op
 381                         }
 382                 } catch ( MWException $e ) {
 383                         // don't lose jobs over this
 384                 }
 385
 386                 return $job;
 387         }
 388
 389         /**
 390          * @see JobQueue::pop()
 391          * @return Job
 392          */
 393         abstract protected function doPop();
 394
 395         /**
 396          * Acknowledge that a job was completed.
 397          *
 398          * This does nothing for certain queue classes or if "claimTTL" is not set.
 399          * Outside callers should use JobQueueGroup::ack() instead of this function.
 400          *
 401          * @param Job $job
 402          * @throws MWException
 403          * @return bool
 404          */
 405         final public function ack( Job $job ) {
 406                 if ( $job->getType() !== $this->type ) {
 407                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 408                 }
 409                 wfProfileIn( __METHOD__ );
 410                 $ok = $this->doAck( $job );
 411                 wfProfileOut( __METHOD__ );
 412
 413                 return $ok;
 414         }
 415
 416         /**
 417          * @see JobQueue::ack()
 418          * @param Job $job
 419          * @return bool
 420          */
 421         abstract protected function doAck( Job $job );
 422
 423         /**
 424          * Register the "root job" of a given job into the queue for de-duplication.
 425          * This should only be called right *after* all the new jobs have been inserted.
 426          * This is used to turn older, duplicate, job entries into no-ops. The root job
 427          * information will remain in the registry until it simply falls out of cache.
 428          *
 429          * This requires that $job has two special fields in the "params" array:
 430          *   - rootJobSignature : hash (e.g. SHA1) that identifies the task
 431          *   - rootJobTimestamp : TS_MW timestamp of this instance of the task
 432          *
 433          * A "root job" is a conceptual job that consist of potentially many smaller jobs
 434          * that are actually inserted into the queue. For example, "refreshLinks" jobs are
 435          * spawned when a template is edited. One can think of the task as "update links
 436          * of pages that use template X" and an instance of that task as a "root job".
 437          * However, what actually goes into the queue are potentially many refreshLinks2 jobs.
 438          * Since these jobs include things like page ID ranges and DB master positions, and morph
 439          * into smaller refreshLinks2 jobs recursively, simple duplicate detection (like job_sha1)
 440          * for individual jobs being identical is not useful.
 441          *
 442          * In the case of "refreshLinks", if these jobs are still in the queue when the template
 443          * is edited again, we want all of these old refreshLinks jobs for that template to become
 444          * no-ops. This can greatly reduce server load, since refreshLinks jobs involves parsing.
 445          * Essentially, the new batch of jobs belong to a new "root job" and the older ones to a
 446          * previous "root job" for the same task of "update links of pages that use template X".
 447          *
 448          * This does nothing for certain queue classes.
 449          *
 450          * @param Job $job
 451          * @throws MWException
 452          * @return bool
 453          */
 454         final public function deduplicateRootJob( Job $job ) {
 455                 if ( $job->getType() !== $this->type ) {
 456                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 457                 }
 458                 wfProfileIn( __METHOD__ );
 459                 $ok = $this->doDeduplicateRootJob( $job );
 460                 wfProfileOut( __METHOD__ );
 461
 462                 return $ok;
 463         }
 464
 465         /**
 466          * @see JobQueue::deduplicateRootJob()
 467          * @param Job $job
 468          * @throws MWException
 469          * @return bool
 470          */
 471         protected function doDeduplicateRootJob( Job $job ) {
 472                 if ( !$job->hasRootJobParams() ) {
 473                         throw new MWException( "Cannot register root job; missing parameters." );
 474                 }
 475                 $params = $job->getRootJobParams();
 476
 477                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 478                 // Callers should call batchInsert() and then this function so that if the insert
 479                 // fails, the de-duplication registration will be aborted. Since the insert is
 480                 // deferred till "transaction idle", do the same here, so that the ordering is
 481                 // maintained. Having only the de-duplication registration succeed would cause
 482                 // jobs to become no-ops without any actual jobs that made them redundant.
 483                 $timestamp = $this->dupCache->get( $key ); // current last timestamp of this job
 484                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 485                         return true; // a newer version of this root job was enqueued
 486                 }
 487
 488                 // Update the timestamp of the last root job started at the location...
 489                 return $this->dupCache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 490         }
 491
 492         /**
 493          * Check if the "root" job of a given job has been superseded by a newer one
 494          *
 495          * @param Job $job
 496          * @throws MWException
 497          * @return bool
 498          */
 499         final protected function isRootJobOldDuplicate( Job $job ) {
 500                 if ( $job->getType() !== $this->type ) {
 501                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 502                 }
 503                 wfProfileIn( __METHOD__ );
 504                 $isDuplicate = $this->doIsRootJobOldDuplicate( $job );
 505                 wfProfileOut( __METHOD__ );
 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                 list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
 535
 536                 return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, 'rootjob', $signature );
 537         }
 538
 539         /**
 540          * Deleted all unclaimed and delayed jobs from the queue
 541          *
 542          * @return bool Success
 543          * @throws JobQueueError
 544          * @since 1.22
 545          */
 546         final public function delete() {
 547                 wfProfileIn( __METHOD__ );
 548                 $res = $this->doDelete();
 549                 wfProfileOut( __METHOD__ );
 550
 551                 return $res;
 552         }
 553
 554         /**
 555          * @see JobQueue::delete()
 556          * @throws MWException
 557          * @return bool Success
 558          */
 559         protected function doDelete() {
 560                 throw new MWException( "This method is not implemented." );
 561         }
 562
 563         /**
 564          * Wait for any slaves or backup servers to catch up.
 565          *
 566          * This does nothing for certain queue classes.
 567          *
 568          * @return void
 569          * @throws JobQueueError
 570          */
 571         final public function waitForBackups() {
 572                 wfProfileIn( __METHOD__ );
 573                 $this->doWaitForBackups();
 574                 wfProfileOut( __METHOD__ );
 575         }
 576
 577         /**
 578          * @see JobQueue::waitForBackups()
 579          * @return void
 580          */
 581         protected function doWaitForBackups() {
 582         }
 583
 584         /**
 585          * Return a map of task names to task definition maps.
 586          * A "task" is a fast periodic queue maintenance action.
 587          * Mutually exclusive tasks must implement their own locking in the callback.
 588          *
 589          * Each task value is an associative array with:
 590          *   - name     : the name of the task
 591          *   - callback : a PHP callable that performs the task
 592          *   - period   : the period in seconds corresponding to the task frequency
 593          *
 594          * @return array
 595          */
 596         final public function getPeriodicTasks() {
 597                 $tasks = $this->doGetPeriodicTasks();
 598                 foreach ( $tasks as $name => &$def ) {
 599                         $def['name'] = $name;
 600                 }
 601
 602                 return $tasks;
 603         }
 604
 605         /**
 606          * @see JobQueue::getPeriodicTasks()
 607          * @return array
 608          */
 609         protected function doGetPeriodicTasks() {
 610                 return array();
 611         }
 612
 613         /**
 614          * Clear any process and persistent caches
 615          *
 616          * @return void
 617          */
 618         final public function flushCaches() {
 619                 wfProfileIn( __METHOD__ );
 620                 $this->doFlushCaches();
 621                 wfProfileOut( __METHOD__ );
 622         }
 623
 624         /**
 625          * @see JobQueue::flushCaches()
 626          * @return void
 627          */
 628         protected function doFlushCaches() {
 629         }
 630
 631         /**
 632          * Get an iterator to traverse over all available jobs in this queue.
 633          * This does not include jobs that are currently acquired or delayed.
 634          * Note: results may be stale if the queue is concurrently modified.
 635          *
 636          * @return Iterator
 637          * @throws JobQueueError
 638          */
 639         abstract public function getAllQueuedJobs();
 640
 641         /**
 642          * Get an iterator to traverse over all delayed jobs in this queue.
 643          * Note: results may be stale if the queue is concurrently modified.
 644          *
 645          * @return Iterator
 646          * @throws JobQueueError
 647          * @since 1.22
 648          */
 649         public function getAllDelayedJobs() {
 650                 return new ArrayIterator( array() ); // not implemented
 651         }
 652
 653         /**
 654          * Do not use this function outside of JobQueue/JobQueueGroup
 655          *
 656          * @return string
 657          * @since 1.22
 658          */
 659         public function getCoalesceLocationInternal() {
 660                 return null;
 661         }
 662
 663         /**
 664          * Check whether each of the given queues are empty.
 665          * This is used for batching checks for queues stored at the same place.
 666          *
 667          * @param array $types List of queues types
 668          * @return array|null (list of non-empty queue types) or null if unsupported
 669          * @throws MWException
 670          * @since 1.22
 671          */
 672         final public function getSiblingQueuesWithJobs( array $types ) {
 673                 $section = new ProfileSection( __METHOD__ );
 674
 675                 return $this->doGetSiblingQueuesWithJobs( $types );
 676         }
 677
 678         /**
 679          * @see JobQueue::getSiblingQueuesWithJobs()
 680          * @param array $types List of queues types
 681          * @return array|null (list of queue types) or null if unsupported
 682          */
 683         protected function doGetSiblingQueuesWithJobs( array $types ) {
 684                 return null; // not supported
 685         }
 686
 687         /**
 688          * Check the size of each of the given queues.
 689          * For queues not served by the same store as this one, 0 is returned.
 690          * This is used for batching checks for queues stored at the same place.
 691          *
 692          * @param array $types List of queues types
 693          * @return array|null (job type => whether queue is empty) or null if unsupported
 694          * @throws MWException
 695          * @since 1.22
 696          */
 697         final public function getSiblingQueueSizes( array $types ) {
 698                 $section = new ProfileSection( __METHOD__ );
 699
 700                 return $this->doGetSiblingQueueSizes( $types );
 701         }
 702
 703         /**
 704          * @see JobQueue::getSiblingQueuesSize()
 705          * @param array $types List of queues types
 706          * @return array|null (list of queue types) or null if unsupported
 707          */
 708         protected function doGetSiblingQueueSizes( array $types ) {
 709                 return null; // not supported
 710         }
 711
 712         /**
 713          * Call wfIncrStats() for the queue overall and for the queue type
 714          *
 715          * @param string $key Event type
 716          * @param string $type Job type
 717          * @param int $delta
 718          * @since 1.22
 719          */
 720         public static function incrStats( $key, $type, $delta = 1 ) {
 721                 wfIncrStats( $key, $delta );
 722                 wfIncrStats( "{$key}-{$type}", $delta );
 723         }
 724
 725         /**
 726          * Namespace the queue with a key to isolate it for testing
 727          *
 728          * @param string $key
 729          * @return void
 730          * @throws MWException
 731          */
 732         public function setTestingPrefix( $key ) {
 733                 throw new MWException( "Queue namespacing not supported for this queue type." );
 734         }
 735 }
 736
 737 /**
 738  * @ingroup JobQueue
 739  * @since 1.22
 740  */
 741 class JobQueueError extends MWException {
 742 }
 743
 744 class JobQueueConnectionError extends JobQueueError {
 745 }