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         protected $wiki; // string; wiki ID
  33         protected $type; // string; job type
  34         protected $order; // string; job priority for pop()
  35         protected $claimTTL; // integer; seconds
  36         protected $maxTries; // integer; maximum number of times to try a job
  37         protected $checkDelay; // boolean; allow delayed jobs
  38
  39         /** @var BagOStuff */
  40         protected $dupCache;
  41
  42         const QOS_ATOMIC = 1; // integer; "all-or-nothing" job insertions
  43         const QoS_Atomic = 1; // integer; "all-or-nothing" job insertions (b/c)
  44
  45         const ROOTJOB_TTL = 2419200; // integer; seconds to remember root jobs (28 days)
  46
  47         /**
  48          * @param $params array
  49          */
  50         protected function __construct( array $params ) {
  51                 $this->wiki = $params['wiki'];
  52                 $this->type = $params['type'];
  53                 $this->claimTTL = isset( $params['claimTTL'] ) ? $params['claimTTL'] : 0;
  54                 $this->maxTries = isset( $params['maxTries'] ) ? $params['maxTries'] : 3;
  55                 if ( isset( $params['order'] ) && $params['order'] !== 'any' ) {
  56                         $this->order = $params['order'];
  57                 } else {
  58                         $this->order = $this->optimalOrder();
  59                 }
  60                 if ( !in_array( $this->order, $this->supportedOrders() ) ) {
  61                         throw new MWException( __CLASS__ . " does not support '{$this->order}' order." );
  62                 }
  63                 $this->checkDelay = !empty( $params['checkDelay'] );
  64                 if ( $this->checkDelay && !$this->supportsDelayedJobs() ) {
  65                         throw new MWException( __CLASS__ . " does not support delayed jobs." );
  66                 }
  67                 $this->dupCache = wfGetCache( CACHE_ANYTHING );
  68         }
  69
  70         /**
  71          * Get a job queue object of the specified type.
  72          * $params includes:
  73          *   - class      : What job class to use (determines job type)
  74          *   - wiki       : wiki ID of the wiki the jobs are for (defaults to current wiki)
  75          *   - type       : The name of the job types this queue handles
  76          *   - order      : Order that pop() selects jobs, one of "fifo", "timestamp" or "random".
  77          *                  If "fifo" is used, the queue will effectively be FIFO. Note that job
  78          *                  completion will not appear to be exactly FIFO if there are multiple
  79          *                  job runners since jobs can take different times to finish once popped.
  80          *                  If "timestamp" is used, the queue will at least be loosely ordered
  81          *                  by timestamp, allowing for some jobs to be popped off out of order.
  82          *                  If "random" is used, pop() will pick jobs in random order.
  83          *                  Note that it may only be weakly random (e.g. a lottery of the oldest X).
  84          *                  If "any" is choosen, the queue will use whatever order is the fastest.
  85          *                  This might be useful for improving concurrency for job acquisition.
  86          *   - claimTTL   : If supported, the queue will recycle jobs that have been popped
  87          *                  but not acknowledged as completed after this many seconds. Recycling
  88          *                  of jobs simple means re-inserting them into the queue. Jobs can be
  89          *                  attempted up to three times before being discarded.
  90          *   - checkDelay : If supported, respect Job::getReleaseTimestamp() in the push functions.
  91          *                  This lets delayed jobs wait in a staging area until a given timestamp is
  92          *                  reached, at which point they will enter the queue. If this is not enabled
  93          *                  or not supported, an exception will be thrown on delayed job insertion.
  94          *
  95          * Queue classes should throw an exception if they do not support the options given.
  96          *
  97          * @param $params array
  98          * @return JobQueue
  99          * @throws MWException
 100          */
 101         final public static function factory( array $params ) {
 102                 $class = $params['class'];
 103                 if ( !class_exists( $class ) ) {
 104                         throw new MWException( "Invalid job queue class '$class'." );
 105                 }
 106                 $obj = new $class( $params );
 107                 if ( !( $obj instanceof self ) ) {
 108                         throw new MWException( "Class '$class' is not a " . __CLASS__ . " class." );
 109                 }
 110                 return $obj;
 111         }
 112
 113         /**
 114          * @return string Wiki ID
 115          */
 116         final public function getWiki() {
 117                 return $this->wiki;
 118         }
 119
 120         /**
 121          * @return string Job type that this queue handles
 122          */
 123         final public function getType() {
 124                 return $this->type;
 125         }
 126
 127         /**
 128          * @return string One of (random, timestamp, fifo, undefined)
 129          */
 130         final public function getOrder() {
 131                 return $this->order;
 132         }
 133
 134         /**
 135          * @return bool Whether delayed jobs are enabled
 136          * @since 1.22
 137          */
 138         final public function delayedJobsEnabled() {
 139                 return $this->checkDelay;
 140         }
 141
 142         /**
 143          * Get the allowed queue orders for configuration validation
 144          *
 145          * @return Array Subset of (random, timestamp, fifo, undefined)
 146          */
 147         abstract protected function supportedOrders();
 148
 149         /**
 150          * Get the default queue order to use if configuration does not specify one
 151          *
 152          * @return string One of (random, timestamp, fifo, undefined)
 153          */
 154         abstract protected function optimalOrder();
 155
 156         /**
 157          * Find out if delayed jobs are supported for configuration validation
 158          *
 159          * @return boolean Whether delayed jobs are supported
 160          */
 161         protected function supportsDelayedJobs() {
 162                 return false; // not implemented
 163         }
 164
 165         /**
 166          * Quickly check if the queue has no available (unacquired, non-delayed) jobs.
 167          * Queue classes should use caching if they are any slower without memcached.
 168          *
 169          * If caching is used, this might return false when there are actually no jobs.
 170          * If pop() is called and returns false then it should correct the cache. Also,
 171          * calling flushCaches() first prevents this. However, this affect is typically
 172          * not distinguishable from the race condition between isEmpty() and pop().
 173          *
 174          * @return bool
 175          * @throws JobQueueError
 176          */
 177         final public function isEmpty() {
 178                 wfProfileIn( __METHOD__ );
 179                 $res = $this->doIsEmpty();
 180                 wfProfileOut( __METHOD__ );
 181                 return $res;
 182         }
 183
 184         /**
 185          * @see JobQueue::isEmpty()
 186          * @return bool
 187          */
 188         abstract protected function doIsEmpty();
 189
 190         /**
 191          * Get the number of available (unacquired, non-delayed) jobs in the queue.
 192          * Queue classes should use caching if they are any slower without memcached.
 193          *
 194          * If caching is used, this number might be out of date for a minute.
 195          *
 196          * @return integer
 197          * @throws JobQueueError
 198          */
 199         final public function getSize() {
 200                 wfProfileIn( __METHOD__ );
 201                 $res = $this->doGetSize();
 202                 wfProfileOut( __METHOD__ );
 203                 return $res;
 204         }
 205
 206         /**
 207          * @see JobQueue::getSize()
 208          * @return integer
 209          */
 210         abstract protected function doGetSize();
 211
 212         /**
 213          * Get the number of acquired jobs (these are temporarily out of the queue).
 214          * Queue classes should use caching if they are any slower without memcached.
 215          *
 216          * If caching is used, this number might be out of date for a minute.
 217          *
 218          * @return integer
 219          * @throws JobQueueError
 220          */
 221         final public function getAcquiredCount() {
 222                 wfProfileIn( __METHOD__ );
 223                 $res = $this->doGetAcquiredCount();
 224                 wfProfileOut( __METHOD__ );
 225                 return $res;
 226         }
 227
 228         /**
 229          * @see JobQueue::getAcquiredCount()
 230          * @return integer
 231          */
 232         abstract protected function doGetAcquiredCount();
 233
 234         /**
 235          * Get the number of delayed jobs (these are temporarily out of the queue).
 236          * Queue classes should use caching if they are any slower without memcached.
 237          *
 238          * If caching is used, this number might be out of date for a minute.
 239          *
 240          * @return integer
 241          * @throws JobQueueError
 242          * @since 1.22
 243          */
 244         final public function getDelayedCount() {
 245                 wfProfileIn( __METHOD__ );
 246                 $res = $this->doGetDelayedCount();
 247                 wfProfileOut( __METHOD__ );
 248                 return $res;
 249         }
 250
 251         /**
 252          * @see JobQueue::getDelayedCount()
 253          * @return integer
 254          */
 255         protected function doGetDelayedCount() {
 256                 return 0; // not implemented
 257         }
 258
 259         /**
 260          * Get the number of acquired jobs that can no longer be attempted.
 261          * Queue classes should use caching if they are any slower without memcached.
 262          *
 263          * If caching is used, this number might be out of date for a minute.
 264          *
 265          * @return integer
 266          * @throws JobQueueError
 267          */
 268         final public function getAbandonedCount() {
 269                 wfProfileIn( __METHOD__ );
 270                 $res = $this->doGetAbandonedCount();
 271                 wfProfileOut( __METHOD__ );
 272                 return $res;
 273         }
 274
 275         /**
 276          * @see JobQueue::getAbandonedCount()
 277          * @return integer
 278          */
 279         protected function doGetAbandonedCount() {
 280                 return 0; // not implemented
 281         }
 282
 283         /**
 284          * Push a single jobs into the queue.
 285          * This does not require $wgJobClasses to be set for the given job type.
 286          * Outside callers should use JobQueueGroup::push() instead of this function.
 287          *
 288          * @param $jobs Job|Array
 289          * @param $flags integer Bitfield (supports JobQueue::QOS_ATOMIC)
 290          * @return bool Returns false on failure
 291          * @throws JobQueueError
 292          */
 293         final public function push( $jobs, $flags = 0 ) {
 294                 return $this->batchPush( is_array( $jobs ) ? $jobs : array( $jobs ), $flags );
 295         }
 296
 297         /**
 298          * Push a batch of jobs into the queue.
 299          * This does not require $wgJobClasses to be set for the given job type.
 300          * Outside callers should use JobQueueGroup::push() instead of this function.
 301          *
 302          * @param array $jobs List of Jobs
 303          * @param $flags integer Bitfield (supports JobQueue::QOS_ATOMIC)
 304          * @return bool Returns false on failure
 305          * @throws JobQueueError
 306          */
 307         final public function batchPush( array $jobs, $flags = 0 ) {
 308                 if ( !count( $jobs ) ) {
 309                         return true; // nothing to do
 310                 }
 311
 312                 foreach ( $jobs as $job ) {
 313                         if ( $job->getType() !== $this->type ) {
 314                                 throw new MWException(
 315                                         "Got '{$job->getType()}' job; expected a '{$this->type}' job." );
 316                         } elseif ( $job->getReleaseTimestamp() && !$this->checkDelay ) {
 317                                 throw new MWException(
 318                                         "Got delayed '{$job->getType()}' job; delays are not supported." );
 319                         }
 320                 }
 321
 322                 wfProfileIn( __METHOD__ );
 323                 $ok = $this->doBatchPush( $jobs, $flags );
 324                 wfProfileOut( __METHOD__ );
 325                 return $ok;
 326         }
 327
 328         /**
 329          * @see JobQueue::batchPush()
 330          * @return bool
 331          */
 332         abstract protected function doBatchPush( array $jobs, $flags );
 333
 334         /**
 335          * Pop a job off of the queue.
 336          * This requires $wgJobClasses to be set for the given job type.
 337          * Outside callers should use JobQueueGroup::pop() instead of this function.
 338          *
 339          * @return Job|bool Returns false if there are no jobs
 340          * @throws JobQueueError
 341          */
 342         final public function pop() {
 343                 global $wgJobClasses;
 344
 345                 if ( $this->wiki !== wfWikiID() ) {
 346                         throw new MWException( "Cannot pop '{$this->type}' job off foreign wiki queue." );
 347                 } elseif ( !isset( $wgJobClasses[$this->type] ) ) {
 348                         // Do not pop jobs if there is no class for the queue type
 349                         throw new MWException( "Unrecognized job type '{$this->type}'." );
 350                 }
 351
 352                 wfProfileIn( __METHOD__ );
 353                 $job = $this->doPop();
 354                 wfProfileOut( __METHOD__ );
 355
 356                 // Flag this job as an old duplicate based on its "root" job...
 357                 try {
 358                         if ( $job && $this->isRootJobOldDuplicate( $job ) ) {
 359                                 JobQueue::incrStats( 'job-pop-duplicate', $this->type );
 360                                 $job = DuplicateJob::newFromJob( $job ); // convert to a no-op
 361                         }
 362                 } catch ( MWException $e ) {} // don't lose jobs over this
 363
 364                 return $job;
 365         }
 366
 367         /**
 368          * @see JobQueue::pop()
 369          * @return Job
 370          */
 371         abstract protected function doPop();
 372
 373         /**
 374          * Acknowledge that a job was completed.
 375          *
 376          * This does nothing for certain queue classes or if "claimTTL" is not set.
 377          * Outside callers should use JobQueueGroup::ack() instead of this function.
 378          *
 379          * @param $job Job
 380          * @return bool
 381          * @throws JobQueueError
 382          */
 383         final public function ack( Job $job ) {
 384                 if ( $job->getType() !== $this->type ) {
 385                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 386                 }
 387                 wfProfileIn( __METHOD__ );
 388                 $ok = $this->doAck( $job );
 389                 wfProfileOut( __METHOD__ );
 390                 return $ok;
 391         }
 392
 393         /**
 394          * @see JobQueue::ack()
 395          * @return bool
 396          */
 397         abstract protected function doAck( Job $job );
 398
 399         /**
 400          * Register the "root job" of a given job into the queue for de-duplication.
 401          * This should only be called right *after* all the new jobs have been inserted.
 402          * This is used to turn older, duplicate, job entries into no-ops. The root job
 403          * information will remain in the registry until it simply falls out of cache.
 404          *
 405          * This requires that $job has two special fields in the "params" array:
 406          *   - rootJobSignature : hash (e.g. SHA1) that identifies the task
 407          *   - rootJobTimestamp : TS_MW timestamp of this instance of the task
 408          *
 409          * A "root job" is a conceptual job that consist of potentially many smaller jobs
 410          * that are actually inserted into the queue. For example, "refreshLinks" jobs are
 411          * spawned when a template is edited. One can think of the task as "update links
 412          * of pages that use template X" and an instance of that task as a "root job".
 413          * However, what actually goes into the queue are potentially many refreshLinks2 jobs.
 414          * Since these jobs include things like page ID ranges and DB master positions, and morph
 415          * into smaller refreshLinks2 jobs recursively, simple duplicate detection (like job_sha1)
 416          * for individual jobs being identical is not useful.
 417          *
 418          * In the case of "refreshLinks", if these jobs are still in the queue when the template
 419          * is edited again, we want all of these old refreshLinks jobs for that template to become
 420          * no-ops. This can greatly reduce server load, since refreshLinks jobs involves parsing.
 421          * Essentially, the new batch of jobs belong to a new "root job" and the older ones to a
 422          * previous "root job" for the same task of "update links of pages that use template X".
 423          *
 424          * This does nothing for certain queue classes.
 425          *
 426          * @param $job Job
 427          * @return bool
 428          * @throws JobQueueError
 429          */
 430         final public function deduplicateRootJob( Job $job ) {
 431                 if ( $job->getType() !== $this->type ) {
 432                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 433                 }
 434                 wfProfileIn( __METHOD__ );
 435                 $ok = $this->doDeduplicateRootJob( $job );
 436                 wfProfileOut( __METHOD__ );
 437                 return $ok;
 438         }
 439
 440         /**
 441          * @see JobQueue::deduplicateRootJob()
 442          * @param $job Job
 443          * @return bool
 444          */
 445         protected function doDeduplicateRootJob( Job $job ) {
 446                 if ( !$job->hasRootJobParams() ) {
 447                         throw new MWException( "Cannot register root job; missing parameters." );
 448                 }
 449                 $params = $job->getRootJobParams();
 450
 451                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 452                 // Callers should call batchInsert() and then this function so that if the insert
 453                 // fails, the de-duplication registration will be aborted. Since the insert is
 454                 // deferred till "transaction idle", do the same here, so that the ordering is
 455                 // maintained. Having only the de-duplication registration succeed would cause
 456                 // jobs to become no-ops without any actual jobs that made them redundant.
 457                 $timestamp = $this->dupCache->get( $key ); // current last timestamp of this job
 458                 if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 459                         return true; // a newer version of this root job was enqueued
 460                 }
 461
 462                 // Update the timestamp of the last root job started at the location...
 463                 return $this->dupCache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
 464         }
 465
 466         /**
 467          * Check if the "root" job of a given job has been superseded by a newer one
 468          *
 469          * @param $job Job
 470          * @return bool
 471          * @throws JobQueueError
 472          */
 473         final protected function isRootJobOldDuplicate( Job $job ) {
 474                 if ( $job->getType() !== $this->type ) {
 475                         throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
 476                 }
 477                 wfProfileIn( __METHOD__ );
 478                 $isDuplicate = $this->doIsRootJobOldDuplicate( $job );
 479                 wfProfileOut( __METHOD__ );
 480                 return $isDuplicate;
 481         }
 482
 483         /**
 484          * @see JobQueue::isRootJobOldDuplicate()
 485          * @param Job $job
 486          * @return bool
 487          */
 488         protected function doIsRootJobOldDuplicate( Job $job ) {
 489                 if ( !$job->hasRootJobParams() ) {
 490                         return false; // job has no de-deplication info
 491                 }
 492                 $params = $job->getRootJobParams();
 493
 494                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 495                 // Get the last time this root job was enqueued
 496                 $timestamp = $this->dupCache->get( $key );
 497
 498                 // Check if a new root job was started at the location after this one's...
 499                 return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
 500         }
 501
 502         /**
 503          * @param string $signature Hash identifier of the root job
 504          * @return string
 505          */
 506         protected function getRootJobCacheKey( $signature ) {
 507                 list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
 508                 return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, 'rootjob', $signature );
 509         }
 510
 511         /**
 512          * Deleted all unclaimed and delayed jobs from the queue
 513          *
 514          * @return bool Success
 515          * @throws JobQueueError
 516          * @since 1.22
 517          */
 518         final public function delete() {
 519                 wfProfileIn( __METHOD__ );
 520                 $res = $this->doDelete();
 521                 wfProfileOut( __METHOD__ );
 522                 return $res;
 523         }
 524
 525         /**
 526          * @see JobQueue::delete()
 527          * @return bool Success
 528          */
 529         protected function doDelete() {
 530                 throw new MWException( "This method is not implemented." );
 531         }
 532
 533         /**
 534          * Wait for any slaves or backup servers to catch up.
 535          *
 536          * This does nothing for certain queue classes.
 537          *
 538          * @return void
 539          * @throws JobQueueError
 540          */
 541         final public function waitForBackups() {
 542                 wfProfileIn( __METHOD__ );
 543                 $this->doWaitForBackups();
 544                 wfProfileOut( __METHOD__ );
 545         }
 546
 547         /**
 548          * @see JobQueue::waitForBackups()
 549          * @return void
 550          */
 551         protected function doWaitForBackups() {}
 552
 553         /**
 554          * Return a map of task names to task definition maps.
 555          * A "task" is a fast periodic queue maintenance action.
 556          * Mutually exclusive tasks must implement their own locking in the callback.
 557          *
 558          * Each task value is an associative array with:
 559          *   - name     : the name of the task
 560          *   - callback : a PHP callable that performs the task
 561          *   - period   : the period in seconds corresponding to the task frequency
 562          *
 563          * @return Array
 564          */
 565         final public function getPeriodicTasks() {
 566                 $tasks = $this->doGetPeriodicTasks();
 567                 foreach ( $tasks as $name => &$def ) {
 568                         $def['name'] = $name;
 569                 }
 570                 return $tasks;
 571         }
 572
 573         /**
 574          * @see JobQueue::getPeriodicTasks()
 575          * @return Array
 576          */
 577         protected function doGetPeriodicTasks() {
 578                 return array();
 579         }
 580
 581         /**
 582          * Clear any process and persistent caches
 583          *
 584          * @return void
 585          */
 586         final public function flushCaches() {
 587                 wfProfileIn( __METHOD__ );
 588                 $this->doFlushCaches();
 589                 wfProfileOut( __METHOD__ );
 590         }
 591
 592         /**
 593          * @see JobQueue::flushCaches()
 594          * @return void
 595          */
 596         protected function doFlushCaches() {}
 597
 598         /**
 599          * Get an iterator to traverse over all available jobs in this queue.
 600          * This does not include jobs that are currently acquired or delayed.
 601          * Note: results may be stale if the queue is concurrently modified.
 602          *
 603          * @return Iterator
 604          * @throws JobQueueError
 605          */
 606         abstract public function getAllQueuedJobs();
 607
 608         /**
 609          * Get an iterator to traverse over all delayed jobs in this queue.
 610          * Note: results may be stale if the queue is concurrently modified.
 611          *
 612          * @return Iterator
 613          * @throws JobQueueError
 614          * @since 1.22
 615          */
 616         public function getAllDelayedJobs() {
 617                 return new ArrayIterator( array() ); // not implemented
 618         }
 619
 620         /**
 621          * Do not use this function outside of JobQueue/JobQueueGroup
 622          *
 623          * @return string
 624          * @since 1.22
 625          */
 626         public function getCoalesceLocationInternal() {
 627                 return null;
 628         }
 629
 630         /**
 631          * Check whether each of the given queues are empty.
 632          * This is used for batching checks for queues stored at the same place.
 633          *
 634          * @param array $types List of queues types
 635          * @return array|null (list of non-empty queue types) or null if unsupported
 636          * @throws MWException
 637          * @since 1.22
 638          */
 639         final public function getSiblingQueuesWithJobs( array $types ) {
 640                 $section = new ProfileSection( __METHOD__ );
 641                 return $this->doGetSiblingQueuesWithJobs( $types );
 642         }
 643
 644         /**
 645          * @see JobQueue::getSiblingQueuesWithJobs()
 646          * @param array $types List of queues types
 647          * @return array|null (list of queue types) or null if unsupported
 648          */
 649         protected function doGetSiblingQueuesWithJobs( array $types ) {
 650                 return null; // not supported
 651         }
 652
 653         /**
 654          * Check the size of each of the given queues.
 655          * For queues not served by the same store as this one, 0 is returned.
 656          * This is used for batching checks for queues stored at the same place.
 657          *
 658          * @param array $types List of queues types
 659          * @return array|null (job type => whether queue is empty) or null if unsupported
 660          * @throws MWException
 661          * @since 1.22
 662          */
 663         final public function getSiblingQueueSizes( array $types ) {
 664                 $section = new ProfileSection( __METHOD__ );
 665                 return $this->doGetSiblingQueueSizes( $types );
 666         }
 667
 668         /**
 669          * @see JobQueue::getSiblingQueuesSize()
 670          * @param array $types List of queues types
 671          * @return array|null (list of queue types) or null if unsupported
 672          */
 673         protected function doGetSiblingQueueSizes( array $types ) {
 674                 return null; // not supported
 675         }
 676
 677         /**
 678          * Call wfIncrStats() for the queue overall and for the queue type
 679          *
 680          * @param string $key Event type
 681          * @param string $type Job type
 682          * @param integer $delta
 683          * @since 1.22
 684          */
 685         public static function incrStats( $key, $type, $delta = 1 ) {
 686                 wfIncrStats( $key, $delta );
 687                 wfIncrStats( "{$key}-{$type}", $delta );
 688         }
 689
 690         /**
 691          * Namespace the queue with a key to isolate it for testing
 692          *
 693          * @param $key string
 694          * @return void
 695          * @throws MWException
 696          */
 697         public function setTestingPrefix( $key ) {
 698                 throw new MWException( "Queue namespacing not supported for this queue type." );
 699         }
 700 }
 701
 702 /**
 703  * @ingroup JobQueue
 704  * @since 1.22
 705  */
 706 class JobQueueError extends MWException {}
 707 class JobQueueConnectionError extends JobQueueError {}