summaryrefslogtreecommitdiff
path: root/includes/jobqueue/JobQueueRedis.php
blob: 3519eac8ebcb4ddef77c825847dff1607e5dce75 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
<?php
/**
 * Redis-backed job queue code.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @author Aaron Schulz
 */

/**
 * Class to handle job queues stored in Redis
 *
 * This is faster, less resource intensive, queue that JobQueueDB.
 * All data for a queue using this class is placed into one redis server.
 *
 * There are eight main redis keys used to track jobs:
 *   - l-unclaimed  : A list of job IDs used for ready unclaimed jobs
 *   - z-claimed    : A sorted set of (job ID, UNIX timestamp as score) used for job retries
 *   - z-abandoned  : A sorted set of (job ID, UNIX timestamp as score) used for broken jobs
 *   - z-delayed    : A sorted set of (job ID, UNIX timestamp as score) used for delayed jobs
 *   - h-idBySha1   : A hash of (SHA1 => job ID) for unclaimed jobs used for de-duplication
 *   - h-sha1ById   : A hash of (job ID => SHA1) for unclaimed jobs used for de-duplication
 *   - h-attempts   : A hash of (job ID => attempt count) used for job claiming/retries
 *   - h-data       : A hash of (job ID => serialized blobs) for job storage
 * A job ID can be in only one of z-delayed, l-unclaimed, z-claimed, and z-abandoned.
 * If an ID appears in any of those lists, it should have a h-data entry for its ID.
 * If a job has a SHA1 de-duplication value and its ID is in l-unclaimed or z-delayed, then
 * there should be no other such jobs with that SHA1. Every h-idBySha1 entry has an h-sha1ById
 * entry and every h-sha1ById must refer to an ID that is l-unclaimed. If a job has its
 * ID in z-claimed or z-abandoned, then it must also have an h-attempts entry for its ID.
 *
 * Additionally, "rootjob:* keys track "root jobs" used for additional de-duplication.
 * Aside from root job keys, all keys have no expiry, and are only removed when jobs are run.
 * All the keys are prefixed with the relevant wiki ID information.
 *
 * This class requires Redis 2.6 as it makes use Lua scripts for fast atomic operations.
 * Additionally, it should be noted that redis has different persistence modes, such
 * as rdb snapshots, journaling, and no persistent. Appropriate configuration should be
 * made on the servers based on what queues are using it and what tolerance they have.
 *
 * @ingroup JobQueue
 * @ingroup Redis
 * @since 1.22
 */
class JobQueueRedis extends JobQueue {
	/** @var RedisConnectionPool */
	protected $redisPool;

	/** @var string Server address */
	protected $server;
	/** @var string Compression method to use */
	protected $compression;
	/** @var bool */
	protected $daemonized;

	const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed (7 days)

	/** @var string Key to prefix the queue keys with (used for testing) */
	protected $key;

	/**
	 * @param array $params Possible keys:
	 *   - redisConfig : An array of parameters to RedisConnectionPool::__construct().
	 *                   Note that the serializer option is ignored as "none" is always used.
	 *   - redisServer : A hostname/port combination or the absolute path of a UNIX socket.
	 *                   If a hostname is specified but no port, the standard port number
	 *                   6379 will be used. Required.
	 *   - compression : The type of compression to use; one of (none,gzip).
	 *   - daemonized  : Set to true if the redisJobRunnerService runs in the background.
	 *                   This will disable job recycling/undelaying from the MediaWiki side
	 *                   to avoid redundance and out-of-sync configuration.
	 */
	public function __construct( array $params ) {
		parent::__construct( $params );
		$params['redisConfig']['serializer'] = 'none'; // make it easy to use Lua
		$this->server = $params['redisServer'];
		$this->compression = isset( $params['compression'] ) ? $params['compression'] : 'none';
		$this->redisPool = RedisConnectionPool::singleton( $params['redisConfig'] );
		$this->daemonized = !empty( $params['daemonized'] );
	}

	protected function supportedOrders() {
		return array( 'timestamp', 'fifo' );
	}

	protected function optimalOrder() {
		return 'fifo';
	}

	protected function supportsDelayedJobs() {
		return true;
	}

	/**
	 * @see JobQueue::doIsEmpty()
	 * @return bool
	 * @throws MWException
	 */
	protected function doIsEmpty() {
		return $this->doGetSize() == 0;
	}

	/**
	 * @see JobQueue::doGetSize()
	 * @return int
	 * @throws MWException
	 */
	protected function doGetSize() {
		$conn = $this->getConnection();
		try {
			return $conn->lSize( $this->getQueueKey( 'l-unclaimed' ) );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::doGetAcquiredCount()
	 * @return int
	 * @throws JobQueueError
	 */
	protected function doGetAcquiredCount() {
		if ( $this->claimTTL <= 0 ) {
			return 0; // no acknowledgements
		}
		$conn = $this->getConnection();
		try {
			$conn->multi( Redis::PIPELINE );
			$conn->zSize( $this->getQueueKey( 'z-claimed' ) );
			$conn->zSize( $this->getQueueKey( 'z-abandoned' ) );

			return array_sum( $conn->exec() );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::doGetDelayedCount()
	 * @return int
	 * @throws JobQueueError
	 */
	protected function doGetDelayedCount() {
		if ( !$this->checkDelay ) {
			return 0; // no delayed jobs
		}
		$conn = $this->getConnection();
		try {
			return $conn->zSize( $this->getQueueKey( 'z-delayed' ) );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::doGetAbandonedCount()
	 * @return int
	 * @throws JobQueueError
	 */
	protected function doGetAbandonedCount() {
		if ( $this->claimTTL <= 0 ) {
			return 0; // no acknowledgements
		}
		$conn = $this->getConnection();
		try {
			return $conn->zSize( $this->getQueueKey( 'z-abandoned' ) );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::doBatchPush()
	 * @param array $jobs
	 * @param int $flags
	 * @return void
	 * @throws JobQueueError
	 */
	protected function doBatchPush( array $jobs, $flags ) {
		// Convert the jobs into field maps (de-duplicated against each other)
		$items = array(); // (job ID => job fields map)
		foreach ( $jobs as $job ) {
			$item = $this->getNewJobFields( $job );
			if ( strlen( $item['sha1'] ) ) { // hash identifier => de-duplicate
				$items[$item['sha1']] = $item;
			} else {
				$items[$item['uuid']] = $item;
			}
		}

		if ( !count( $items ) ) {
			return; // nothing to do
		}

		$conn = $this->getConnection();
		try {
			// Actually push the non-duplicate jobs into the queue...
			if ( $flags & self::QOS_ATOMIC ) {
				$batches = array( $items ); // all or nothing
			} else {
				$batches = array_chunk( $items, 500 ); // avoid tying up the server
			}
			$failed = 0;
			$pushed = 0;
			foreach ( $batches as $itemBatch ) {
				$added = $this->pushBlobs( $conn, $itemBatch );
				if ( is_int( $added ) ) {
					$pushed += $added;
				} else {
					$failed += count( $itemBatch );
				}
			}
			if ( $failed > 0 ) {
				wfDebugLog( 'JobQueueRedis', "Could not insert {$failed} {$this->type} job(s)." );

				throw new RedisException( "Could not insert {$failed} {$this->type} job(s)." );
			}
			JobQueue::incrStats( 'job-insert', $this->type, count( $items ), $this->wiki );
			JobQueue::incrStats( 'job-insert-duplicate', $this->type,
				count( $items ) - $failed - $pushed, $this->wiki );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @param RedisConnRef $conn
	 * @param array $items List of results from JobQueueRedis::getNewJobFields()
	 * @return int Number of jobs inserted (duplicates are ignored)
	 * @throws RedisException
	 */
	protected function pushBlobs( RedisConnRef $conn, array $items ) {
		$args = array(); // ([id, sha1, rtime, blob [, id, sha1, rtime, blob ... ] ] )
		foreach ( $items as $item ) {
			$args[] = (string)$item['uuid'];
			$args[] = (string)$item['sha1'];
			$args[] = (string)$item['rtimestamp'];
			$args[] = (string)$this->serialize( $item );
		}
		static $script =
<<<LUA
		local kUnclaimed, kSha1ById, kIdBySha1, kDelayed, kData = unpack(KEYS)
		if #ARGV % 4 ~= 0 then return redis.error_reply('Unmatched arguments') end
		local pushed = 0
		for i = 1,#ARGV,4 do
			local id,sha1,rtimestamp,blob = ARGV[i],ARGV[i+1],ARGV[i+2],ARGV[i+3]
			if sha1 == '' or redis.call('hExists',kIdBySha1,sha1) == 0 then
				if 1*rtimestamp > 0 then
					-- Insert into delayed queue (release time as score)
					redis.call('zAdd',kDelayed,rtimestamp,id)
				else
					-- Insert into unclaimed queue
					redis.call('lPush',kUnclaimed,id)
				end
				if sha1 ~= '' then
					redis.call('hSet',kSha1ById,id,sha1)
					redis.call('hSet',kIdBySha1,sha1,id)
				end
				redis.call('hSet',kData,id,blob)
				pushed = pushed + 1
			end
		end
		return pushed
LUA;
		return $conn->luaEval( $script,
			array_merge(
				array(
					$this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
					$this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
					$this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
					$this->getQueueKey( 'z-delayed' ), # KEYS[4]
					$this->getQueueKey( 'h-data' ), # KEYS[5]
				),
				$args
			),
			5 # number of first argument(s) that are keys
		);
	}

	/**
	 * @see JobQueue::doPop()
	 * @return Job|bool
	 * @throws JobQueueError
	 */
	protected function doPop() {
		$job = false;

		// Push ready delayed jobs into the queue every 10 jobs to spread the load.
		// This is also done as a periodic task, but we don't want too much done at once.
		if ( $this->checkDelay && mt_rand( 0, 9 ) == 0 ) {
			$this->recyclePruneAndUndelayJobs();
		}

		$conn = $this->getConnection();
		try {
			do {
				if ( $this->claimTTL > 0 ) {
					// Keep the claimed job list down for high-traffic queues
					if ( mt_rand( 0, 99 ) == 0 ) {
						$this->recyclePruneAndUndelayJobs();
					}
					$blob = $this->popAndAcquireBlob( $conn );
				} else {
					$blob = $this->popAndDeleteBlob( $conn );
				}
				if ( !is_string( $blob ) ) {
					break; // no jobs; nothing to do
				}

				JobQueue::incrStats( 'job-pop', $this->type, 1, $this->wiki );
				$item = $this->unserialize( $blob );
				if ( $item === false ) {
					wfDebugLog( 'JobQueueRedis', "Could not unserialize {$this->type} job." );
					continue;
				}

				// If $item is invalid, recyclePruneAndUndelayJobs() will cleanup as needed
				$job = $this->getJobFromFields( $item ); // may be false
			} while ( !$job ); // job may be false if invalid
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}

		return $job;
	}

	/**
	 * @param RedisConnRef $conn
	 * @return array Serialized string or false
	 * @throws RedisException
	 */
	protected function popAndDeleteBlob( RedisConnRef $conn ) {
		static $script =
<<<LUA
		local kUnclaimed, kSha1ById, kIdBySha1, kData = unpack(KEYS)
		-- Pop an item off the queue
		local id = redis.call('rpop',kUnclaimed)
		if not id then return false end
		-- Get the job data and remove it
		local item = redis.call('hGet',kData,id)
		redis.call('hDel',kData,id)
		-- Allow new duplicates of this job
		local sha1 = redis.call('hGet',kSha1ById,id)
		if sha1 then redis.call('hDel',kIdBySha1,sha1) end
		redis.call('hDel',kSha1ById,id)
		-- Return the job data
		return item
LUA;
		return $conn->luaEval( $script,
			array(
				$this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
				$this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
				$this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
				$this->getQueueKey( 'h-data' ), # KEYS[4]
			),
			4 # number of first argument(s) that are keys
		);
	}

	/**
	 * @param RedisConnRef $conn
	 * @return array Serialized string or false
	 * @throws RedisException
	 */
	protected function popAndAcquireBlob( RedisConnRef $conn ) {
		static $script =
<<<LUA
		local kUnclaimed, kSha1ById, kIdBySha1, kClaimed, kAttempts, kData = unpack(KEYS)
		-- Pop an item off the queue
		local id = redis.call('rPop',kUnclaimed)
		if not id then return false end
		-- Allow new duplicates of this job
		local sha1 = redis.call('hGet',kSha1ById,id)
		if sha1 then redis.call('hDel',kIdBySha1,sha1) end
		redis.call('hDel',kSha1ById,id)
		-- Mark the jobs as claimed and return it
		redis.call('zAdd',kClaimed,ARGV[1],id)
		redis.call('hIncrBy',kAttempts,id,1)
		return redis.call('hGet',kData,id)
LUA;
		return $conn->luaEval( $script,
			array(
				$this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
				$this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
				$this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
				$this->getQueueKey( 'z-claimed' ), # KEYS[4]
				$this->getQueueKey( 'h-attempts' ), # KEYS[5]
				$this->getQueueKey( 'h-data' ), # KEYS[6]
				time(), # ARGV[1] (injected to be replication-safe)
			),
			6 # number of first argument(s) that are keys
		);
	}

	/**
	 * @see JobQueue::doAck()
	 * @param Job $job
	 * @return Job|bool
	 * @throws MWException|JobQueueError
	 */
	protected function doAck( Job $job ) {
		if ( !isset( $job->metadata['uuid'] ) ) {
			throw new MWException( "Job of type '{$job->getType()}' has no UUID." );
		}
		if ( $this->claimTTL > 0 ) {
			$conn = $this->getConnection();
			try {
				static $script =
<<<LUA
				local kClaimed, kAttempts, kData = unpack(KEYS)
				-- Unmark the job as claimed
				redis.call('zRem',kClaimed,ARGV[1])
				redis.call('hDel',kAttempts,ARGV[1])
				-- Delete the job data itself
				return redis.call('hDel',kData,ARGV[1])
LUA;
				$res = $conn->luaEval( $script,
					array(
						$this->getQueueKey( 'z-claimed' ), # KEYS[1]
						$this->getQueueKey( 'h-attempts' ), # KEYS[2]
						$this->getQueueKey( 'h-data' ), # KEYS[3]
						$job->metadata['uuid'] # ARGV[1]
					),
					3 # number of first argument(s) that are keys
				);

				if ( !$res ) {
					wfDebugLog( 'JobQueueRedis', "Could not acknowledge {$this->type} job." );

					return false;
				}
			} catch ( RedisException $e ) {
				$this->throwRedisException( $conn, $e );
			}
		}

		return true;
	}

	/**
	 * @see JobQueue::doDeduplicateRootJob()
	 * @param Job $job
	 * @return bool
	 * @throws MWException|JobQueueError
	 */
	protected function doDeduplicateRootJob( Job $job ) {
		if ( !$job->hasRootJobParams() ) {
			throw new MWException( "Cannot register root job; missing parameters." );
		}
		$params = $job->getRootJobParams();

		$key = $this->getRootJobCacheKey( $params['rootJobSignature'] );

		$conn = $this->getConnection();
		try {
			$timestamp = $conn->get( $key ); // current last timestamp of this job
			if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
				return true; // a newer version of this root job was enqueued
			}

			// Update the timestamp of the last root job started at the location...
			return $conn->set( $key, $params['rootJobTimestamp'], self::ROOTJOB_TTL ); // 2 weeks
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::doIsRootJobOldDuplicate()
	 * @param Job $job
	 * @return bool
	 * @throws JobQueueError
	 */
	protected function doIsRootJobOldDuplicate( Job $job ) {
		if ( !$job->hasRootJobParams() ) {
			return false; // job has no de-deplication info
		}
		$params = $job->getRootJobParams();

		$conn = $this->getConnection();
		try {
			// Get the last time this root job was enqueued
			$timestamp = $conn->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}

		// Check if a new root job was started at the location after this one's...
		return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
	}

	/**
	 * @see JobQueue::doDelete()
	 * @return bool
	 * @throws JobQueueError
	 */
	protected function doDelete() {
		static $props = array( 'l-unclaimed', 'z-claimed', 'z-abandoned',
			'z-delayed', 'h-idBySha1', 'h-sha1ById', 'h-attempts', 'h-data' );

		$conn = $this->getConnection();
		try {
			$keys = array();
			foreach ( $props as $prop ) {
				$keys[] = $this->getQueueKey( $prop );
			}

			return ( $conn->delete( $keys ) !== false );
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::getAllQueuedJobs()
	 * @return Iterator
	 */
	public function getAllQueuedJobs() {
		$conn = $this->getConnection();
		try {
			$that = $this;

			return new MappedIterator(
				$conn->lRange( $this->getQueueKey( 'l-unclaimed' ), 0, -1 ),
				function ( $uid ) use ( $that, $conn ) {
					return $that->getJobFromUidInternal( $uid, $conn );
				},
				array( 'accept' => function ( $job ) {
					return is_object( $job );
				} )
			);
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * @see JobQueue::getAllQueuedJobs()
	 * @return Iterator
	 */
	public function getAllDelayedJobs() {
		$conn = $this->getConnection();
		try {
			$that = $this;

			return new MappedIterator( // delayed jobs
				$conn->zRange( $this->getQueueKey( 'z-delayed' ), 0, -1 ),
				function ( $uid ) use ( $that, $conn ) {
					return $that->getJobFromUidInternal( $uid, $conn );
				},
				array( 'accept' => function ( $job ) {
					return is_object( $job );
				} )
			);
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	public function getCoalesceLocationInternal() {
		return "RedisServer:" . $this->server;
	}

	protected function doGetSiblingQueuesWithJobs( array $types ) {
		return array_keys( array_filter( $this->doGetSiblingQueueSizes( $types ) ) );
	}

	protected function doGetSiblingQueueSizes( array $types ) {
		$sizes = array(); // (type => size)
		$types = array_values( $types ); // reindex
		$conn = $this->getConnection();
		try {
			$conn->multi( Redis::PIPELINE );
			foreach ( $types as $type ) {
				$conn->lSize( $this->getQueueKey( 'l-unclaimed', $type ) );
			}
			$res = $conn->exec();
			if ( is_array( $res ) ) {
				foreach ( $res as $i => $size ) {
					$sizes[$types[$i]] = $size;
				}
			}
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}

		return $sizes;
	}

	/**
	 * This function should not be called outside JobQueueRedis
	 *
	 * @param string $uid
	 * @param RedisConnRef $conn
	 * @return Job|bool Returns false if the job does not exist
	 * @throws MWException|JobQueueError
	 */
	public function getJobFromUidInternal( $uid, RedisConnRef $conn ) {
		try {
			$data = $conn->hGet( $this->getQueueKey( 'h-data' ), $uid );
			if ( $data === false ) {
				return false; // not found
			}
			$item = $this->unserialize( $conn->hGet( $this->getQueueKey( 'h-data' ), $uid ) );
			if ( !is_array( $item ) ) { // this shouldn't happen
				throw new MWException( "Could not find job with ID '$uid'." );
			}
			$title = Title::makeTitle( $item['namespace'], $item['title'] );
			$job = Job::factory( $item['type'], $title, $item['params'] );
			$job->metadata['uuid'] = $item['uuid'];

			return $job;
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}
	}

	/**
	 * Recycle or destroy any jobs that have been claimed for too long
	 * and release any ready delayed jobs into the queue
	 *
	 * @return int Number of jobs recycled/deleted/undelayed
	 * @throws MWException|JobQueueError
	 */
	public function recyclePruneAndUndelayJobs() {
		$count = 0;
		// For each job item that can be retried, we need to add it back to the
		// main queue and remove it from the list of currenty claimed job items.
		// For those that cannot, they are marked as dead and kept around for
		// investigation and manual job restoration but are eventually deleted.
		$conn = $this->getConnection();
		try {
			$now = time();
			static $script =
<<<LUA
			local kClaimed, kAttempts, kUnclaimed, kData, kAbandoned, kDelayed = unpack(KEYS)
			local released,abandoned,pruned,undelayed = 0,0,0,0
			-- Get all non-dead jobs that have an expired claim on them.
			-- The score for each item is the last claim timestamp (UNIX).
			local staleClaims = redis.call('zRangeByScore',kClaimed,0,ARGV[1])
			for k,id in ipairs(staleClaims) do
				local timestamp = redis.call('zScore',kClaimed,id)
				local attempts = redis.call('hGet',kAttempts,id)
				if attempts < ARGV[3] then
					-- Claim expired and retries left: re-enqueue the job
					redis.call('lPush',kUnclaimed,id)
					redis.call('hIncrBy',kAttempts,id,1)
					released = released + 1
				else
					-- Claim expired and no retries left: mark the job as dead
					redis.call('zAdd',kAbandoned,timestamp,id)
					abandoned = abandoned + 1
				end
				redis.call('zRem',kClaimed,id)
			end
			-- Get all of the dead jobs that have been marked as dead for too long.
			-- The score for each item is the last claim timestamp (UNIX).
			local deadClaims = redis.call('zRangeByScore',kAbandoned,0,ARGV[2])
			for k,id in ipairs(deadClaims) do
				-- Stale and out of retries: remove any traces of the job
				redis.call('zRem',kAbandoned,id)
				redis.call('hDel',kAttempts,id)
				redis.call('hDel',kData,id)
				pruned = pruned + 1
			end
			-- Get the list of ready delayed jobs, sorted by readiness (UNIX timestamp)
			local ids = redis.call('zRangeByScore',kDelayed,0,ARGV[4])
			-- Migrate the jobs from the "delayed" set to the "unclaimed" list
			for k,id in ipairs(ids) do
				redis.call('lPush',kUnclaimed,id)
				redis.call('zRem',kDelayed,id)
			end
			undelayed = #ids
			return {released,abandoned,pruned,undelayed}
LUA;
			$res = $conn->luaEval( $script,
				array(
					$this->getQueueKey( 'z-claimed' ), # KEYS[1]
					$this->getQueueKey( 'h-attempts' ), # KEYS[2]
					$this->getQueueKey( 'l-unclaimed' ), # KEYS[3]
					$this->getQueueKey( 'h-data' ), # KEYS[4]
					$this->getQueueKey( 'z-abandoned' ), # KEYS[5]
					$this->getQueueKey( 'z-delayed' ), # KEYS[6]
					$now - $this->claimTTL, # ARGV[1]
					$now - self::MAX_AGE_PRUNE, # ARGV[2]
					$this->maxTries, # ARGV[3]
					$now # ARGV[4]
				),
				6 # number of first argument(s) that are keys
			);
			if ( $res ) {
				list( $released, $abandoned, $pruned, $undelayed ) = $res;
				$count += $released + $pruned + $undelayed;
				JobQueue::incrStats( 'job-recycle', $this->type, $released, $this->wiki );
				JobQueue::incrStats( 'job-abandon', $this->type, $abandoned, $this->wiki );
				JobQueue::incrStats( 'job-undelay', $this->type, $undelayed, $this->wiki );
			}
		} catch ( RedisException $e ) {
			$this->throwRedisException( $conn, $e );
		}

		return $count;
	}

	/**
	 * @return array
	 */
	protected function doGetPeriodicTasks() {
		if ( $this->daemonized ) {
			return array(); // managed in the runner loop
		}
		$periods = array( 3600 ); // standard cleanup (useful on config change)
		if ( $this->claimTTL > 0 ) {
			$periods[] = ceil( $this->claimTTL / 2 ); // avoid bad timing
		}
		if ( $this->checkDelay ) {
			$periods[] = 300; // 5 minutes
		}
		$period = min( $periods );
		$period = max( $period, 30 ); // sanity

		return array(
			'recyclePruneAndUndelayJobs' => array(
				'callback' => array( $this, 'recyclePruneAndUndelayJobs' ),
				'period'   => $period,
			)
		);
	}

	/**
	 * @param IJobSpecification $job
	 * @return array
	 */
	protected function getNewJobFields( IJobSpecification $job ) {
		return array(
			// Fields that describe the nature of the job
			'type' => $job->getType(),
			'namespace' => $job->getTitle()->getNamespace(),
			'title' => $job->getTitle()->getDBkey(),
			'params' => $job->getParams(),
			// Some jobs cannot run until a "release timestamp"
			'rtimestamp' => $job->getReleaseTimestamp() ?: 0,
			// Additional job metadata
			'uuid' => UIDGenerator::newRawUUIDv4( UIDGenerator::QUICK_RAND ),
			'sha1' => $job->ignoreDuplicates()
				? wfBaseConvert( sha1( serialize( $job->getDeduplicationInfo() ) ), 16, 36, 31 )
				: '',
			'timestamp' => time() // UNIX timestamp
		);
	}

	/**
	 * @param array $fields
	 * @return Job|bool
	 */
	protected function getJobFromFields( array $fields ) {
		$title = Title::makeTitleSafe( $fields['namespace'], $fields['title'] );
		if ( $title ) {
			$job = Job::factory( $fields['type'], $title, $fields['params'] );
			$job->metadata['uuid'] = $fields['uuid'];

			return $job;
		}

		return false;
	}

	/**
	 * @param array $fields
	 * @return string Serialized and possibly compressed version of $fields
	 */
	protected function serialize( array $fields ) {
		$blob = serialize( $fields );
		if ( $this->compression === 'gzip'
			&& strlen( $blob ) >= 1024
			&& function_exists( 'gzdeflate' )
		) {
			$object = (object)array( 'blob' => gzdeflate( $blob ), 'enc' => 'gzip' );
			$blobz = serialize( $object );

			return ( strlen( $blobz ) < strlen( $blob ) ) ? $blobz : $blob;
		} else {
			return $blob;
		}
	}

	/**
	 * @param string $blob
	 * @return array|bool Unserialized version of $blob or false
	 */
	protected function unserialize( $blob ) {
		$fields = unserialize( $blob );
		if ( is_object( $fields ) ) {
			if ( $fields->enc === 'gzip' && function_exists( 'gzinflate' ) ) {
				$fields = unserialize( gzinflate( $fields->blob ) );
			} else {
				$fields = false;
			}
		}

		return is_array( $fields ) ? $fields : false;
	}

	/**
	 * Get a connection to the server that handles all sub-queues for this queue
	 *
	 * @return RedisConnRef
	 * @throws JobQueueConnectionError
	 */
	protected function getConnection() {
		$conn = $this->redisPool->getConnection( $this->server );
		if ( !$conn ) {
			throw new JobQueueConnectionError( "Unable to connect to redis server." );
		}

		return $conn;
	}

	/**
	 * @param RedisConnRef $conn
	 * @param RedisException $e
	 * @throws JobQueueError
	 */
	protected function throwRedisException( RedisConnRef $conn, $e ) {
		$this->redisPool->handleError( $conn, $e );
		throw new JobQueueError( "Redis server error: {$e->getMessage()}\n" );
	}

	/**
	 * @param string $prop
	 * @param string|null $type
	 * @return string
	 */
	private function getQueueKey( $prop, $type = null ) {
		$type = is_string( $type ) ? $type : $this->type;
		list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
		if ( strlen( $this->key ) ) { // namespaced queue (for testing)
			return wfForeignMemcKey( $db, $prefix, 'jobqueue', $type, $this->key, $prop );
		} else {
			return wfForeignMemcKey( $db, $prefix, 'jobqueue', $type, $prop );
		}
	}

	/**
	 * @param string $key
	 * @return void
	 */
	public function setTestingPrefix( $key ) {
		$this->key = $key;
	}
}