includes/job/JobQueueRedis.php

   1 <?php
   2 /**
   3  * Redis-backed job queue 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  * @author Aaron Schulz
  22  */
  23
  24 /**
  25  * Class to handle job queues stored in Redis
  26  *
  27  * This is faster, less resource intensive, queue that JobQueueDB.
  28  * All data for a queue using this class is placed into one redis server.
  29  *
  30  * There are eight main redis keys used to track jobs:
  31  *   - l-unclaimed  : A list of job IDs used for ready unclaimed jobs
  32  *   - z-claimed    : A sorted set of (job ID, UNIX timestamp as score) used for job retries
  33  *   - z-abandoned  : A sorted set of (job ID, UNIX timestamp as score) used for broken jobs
  34  *   - z-delayed    : A sorted set of (job ID, UNIX timestamp as score) used for delayed jobs
  35  *   - h-idBySha1   : A hash of (SHA1 => job ID) for unclaimed jobs used for de-duplication
  36  *   - h-sha1ById   : A hash of (job ID => SHA1) for unclaimed jobs used for de-duplication
  37  *   - h-attempts   : A hash of (job ID => attempt count) used for job claiming/retries
  38  *   - h-data       : A hash of (job ID => serialized blobs) for job storage
  39  * A job ID can be in only one of z-delayed, l-unclaimed, z-claimed, and z-abandoned.
  40  * If an ID appears in any of those lists, it should have a h-data entry for its ID.
  41  * If a job has a SHA1 de-duplication value and its ID is in l-unclaimed or z-delayed, then
  42  * there should be no other such jobs with that SHA1. Every h-idBySha1 entry has an h-sha1ById
  43  * entry and every h-sha1ById must refer to an ID that is l-unclaimed. If a job has its
  44  * ID in z-claimed or z-abandoned, then it must also have an h-attempts entry for its ID.
  45  *
  46  * Additionally, "rootjob:* keys track "root jobs" used for additional de-duplication.
  47  * Aside from root job keys, all keys have no expiry, and are only removed when jobs are run.
  48  * All the keys are prefixed with the relevant wiki ID information.
  49  *
  50  * This class requires Redis 2.6 as it makes use Lua scripts for fast atomic operations.
  51  * Additionally, it should be noted that redis has different persistence modes, such
  52  * as rdb snapshots, journaling, and no persistent. Appropriate configuration should be
  53  * made on the servers based on what queues are using it and what tolerance they have.
  54  *
  55  * @ingroup JobQueue
  56  * @ingroup Redis
  57  * @since 1.21
  58  */
  59 class JobQueueRedis extends JobQueue {
  60         /** @var RedisConnectionPool */
  61         protected $redisPool;
  62
  63         protected $server; // string; server address
  64
  65         const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed (7 days)
  66
  67         protected $key; // string; key to prefix the queue keys with (used for testing)
  68
  69         /**
  70          * @params include:
  71          *   - redisConfig : An array of parameters to RedisConnectionPool::__construct().
  72          *                   Note that the serializer option is ignored "none" is always used.
  73          *   - redisServer : A hostname/port combination or the absolute path of a UNIX socket.
  74          *                   If a hostname is specified but no port, the standard port number
  75          *                   6379 will be used. Required.
  76          * @param array $params
  77          */
  78         public function __construct( array $params ) {
  79                 parent::__construct( $params );
  80                 $params['redisConfig']['serializer'] = 'none'; // make it easy to use Lua
  81                 $this->server = $params['redisServer'];
  82                 $this->redisPool = RedisConnectionPool::singleton( $params['redisConfig'] );
  83         }
  84
  85         protected function supportedOrders() {
  86                 return array( 'timestamp', 'fifo' );
  87         }
  88
  89         protected function optimalOrder() {
  90                 return 'fifo';
  91         }
  92
  93         protected function supportsDelayedJobs() {
  94                 return true;
  95         }
  96
  97         /**
  98          * @see JobQueue::doIsEmpty()
  99          * @return bool
 100          * @throws MWException
 101          */
 102         protected function doIsEmpty() {
 103                 return $this->doGetSize() == 0;
 104         }
 105
 106         /**
 107          * @see JobQueue::doGetSize()
 108          * @return integer
 109          * @throws MWException
 110          */
 111         protected function doGetSize() {
 112                 $conn = $this->getConnection();
 113                 try {
 114                         return $conn->lSize( $this->getQueueKey( 'l-unclaimed' ) );
 115                 } catch ( RedisException $e ) {
 116                         $this->throwRedisException( $this->server, $conn, $e );
 117                 }
 118         }
 119
 120         /**
 121          * @see JobQueue::doGetAcquiredCount()
 122          * @return integer
 123          * @throws MWException
 124          */
 125         protected function doGetAcquiredCount() {
 126                 if ( $this->claimTTL <= 0 ) {
 127                         return 0; // no acknowledgements
 128                 }
 129                 $conn = $this->getConnection();
 130                 try {
 131                         $conn->multi( Redis::PIPELINE );
 132                         $conn->zSize( $this->getQueueKey( 'z-claimed' ) );
 133                         $conn->zSize( $this->getQueueKey( 'z-abandoned' ) );
 134                         return array_sum( $conn->exec() );
 135                 } catch ( RedisException $e ) {
 136                         $this->throwRedisException( $this->server, $conn, $e );
 137                 }
 138         }
 139
 140         /**
 141          * @see JobQueue::doGetDelayedCount()
 142          * @return integer
 143          * @throws MWException
 144          */
 145         protected function doGetDelayedCount() {
 146                 if ( !$this->checkDelay ) {
 147                         return 0; // no delayed jobs
 148                 }
 149                 $conn = $this->getConnection();
 150                 try {
 151                         return $conn->zSize( $this->getQueueKey( 'z-delayed' ) );
 152                 } catch ( RedisException $e ) {
 153                         $this->throwRedisException( $this->server, $conn, $e );
 154                 }
 155         }
 156
 157         /**
 158          * @see JobQueue::doGetAbandonedCount()
 159          * @return integer
 160          * @throws MWException
 161          */
 162         protected function doGetAbandonedCount() {
 163                 if ( $this->claimTTL <= 0 ) {
 164                         return 0; // no acknowledgements
 165                 }
 166                 $conn = $this->getConnection();
 167                 try {
 168                         return $conn->zSize( $this->getQueueKey( 'z-abandoned' ) );
 169                 } catch ( RedisException $e ) {
 170                         $this->throwRedisException( $this->server, $conn, $e );
 171                 }
 172         }
 173
 174         /**
 175          * @see JobQueue::doBatchPush()
 176          * @param array $jobs
 177          * @param $flags
 178          * @return bool
 179          * @throws MWException
 180          */
 181         protected function doBatchPush( array $jobs, $flags ) {
 182                 // Convert the jobs into field maps (de-duplicated against each other)
 183                 $items = array(); // (job ID => job fields map)
 184                 foreach ( $jobs as $job ) {
 185                         $item = $this->getNewJobFields( $job );
 186                         if ( strlen( $item['sha1'] ) ) { // hash identifier => de-duplicate
 187                                 $items[$item['sha1']] = $item;
 188                         } else {
 189                                 $items[$item['uuid']] = $item;
 190                         }
 191                 }
 192
 193                 if ( !count( $items ) ) {
 194                         return true; // nothing to do
 195                 }
 196
 197                 $conn = $this->getConnection();
 198                 try {
 199                         // Actually push the non-duplicate jobs into the queue...
 200                         if ( $flags & self::QOS_ATOMIC ) {
 201                                 $batches = array( $items ); // all or nothing
 202                         } else {
 203                                 $batches = array_chunk( $items, 500 ); // avoid tying up the server
 204                         }
 205                         $failed = 0;
 206                         $pushed = 0;
 207                         foreach ( $batches as $itemBatch ) {
 208                                 $added = $this->pushBlobs( $conn, $itemBatch );
 209                                 if ( is_int( $added ) ) {
 210                                         $pushed += $added;
 211                                 } else {
 212                                         $failed += count( $itemBatch );
 213                                 }
 214                         }
 215                         if ( $failed > 0 ) {
 216                                 wfDebugLog( 'JobQueueRedis', "Could not insert {$failed} {$this->type} job(s)." );
 217                                 return false;
 218                         }
 219                         JobQueue::incrStats( 'job-insert', $this->type, count( $items ) );
 220                         JobQueue::incrStats( 'job-insert-duplicate', $this->type,
 221                                 count( $items ) - $failed - $pushed );
 222                 } catch ( RedisException $e ) {
 223                         $this->throwRedisException( $this->server, $conn, $e );
 224                 }
 225
 226                 return true;
 227         }
 228
 229         /**
 230          * @param RedisConnRef $conn
 231          * @param array $items List of results from JobQueueRedis::getNewJobFields()
 232          * @return integer Number of jobs inserted (duplicates are ignored)
 233          * @throws RedisException
 234          */
 235         protected function pushBlobs( RedisConnRef $conn, array $items ) {
 236                 $args = array(); // ([id, sha1, rtime, blob [, id, sha1, rtime, blob ... ] ] )
 237                 foreach ( $items as $item ) {
 238                         $args[] = (string)$item['uuid'];
 239                         $args[] = (string)$item['sha1'];
 240                         $args[] = (string)$item['rtimestamp'];
 241                         $args[] = (string)serialize( $item );
 242                 }
 243                 static $script =
 244 <<<LUA
 245                 if #ARGV % 4 ~= 0 then return redis.error_reply('Unmatched arguments') end
 246                 local pushed = 0
 247                 for i = 1,#ARGV,4 do
 248                         local id,sha1,rtimestamp,blob = ARGV[i],ARGV[i+1],ARGV[i+2],ARGV[i+3]
 249                         if sha1 == '' or redis.call('hExists',KEYS[3],sha1) == 0 then
 250                                 if 1*rtimestamp > 0 then
 251                                         -- Insert into delayed queue (release time as score)
 252                                         redis.call('zAdd',KEYS[4],rtimestamp,id)
 253                                 else
 254                                         -- Insert into unclaimed queue
 255                                         redis.call('lPush',KEYS[1],id)
 256                                 end
 257                                 if sha1 ~= '' then
 258                                         redis.call('hSet',KEYS[2],id,sha1)
 259                                         redis.call('hSet',KEYS[3],sha1,id)
 260                                 end
 261                                 redis.call('hSet',KEYS[5],id,blob)
 262                                 pushed = pushed + 1
 263                         end
 264                 end
 265                 return pushed
 266 LUA;
 267                 return $this->redisEval( $conn, $script,
 268                         array_merge(
 269                                 array(
 270                                         $this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
 271                                         $this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
 272                                         $this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
 273                                         $this->getQueueKey( 'z-delayed' ), # KEYS[4]
 274                                         $this->getQueueKey( 'h-data' ), # KEYS[5]
 275                                 ),
 276                                 $args
 277                         ),
 278                         5 # number of first argument(s) that are keys
 279                 );
 280         }
 281
 282         /**
 283          * @see JobQueue::doPop()
 284          * @return Job|bool
 285          * @throws MWException
 286          */
 287         protected function doPop() {
 288                 $job = false;
 289
 290                 // Push ready delayed jobs into the queue every 10 jobs to spread the load.
 291                 // This is also done as a periodic task, but we don't want too much done at once.
 292                 if ( $this->checkDelay && mt_rand( 0, 9 ) == 0 ) {
 293                         $this->releaseReadyDelayedJobs();
 294                 }
 295
 296                 $conn = $this->getConnection();
 297                 try {
 298                         do {
 299                                 if ( $this->claimTTL > 0 ) {
 300                                         // Keep the claimed job list down for high-traffic queues
 301                                         if ( mt_rand( 0, 99 ) == 0 ) {
 302                                                 $this->recycleAndDeleteStaleJobs();
 303                                         }
 304                                         $blob = $this->popAndAcquireBlob( $conn );
 305                                 } else {
 306                                         $blob = $this->popAndDeleteBlob( $conn );
 307                                 }
 308                                 if ( $blob === false ) {
 309                                         break; // no jobs; nothing to do
 310                                 }
 311
 312                                 JobQueue::incrStats( 'job-pop', $this->type );
 313                                 $item = unserialize( $blob );
 314                                 if ( $item === false ) {
 315                                         wfDebugLog( 'JobQueueRedis', "Could not unserialize {$this->type} job." );
 316                                         continue;
 317                                 }
 318
 319                                 // If $item is invalid, recycleAndDeleteStaleJobs() will cleanup as needed
 320                                 $job = $this->getJobFromFields( $item ); // may be false
 321                         } while ( !$job ); // job may be false if invalid
 322                 } catch ( RedisException $e ) {
 323                         $this->throwRedisException( $this->server, $conn, $e );
 324                 }
 325
 326                 return $job;
 327         }
 328
 329         /**
 330          * @param RedisConnRef $conn
 331          * @return array serialized string or false
 332          * @throws RedisException
 333          */
 334         protected function popAndDeleteBlob( RedisConnRef $conn ) {
 335                 static $script =
 336 <<<LUA
 337                 -- Pop an item off the queue
 338                 local id = redis.call('rpop',KEYS[1])
 339                 if not id then return false end
 340                 -- Get the job data and remove it
 341                 local item = redis.call('hGet',KEYS[4],id)
 342                 redis.call('hDel',KEYS[4],id)
 343                 -- Allow new duplicates of this job
 344                 local sha1 = redis.call('hGet',KEYS[2],id)
 345                 if sha1 then redis.call('hDel',KEYS[3],sha1) end
 346                 redis.call('hDel',KEYS[2],id)
 347                 -- Return the job data
 348                 return item
 349 LUA;
 350                 return $this->redisEval( $conn, $script,
 351                         array(
 352                                 $this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
 353                                 $this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
 354                                 $this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
 355                                 $this->getQueueKey( 'h-data' ), # KEYS[4]
 356                         ),
 357                         4 # number of first argument(s) that are keys
 358                 );
 359         }
 360
 361         /**
 362          * @param RedisConnRef $conn
 363          * @return array serialized string or false
 364          * @throws RedisException
 365          */
 366         protected function popAndAcquireBlob( RedisConnRef $conn ) {
 367                 static $script =
 368 <<<LUA
 369                 -- Pop an item off the queue
 370                 local id = redis.call('rPop',KEYS[1])
 371                 if not id then return false end
 372                 -- Allow new duplicates of this job
 373                 local sha1 = redis.call('hGet',KEYS[2],id)
 374                 if sha1 then redis.call('hDel',KEYS[3],sha1) end
 375                 redis.call('hDel',KEYS[2],id)
 376                 -- Mark the jobs as claimed and return it
 377                 redis.call('zAdd',KEYS[4],ARGV[1],id)
 378                 redis.call('hIncrBy',KEYS[5],id,1)
 379                 return redis.call('hGet',KEYS[6],id)
 380 LUA;
 381                 return $this->redisEval( $conn, $script,
 382                         array(
 383                                 $this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
 384                                 $this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
 385                                 $this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
 386                                 $this->getQueueKey( 'z-claimed' ), # KEYS[4]
 387                                 $this->getQueueKey( 'h-attempts' ), # KEYS[5]
 388                                 $this->getQueueKey( 'h-data' ), # KEYS[6]
 389                                 time(), # ARGV[1] (injected to be replication-safe)
 390                         ),
 391                         6 # number of first argument(s) that are keys
 392                 );
 393         }
 394
 395         /**
 396          * @see JobQueue::doAck()
 397          * @param Job $job
 398          * @return Job|bool
 399          * @throws MWException
 400          */
 401         protected function doAck( Job $job ) {
 402                 if ( $this->claimTTL > 0 ) {
 403                         $conn = $this->getConnection();
 404                         try {
 405                                 // Get the exact field map this Job came from, regardless of whether
 406                                 // the job was transformed into a DuplicateJob or anything of the sort.
 407                                 $item = $job->metadata['sourceFields'];
 408
 409                                 static $script =
 410 <<<LUA
 411                                 -- Unmark the job as claimed
 412                                 redis.call('zRem',KEYS[1],ARGV[1])
 413                                 redis.call('hDel',KEYS[2],ARGV[1])
 414                                 -- Delete the job data itself
 415                                 return redis.call('hDel',KEYS[3],ARGV[1])
 416 LUA;
 417                                 $res = $this->redisEval( $conn, $script,
 418                                         array(
 419                                                 $this->getQueueKey( 'z-claimed' ), # KEYS[1]
 420                                                 $this->getQueueKey( 'h-attempts' ), # KEYS[2]
 421                                                 $this->getQueueKey( 'h-data' ), # KEYS[3]
 422                                                 $item['uuid'] # ARGV[1]
 423                                         ),
 424                                         3 # number of first argument(s) that are keys
 425                                 );
 426
 427                                 if ( !$res ) {
 428                                         wfDebugLog( 'JobQueueRedis', "Could not acknowledge {$this->type} job." );
 429                                         return false;
 430                                 }
 431                         } catch ( RedisException $e ) {
 432                                 $this->throwRedisException( $this->server, $conn, $e );
 433                         }
 434                 }
 435                 return true;
 436         }
 437
 438         /**
 439          * @see JobQueue::doDeduplicateRootJob()
 440          * @param Job $job
 441          * @return bool
 442          * @throws MWException
 443          */
 444         protected function doDeduplicateRootJob( Job $job ) {
 445                 if ( !$job->hasRootJobParams() ) {
 446                         throw new MWException( "Cannot register root job; missing parameters." );
 447                 }
 448                 $params = $job->getRootJobParams();
 449
 450                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 451
 452                 $conn = $this->getConnection();
 453                 try {
 454                         $timestamp = $conn->get( $key ); // current last timestamp of this job
 455                         if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 456                                 return true; // a newer version of this root job was enqueued
 457                         }
 458                         // Update the timestamp of the last root job started at the location...
 459                         return $conn->set( $key, $params['rootJobTimestamp'], self::ROOTJOB_TTL ); // 2 weeks
 460                 } catch ( RedisException $e ) {
 461                         $this->throwRedisException( $this->server, $conn, $e );
 462                 }
 463         }
 464
 465         /**
 466          * @see JobQueue::doIsRootJobOldDuplicate()
 467          * @param Job $job
 468          * @return bool
 469          */
 470         protected function doIsRootJobOldDuplicate( Job $job ) {
 471                 $params = $job->getParams();
 472                 if ( !isset( $params['rootJobSignature'] ) ) {
 473                         return false; // job has no de-deplication info
 474                 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
 475                         wfDebugLog( 'JobQueueRedis', "Cannot check root job; missing 'rootJobTimestamp'." );
 476                         return false;
 477                 }
 478
 479                 $conn = $this->getConnection();
 480                 try {
 481                         // Get the last time this root job was enqueued
 482                         $timestamp = $conn->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) );
 483                 } catch ( RedisException $e ) {
 484                         $this->throwRedisException( $this->server, $conn, $e );
 485                 }
 486
 487                 // Check if a new root job was started at the location after this one's...
 488                 return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
 489         }
 490
 491         /**
 492          * @see JobQueue::getAllQueuedJobs()
 493          * @return Iterator
 494          */
 495         public function getAllQueuedJobs() {
 496                 $conn = $this->getConnection();
 497                 if ( !$conn ) {
 498                         throw new MWException( "Unable to connect to redis server." );
 499                 }
 500                 try {
 501                         $that = $this;
 502                         return new MappedIterator(
 503                                 $conn->lRange( $this->getQueueKey( 'l-unclaimed' ), 0, -1 ),
 504                                 function( $uid ) use ( $that, $conn ) {
 505                                         return $that->getJobFromUidInternal( $uid, $conn );
 506                                 }
 507                         );
 508                 } catch ( RedisException $e ) {
 509                         $this->throwRedisException( $this->server, $conn, $e );
 510                 }
 511         }
 512
 513         /**
 514          * @see JobQueue::getAllQueuedJobs()
 515          * @return Iterator
 516          */
 517         public function getAllDelayedJobs() {
 518                 $conn = $this->getConnection();
 519                 if ( !$conn ) {
 520                         throw new MWException( "Unable to connect to redis server." );
 521                 }
 522                 try {
 523                         $that = $this;
 524                         return new MappedIterator( // delayed jobs
 525                                 $conn->zRange( $this->getQueueKey( 'z-delayed' ), 0, -1 ),
 526                                 function( $uid ) use ( $that, $conn ) {
 527                                         return $that->getJobFromUidInternal( $uid, $conn );
 528                                 }
 529                         );
 530                 } catch ( RedisException $e ) {
 531                         $this->throwRedisException( $this->server, $conn, $e );
 532                 }
 533         }
 534
 535         /**
 536          * This function should not be called outside JobQueueRedis
 537          *
 538          * @param $uid string
 539          * @param $conn RedisConnRef
 540          * @return Job
 541          * @throws MWException
 542          */
 543         public function getJobFromUidInternal( $uid, RedisConnRef $conn ) {
 544                 try {
 545                         $item = unserialize( $conn->hGet( $this->getQueueKey( 'h-data' ), $uid ) );
 546                         if ( !is_array( $item ) ) { // this shouldn't happen
 547                                 throw new MWException( "Could not find job with ID '$uid'." );
 548                         }
 549                         $title = Title::makeTitle( $item['namespace'], $item['title'] );
 550                         $job = Job::factory( $item['type'], $title, $item['params'] );
 551                         $job->metadata['sourceFields'] = $item;
 552                         return $job;
 553                 } catch ( RedisException $e ) {
 554                         $this->throwRedisException( $this->server, $conn, $e );
 555                 }
 556         }
 557
 558         /**
 559          * Release any ready delayed jobs into the queue
 560          *
 561          * @return integer Number of jobs released
 562          * @throws MWException
 563          */
 564         public function releaseReadyDelayedJobs() {
 565                 $count = 0;
 566
 567                 $conn = $this->getConnection();
 568                 try {
 569                         static $script =
 570 <<<LUA
 571                         -- Get the list of ready delayed jobs, sorted by readiness
 572                         local ids = redis.call('zRangeByScore',KEYS[1],0,ARGV[1])
 573                         -- Migrate the jobs from the "delayed" set to the "unclaimed" list
 574                         for k,id in ipairs(ids) do
 575                                 redis.call('lPush',KEYS[2],id)
 576                                 redis.call('zRem',KEYS[1],id)
 577                         end
 578                         return #ids
 579 LUA;
 580                         $count += (int)$this->redisEval( $conn, $script,
 581                                 array(
 582                                         $this->getQueueKey( 'z-delayed' ), // KEYS[1]
 583                                         $this->getQueueKey( 'l-unclaimed' ), // KEYS[2]
 584                                         time() // ARGV[1]; max "delay until" UNIX timestamp
 585                                 ),
 586                                 2 # first two arguments are keys
 587                         );
 588                 } catch ( RedisException $e ) {
 589                         $this->throwRedisException( $this->server, $conn, $e );
 590                 }
 591
 592                 return $count;
 593         }
 594
 595         /**
 596          * Recycle or destroy any jobs that have been claimed for too long
 597          *
 598          * @return integer Number of jobs recycled/deleted
 599          * @throws MWException
 600          */
 601         public function recycleAndDeleteStaleJobs() {
 602                 if ( $this->claimTTL <= 0 ) { // sanity
 603                         throw new MWException( "Cannot recycle jobs since acknowledgements are disabled." );
 604                 }
 605                 $count = 0;
 606                 // For each job item that can be retried, we need to add it back to the
 607                 // main queue and remove it from the list of currenty claimed job items.
 608                 // For those that cannot, they are marked as dead and kept around for
 609                 // investigation and manual job restoration but are eventually deleted.
 610                 $conn = $this->getConnection();
 611                 try {
 612                         $now = time();
 613                         static $script =
 614 <<<LUA
 615                         local released,abandoned,pruned = 0,0,0
 616                         -- Get all non-dead jobs that have an expired claim on them.
 617                         -- The score for each item is the last claim timestamp (UNIX).
 618                         local staleClaims = redis.call('zRangeByScore',KEYS[1],0,ARGV[1])
 619                         for k,id in ipairs(staleClaims) do
 620                                 local timestamp = redis.call('zScore',KEYS[1],id)
 621                                 local attempts = redis.call('hGet',KEYS[2],id)
 622                                 if attempts < ARGV[3] then
 623                                         -- Claim expired and retries left: re-enqueue the job
 624                                         redis.call('lPush',KEYS[3],id)
 625                                         redis.call('hIncrBy',KEYS[2],id,1)
 626                                         released = released + 1
 627                                 else
 628                                         -- Claim expired and no retries left: mark the job as dead
 629                                         redis.call('zAdd',KEYS[5],timestamp,id)
 630                                         abandoned = abandoned + 1
 631                                 end
 632                                 redis.call('zRem',KEYS[1],id)
 633                         end
 634                         -- Get all of the dead jobs that have been marked as dead for too long.
 635                         -- The score for each item is the last claim timestamp (UNIX).
 636                         local deadClaims = redis.call('zRangeByScore',KEYS[5],0,ARGV[2])
 637                         for k,id in ipairs(deadClaims) do
 638                                 -- Stale and out of retries: remove any traces of the job
 639                                 redis.call('zRem',KEYS[5],id)
 640                                 redis.call('hDel',KEYS[2],id)
 641                                 redis.call('hDel',KEYS[4],id)
 642                                 pruned = pruned + 1
 643                         end
 644                         return {released,abandoned,pruned}
 645 LUA;
 646                         $res = $this->redisEval( $conn, $script,
 647                                 array(
 648                                         $this->getQueueKey( 'z-claimed' ), # KEYS[1]
 649                                         $this->getQueueKey( 'h-attempts' ), # KEYS[2]
 650                                         $this->getQueueKey( 'l-unclaimed' ), # KEYS[3]
 651                                         $this->getQueueKey( 'h-data' ), # KEYS[4]
 652                                         $this->getQueueKey( 'z-abandoned' ), # KEYS[5]
 653                                         $now - $this->claimTTL, # ARGV[1]
 654                                         $now - self::MAX_AGE_PRUNE, # ARGV[2]
 655                                         $this->maxTries # ARGV[3]
 656                                 ),
 657                                 5 # number of first argument(s) that are keys
 658                         );
 659                         if ( $res ) {
 660                                 list( $released, $abandoned, $pruned ) = $res;
 661                                 $count += $released + $pruned;
 662                                 JobQueue::incrStats( 'job-recycle', $this->type, count( $released ) );
 663                         }
 664                 } catch ( RedisException $e ) {
 665                         $this->throwRedisException( $this->server, $conn, $e );
 666                 }
 667
 668                 return $count;
 669         }
 670
 671         /**
 672          * @return Array
 673          */
 674         protected function doGetPeriodicTasks() {
 675                 $tasks = array();
 676                 if ( $this->claimTTL > 0 ) {
 677                         $tasks['recycleAndDeleteStaleJobs'] = array(
 678                                 'callback' => array( $this, 'recycleAndDeleteStaleJobs' ),
 679                                 'period'   => ceil( $this->claimTTL / 2 )
 680                         );
 681                 }
 682                 if ( $this->checkDelay ) {
 683                         $tasks['releaseReadyDelayedJobs'] = array(
 684                                 'callback' => array( $this, 'releaseReadyDelayedJobs' ),
 685                                 'period'   => 300 // 5 minutes
 686                         );
 687                 }
 688                 return $tasks;
 689         }
 690
 691         /**
 692          * @param RedisConnRef $conn
 693          * @param string $script
 694          * @param array $params
 695          * @param integer $numKeys
 696          * @return mixed
 697          */
 698         protected function redisEval( RedisConnRef $conn, $script, array $params, $numKeys ) {
 699                 $sha1 = sha1( $script ); // 40 char hex
 700
 701                 // Try to run the server-side cached copy of the script
 702                 $conn->clearLastError();
 703                 $res = $conn->evalSha( $sha1, $params, $numKeys );
 704                 // If the script is not in cache, use eval() to retry and cache it
 705                 if ( $conn->getLastError() && $conn->script( 'exists', $sha1 ) === array( 0 ) ) {
 706                         $conn->clearLastError();
 707                         $res = $conn->eval( $script, $params, $numKeys );
 708                         wfDebugLog( 'JobQueueRedis', "Used eval() for Lua script $sha1." );
 709                 }
 710
 711                 if ( $conn->getLastError() ) { // script bug?
 712                         wfDebugLog( 'JobQueueRedis', "Lua script error: " . $conn->getLastError() );
 713                 }
 714
 715                 return $res;
 716         }
 717
 718         /**
 719          * @param $job Job
 720          * @return array
 721          */
 722         protected function getNewJobFields( Job $job ) {
 723                 return array(
 724                         // Fields that describe the nature of the job
 725                         'type'       => $job->getType(),
 726                         'namespace'  => $job->getTitle()->getNamespace(),
 727                         'title'      => $job->getTitle()->getDBkey(),
 728                         'params'     => $job->getParams(),
 729                         // Some jobs cannot run until a "release timestamp"
 730                         'rtimestamp' => $job->getReleaseTimestamp() ?: 0,
 731                         // Additional job metadata
 732                         'uuid'       => UIDGenerator::newRawUUIDv4( UIDGenerator::QUICK_RAND ),
 733                         'sha1'       => $job->ignoreDuplicates()
 734                                 ? wfBaseConvert( sha1( serialize( $job->getDeduplicationInfo() ) ), 16, 36, 31 )
 735                                 : '',
 736                         'timestamp'  => time() // UNIX timestamp
 737                 );
 738         }
 739
 740         /**
 741          * @param $fields array
 742          * @return Job|bool
 743          */
 744         protected function getJobFromFields( array $fields ) {
 745                 $title = Title::makeTitleSafe( $fields['namespace'], $fields['title'] );
 746                 if ( $title ) {
 747                         $job = Job::factory( $fields['type'], $title, $fields['params'] );
 748                         $job->metadata['sourceFields'] = $fields;
 749                         return $job;
 750                 }
 751                 return false;
 752         }
 753
 754         /**
 755          * Get a connection to the server that handles all sub-queues for this queue
 756          *
 757          * @return Array (server name, Redis instance)
 758          * @throws MWException
 759          */
 760         protected function getConnection() {
 761                 $conn = $this->redisPool->getConnection( $this->server );
 762                 if ( !$conn ) {
 763                         throw new MWException( "Unable to connect to redis server." );
 764                 }
 765                 return $conn;
 766         }
 767
 768         /**
 769          * @param $server string
 770          * @param $conn RedisConnRef
 771          * @param $e RedisException
 772          * @throws MWException
 773          */
 774         protected function throwRedisException( $server, RedisConnRef $conn, $e ) {
 775                 $this->redisPool->handleException( $server, $conn, $e );
 776                 throw new MWException( "Redis server error: {$e->getMessage()}\n" );
 777         }
 778
 779         /**
 780          * @param $prop string
 781          * @return string
 782          */
 783         private function getQueueKey( $prop ) {
 784                 list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
 785                 if ( strlen( $this->key ) ) { // namespaced queue (for testing)
 786                         return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, $this->key, $prop );
 787                 } else {
 788                         return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, $prop );
 789                 }
 790         }
 791
 792         /**
 793          * @param $key string
 794          * @return void
 795          */
 796         public function setTestingPrefix( $key ) {
 797                 $this->key = $key;
 798         }
 799 }