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                         wfIncrStats( 'job-insert', count( $items ) );
 220                         wfIncrStats( 'job-insert-duplicate', count( $items ) - $failed - $pushed );
 221                 } catch ( RedisException $e ) {
 222                         $this->throwRedisException( $this->server, $conn, $e );
 223                 }
 224
 225                 return true;
 226         }
 227
 228         /**
 229          * @param RedisConnRef $conn
 230          * @param array $items List of results from JobQueueRedis::getNewJobFields()
 231          * @return integer Number of jobs inserted (duplicates are ignored)
 232          * @throws RedisException
 233          */
 234         protected function pushBlobs( RedisConnRef $conn, array $items ) {
 235                 $args = array(); // ([id, sha1, rtime, blob [, id, sha1, rtime, blob ... ] ] )
 236                 foreach ( $items as $item ) {
 237                         $args[] = (string)$item['uuid'];
 238                         $args[] = (string)$item['sha1'];
 239                         $args[] = (string)$item['rtimestamp'];
 240                         $args[] = (string)serialize( $item );
 241                 }
 242                 static $script =
 243 <<<LUA
 244                 if #ARGV % 4 ~= 0 then return redis.error_reply('Unmatched arguments') end
 245                 local pushed = 0
 246                 for i = 1,#ARGV,4 do
 247                         local id,sha1,rtimestamp,blob = ARGV[i],ARGV[i+1],ARGV[i+2],ARGV[i+3]
 248                         if sha1 == '' or redis.call('hExists',KEYS[3],sha1) == 0 then
 249                                 if 1*rtimestamp > 0 then
 250                                         -- Insert into delayed queue (release time as score)
 251                                         redis.call('zAdd',KEYS[4],rtimestamp,id)
 252                                 else
 253                                         -- Insert into unclaimed queue
 254                                         redis.call('lPush',KEYS[1],id)
 255                                 end
 256                                 if sha1 ~= '' then
 257                                         redis.call('hSet',KEYS[2],id,sha1)
 258                                         redis.call('hSet',KEYS[3],sha1,id)
 259                                 end
 260                                 redis.call('hSet',KEYS[5],id,blob)
 261                                 pushed = pushed + 1
 262                         end
 263                 end
 264                 return pushed
 265 LUA;
 266                 return $this->redisEval( $conn, $script,
 267                         array_merge(
 268                                 array(
 269                                         $this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
 270                                         $this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
 271                                         $this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
 272                                         $this->getQueueKey( 'z-delayed' ), # KEYS[4]
 273                                         $this->getQueueKey( 'h-data' ), # KEYS[5]
 274                                 ),
 275                                 $args
 276                         ),
 277                         5 # number of first argument(s) that are keys
 278                 );
 279         }
 280
 281         /**
 282          * @see JobQueue::doPop()
 283          * @return Job|bool
 284          * @throws MWException
 285          */
 286         protected function doPop() {
 287                 $job = false;
 288
 289                 // Push ready delayed jobs into the queue every 10 jobs to spread the load.
 290                 // This is also done as a periodic task, but we don't want too much done at once.
 291                 if ( $this->checkDelay && mt_rand( 0, 9 ) == 0 ) {
 292                         $this->releaseReadyDelayedJobs();
 293                 }
 294
 295                 $conn = $this->getConnection();
 296                 try {
 297                         do {
 298                                 if ( $this->claimTTL > 0 ) {
 299                                         // Keep the claimed job list down for high-traffic queues
 300                                         if ( mt_rand( 0, 99 ) == 0 ) {
 301                                                 $this->recycleAndDeleteStaleJobs();
 302                                         }
 303                                         $blob = $this->popAndAcquireBlob( $conn );
 304                                 } else {
 305                                         $blob = $this->popAndDeleteBlob( $conn );
 306                                 }
 307                                 if ( $blob === false ) {
 308                                         break; // no jobs; nothing to do
 309                                 }
 310
 311                                 wfIncrStats( 'job-pop' );
 312                                 $item = unserialize( $blob );
 313                                 if ( $item === false ) {
 314                                         wfDebugLog( 'JobQueueRedis', "Could not unserialize {$this->type} job." );
 315                                         continue;
 316                                 }
 317
 318                                 // If $item is invalid, recycleAndDeleteStaleJobs() will cleanup as needed
 319                                 $job = $this->getJobFromFields( $item ); // may be false
 320                         } while ( !$job ); // job may be false if invalid
 321                 } catch ( RedisException $e ) {
 322                         $this->throwRedisException( $this->server, $conn, $e );
 323                 }
 324
 325                 return $job;
 326         }
 327
 328         /**
 329          * @param RedisConnRef $conn
 330          * @return array serialized string or false
 331          * @throws RedisException
 332          */
 333         protected function popAndDeleteBlob( RedisConnRef $conn ) {
 334                 static $script =
 335 <<<LUA
 336                 -- Pop an item off the queue
 337                 local id = redis.call('rpop',KEYS[1])
 338                 if not id then return false end
 339                 -- Get the job data and remove it
 340                 local item = redis.call('hGet',KEYS[4],id)
 341                 redis.call('hDel',KEYS[4],id)
 342                 -- Allow new duplicates of this job
 343                 local sha1 = redis.call('hGet',KEYS[2],id)
 344                 if sha1 then redis.call('hDel',KEYS[3],sha1) end
 345                 redis.call('hDel',KEYS[2],id)
 346                 -- Return the job data
 347                 return item
 348 LUA;
 349                 return $this->redisEval( $conn, $script,
 350                         array(
 351                                 $this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
 352                                 $this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
 353                                 $this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
 354                                 $this->getQueueKey( 'h-data' ), # KEYS[4]
 355                         ),
 356                         4 # number of first argument(s) that are keys
 357                 );
 358         }
 359
 360         /**
 361          * @param RedisConnRef $conn
 362          * @return array serialized string or false
 363          * @throws RedisException
 364          */
 365         protected function popAndAcquireBlob( RedisConnRef $conn ) {
 366                 static $script =
 367 <<<LUA
 368                 -- Pop an item off the queue
 369                 local id = redis.call('rPop',KEYS[1])
 370                 if not id then return false end
 371                 -- Allow new duplicates of this job
 372                 local sha1 = redis.call('hGet',KEYS[2],id)
 373                 if sha1 then redis.call('hDel',KEYS[3],sha1) end
 374                 redis.call('hDel',KEYS[2],id)
 375                 -- Mark the jobs as claimed and return it
 376                 redis.call('zAdd',KEYS[4],ARGV[1],id)
 377                 redis.call('hIncrBy',KEYS[5],id,1)
 378                 return redis.call('hGet',KEYS[6],id)
 379 LUA;
 380                 return $this->redisEval( $conn, $script,
 381                         array(
 382                                 $this->getQueueKey( 'l-unclaimed' ), # KEYS[1]
 383                                 $this->getQueueKey( 'h-sha1ById' ), # KEYS[2]
 384                                 $this->getQueueKey( 'h-idBySha1' ), # KEYS[3]
 385                                 $this->getQueueKey( 'z-claimed' ), # KEYS[4]
 386                                 $this->getQueueKey( 'h-attempts' ), # KEYS[5]
 387                                 $this->getQueueKey( 'h-data' ), # KEYS[6]
 388                                 time(), # ARGV[1] (injected to be replication-safe)
 389                         ),
 390                         6 # number of first argument(s) that are keys
 391                 );
 392         }
 393
 394         /**
 395          * @see JobQueue::doAck()
 396          * @param Job $job
 397          * @return Job|bool
 398          * @throws MWException
 399          */
 400         protected function doAck( Job $job ) {
 401                 if ( $this->claimTTL > 0 ) {
 402                         $conn = $this->getConnection();
 403                         try {
 404                                 // Get the exact field map this Job came from, regardless of whether
 405                                 // the job was transformed into a DuplicateJob or anything of the sort.
 406                                 $item = $job->metadata['sourceFields'];
 407
 408                                 static $script =
 409 <<<LUA
 410                                 -- Unmark the job as claimed
 411                                 redis.call('zRem',KEYS[1],ARGV[1])
 412                                 redis.call('hDel',KEYS[2],ARGV[1])
 413                                 -- Delete the job data itself
 414                                 return redis.call('hDel',KEYS[3],ARGV[1])
 415 LUA;
 416                                 $res = $this->redisEval( $conn, $script,
 417                                         array(
 418                                                 $this->getQueueKey( 'z-claimed' ), # KEYS[1]
 419                                                 $this->getQueueKey( 'h-attempts' ), # KEYS[2]
 420                                                 $this->getQueueKey( 'h-data' ), # KEYS[3]
 421                                                 $item['uuid'] # ARGV[1]
 422                                         ),
 423                                         3 # number of first argument(s) that are keys
 424                                 );
 425
 426                                 if ( !$res ) {
 427                                         wfDebugLog( 'JobQueueRedis', "Could not acknowledge {$this->type} job." );
 428                                         return false;
 429                                 }
 430                         } catch ( RedisException $e ) {
 431                                 $this->throwRedisException( $this->server, $conn, $e );
 432                         }
 433                 }
 434                 return true;
 435         }
 436
 437         /**
 438          * @see JobQueue::doDeduplicateRootJob()
 439          * @param Job $job
 440          * @return bool
 441          * @throws MWException
 442          */
 443         protected function doDeduplicateRootJob( Job $job ) {
 444                 if ( !$job->hasRootJobParams() ) {
 445                         throw new MWException( "Cannot register root job; missing parameters." );
 446                 }
 447                 $params = $job->getRootJobParams();
 448
 449                 $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
 450
 451                 $conn = $this->getConnection();
 452                 try {
 453                         $timestamp = $conn->get( $key ); // current last timestamp of this job
 454                         if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
 455                                 return true; // a newer version of this root job was enqueued
 456                         }
 457                         // Update the timestamp of the last root job started at the location...
 458                         return $conn->set( $key, $params['rootJobTimestamp'], self::ROOTJOB_TTL ); // 2 weeks
 459                 } catch ( RedisException $e ) {
 460                         $this->throwRedisException( $this->server, $conn, $e );
 461                 }
 462         }
 463
 464         /**
 465          * @see JobQueue::doIsRootJobOldDuplicate()
 466          * @param Job $job
 467          * @return bool
 468          */
 469         protected function doIsRootJobOldDuplicate( Job $job ) {
 470                 $params = $job->getParams();
 471                 if ( !isset( $params['rootJobSignature'] ) ) {
 472                         return false; // job has no de-deplication info
 473                 } elseif ( !isset( $params['rootJobTimestamp'] ) ) {
 474                         wfDebugLog( 'JobQueueRedis', "Cannot check root job; missing 'rootJobTimestamp'." );
 475                         return false;
 476                 }
 477
 478                 $conn = $this->getConnection();
 479                 try {
 480                         // Get the last time this root job was enqueued
 481                         $timestamp = $conn->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) );
 482                 } catch ( RedisException $e ) {
 483                         $this->throwRedisException( $this->server, $conn, $e );
 484                 }
 485
 486                 // Check if a new root job was started at the location after this one's...
 487                 return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
 488         }
 489
 490         /**
 491          * @see JobQueue::getAllQueuedJobs()
 492          * @return Iterator
 493          */
 494         public function getAllQueuedJobs() {
 495                 $conn = $this->getConnection();
 496                 if ( !$conn ) {
 497                         throw new MWException( "Unable to connect to redis server." );
 498                 }
 499                 try {
 500                         $that = $this;
 501                         return new MappedIterator(
 502                                 $conn->lRange( $this->getQueueKey( 'l-unclaimed' ), 0, -1 ),
 503                                 function( $uid ) use ( $that, $conn ) {
 504                                         return $that->getJobFromUidInternal( $uid, $conn );
 505                                 }
 506                         );
 507                 } catch ( RedisException $e ) {
 508                         $this->throwRedisException( $this->server, $conn, $e );
 509                 }
 510         }
 511
 512         /**
 513          * @see JobQueue::getAllQueuedJobs()
 514          * @return Iterator
 515          */
 516         public function getAllDelayedJobs() {
 517                 $conn = $this->getConnection();
 518                 if ( !$conn ) {
 519                         throw new MWException( "Unable to connect to redis server." );
 520                 }
 521                 try {
 522                         $that = $this;
 523                         return new MappedIterator( // delayed jobs
 524                                 $conn->zRange( $this->getQueueKey( 'z-delayed' ), 0, -1 ),
 525                                 function( $uid ) use ( $that, $conn ) {
 526                                         return $that->getJobFromUidInternal( $uid, $conn );
 527                                 }
 528                         );
 529                 } catch ( RedisException $e ) {
 530                         $this->throwRedisException( $this->server, $conn, $e );
 531                 }
 532         }
 533
 534         /**
 535          * This function should not be called outside JobQueueRedis
 536          *
 537          * @param $uid string
 538          * @param $conn RedisConnRef
 539          * @return Job
 540          * @throws MWException
 541          */
 542         public function getJobFromUidInternal( $uid, RedisConnRef $conn ) {
 543                 try {
 544                         $item = unserialize( $conn->hGet( $this->getQueueKey( 'h-data' ), $uid ) );
 545                         if ( !is_array( $item ) ) { // this shouldn't happen
 546                                 throw new MWException( "Could not find job with ID '$uid'." );
 547                         }
 548                         $title = Title::makeTitle( $item['namespace'], $item['title'] );
 549                         $job = Job::factory( $item['type'], $title, $item['params'] );
 550                         $job->metadata['sourceFields'] = $item;
 551                         return $job;
 552                 } catch ( RedisException $e ) {
 553                         $this->throwRedisException( $this->server, $conn, $e );
 554                 }
 555         }
 556
 557         /**
 558          * Release any ready delayed jobs into the queue
 559          *
 560          * @return integer Number of jobs released
 561          * @throws MWException
 562          */
 563         public function releaseReadyDelayedJobs() {
 564                 $count = 0;
 565
 566                 $conn = $this->getConnection();
 567                 try {
 568                         static $script =
 569 <<<LUA
 570                         -- Get the list of ready delayed jobs, sorted by readiness
 571                         local ids = redis.call('zRangeByScore',KEYS[1],0,ARGV[1])
 572                         -- Migrate the jobs from the "delayed" set to the "unclaimed" list
 573                         for k,id in ipairs(ids) do
 574                                 redis.call('lPush',KEYS[2],id)
 575                                 redis.call('zRem',KEYS[1],id)
 576                         end
 577                         return #ids
 578 LUA;
 579                         $count += (int)$this->redisEval( $conn, $script,
 580                                 array(
 581                                         $this->getQueueKey( 'z-delayed' ), // KEYS[1]
 582                                         $this->getQueueKey( 'l-unclaimed' ), // KEYS[2]
 583                                         time() // ARGV[1]; max "delay until" UNIX timestamp
 584                                 ),
 585                                 2 # first two arguments are keys
 586                         );
 587                 } catch ( RedisException $e ) {
 588                         $this->throwRedisException( $this->server, $conn, $e );
 589                 }
 590
 591                 return $count;
 592         }
 593
 594         /**
 595          * Recycle or destroy any jobs that have been claimed for too long
 596          *
 597          * @return integer Number of jobs recycled/deleted
 598          * @throws MWException
 599          */
 600         public function recycleAndDeleteStaleJobs() {
 601                 if ( $this->claimTTL <= 0 ) { // sanity
 602                         throw new MWException( "Cannot recycle jobs since acknowledgements are disabled." );
 603                 }
 604                 $count = 0;
 605                 // For each job item that can be retried, we need to add it back to the
 606                 // main queue and remove it from the list of currenty claimed job items.
 607                 // For those that cannot, they are marked as dead and kept around for
 608                 // investigation and manual job restoration but are eventually deleted.
 609                 $conn = $this->getConnection();
 610                 try {
 611                         $now = time();
 612                         static $script =
 613 <<<LUA
 614                         local released,abandoned,pruned = 0,0,0
 615                         -- Get all non-dead jobs that have an expired claim on them.
 616                         -- The score for each item is the last claim timestamp (UNIX).
 617                         local staleClaims = redis.call('zRangeByScore',KEYS[1],0,ARGV[1])
 618                         for k,id in ipairs(staleClaims) do
 619                                 local timestamp = redis.call('zScore',KEYS[1],id)
 620                                 local attempts = redis.call('hGet',KEYS[2],id)
 621                                 if attempts < ARGV[3] then
 622                                         -- Claim expired and retries left: re-enqueue the job
 623                                         redis.call('lPush',KEYS[3],id)
 624                                         redis.call('hIncrBy',KEYS[2],id,1)
 625                                         released = released + 1
 626                                 else
 627                                         -- Claim expired and no retries left: mark the job as dead
 628                                         redis.call('zAdd',KEYS[5],timestamp,id)
 629                                         abandoned = abandoned + 1
 630                                 end
 631                                 redis.call('zRem',KEYS[1],id)
 632                         end
 633                         -- Get all of the dead jobs that have been marked as dead for too long.
 634                         -- The score for each item is the last claim timestamp (UNIX).
 635                         local deadClaims = redis.call('zRangeByScore',KEYS[5],0,ARGV[2])
 636                         for k,id in ipairs(deadClaims) do
 637                                 -- Stale and out of retries: remove any traces of the job
 638                                 redis.call('zRem',KEYS[5],id)
 639                                 redis.call('hDel',KEYS[2],id)
 640                                 redis.call('hDel',KEYS[4],id)
 641                                 pruned = pruned + 1
 642                         end
 643                         return {released,abandoned,pruned}
 644 LUA;
 645                         $res = $this->redisEval( $conn, $script,
 646                                 array(
 647                                         $this->getQueueKey( 'z-claimed' ), # KEYS[1]
 648                                         $this->getQueueKey( 'h-attempts' ), # KEYS[2]
 649                                         $this->getQueueKey( 'l-unclaimed' ), # KEYS[3]
 650                                         $this->getQueueKey( 'h-data' ), # KEYS[4]
 651                                         $this->getQueueKey( 'z-abandoned' ), # KEYS[5]
 652                                         $now - $this->claimTTL, # ARGV[1]
 653                                         $now - self::MAX_AGE_PRUNE, # ARGV[2]
 654                                         $this->maxTries # ARGV[3]
 655                                 ),
 656                                 5 # number of first argument(s) that are keys
 657                         );
 658                         if ( $res ) {
 659                                 list( $released, $abandoned, $pruned ) = $res;
 660                                 $count += $released + $pruned;
 661                                 wfIncrStats( 'job-recycle', count( $released ) );
 662                         }
 663                 } catch ( RedisException $e ) {
 664                         $this->throwRedisException( $this->server, $conn, $e );
 665                 }
 666
 667                 return $count;
 668         }
 669
 670         /**
 671          * @return Array
 672          */
 673         protected function doGetPeriodicTasks() {
 674                 $tasks = array();
 675                 if ( $this->claimTTL > 0 ) {
 676                         $tasks['recycleAndDeleteStaleJobs'] = array(
 677                                 'callback' => array( $this, 'recycleAndDeleteStaleJobs' ),
 678                                 'period'   => ceil( $this->claimTTL / 2 )
 679                         );
 680                 }
 681                 if ( $this->checkDelay ) {
 682                         $tasks['releaseReadyDelayedJobs'] = array(
 683                                 'callback' => array( $this, 'releaseReadyDelayedJobs' ),
 684                                 'period'   => 300 // 5 minutes
 685                         );
 686                 }
 687                 return $tasks;
 688         }
 689
 690         /**
 691          * @param RedisConnRef $conn
 692          * @param string $script
 693          * @param array $params
 694          * @param integer $numKeys
 695          * @return mixed
 696          */
 697         protected function redisEval( RedisConnRef $conn, $script, array $params, $numKeys ) {
 698                 $sha1 = sha1( $script ); // 40 char hex
 699
 700                 // Try to run the server-side cached copy of the script
 701                 $conn->clearLastError();
 702                 $res = $conn->evalSha( $sha1, $params, $numKeys );
 703                 // If the script is not in cache, use eval() to retry and cache it
 704                 if ( $conn->getLastError() && $conn->script( 'exists', $sha1 ) === array( 0 ) ) {
 705                         $conn->clearLastError();
 706                         $res = $conn->eval( $script, $params, $numKeys );
 707                         wfDebugLog( 'JobQueueRedis', "Used eval() for Lua script $sha1." );
 708                 }
 709
 710                 if ( $conn->getLastError() ) { // script bug?
 711                         wfDebugLog( 'JobQueueRedis', "Lua script error: " . $conn->getLastError() );
 712                 }
 713
 714                 return $res;
 715         }
 716
 717         /**
 718          * @param $job Job
 719          * @return array
 720          */
 721         protected function getNewJobFields( Job $job ) {
 722                 return array(
 723                         // Fields that describe the nature of the job
 724                         'type'       => $job->getType(),
 725                         'namespace'  => $job->getTitle()->getNamespace(),
 726                         'title'      => $job->getTitle()->getDBkey(),
 727                         'params'     => $job->getParams(),
 728                         // Some jobs cannot run until a "release timestamp"
 729                         'rtimestamp' => $job->getReleaseTimestamp() ?: 0,
 730                         // Additional job metadata
 731                         'uuid'       => UIDGenerator::newRawUUIDv4( UIDGenerator::QUICK_RAND ),
 732                         'sha1'       => $job->ignoreDuplicates()
 733                                 ? wfBaseConvert( sha1( serialize( $job->getDeduplicationInfo() ) ), 16, 36, 31 )
 734                                 : '',
 735                         'timestamp'  => time() // UNIX timestamp
 736                 );
 737         }
 738
 739         /**
 740          * @param $fields array
 741          * @return Job|bool
 742          */
 743         protected function getJobFromFields( array $fields ) {
 744                 $title = Title::makeTitleSafe( $fields['namespace'], $fields['title'] );
 745                 if ( $title ) {
 746                         $job = Job::factory( $fields['type'], $title, $fields['params'] );
 747                         $job->metadata['sourceFields'] = $fields;
 748                         return $job;
 749                 }
 750                 return false;
 751         }
 752
 753         /**
 754          * Get a connection to the server that handles all sub-queues for this queue
 755          *
 756          * @return Array (server name, Redis instance)
 757          * @throws MWException
 758          */
 759         protected function getConnection() {
 760                 $conn = $this->redisPool->getConnection( $this->server );
 761                 if ( !$conn ) {
 762                         throw new MWException( "Unable to connect to redis server." );
 763                 }
 764                 return $conn;
 765         }
 766
 767         /**
 768          * @param $server string
 769          * @param $conn RedisConnRef
 770          * @param $e RedisException
 771          * @throws MWException
 772          */
 773         protected function throwRedisException( $server, RedisConnRef $conn, $e ) {
 774                 $this->redisPool->handleException( $server, $conn, $e );
 775                 throw new MWException( "Redis server error: {$e->getMessage()}\n" );
 776         }
 777
 778         /**
 779          * @param $prop string
 780          * @return string
 781          */
 782         private function getQueueKey( $prop ) {
 783                 list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
 784                 if ( strlen( $this->key ) ) { // namespaced queue (for testing)
 785                         return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, $this->key, $prop );
 786                 } else {
 787                         return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, $prop );
 788                 }
 789         }
 790
 791         /**
 792          * @param $key string
 793          * @return void
 794          */
 795         public function setTestingPrefix( $key ) {
 796                 $this->key = $key;
 797         }
 798 }