Update to MediaWiki 1.22.0

1 files changed, 856 insertions, 0 deletions

diff --git a/includes/job/JobQueueRedis.php b/includes/job/JobQueueRedis.php
new file mode 100644
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--- /dev/null
+++ b/includes/job/JobQueueRedis.php
@@ -0,0 +1,856 @@
+<?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;
+
+	protected $server; // string; server address
+	protected $compression; // string; compression method to use
+
+	const MAX_AGE_PRUNE = 604800; // integer; seconds a job can live once claimed (7 days)
+
+	protected $key; // string; key to prefix the queue keys with (used for testing)
+
+	/**
+	 * @params include:
+	 *   - redisConfig : An array of parameters to RedisConnectionPool::__construct().
+	 *                   Note that the serializer option is ignored "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).
+	 * @param array $params
+	 */
+	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'] );
+	}
+
+	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 integer
+	 * @throws MWException
+	 */
+	protected function doGetSize() {
+		$conn = $this->getConnection();
+		try {
+			return $conn->lSize( $this->getQueueKey( 'l-unclaimed' ) );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $this->server, $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doGetAcquiredCount()
+	 * @return integer
+	 * @throws MWException
+	 */
+	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( $this->server, $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doGetDelayedCount()
+	 * @return integer
+	 * @throws MWException
+	 */
+	protected function doGetDelayedCount() {
+		if ( !$this->checkDelay ) {
+			return 0; // no delayed jobs
+		}
+		$conn = $this->getConnection();
+		try {
+			return $conn->zSize( $this->getQueueKey( 'z-delayed' ) );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $this->server, $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doGetAbandonedCount()
+	 * @return integer
+	 * @throws MWException
+	 */
+	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( $this->server, $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doBatchPush()
+	 * @param array $jobs
+	 * @param $flags
+	 * @return bool
+	 * @throws MWException
+	 */
+	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 true; // 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)." );
+				return false;
+			}
+			JobQueue::incrStats( 'job-insert', $this->type, count( $items ) );
+			JobQueue::incrStats( 'job-insert-duplicate', $this->type,
+				count( $items ) - $failed - $pushed );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $this->server, $conn, $e );
+		}
+
+		return true;
+	}
+
+	/**
+	 * @param RedisConnRef $conn
+	 * @param array $items List of results from JobQueueRedis::getNewJobFields()
+	 * @return integer 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
+		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',KEYS[3],sha1) == 0 then
+				if 1*rtimestamp > 0 then
+					-- Insert into delayed queue (release time as score)
+					redis.call('zAdd',KEYS[4],rtimestamp,id)
+				else
+					-- Insert into unclaimed queue
+					redis.call('lPush',KEYS[1],id)
+				end
+				if sha1 ~= '' then
+					redis.call('hSet',KEYS[2],id,sha1)
+					redis.call('hSet',KEYS[3],sha1,id)
+				end
+				redis.call('hSet',KEYS[5],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 MWException
+	 */
+	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->releaseReadyDelayedJobs();
+		}
+
+		$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->recycleAndDeleteStaleJobs();
+					}
+					$blob = $this->popAndAcquireBlob( $conn );
+				} else {
+					$blob = $this->popAndDeleteBlob( $conn );
+				}
+				if ( $blob === false ) {
+					break; // no jobs; nothing to do
+				}
+
+				JobQueue::incrStats( 'job-pop', $this->type );
+				$item = $this->unserialize( $blob );
+				if ( $item === false ) {
+					wfDebugLog( 'JobQueueRedis', "Could not unserialize {$this->type} job." );
+					continue;
+				}
+
+				// If $item is invalid, recycleAndDeleteStaleJobs() will cleanup as needed
+				$job = $this->getJobFromFields( $item ); // may be false
+			} while ( !$job ); // job may be false if invalid
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $this->server, $conn, $e );
+		}
+
+		return $job;
+	}
+
+	/**
+	 * @param RedisConnRef $conn
+	 * @return array serialized string or false
+	 * @throws RedisException
+	 */
+	protected function popAndDeleteBlob( RedisConnRef $conn ) {
+		static $script =
+<<<LUA
+		-- Pop an item off the queue
+		local id = redis.call('rpop',KEYS[1])
+		if not id then return false end
+		-- Get the job data and remove it
+		local item = redis.call('hGet',KEYS[4],id)
+		redis.call('hDel',KEYS[4],id)
+		-- Allow new duplicates of this job
+		local sha1 = redis.call('hGet',KEYS[2],id)
+		if sha1 then redis.call('hDel',KEYS[3],sha1) end
+		redis.call('hDel',KEYS[2],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
+		-- Pop an item off the queue
+		local id = redis.call('rPop',KEYS[1])
+		if not id then return false end
+		-- Allow new duplicates of this job
+		local sha1 = redis.call('hGet',KEYS[2],id)
+		if sha1 then redis.call('hDel',KEYS[3],sha1) end
+		redis.call('hDel',KEYS[2],id)
+		-- Mark the jobs as claimed and return it
+		redis.call('zAdd',KEYS[4],ARGV[1],id)
+		redis.call('hIncrBy',KEYS[5],id,1)
+		return redis.call('hGet',KEYS[6],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
+	 */
+	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
+				-- Unmark the job as claimed
+				redis.call('zRem',KEYS[1],ARGV[1])
+				redis.call('hDel',KEYS[2],ARGV[1])
+				-- Delete the job data itself
+				return redis.call('hDel',KEYS[3],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( $this->server, $conn, $e );
+			}
+		}
+		return true;
+	}
+
+	/**
+	 * @see JobQueue::doDeduplicateRootJob()
+	 * @param Job $job
+	 * @return bool
+	 * @throws MWException
+	 */
+	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( $this->server, $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doIsRootJobOldDuplicate()
+	 * @param Job $job
+	 * @return bool
+	 */
+	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( $this->server, $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
+	 */
+	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( $this->server, $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( $this->server, $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( $this->server, $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
+		try {
+			$conn = $this->getConnection();
+			$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( $this->server, $conn, $e );
+		}
+		return $sizes;
+	}
+
+	/**
+	 * This function should not be called outside JobQueueRedis
+	 *
+	 * @param $uid string
+	 * @param $conn RedisConnRef
+	 * @return Job|bool Returns false if the job does not exist
+	 * @throws MWException
+	 */
+	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( $this->server, $conn, $e );
+		}
+	}
+
+	/**
+	 * Release any ready delayed jobs into the queue
+	 *
+	 * @return integer Number of jobs released
+	 * @throws MWException
+	 */
+	public function releaseReadyDelayedJobs() {
+		$count = 0;
+
+		$conn = $this->getConnection();
+		try {
+			static $script =
+<<<LUA
+			-- Get the list of ready delayed jobs, sorted by readiness
+			local ids = redis.call('zRangeByScore',KEYS[1],0,ARGV[1])
+			-- Migrate the jobs from the "delayed" set to the "unclaimed" list
+			for k,id in ipairs(ids) do
+				redis.call('lPush',KEYS[2],id)
+				redis.call('zRem',KEYS[1],id)
+			end
+			return #ids
+LUA;
+			$count += (int)$conn->luaEval( $script,
+				array(
+					$this->getQueueKey( 'z-delayed' ), // KEYS[1]
+					$this->getQueueKey( 'l-unclaimed' ), // KEYS[2]
+					time() // ARGV[1]; max "delay until" UNIX timestamp
+				),
+				2 # first two arguments are keys
+			);
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $this->server, $conn, $e );
+		}
+
+		return $count;
+	}
+
+	/**
+	 * Recycle or destroy any jobs that have been claimed for too long
+	 *
+	 * @return integer Number of jobs recycled/deleted
+	 * @throws MWException
+	 */
+	public function recycleAndDeleteStaleJobs() {
+		if ( $this->claimTTL <= 0 ) { // sanity
+			throw new MWException( "Cannot recycle jobs since acknowledgements are disabled." );
+		}
+		$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 released,abandoned,pruned = 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',KEYS[1],0,ARGV[1])
+			for k,id in ipairs(staleClaims) do
+				local timestamp = redis.call('zScore',KEYS[1],id)
+				local attempts = redis.call('hGet',KEYS[2],id)
+				if attempts < ARGV[3] then
+					-- Claim expired and retries left: re-enqueue the job
+					redis.call('lPush',KEYS[3],id)
+					redis.call('hIncrBy',KEYS[2],id,1)
+					released = released + 1
+				else
+					-- Claim expired and no retries left: mark the job as dead
+					redis.call('zAdd',KEYS[5],timestamp,id)
+					abandoned = abandoned + 1
+				end
+				redis.call('zRem',KEYS[1],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',KEYS[5],0,ARGV[2])
+			for k,id in ipairs(deadClaims) do
+				-- Stale and out of retries: remove any traces of the job
+				redis.call('zRem',KEYS[5],id)
+				redis.call('hDel',KEYS[2],id)
+				redis.call('hDel',KEYS[4],id)
+				pruned = pruned + 1
+			end
+			return {released,abandoned,pruned}
+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]
+					$now - $this->claimTTL, # ARGV[1]
+					$now - self::MAX_AGE_PRUNE, # ARGV[2]
+					$this->maxTries # ARGV[3]
+				),
+				5 # number of first argument(s) that are keys
+			);
+			if ( $res ) {
+				list( $released, $abandoned, $pruned ) = $res;
+				$count += $released + $pruned;
+				JobQueue::incrStats( 'job-recycle', $this->type, $released );
+				JobQueue::incrStats( 'job-abandon', $this->type, $abandoned );
+			}
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $this->server, $conn, $e );
+		}
+
+		return $count;
+	}
+
+	/**
+	 * @return Array
+	 */
+	protected function doGetPeriodicTasks() {
+		$tasks = array();
+		if ( $this->claimTTL > 0 ) {
+			$tasks['recycleAndDeleteStaleJobs'] = array(
+				'callback' => array( $this, 'recycleAndDeleteStaleJobs' ),
+				'period' => ceil( $this->claimTTL / 2 )
+			);
+		}
+		if ( $this->checkDelay ) {
+			$tasks['releaseReadyDelayedJobs'] = array(
+				'callback' => array( $this, 'releaseReadyDelayedJobs' ),
+				'period' => 300 // 5 minutes
+			);
+		}
+		return $tasks;
+	}
+
+	/**
+	 * @param $job Job
+	 * @return array
+	 */
+	protected function getNewJobFields( Job $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 $fields array
+	 * @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 Array (server name, Redis instance)
+	 * @throws MWException
+	 */
+	protected function getConnection() {
+		$conn = $this->redisPool->getConnection( $this->server );
+		if ( !$conn ) {
+			throw new JobQueueConnectionError( "Unable to connect to redis server." );
+		}
+		return $conn;
+	}
+
+	/**
+	 * @param $server string
+	 * @param $conn RedisConnRef
+	 * @param $e RedisException
+	 * @throws MWException
+	 */
+	protected function throwRedisException( $server, RedisConnRef $conn, $e ) {
+		$this->redisPool->handleException( $server, $conn, $e );
+		throw new JobQueueError( "Redis server error: {$e->getMessage()}\n" );
+	}
+
+	/**
+	 * @param $prop string
+	 * @param $type string|null
+	 * @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 $key string
+	 * @return void
+	 */
+	public function setTestingPrefix( $key ) {
+		$this->key = $key;
+	}
+}