X-Git-Url: https://scripts.mit.edu/gitweb/autoinstallsdev/mediawiki.git/blobdiff_plain/19e297c21b10b1b8a3acad5e73fc71dcb35db44a..6932310fd58ebef145fa01eb76edf7150284d8ea:/includes/jobqueue/JobQueueRedis.php

diff --git a/includes/jobqueue/JobQueueRedis.php b/includes/jobqueue/JobQueueRedis.php
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+<?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
+ */
+use Psr\Log\LoggerInterface;
+
+/**
+ * Class to handle job queues stored in Redis
+ *
+ * This is a faster and less resource-intensive job queue than JobQueueDB.
+ * All data for a queue using this class is placed into one redis server.
+ * The mediawiki/services/jobrunner background service must be set up and running.
+ *
+ * There are eight main redis keys (per queue) 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.
+ *
+ * The following keys are used to track queue states:
+ *   - s-queuesWithJobs : A set of all queues with non-abandoned jobs
+ *
+ * The background service takes care of undelaying, recycling, and pruning jobs as well as
+ * removing s-queuesWithJobs entries as queues empty.
+ *
+ * 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 persistence. Appropriate configuration should be
+ * made on the servers based on what queues are using it and what tolerance they have.
+ *
+ * @ingroup JobQueue
+ * @ingroup Redis
+ * @since 1.22
+ */
+class JobQueueRedis extends JobQueue {
+	/** @var RedisConnectionPool */
+	protected $redisPool;
+	/** @var LoggerInterface */
+	protected $logger;
+
+	/** @var string Server address */
+	protected $server;
+	/** @var string Compression method to use */
+	protected $compression;
+
+	const MAX_PUSH_SIZE = 25; // avoid tying up the server
+
+	/**
+	 * @param array $params Possible keys:
+	 *   - redisConfig : An array of parameters to RedisConnectionPool::__construct().
+	 *                   Note that the serializer option is ignored as "none" is always used.
+	 *   - redisServer : A hostname/port combination or the absolute path of a UNIX socket.
+	 *                   If a hostname is specified but no port, the standard port number
+	 *                   6379 will be used. Required.
+	 *   - compression : The type of compression to use; one of (none,gzip).
+	 *   - daemonized  : Set to true if the redisJobRunnerService runs in the background.
+	 *                   This will disable job recycling/undelaying from the MediaWiki side
+	 *                   to avoid redundance and out-of-sync configuration.
+	 * @throws InvalidArgumentException
+	 */
+	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'] );
+		if ( empty( $params['daemonized'] ) ) {
+			throw new InvalidArgumentException(
+				"Non-daemonized mode is no longer supported. Please install the " .
+				"mediawiki/services/jobrunner service and update \$wgJobTypeConf as needed." );
+		}
+		$this->logger = \MediaWiki\Logger\LoggerFactory::getInstance( 'redis' );
+	}
+
+	protected function supportedOrders() {
+		return [ 'timestamp', 'fifo' ];
+	}
+
+	protected function optimalOrder() {
+		return 'fifo';
+	}
+
+	protected function supportsDelayedJobs() {
+		return true;
+	}
+
+	/**
+	 * @see JobQueue::doIsEmpty()
+	 * @return bool
+	 * @throws JobQueueError
+	 */
+	protected function doIsEmpty() {
+		return $this->doGetSize() == 0;
+	}
+
+	/**
+	 * @see JobQueue::doGetSize()
+	 * @return int
+	 * @throws JobQueueError
+	 */
+	protected function doGetSize() {
+		$conn = $this->getConnection();
+		try {
+			return $conn->lSize( $this->getQueueKey( 'l-unclaimed' ) );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doGetAcquiredCount()
+	 * @return int
+	 * @throws JobQueueError
+	 */
+	protected function doGetAcquiredCount() {
+		$conn = $this->getConnection();
+		try {
+			$conn->multi( Redis::PIPELINE );
+			$conn->zSize( $this->getQueueKey( 'z-claimed' ) );
+			$conn->zSize( $this->getQueueKey( 'z-abandoned' ) );
+
+			return array_sum( $conn->exec() );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doGetDelayedCount()
+	 * @return int
+	 * @throws JobQueueError
+	 */
+	protected function doGetDelayedCount() {
+		$conn = $this->getConnection();
+		try {
+			return $conn->zSize( $this->getQueueKey( 'z-delayed' ) );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doGetAbandonedCount()
+	 * @return int
+	 * @throws JobQueueError
+	 */
+	protected function doGetAbandonedCount() {
+		$conn = $this->getConnection();
+		try {
+			return $conn->zSize( $this->getQueueKey( 'z-abandoned' ) );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doBatchPush()
+	 * @param IJobSpecification[] $jobs
+	 * @param int $flags
+	 * @return void
+	 * @throws JobQueueError
+	 */
+	protected function doBatchPush( array $jobs, $flags ) {
+		// Convert the jobs into field maps (de-duplicated against each other)
+		$items = []; // (job ID => job fields map)
+		foreach ( $jobs as $job ) {
+			$item = $this->getNewJobFields( $job );
+			if ( strlen( $item['sha1'] ) ) { // hash identifier => de-duplicate
+				$items[$item['sha1']] = $item;
+			} else {
+				$items[$item['uuid']] = $item;
+			}
+		}
+
+		if ( !count( $items ) ) {
+			return; // nothing to do
+		}
+
+		$conn = $this->getConnection();
+		try {
+			// Actually push the non-duplicate jobs into the queue...
+			if ( $flags & self::QOS_ATOMIC ) {
+				$batches = [ $items ]; // all or nothing
+			} else {
+				$batches = array_chunk( $items, self::MAX_PUSH_SIZE );
+			}
+			$failed = 0;
+			$pushed = 0;
+			foreach ( $batches as $itemBatch ) {
+				$added = $this->pushBlobs( $conn, $itemBatch );
+				if ( is_int( $added ) ) {
+					$pushed += $added;
+				} else {
+					$failed += count( $itemBatch );
+				}
+			}
+			JobQueue::incrStats( 'inserts', $this->type, count( $items ) );
+			JobQueue::incrStats( 'inserts_actual', $this->type, $pushed );
+			JobQueue::incrStats( 'dupe_inserts', $this->type,
+				count( $items ) - $failed - $pushed );
+			if ( $failed > 0 ) {
+				$err = "Could not insert {$failed} {$this->type} job(s).";
+				wfDebugLog( 'JobQueueRedis', $err );
+				throw new RedisException( $err );
+			}
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @param RedisConnRef $conn
+	 * @param array $items List of results from JobQueueRedis::getNewJobFields()
+	 * @return int Number of jobs inserted (duplicates are ignored)
+	 * @throws RedisException
+	 */
+	protected function pushBlobs( RedisConnRef $conn, array $items ) {
+		$args = [ $this->encodeQueueName() ];
+		// Next args come in 4s ([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 =
+		/** @lang Lua */
+<<<LUA
+		local kUnclaimed, kSha1ById, kIdBySha1, kDelayed, kData, kQwJobs = unpack(KEYS)
+		-- First argument is the queue ID
+		local queueId = ARGV[1]
+		-- Next arguments all come in 4s (one per job)
+		local variadicArgCount = #ARGV - 1
+		if variadicArgCount % 4 ~= 0 then
+			return redis.error_reply('Unmatched arguments')
+		end
+		-- Insert each job into this queue as needed
+		local pushed = 0
+		for i = 2,#ARGV,4 do
+			local id,sha1,rtimestamp,blob = ARGV[i],ARGV[i+1],ARGV[i+2],ARGV[i+3]
+			if sha1 == '' or redis.call('hExists',kIdBySha1,sha1) == 0 then
+				if 1*rtimestamp > 0 then
+					-- Insert into delayed queue (release time as score)
+					redis.call('zAdd',kDelayed,rtimestamp,id)
+				else
+					-- Insert into unclaimed queue
+					redis.call('lPush',kUnclaimed,id)
+				end
+				if sha1 ~= '' then
+					redis.call('hSet',kSha1ById,id,sha1)
+					redis.call('hSet',kIdBySha1,sha1,id)
+				end
+				redis.call('hSet',kData,id,blob)
+				pushed = pushed + 1
+			end
+		end
+		-- Mark this queue as having jobs
+		redis.call('sAdd',kQwJobs,queueId)
+		return pushed
+LUA;
+		return $conn->luaEval( $script,
+			array_merge(
+				[
+					$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]
+					$this->getGlobalKey( 's-queuesWithJobs' ), # KEYS[6]
+				],
+				$args
+			),
+			6 # number of first argument(s) that are keys
+		);
+	}
+
+	/**
+	 * @see JobQueue::doPop()
+	 * @return Job|bool
+	 * @throws JobQueueError
+	 */
+	protected function doPop() {
+		$job = false;
+
+		$conn = $this->getConnection();
+		try {
+			do {
+				$blob = $this->popAndAcquireBlob( $conn );
+				if ( !is_string( $blob ) ) {
+					break; // no jobs; nothing to do
+				}
+
+				JobQueue::incrStats( 'pops', $this->type );
+				$item = $this->unserialize( $blob );
+				if ( $item === false ) {
+					wfDebugLog( 'JobQueueRedis', "Could not unserialize {$this->type} job." );
+					continue;
+				}
+
+				// If $item is invalid, the runner loop recyling will cleanup as needed
+				$job = $this->getJobFromFields( $item ); // may be false
+			} while ( !$job ); // job may be false if invalid
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $job;
+	}
+
+	/**
+	 * @param RedisConnRef $conn
+	 * @return array Serialized string or false
+	 * @throws RedisException
+	 */
+	protected function popAndAcquireBlob( RedisConnRef $conn ) {
+		static $script =
+		/** @lang Lua */
+<<<LUA
+		local kUnclaimed, kSha1ById, kIdBySha1, kClaimed, kAttempts, kData = unpack(KEYS)
+		local rTime = unpack(ARGV)
+		-- Pop an item off the queue
+		local id = redis.call('rPop',kUnclaimed)
+		if not id then
+			return false
+		end
+		-- Allow new duplicates of this job
+		local sha1 = redis.call('hGet',kSha1ById,id)
+		if sha1 then redis.call('hDel',kIdBySha1,sha1) end
+		redis.call('hDel',kSha1ById,id)
+		-- Mark the jobs as claimed and return it
+		redis.call('zAdd',kClaimed,rTime,id)
+		redis.call('hIncrBy',kAttempts,id,1)
+		return redis.call('hGet',kData,id)
+LUA;
+		return $conn->luaEval( $script,
+			[
+				$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 UnexpectedValueException
+	 * @throws JobQueueError
+	 */
+	protected function doAck( Job $job ) {
+		if ( !isset( $job->metadata['uuid'] ) ) {
+			throw new UnexpectedValueException( "Job of type '{$job->getType()}' has no UUID." );
+		}
+
+		$uuid = $job->metadata['uuid'];
+		$conn = $this->getConnection();
+		try {
+			static $script =
+			/** @lang Lua */
+<<<LUA
+			local kClaimed, kAttempts, kData = unpack(KEYS)
+			local id = unpack(ARGV)
+			-- Unmark the job as claimed
+			local removed = redis.call('zRem',kClaimed,id)
+			-- Check if the job was recycled
+			if removed == 0 then
+				return 0
+			end
+			-- Delete the retry data
+			redis.call('hDel',kAttempts,id)
+			-- Delete the job data itself
+			return redis.call('hDel',kData,id)
+LUA;
+			$res = $conn->luaEval( $script,
+				[
+					$this->getQueueKey( 'z-claimed' ), # KEYS[1]
+					$this->getQueueKey( 'h-attempts' ), # KEYS[2]
+					$this->getQueueKey( 'h-data' ), # KEYS[3]
+					$uuid # ARGV[1]
+				],
+				3 # number of first argument(s) that are keys
+			);
+
+			if ( !$res ) {
+				wfDebugLog( 'JobQueueRedis', "Could not acknowledge {$this->type} job $uuid." );
+
+				return false;
+			}
+
+			JobQueue::incrStats( 'acks', $this->type );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return true;
+	}
+
+	/**
+	 * @see JobQueue::doDeduplicateRootJob()
+	 * @param IJobSpecification $job
+	 * @return bool
+	 * @throws JobQueueError
+	 * @throws LogicException
+	 */
+	protected function doDeduplicateRootJob( IJobSpecification $job ) {
+		if ( !$job->hasRootJobParams() ) {
+			throw new LogicException( "Cannot register root job; missing parameters." );
+		}
+		$params = $job->getRootJobParams();
+
+		$key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
+
+		$conn = $this->getConnection();
+		try {
+			$timestamp = $conn->get( $key ); // current last timestamp of this job
+			if ( $timestamp && $timestamp >= $params['rootJobTimestamp'] ) {
+				return true; // a newer version of this root job was enqueued
+			}
+
+			// Update the timestamp of the last root job started at the location...
+			return $conn->set( $key, $params['rootJobTimestamp'], self::ROOTJOB_TTL ); // 2 weeks
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::doIsRootJobOldDuplicate()
+	 * @param Job $job
+	 * @return bool
+	 * @throws JobQueueError
+	 */
+	protected function doIsRootJobOldDuplicate( Job $job ) {
+		if ( !$job->hasRootJobParams() ) {
+			return false; // job has no de-deplication info
+		}
+		$params = $job->getRootJobParams();
+
+		$conn = $this->getConnection();
+		try {
+			// Get the last time this root job was enqueued
+			$timestamp = $conn->get( $this->getRootJobCacheKey( $params['rootJobSignature'] ) );
+		} catch ( RedisException $e ) {
+			$timestamp = false;
+			$this->throwRedisException( $conn, $e );
+		}
+
+		// Check if a new root job was started at the location after this one's...
+		return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
+	}
+
+	/**
+	 * @see JobQueue::doDelete()
+	 * @return bool
+	 * @throws JobQueueError
+	 */
+	protected function doDelete() {
+		static $props = [ 'l-unclaimed', 'z-claimed', 'z-abandoned',
+			'z-delayed', 'h-idBySha1', 'h-sha1ById', 'h-attempts', 'h-data' ];
+
+		$conn = $this->getConnection();
+		try {
+			$keys = [];
+			foreach ( $props as $prop ) {
+				$keys[] = $this->getQueueKey( $prop );
+			}
+
+			$ok = ( $conn->delete( $keys ) !== false );
+			$conn->sRem( $this->getGlobalKey( 's-queuesWithJobs' ), $this->encodeQueueName() );
+
+			return $ok;
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @see JobQueue::getAllQueuedJobs()
+	 * @return Iterator
+	 * @throws JobQueueError
+	 */
+	public function getAllQueuedJobs() {
+		$conn = $this->getConnection();
+		try {
+			$uids = $conn->lRange( $this->getQueueKey( 'l-unclaimed' ), 0, -1 );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $this->getJobIterator( $conn, $uids );
+	}
+
+	/**
+	 * @see JobQueue::getAllDelayedJobs()
+	 * @return Iterator
+	 * @throws JobQueueError
+	 */
+	public function getAllDelayedJobs() {
+		$conn = $this->getConnection();
+		try {
+			$uids = $conn->zRange( $this->getQueueKey( 'z-delayed' ), 0, -1 );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $this->getJobIterator( $conn, $uids );
+	}
+
+	/**
+	 * @see JobQueue::getAllAcquiredJobs()
+	 * @return Iterator
+	 * @throws JobQueueError
+	 */
+	public function getAllAcquiredJobs() {
+		$conn = $this->getConnection();
+		try {
+			$uids = $conn->zRange( $this->getQueueKey( 'z-claimed' ), 0, -1 );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $this->getJobIterator( $conn, $uids );
+	}
+
+	/**
+	 * @see JobQueue::getAllAbandonedJobs()
+	 * @return Iterator
+	 * @throws JobQueueError
+	 */
+	public function getAllAbandonedJobs() {
+		$conn = $this->getConnection();
+		try {
+			$uids = $conn->zRange( $this->getQueueKey( 'z-abandoned' ), 0, -1 );
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $this->getJobIterator( $conn, $uids );
+	}
+
+	/**
+	 * @param RedisConnRef $conn
+	 * @param array $uids List of job UUIDs
+	 * @return MappedIterator
+	 */
+	protected function getJobIterator( RedisConnRef $conn, array $uids ) {
+		return new MappedIterator(
+			$uids,
+			function ( $uid ) use ( $conn ) {
+				return $this->getJobFromUidInternal( $uid, $conn );
+			},
+			[ 'accept' => function ( $job ) {
+				return is_object( $job );
+			} ]
+		);
+	}
+
+	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 = []; // (type => size)
+		$types = array_values( $types ); // reindex
+		$conn = $this->getConnection();
+		try {
+			$conn->multi( Redis::PIPELINE );
+			foreach ( $types as $type ) {
+				$conn->lSize( $this->getQueueKey( 'l-unclaimed', $type ) );
+			}
+			$res = $conn->exec();
+			if ( is_array( $res ) ) {
+				foreach ( $res as $i => $size ) {
+					$sizes[$types[$i]] = $size;
+				}
+			}
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $sizes;
+	}
+
+	/**
+	 * This function should not be called outside JobQueueRedis
+	 *
+	 * @param string $uid
+	 * @param RedisConnRef $conn
+	 * @return Job|bool Returns false if the job does not exist
+	 * @throws JobQueueError
+	 * @throws UnexpectedValueException
+	 */
+	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( $data );
+			if ( !is_array( $item ) ) { // this shouldn't happen
+				throw new UnexpectedValueException( "Could not find job with ID '$uid'." );
+			}
+			$title = Title::makeTitle( $item['namespace'], $item['title'] );
+			$job = Job::factory( $item['type'], $title, $item['params'] );
+			$job->metadata['uuid'] = $item['uuid'];
+			$job->metadata['timestamp'] = $item['timestamp'];
+			// Add in attempt count for debugging at showJobs.php
+			$job->metadata['attempts'] = $conn->hGet( $this->getQueueKey( 'h-attempts' ), $uid );
+
+			return $job;
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+	}
+
+	/**
+	 * @return array List of (wiki,type) tuples for queues with non-abandoned jobs
+	 * @throws JobQueueConnectionError
+	 * @throws JobQueueError
+	 */
+	public function getServerQueuesWithJobs() {
+		$queues = [];
+
+		$conn = $this->getConnection();
+		try {
+			$set = $conn->sMembers( $this->getGlobalKey( 's-queuesWithJobs' ) );
+			foreach ( $set as $queue ) {
+				$queues[] = $this->decodeQueueName( $queue );
+			}
+		} catch ( RedisException $e ) {
+			$this->throwRedisException( $conn, $e );
+		}
+
+		return $queues;
+	}
+
+	/**
+	 * @param IJobSpecification $job
+	 * @return array
+	 */
+	protected function getNewJobFields( IJobSpecification $job ) {
+		return [
+			// 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()
+				? Wikimedia\base_convert( sha1( serialize( $job->getDeduplicationInfo() ) ), 16, 36, 31 )
+				: '',
+			'timestamp' => time() // UNIX timestamp
+		];
+	}
+
+	/**
+	 * @param array $fields
+	 * @return Job|bool
+	 */
+	protected function getJobFromFields( array $fields ) {
+		$title = Title::makeTitle( $fields['namespace'], $fields['title'] );
+		$job = Job::factory( $fields['type'], $title, $fields['params'] );
+		$job->metadata['uuid'] = $fields['uuid'];
+		$job->metadata['timestamp'] = $fields['timestamp'];
+
+		return $job;
+	}
+
+	/**
+	 * @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)[ 'blob' => gzdeflate( $blob ), 'enc' => 'gzip' ];
+			$blobz = serialize( $object );
+
+			return ( strlen( $blobz ) < strlen( $blob ) ) ? $blobz : $blob;
+		} else {
+			return $blob;
+		}
+	}
+
+	/**
+	 * @param string $blob
+	 * @return array|bool Unserialized version of $blob or false
+	 */
+	protected function unserialize( $blob ) {
+		$fields = unserialize( $blob );
+		if ( is_object( $fields ) ) {
+			if ( $fields->enc === 'gzip' && function_exists( 'gzinflate' ) ) {
+				$fields = unserialize( gzinflate( $fields->blob ) );
+			} else {
+				$fields = false;
+			}
+		}
+
+		return is_array( $fields ) ? $fields : false;
+	}
+
+	/**
+	 * Get a connection to the server that handles all sub-queues for this queue
+	 *
+	 * @return RedisConnRef
+	 * @throws JobQueueConnectionError
+	 */
+	protected function getConnection() {
+		$conn = $this->redisPool->getConnection( $this->server, $this->logger );
+		if ( !$conn ) {
+			throw new JobQueueConnectionError(
+				"Unable to connect to redis server {$this->server}." );
+		}
+
+		return $conn;
+	}
+
+	/**
+	 * @param RedisConnRef $conn
+	 * @param RedisException $e
+	 * @throws JobQueueError
+	 */
+	protected function throwRedisException( RedisConnRef $conn, $e ) {
+		$this->redisPool->handleError( $conn, $e );
+		throw new JobQueueError( "Redis server error: {$e->getMessage()}\n" );
+	}
+
+	/**
+	 * @return string JSON
+	 */
+	private function encodeQueueName() {
+		return json_encode( [ $this->type, $this->wiki ] );
+	}
+
+	/**
+	 * @param string $name JSON
+	 * @return array (type, wiki)
+	 */
+	private function decodeQueueName( $name ) {
+		return json_decode( $name );
+	}
+
+	/**
+	 * @param string $name
+	 * @return string
+	 */
+	private function getGlobalKey( $name ) {
+		$parts = [ 'global', 'jobqueue', $name ];
+		foreach ( $parts as $part ) {
+			if ( !preg_match( '/[a-zA-Z0-9_-]+/', $part ) ) {
+				throw new InvalidArgumentException( "Key part characters are out of range." );
+			}
+		}
+
+		return implode( ':', $parts );
+	}
+
+	/**
+	 * @param string $prop
+	 * @param string|null $type Override this for sibling queues
+	 * @return string
+	 */
+	private function getQueueKey( $prop, $type = null ) {
+		$type = is_string( $type ) ? $type : $this->type;
+		list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
+		$keyspace = $prefix ? "$db-$prefix" : $db;
+
+		$parts = [ $keyspace, 'jobqueue', $type, $prop ];
+
+		// Parts are typically ASCII, but encode for sanity to escape ":"
+		return implode( ':', array_map( 'rawurlencode', $parts ) );
+	}
+}