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[autoinstallsdev/mediawiki.git] / 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 ) );
+       }
+}