--- /dev/null
+<?php
+/**
+ * Job queue base 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
+ * @defgroup JobQueue JobQueue
+ */
+use MediaWiki\MediaWikiServices;
+
+/**
+ * Class to handle enqueueing and running of background jobs
+ *
+ * @ingroup JobQueue
+ * @since 1.21
+ */
+abstract class JobQueue {
+ /** @var string Wiki ID */
+ protected $wiki;
+ /** @var string Job type */
+ protected $type;
+ /** @var string Job priority for pop() */
+ protected $order;
+ /** @var int Time to live in seconds */
+ protected $claimTTL;
+ /** @var int Maximum number of times to try a job */
+ protected $maxTries;
+ /** @var string|bool Read only rationale (or false if r/w) */
+ protected $readOnlyReason;
+
+ /** @var BagOStuff */
+ protected $dupCache;
+ /** @var JobQueueAggregator */
+ protected $aggr;
+
+ const QOS_ATOMIC = 1; // integer; "all-or-nothing" job insertions
+
+ const ROOTJOB_TTL = 2419200; // integer; seconds to remember root jobs (28 days)
+
+ /**
+ * @param array $params
+ * @throws MWException
+ */
+ protected function __construct( array $params ) {
+ $this->wiki = $params['wiki'];
+ $this->type = $params['type'];
+ $this->claimTTL = isset( $params['claimTTL'] ) ? $params['claimTTL'] : 0;
+ $this->maxTries = isset( $params['maxTries'] ) ? $params['maxTries'] : 3;
+ if ( isset( $params['order'] ) && $params['order'] !== 'any' ) {
+ $this->order = $params['order'];
+ } else {
+ $this->order = $this->optimalOrder();
+ }
+ if ( !in_array( $this->order, $this->supportedOrders() ) ) {
+ throw new MWException( __CLASS__ . " does not support '{$this->order}' order." );
+ }
+ $this->dupCache = wfGetCache( CACHE_ANYTHING );
+ $this->aggr = isset( $params['aggregator'] )
+ ? $params['aggregator']
+ : new JobQueueAggregatorNull( [] );
+ $this->readOnlyReason = isset( $params['readOnlyReason'] )
+ ? $params['readOnlyReason']
+ : false;
+ }
+
+ /**
+ * Get a job queue object of the specified type.
+ * $params includes:
+ * - class : What job class to use (determines job type)
+ * - wiki : wiki ID of the wiki the jobs are for (defaults to current wiki)
+ * - type : The name of the job types this queue handles
+ * - order : Order that pop() selects jobs, one of "fifo", "timestamp" or "random".
+ * If "fifo" is used, the queue will effectively be FIFO. Note that job
+ * completion will not appear to be exactly FIFO if there are multiple
+ * job runners since jobs can take different times to finish once popped.
+ * If "timestamp" is used, the queue will at least be loosely ordered
+ * by timestamp, allowing for some jobs to be popped off out of order.
+ * If "random" is used, pop() will pick jobs in random order.
+ * Note that it may only be weakly random (e.g. a lottery of the oldest X).
+ * If "any" is choosen, the queue will use whatever order is the fastest.
+ * This might be useful for improving concurrency for job acquisition.
+ * - claimTTL : If supported, the queue will recycle jobs that have been popped
+ * but not acknowledged as completed after this many seconds. Recycling
+ * of jobs simply means re-inserting them into the queue. Jobs can be
+ * attempted up to three times before being discarded.
+ * - readOnlyReason : Set this to a string to make the queue read-only.
+ *
+ * Queue classes should throw an exception if they do not support the options given.
+ *
+ * @param array $params
+ * @return JobQueue
+ * @throws MWException
+ */
+ final public static function factory( array $params ) {
+ $class = $params['class'];
+ if ( !class_exists( $class ) ) {
+ throw new MWException( "Invalid job queue class '$class'." );
+ }
+ $obj = new $class( $params );
+ if ( !( $obj instanceof self ) ) {
+ throw new MWException( "Class '$class' is not a " . __CLASS__ . " class." );
+ }
+
+ return $obj;
+ }
+
+ /**
+ * @return string Wiki ID
+ */
+ final public function getWiki() {
+ return $this->wiki;
+ }
+
+ /**
+ * @return string Job type that this queue handles
+ */
+ final public function getType() {
+ return $this->type;
+ }
+
+ /**
+ * @return string One of (random, timestamp, fifo, undefined)
+ */
+ final public function getOrder() {
+ return $this->order;
+ }
+
+ /**
+ * Get the allowed queue orders for configuration validation
+ *
+ * @return array Subset of (random, timestamp, fifo, undefined)
+ */
+ abstract protected function supportedOrders();
+
+ /**
+ * Get the default queue order to use if configuration does not specify one
+ *
+ * @return string One of (random, timestamp, fifo, undefined)
+ */
+ abstract protected function optimalOrder();
+
+ /**
+ * Find out if delayed jobs are supported for configuration validation
+ *
+ * @return bool Whether delayed jobs are supported
+ */
+ protected function supportsDelayedJobs() {
+ return false; // not implemented
+ }
+
+ /**
+ * @return bool Whether delayed jobs are enabled
+ * @since 1.22
+ */
+ final public function delayedJobsEnabled() {
+ return $this->supportsDelayedJobs();
+ }
+
+ /**
+ * @return string|bool Read-only rational or false if r/w
+ * @since 1.27
+ */
+ public function getReadOnlyReason() {
+ return $this->readOnlyReason;
+ }
+
+ /**
+ * Quickly check if the queue has no available (unacquired, non-delayed) jobs.
+ * Queue classes should use caching if they are any slower without memcached.
+ *
+ * If caching is used, this might return false when there are actually no jobs.
+ * If pop() is called and returns false then it should correct the cache. Also,
+ * calling flushCaches() first prevents this. However, this affect is typically
+ * not distinguishable from the race condition between isEmpty() and pop().
+ *
+ * @return bool
+ * @throws JobQueueError
+ */
+ final public function isEmpty() {
+ $res = $this->doIsEmpty();
+
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::isEmpty()
+ * @return bool
+ */
+ abstract protected function doIsEmpty();
+
+ /**
+ * Get the number of available (unacquired, non-delayed) jobs in the queue.
+ * Queue classes should use caching if they are any slower without memcached.
+ *
+ * If caching is used, this number might be out of date for a minute.
+ *
+ * @return int
+ * @throws JobQueueError
+ */
+ final public function getSize() {
+ $res = $this->doGetSize();
+
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::getSize()
+ * @return int
+ */
+ abstract protected function doGetSize();
+
+ /**
+ * Get the number of acquired jobs (these are temporarily out of the queue).
+ * Queue classes should use caching if they are any slower without memcached.
+ *
+ * If caching is used, this number might be out of date for a minute.
+ *
+ * @return int
+ * @throws JobQueueError
+ */
+ final public function getAcquiredCount() {
+ $res = $this->doGetAcquiredCount();
+
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::getAcquiredCount()
+ * @return int
+ */
+ abstract protected function doGetAcquiredCount();
+
+ /**
+ * Get the number of delayed jobs (these are temporarily out of the queue).
+ * Queue classes should use caching if they are any slower without memcached.
+ *
+ * If caching is used, this number might be out of date for a minute.
+ *
+ * @return int
+ * @throws JobQueueError
+ * @since 1.22
+ */
+ final public function getDelayedCount() {
+ $res = $this->doGetDelayedCount();
+
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::getDelayedCount()
+ * @return int
+ */
+ protected function doGetDelayedCount() {
+ return 0; // not implemented
+ }
+
+ /**
+ * Get the number of acquired jobs that can no longer be attempted.
+ * Queue classes should use caching if they are any slower without memcached.
+ *
+ * If caching is used, this number might be out of date for a minute.
+ *
+ * @return int
+ * @throws JobQueueError
+ */
+ final public function getAbandonedCount() {
+ $res = $this->doGetAbandonedCount();
+
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::getAbandonedCount()
+ * @return int
+ */
+ protected function doGetAbandonedCount() {
+ return 0; // not implemented
+ }
+
+ /**
+ * Push one or more jobs into the queue.
+ * This does not require $wgJobClasses to be set for the given job type.
+ * Outside callers should use JobQueueGroup::push() instead of this function.
+ *
+ * @param IJobSpecification|IJobSpecification[] $jobs
+ * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
+ * @return void
+ * @throws JobQueueError
+ */
+ final public function push( $jobs, $flags = 0 ) {
+ $jobs = is_array( $jobs ) ? $jobs : [ $jobs ];
+ $this->batchPush( $jobs, $flags );
+ }
+
+ /**
+ * Push a batch of jobs into the queue.
+ * This does not require $wgJobClasses to be set for the given job type.
+ * Outside callers should use JobQueueGroup::push() instead of this function.
+ *
+ * @param IJobSpecification[] $jobs
+ * @param int $flags Bitfield (supports JobQueue::QOS_ATOMIC)
+ * @return void
+ * @throws MWException
+ */
+ final public function batchPush( array $jobs, $flags = 0 ) {
+ $this->assertNotReadOnly();
+
+ if ( !count( $jobs ) ) {
+ return; // nothing to do
+ }
+
+ foreach ( $jobs as $job ) {
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException(
+ "Got '{$job->getType()}' job; expected a '{$this->type}' job." );
+ } elseif ( $job->getReleaseTimestamp() && !$this->supportsDelayedJobs() ) {
+ throw new MWException(
+ "Got delayed '{$job->getType()}' job; delays are not supported." );
+ }
+ }
+
+ $this->doBatchPush( $jobs, $flags );
+ $this->aggr->notifyQueueNonEmpty( $this->wiki, $this->type );
+
+ foreach ( $jobs as $job ) {
+ if ( $job->isRootJob() ) {
+ $this->deduplicateRootJob( $job );
+ }
+ }
+ }
+
+ /**
+ * @see JobQueue::batchPush()
+ * @param IJobSpecification[] $jobs
+ * @param int $flags
+ */
+ abstract protected function doBatchPush( array $jobs, $flags );
+
+ /**
+ * Pop a job off of the queue.
+ * This requires $wgJobClasses to be set for the given job type.
+ * Outside callers should use JobQueueGroup::pop() instead of this function.
+ *
+ * @throws MWException
+ * @return Job|bool Returns false if there are no jobs
+ */
+ final public function pop() {
+ global $wgJobClasses;
+
+ $this->assertNotReadOnly();
+ if ( $this->wiki !== wfWikiID() ) {
+ throw new MWException( "Cannot pop '{$this->type}' job off foreign wiki queue." );
+ } elseif ( !isset( $wgJobClasses[$this->type] ) ) {
+ // Do not pop jobs if there is no class for the queue type
+ throw new MWException( "Unrecognized job type '{$this->type}'." );
+ }
+
+ $job = $this->doPop();
+
+ if ( !$job ) {
+ $this->aggr->notifyQueueEmpty( $this->wiki, $this->type );
+ }
+
+ // Flag this job as an old duplicate based on its "root" job...
+ try {
+ if ( $job && $this->isRootJobOldDuplicate( $job ) ) {
+ self::incrStats( 'dupe_pops', $this->type );
+ $job = DuplicateJob::newFromJob( $job ); // convert to a no-op
+ }
+ } catch ( Exception $e ) {
+ // don't lose jobs over this
+ }
+
+ return $job;
+ }
+
+ /**
+ * @see JobQueue::pop()
+ * @return Job|bool
+ */
+ abstract protected function doPop();
+
+ /**
+ * Acknowledge that a job was completed.
+ *
+ * This does nothing for certain queue classes or if "claimTTL" is not set.
+ * Outside callers should use JobQueueGroup::ack() instead of this function.
+ *
+ * @param Job $job
+ * @return void
+ * @throws MWException
+ */
+ final public function ack( Job $job ) {
+ $this->assertNotReadOnly();
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
+ }
+
+ $this->doAck( $job );
+ }
+
+ /**
+ * @see JobQueue::ack()
+ * @param Job $job
+ */
+ abstract protected function doAck( Job $job );
+
+ /**
+ * Register the "root job" of a given job into the queue for de-duplication.
+ * This should only be called right *after* all the new jobs have been inserted.
+ * This is used to turn older, duplicate, job entries into no-ops. The root job
+ * information will remain in the registry until it simply falls out of cache.
+ *
+ * This requires that $job has two special fields in the "params" array:
+ * - rootJobSignature : hash (e.g. SHA1) that identifies the task
+ * - rootJobTimestamp : TS_MW timestamp of this instance of the task
+ *
+ * A "root job" is a conceptual job that consist of potentially many smaller jobs
+ * that are actually inserted into the queue. For example, "refreshLinks" jobs are
+ * spawned when a template is edited. One can think of the task as "update links
+ * of pages that use template X" and an instance of that task as a "root job".
+ * However, what actually goes into the queue are range and leaf job subtypes.
+ * Since these jobs include things like page ID ranges and DB master positions,
+ * and can morph into smaller jobs recursively, simple duplicate detection
+ * for individual jobs being identical (like that of job_sha1) is not useful.
+ *
+ * In the case of "refreshLinks", if these jobs are still in the queue when the template
+ * is edited again, we want all of these old refreshLinks jobs for that template to become
+ * no-ops. This can greatly reduce server load, since refreshLinks jobs involves parsing.
+ * Essentially, the new batch of jobs belong to a new "root job" and the older ones to a
+ * previous "root job" for the same task of "update links of pages that use template X".
+ *
+ * This does nothing for certain queue classes.
+ *
+ * @param IJobSpecification $job
+ * @throws MWException
+ * @return bool
+ */
+ final public function deduplicateRootJob( IJobSpecification $job ) {
+ $this->assertNotReadOnly();
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
+ }
+
+ return $this->doDeduplicateRootJob( $job );
+ }
+
+ /**
+ * @see JobQueue::deduplicateRootJob()
+ * @param IJobSpecification $job
+ * @throws MWException
+ * @return bool
+ */
+ protected function doDeduplicateRootJob( IJobSpecification $job ) {
+ if ( !$job->hasRootJobParams() ) {
+ throw new MWException( "Cannot register root job; missing parameters." );
+ }
+ $params = $job->getRootJobParams();
+
+ $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
+ // Callers should call batchInsert() and then this function so that if the insert
+ // fails, the de-duplication registration will be aborted. Since the insert is
+ // deferred till "transaction idle", do the same here, so that the ordering is
+ // maintained. Having only the de-duplication registration succeed would cause
+ // jobs to become no-ops without any actual jobs that made them redundant.
+ $timestamp = $this->dupCache->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 $this->dupCache->set( $key, $params['rootJobTimestamp'], JobQueueDB::ROOTJOB_TTL );
+ }
+
+ /**
+ * Check if the "root" job of a given job has been superseded by a newer one
+ *
+ * @param Job $job
+ * @throws MWException
+ * @return bool
+ */
+ final protected function isRootJobOldDuplicate( Job $job ) {
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
+ }
+ $isDuplicate = $this->doIsRootJobOldDuplicate( $job );
+
+ return $isDuplicate;
+ }
+
+ /**
+ * @see JobQueue::isRootJobOldDuplicate()
+ * @param Job $job
+ * @return bool
+ */
+ protected function doIsRootJobOldDuplicate( Job $job ) {
+ if ( !$job->hasRootJobParams() ) {
+ return false; // job has no de-deplication info
+ }
+ $params = $job->getRootJobParams();
+
+ $key = $this->getRootJobCacheKey( $params['rootJobSignature'] );
+ // Get the last time this root job was enqueued
+ $timestamp = $this->dupCache->get( $key );
+
+ // Check if a new root job was started at the location after this one's...
+ return ( $timestamp && $timestamp > $params['rootJobTimestamp'] );
+ }
+
+ /**
+ * @param string $signature Hash identifier of the root job
+ * @return string
+ */
+ protected function getRootJobCacheKey( $signature ) {
+ list( $db, $prefix ) = wfSplitWikiID( $this->wiki );
+
+ return wfForeignMemcKey( $db, $prefix, 'jobqueue', $this->type, 'rootjob', $signature );
+ }
+
+ /**
+ * Deleted all unclaimed and delayed jobs from the queue
+ *
+ * @throws JobQueueError
+ * @since 1.22
+ * @return void
+ */
+ final public function delete() {
+ $this->assertNotReadOnly();
+
+ $this->doDelete();
+ }
+
+ /**
+ * @see JobQueue::delete()
+ * @throws MWException
+ */
+ protected function doDelete() {
+ throw new MWException( "This method is not implemented." );
+ }
+
+ /**
+ * Wait for any replica DBs or backup servers to catch up.
+ *
+ * This does nothing for certain queue classes.
+ *
+ * @return void
+ * @throws JobQueueError
+ */
+ final public function waitForBackups() {
+ $this->doWaitForBackups();
+ }
+
+ /**
+ * @see JobQueue::waitForBackups()
+ * @return void
+ */
+ protected function doWaitForBackups() {
+ }
+
+ /**
+ * Clear any process and persistent caches
+ *
+ * @return void
+ */
+ final public function flushCaches() {
+ $this->doFlushCaches();
+ }
+
+ /**
+ * @see JobQueue::flushCaches()
+ * @return void
+ */
+ protected function doFlushCaches() {
+ }
+
+ /**
+ * Get an iterator to traverse over all available jobs in this queue.
+ * This does not include jobs that are currently acquired or delayed.
+ * Note: results may be stale if the queue is concurrently modified.
+ *
+ * @return Iterator
+ * @throws JobQueueError
+ */
+ abstract public function getAllQueuedJobs();
+
+ /**
+ * Get an iterator to traverse over all delayed jobs in this queue.
+ * Note: results may be stale if the queue is concurrently modified.
+ *
+ * @return Iterator
+ * @throws JobQueueError
+ * @since 1.22
+ */
+ public function getAllDelayedJobs() {
+ return new ArrayIterator( [] ); // not implemented
+ }
+
+ /**
+ * Get an iterator to traverse over all claimed jobs in this queue
+ *
+ * Callers should be quick to iterator over it or few results
+ * will be returned due to jobs being acknowledged and deleted
+ *
+ * @return Iterator
+ * @throws JobQueueError
+ * @since 1.26
+ */
+ public function getAllAcquiredJobs() {
+ return new ArrayIterator( [] ); // not implemented
+ }
+
+ /**
+ * Get an iterator to traverse over all abandoned jobs in this queue
+ *
+ * @return Iterator
+ * @throws JobQueueError
+ * @since 1.25
+ */
+ public function getAllAbandonedJobs() {
+ return new ArrayIterator( [] ); // not implemented
+ }
+
+ /**
+ * Do not use this function outside of JobQueue/JobQueueGroup
+ *
+ * @return string
+ * @since 1.22
+ */
+ public function getCoalesceLocationInternal() {
+ return null;
+ }
+
+ /**
+ * Check whether each of the given queues are empty.
+ * This is used for batching checks for queues stored at the same place.
+ *
+ * @param array $types List of queues types
+ * @return array|null (list of non-empty queue types) or null if unsupported
+ * @throws MWException
+ * @since 1.22
+ */
+ final public function getSiblingQueuesWithJobs( array $types ) {
+ return $this->doGetSiblingQueuesWithJobs( $types );
+ }
+
+ /**
+ * @see JobQueue::getSiblingQueuesWithJobs()
+ * @param array $types List of queues types
+ * @return array|null (list of queue types) or null if unsupported
+ */
+ protected function doGetSiblingQueuesWithJobs( array $types ) {
+ return null; // not supported
+ }
+
+ /**
+ * Check the size of each of the given queues.
+ * For queues not served by the same store as this one, 0 is returned.
+ * This is used for batching checks for queues stored at the same place.
+ *
+ * @param array $types List of queues types
+ * @return array|null (job type => whether queue is empty) or null if unsupported
+ * @throws MWException
+ * @since 1.22
+ */
+ final public function getSiblingQueueSizes( array $types ) {
+ return $this->doGetSiblingQueueSizes( $types );
+ }
+
+ /**
+ * @see JobQueue::getSiblingQueuesSize()
+ * @param array $types List of queues types
+ * @return array|null (list of queue types) or null if unsupported
+ */
+ protected function doGetSiblingQueueSizes( array $types ) {
+ return null; // not supported
+ }
+
+ /**
+ * @throws JobQueueReadOnlyError
+ */
+ protected function assertNotReadOnly() {
+ if ( $this->readOnlyReason !== false ) {
+ throw new JobQueueReadOnlyError( "Job queue is read-only: {$this->readOnlyReason}" );
+ }
+ }
+
+ /**
+ * Call wfIncrStats() for the queue overall and for the queue type
+ *
+ * @param string $key Event type
+ * @param string $type Job type
+ * @param int $delta
+ * @since 1.22
+ */
+ public static function incrStats( $key, $type, $delta = 1 ) {
+ static $stats;
+ if ( !$stats ) {
+ $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
+ }
+ $stats->updateCount( "jobqueue.{$key}.all", $delta );
+ $stats->updateCount( "jobqueue.{$key}.{$type}", $delta );
+ }
+}
+
+/**
+ * @ingroup JobQueue
+ * @since 1.22
+ */
+class JobQueueError extends MWException {
+}
+
+class JobQueueConnectionError extends JobQueueError {
+}
+
+class JobQueueReadOnlyError extends JobQueueError {
+
+}
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