includes/jobqueue/JobQueue.php
<?php
/**
* 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 Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
use MediaWiki\JobQueue\JobFactory;
use MediaWiki\MediaWikiServices;
use Wikimedia\RequestTimeout\TimeoutException;
use Wikimedia\UUID\GlobalIdGenerator;
/**
* @defgroup JobQueue JobQueue
*
*
* See [the architecture doc](@ref jobqueuearch) for more information.
*/
/**
* Base class for queueing and running background jobs from a storage backend.
*
* See [the architecture doc](@ref jobqueuearch) for more information.
*
* @ingroup JobQueue
* @since 1.21
* @stable to extend
*/
abstract class JobQueue {
/** @var string DB domain ID */
protected $domain;
/** @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|false Read only rationale (or false if r/w) */
protected $readOnlyReason;
/** @var StatsdDataFactoryInterface */
protected $stats;
/** @var GlobalIdGenerator */
protected $idGenerator;
/** @var WANObjectCache */
protected $wanCache;
/** @var bool */
protected $typeAgnostic;
private JobFactory $jobFactory;
/* Bit flag for "all-or-nothing" job insertions */
protected const QOS_ATOMIC = 1;
/* Seconds to remember root jobs (28 days) */
protected const ROOTJOB_TTL = 28 * 24 * 3600;
/**
* @stable to call
*
* @param array $params
* - type : A job type, 'default' if typeAgnostic is set
* - domain : A DB domain ID
* - idGenerator : A GlobalIdGenerator instance.
* - wanCache : An instance of WANObjectCache to use for caching [default: none]
* - stats : An instance of StatsdDataFactoryInterface [default: none]
* - claimTTL : Seconds a job can be claimed for exclusive execution [default: forever]
* - maxTries : Total times a job can be tried, assuming claims expire [default: 3]
* - order : Queue order, one of ("fifo", "timestamp", "random") [default: variable]
* - readOnlyReason : Mark the queue as read-only with this reason [default: false]
* - typeAgnostic : If the jobqueue should operate agnostic to the job types
* @throws JobQueueError
*
*/
protected function __construct( array $params ) {
$this->domain = $params['domain'] ?? $params['wiki']; // b/c
$this->type = $params['type'];
$this->claimTTL = $params['claimTTL'] ?? 0;
$this->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, $this->supportedOrders() ) ) {
throw new JobQueueError( __CLASS__ . " does not support '{$this->order}' order." );
}
$this->readOnlyReason = $params['readOnlyReason'] ?? false;
$this->stats = $params['stats'] ?? new NullStatsdDataFactory();
$this->wanCache = $params['wanCache'] ?? WANObjectCache::newEmpty();
$this->idGenerator = $params['idGenerator'];
if ( ( $params['typeAgnostic'] ?? false ) && !$this->supportsTypeAgnostic() ) {
throw new JobQueueError( __CLASS__ . " does not support type agnostic queues." );
}
$this->typeAgnostic = ( $params['typeAgnostic'] ?? false );
if ( $this->typeAgnostic ) {
$this->type = 'default';
}
$this->jobFactory = MediaWikiServices::getInstance()->getJobFactory();
}
/**
* Get a job queue object of the specified type.
* $params includes:
* - class : What job class to use (determines job type)
* - domain : Database domain 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 chosen, 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. [optional]
* - idGenerator : A GlobalIdGenerator instance.
* - stats : A StatsdDataFactoryInterface. [optional]
*
* Queue classes should throw an exception if they do not support the options given.
*
* @param array $params
* @return JobQueue
* @throws JobQueueError
*/
final public static function factory( array $params ) {
$class = $params['class'];
if ( !class_exists( $class ) ) {
throw new JobQueueError( "Invalid job queue class '$class'." );
}
$obj = new $class( $params );
if ( !( $obj instanceof self ) ) {
throw new JobQueueError( "Class '$class' is not a " . __CLASS__ . " class." );
}
return $obj;
}
/**
* @return string Database domain ID
*/
final public function getDomain() {
return $this->domain;
}
/**
* @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
*
* @stable to override
* @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|false 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 effect 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;
}
/**
* @stable to override
* @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;
}
/**
* @stable to override
* @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 JobQueueError
*/
final public function batchPush( array $jobs, $flags = 0 ) {
$this->assertNotReadOnly();
if ( $jobs === [] ) {
return; // nothing to do
}
foreach ( $jobs as $job ) {
$this->assertMatchingJobType( $job );
if ( $job->getReleaseTimestamp() && !$this->supportsDelayedJobs() ) {
throw new JobQueueError(
"Got delayed '{$job->getType()}' job; delays are not supported." );
}
}
$this->doBatchPush( $jobs, $flags );
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 JobQueueError
* @return RunnableJob|false Returns false if there are no jobs
*/
final public function pop() {
$this->assertNotReadOnly();
$job = $this->doPop();
// Flag this job as an old duplicate based on its "root" job...
try {
if ( $job && $this->isRootJobOldDuplicate( $job ) ) {
$this->incrStats( 'dupe_pops', $job->getType() );
$job = DuplicateJob::newFromJob( $job ); // convert to a no-op
}
} catch ( TimeoutException $e ) {
throw $e;
} catch ( Exception $e ) {
// don't lose jobs over this
}
return $job;
}
/**
* @see JobQueue::pop()
* @return RunnableJob|false
*/
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 RunnableJob $job
* @return void
* @throws JobQueueError
*/
final public function ack( RunnableJob $job ) {
$this->assertNotReadOnly();
$this->assertMatchingJobType( $job );
$this->doAck( $job );
}
/**
* @see JobQueue::ack()
* @param RunnableJob $job
*/
abstract protected function doAck( RunnableJob $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 primary 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.
*
* @internal For use within JobQueue only
* @param IJobSpecification $job
* @throws JobQueueError
* @return bool
*/
final public function deduplicateRootJob( IJobSpecification $job ) {
$this->assertNotReadOnly();
$this->assertMatchingJobType( $job );
return $this->doDeduplicateRootJob( $job );
}
/**
* @stable to override
* @see JobQueue::deduplicateRootJob()
* @param IJobSpecification $job
* @throws JobQueueError
* @return bool
*/
protected function doDeduplicateRootJob( IJobSpecification $job ) {
$params = $job->hasRootJobParams() ? $job->getRootJobParams() : null;
if ( !$params ) {
throw new JobQueueError( "Cannot register root job; missing parameters." );
}
$key = $this->getRootJobCacheKey( $params['rootJobSignature'], $job->getType() );
// Callers should call JobQueueGroup::push() before this method so that if the
// insert fails, the de-duplication registration will be aborted. Having only the
// de-duplication registration succeed would cause jobs to become no-ops without
// any actual jobs that made them redundant.
$timestamp = $this->wanCache->get( $key ); // last known timestamp of such a root job
if ( $timestamp !== false && $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->wanCache->set( $key, $params['rootJobTimestamp'], self::ROOTJOB_TTL );
}
/**
* Check if the "root" job of a given job has been superseded by a newer one
*
* @param IJobSpecification $job
* @throws JobQueueError
* @return bool
*/
final protected function isRootJobOldDuplicate( IJobSpecification $job ) {
$this->assertMatchingJobType( $job );
return $this->doIsRootJobOldDuplicate( $job );
}
/**
* @stable to override
* @see JobQueue::isRootJobOldDuplicate()
* @param IJobSpecification $job
* @return bool
*/
protected function doIsRootJobOldDuplicate( IJobSpecification $job ) {
$params = $job->hasRootJobParams() ? $job->getRootJobParams() : null;
if ( !$params ) {
return false; // job has no de-duplication info
}
$key = $this->getRootJobCacheKey( $params['rootJobSignature'], $job->getType() );
// Get the last time this root job was enqueued
$timestamp = $this->wanCache->get( $key );
if ( $timestamp === false || $params['rootJobTimestamp'] > $timestamp ) {
// Update the timestamp of the last known root job started at the location...
$this->wanCache->set( $key, $params['rootJobTimestamp'], self::ROOTJOB_TTL );
}
// 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
* @param string $type job type
* @return string
*/
protected function getRootJobCacheKey( $signature, $type ) {
return $this->wanCache->makeGlobalKey(
'jobqueue',
$this->domain,
$type,
'rootjob',
$signature
);
}
/**
* Delete all unclaimed and delayed jobs from the queue
*
* @throws JobQueueError
* @since 1.22
* @return void
*/
final public function delete() {
$this->assertNotReadOnly();
$this->doDelete();
}
/**
* @stable to override
* @see JobQueue::delete()
* @throws JobQueueError
*/
protected function doDelete() {
throw new JobQueueError( "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();
}
/**
* @stable to override
* @see JobQueue::waitForBackups()
* @return void
*/
protected function doWaitForBackups() {
}
/**
* Clear any process and persistent caches
*
* @return void
*/
final public function flushCaches() {
$this->doFlushCaches();
}
/**
* @stable to override
* @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<RunnableJob>
* @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.
*
* @stable to override
* @return Iterator<RunnableJob>
* @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
*
* @stable to override
* @return Iterator<RunnableJob>
* @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
*
* @stable to override
* @return Iterator<RunnableJob>
* @throws JobQueueError
* @since 1.25
*/
public function getAllAbandonedJobs() {
return new ArrayIterator( [] ); // not implemented
}
/**
* Do not use this function outside of JobQueue/JobQueueGroup
*
* @stable to override
* @return string|null
* @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 JobQueueError
* @since 1.22
*/
final public function getSiblingQueuesWithJobs( array $types ) {
return $this->doGetSiblingQueuesWithJobs( $types );
}
/**
* @stable to override
* @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 JobQueueError
* @since 1.22
*/
final public function getSiblingQueueSizes( array $types ) {
return $this->doGetSiblingQueueSizes( $types );
}
/**
* @stable to override
* @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
}
/**
* @param string $command
* @param array $params
* @return Job
*/
protected function factoryJob( $command, $params ) {
return $this->jobFactory->newJob( $command, $params );
}
/**
* @throws JobQueueReadOnlyError
*/
protected function assertNotReadOnly() {
if ( $this->readOnlyReason !== false ) {
throw new JobQueueReadOnlyError( "Job queue is read-only: {$this->readOnlyReason}" );
}
}
/**
* @param IJobSpecification $job
* @throws JobQueueError
*/
private function assertMatchingJobType( IJobSpecification $job ) {
if ( $this->typeAgnostic ) {
return;
}
if ( $job->getType() !== $this->type ) {
throw new JobQueueError( "Got '{$job->getType()}' job; expected '{$this->type}'." );
}
}
/**
* Call StatsdDataFactoryInterface::updateCount() 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
*/
protected function incrStats( $key, $type, $delta = 1 ) {
$this->stats->updateCount( "jobqueue.{$key}.all", $delta );
$this->stats->updateCount( "jobqueue.{$key}.{$type}", $delta );
}
/**
* Subclasses should set this to true if they support type agnostic queues
*
* @return bool
* @since 1.38
*/
protected function supportsTypeAgnostic(): bool {
return false;
}
}