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authorPierre Schmitz <pierre@archlinux.de>2013-08-12 09:28:15 +0200
committerPierre Schmitz <pierre@archlinux.de>2013-08-12 09:28:15 +0200
commit08aa4418c30cfc18ccc69a0f0f9cb9e17be6c196 (patch)
tree577a29fb579188d16003a209ce2a2e9c5b0aa2bd /includes/job/JobQueue.php
parentcacc939b34e315b85e2d72997811eb6677996cc1 (diff)
Update to MediaWiki 1.21.1
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+<?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
+ * @author Aaron Schulz
+ */
+
+/**
+ * Class to handle enqueueing and running of background jobs
+ *
+ * @ingroup JobQueue
+ * @since 1.21
+ */
+abstract class JobQueue {
+ protected $wiki; // string; wiki ID
+ protected $type; // string; job type
+ protected $order; // string; job priority for pop()
+ protected $claimTTL; // integer; seconds
+ protected $maxTries; // integer; maximum number of times to try a job
+
+ const QoS_Atomic = 1; // integer; "all-or-nothing" job insertions
+
+ /**
+ * @param $params array
+ */
+ 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." );
+ }
+ }
+
+ /**
+ * 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 simple means re-inserting them into the queue. Jobs can be
+ * attempted up to three times before being discarded.
+ *
+ * Queue classes should throw an exception if they do not support the options given.
+ *
+ * @param $params array
+ * @return JobQueue
+ * @throws MWException
+ */
+ final public static function factory( array $params ) {
+ $class = $params['class'];
+ if ( !MWInit::classExists( $class ) ) {
+ throw new MWException( "Invalid job queue class '$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)
+ */
+ final public function getOrder() {
+ return $this->order;
+ }
+
+ /**
+ * @return Array Subset of (random, timestamp, fifo)
+ */
+ abstract protected function supportedOrders();
+
+ /**
+ * @return string One of (random, timestamp, fifo)
+ */
+ abstract protected function optimalOrder();
+
+ /**
+ * Quickly check if the queue is empty (has no available 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 MWException
+ */
+ final public function isEmpty() {
+ wfProfileIn( __METHOD__ );
+ $res = $this->doIsEmpty();
+ wfProfileOut( __METHOD__ );
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::isEmpty()
+ * @return bool
+ */
+ abstract protected function doIsEmpty();
+
+ /**
+ * Get the number of available (unacquired) 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 integer
+ * @throws MWException
+ */
+ final public function getSize() {
+ wfProfileIn( __METHOD__ );
+ $res = $this->doGetSize();
+ wfProfileOut( __METHOD__ );
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::getSize()
+ * @return integer
+ */
+ 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 integer
+ * @throws MWException
+ */
+ final public function getAcquiredCount() {
+ wfProfileIn( __METHOD__ );
+ $res = $this->doGetAcquiredCount();
+ wfProfileOut( __METHOD__ );
+ return $res;
+ }
+
+ /**
+ * @see JobQueue::getAcquiredCount()
+ * @return integer
+ */
+ abstract protected function doGetAcquiredCount();
+
+ /**
+ * Push a single 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 $jobs Job|Array
+ * @param $flags integer Bitfield (supports JobQueue::QoS_Atomic)
+ * @return bool Returns false on failure
+ * @throws MWException
+ */
+ final public function push( $jobs, $flags = 0 ) {
+ return $this->batchPush( is_array( $jobs ) ? $jobs : array( $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 array $jobs List of Jobs
+ * @param $flags integer Bitfield (supports JobQueue::QoS_Atomic)
+ * @return bool Returns false on failure
+ * @throws MWException
+ */
+ final public function batchPush( array $jobs, $flags = 0 ) {
+ if ( !count( $jobs ) ) {
+ return true; // nothing to do
+ }
+
+ foreach ( $jobs as $job ) {
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
+ }
+ }
+
+ wfProfileIn( __METHOD__ );
+ $ok = $this->doBatchPush( $jobs, $flags );
+ wfProfileOut( __METHOD__ );
+ return $ok;
+ }
+
+ /**
+ * @see JobQueue::batchPush()
+ * @return bool
+ */
+ 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.
+ *
+ * @return Job|bool Returns false if there are no jobs
+ * @throws MWException
+ */
+ final public function pop() {
+ global $wgJobClasses;
+
+ 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}'." );
+ }
+
+ wfProfileIn( __METHOD__ );
+ $job = $this->doPop();
+ wfProfileOut( __METHOD__ );
+ return $job;
+ }
+
+ /**
+ * @see JobQueue::pop()
+ * @return Job
+ */
+ 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 bool
+ * @throws MWException
+ */
+ final public function ack( Job $job ) {
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
+ }
+ wfProfileIn( __METHOD__ );
+ $ok = $this->doAck( $job );
+ wfProfileOut( __METHOD__ );
+ return $ok;
+ }
+
+ /**
+ * @see JobQueue::ack()
+ * @return bool
+ */
+ 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 potentially many refreshLinks2 jobs.
+ * Since these jobs include things like page ID ranges and DB master positions, and morph
+ * into smaller refreshLinks2 jobs recursively, simple duplicate detection (like job_sha1)
+ * for individual jobs being identical 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 $job Job
+ * @return bool
+ * @throws MWException
+ */
+ final public function deduplicateRootJob( Job $job ) {
+ if ( $job->getType() !== $this->type ) {
+ throw new MWException( "Got '{$job->getType()}' job; expected '{$this->type}'." );
+ }
+ wfProfileIn( __METHOD__ );
+ $ok = $this->doDeduplicateRootJob( $job );
+ wfProfileOut( __METHOD__ );
+ return $ok;
+ }
+
+ /**
+ * @see JobQueue::deduplicateRootJob()
+ * @param $job Job
+ * @return bool
+ */
+ protected function doDeduplicateRootJob( Job $job ) {
+ return true;
+ }
+
+ /**
+ * Wait for any slaves or backup servers to catch up.
+ *
+ * This does nothing for certain queue classes.
+ *
+ * @return void
+ * @throws MWException
+ */
+ final public function waitForBackups() {
+ wfProfileIn( __METHOD__ );
+ $this->doWaitForBackups();
+ wfProfileOut( __METHOD__ );
+ }
+
+ /**
+ * @see JobQueue::waitForBackups()
+ * @return void
+ */
+ protected function doWaitForBackups() {}
+
+ /**
+ * Return a map of task names to task definition maps.
+ * A "task" is a fast periodic queue maintenance action.
+ * Mutually exclusive tasks must implement their own locking in the callback.
+ *
+ * Each task value is an associative array with:
+ * - name : the name of the task
+ * - callback : a PHP callable that performs the task
+ * - period : the period in seconds corresponding to the task frequency
+ *
+ * @return Array
+ */
+ final public function getPeriodicTasks() {
+ $tasks = $this->doGetPeriodicTasks();
+ foreach ( $tasks as $name => &$def ) {
+ $def['name'] = $name;
+ }
+ return $tasks;
+ }
+
+ /**
+ * @see JobQueue::getPeriodicTasks()
+ * @return Array
+ */
+ protected function doGetPeriodicTasks() {
+ return array();
+ }
+
+ /**
+ * Clear any process and persistent caches
+ *
+ * @return void
+ */
+ final public function flushCaches() {
+ wfProfileIn( __METHOD__ );
+ $this->doFlushCaches();
+ wfProfileOut( __METHOD__ );
+ }
+
+ /**
+ * @see JobQueue::flushCaches()
+ * @return void
+ */
+ protected function doFlushCaches() {}
+
+ /**
+ * Get an iterator to traverse over all of the jobs in this queue.
+ * This does not include jobs that are current acquired. In general,
+ * this should only be called on a queue that is no longer being popped.
+ *
+ * @return Iterator|Traversable|Array
+ * @throws MWException
+ */
+ abstract public function getAllQueuedJobs();
+
+ /**
+ * Namespace the queue with a key to isolate it for testing
+ *
+ * @param $key string
+ * @return void
+ * @throws MWException
+ */
+ public function setTestingPrefix( $key ) {
+ throw new MWException( "Queue namespacing not supported for this queue type." );
+ }
+}