397 lines
14 KiB
PHP
397 lines
14 KiB
PHP
<?php
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/**
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* Interface and manager for deferred updates.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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*/
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use Wikimedia\Rdbms\IDatabase;
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use MediaWiki\MediaWikiServices;
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use Wikimedia\Rdbms\LBFactory;
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use Wikimedia\Rdbms\LoadBalancer;
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/**
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* Class for managing the deferred updates
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*
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* In web request mode, deferred updates can be run at the end of the request, either before or
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* after the HTTP response has been sent. In either case, they run after the DB commit step. If
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* an update runs after the response is sent, it will not block clients. If sent before, it will
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* run synchronously. These two modes are defined via PRESEND and POSTSEND constants, the latter
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* being the default for addUpdate() and addCallableUpdate().
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*
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* Updates that work through this system will be more likely to complete by the time the client
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* makes their next request after this one than with the JobQueue system.
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*
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* In CLI mode, deferred updates will run:
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* - a) During DeferredUpdates::addUpdate if no LBFactory DB handles have writes pending
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* - b) On commit of an LBFactory DB handle if no other such handles have writes pending
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* - c) During an LBFactory::waitForReplication call if no LBFactory DBs have writes pending
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* - d) When the queue is large and an LBFactory DB handle commits (EnqueueableDataUpdate only)
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* - e) At the completion of Maintenance::execute()
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*
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* @see Maintenance::setLBFactoryTriggers
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*
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* When updates are deferred, they go into one two FIFO "top-queues" (one for pre-send and one
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* for post-send). Updates enqueued *during* doUpdate() of a "top" update go into the "sub-queue"
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* for that update. After that method finishes, the sub-queue is run until drained. This continues
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* for each top-queue job until the entire top queue is drained. This happens for the pre-send
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* top-queue, and later on, the post-send top-queue, in execute().
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*
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* @since 1.19
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*/
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class DeferredUpdates {
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/** @var DeferrableUpdate[] Updates to be deferred until before request end */
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private static $preSendUpdates = [];
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/** @var DeferrableUpdate[] Updates to be deferred until after request end */
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private static $postSendUpdates = [];
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const ALL = 0; // all updates; in web requests, use only after flushing the output buffer
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const PRESEND = 1; // for updates that should run before flushing output buffer
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const POSTSEND = 2; // for updates that should run after flushing output buffer
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const BIG_QUEUE_SIZE = 100;
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/** @var array|null Information about the current execute() call or null if not running */
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private static $executeContext;
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/**
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* Add an update to the deferred list to be run later by execute()
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*
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* In CLI mode, callback magic will also be used to run updates when safe
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*
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* @param DeferrableUpdate $update Some object that implements doUpdate()
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* @param int $stage DeferredUpdates constant (PRESEND or POSTSEND) (since 1.27)
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*/
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public static function addUpdate( DeferrableUpdate $update, $stage = self::POSTSEND ) {
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global $wgCommandLineMode;
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if (
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self::$executeContext &&
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self::$executeContext['stage'] >= $stage &&
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!( $update instanceof MergeableUpdate )
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) {
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// This is a sub-DeferredUpdate; run it right after its parent update.
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// Also, while post-send updates are running, push any "pre-send" jobs to the
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// active post-send queue to make sure they get run this round (or at all).
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self::$executeContext['subqueue'][] = $update;
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return;
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}
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if ( $stage === self::PRESEND ) {
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self::push( self::$preSendUpdates, $update );
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} else {
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self::push( self::$postSendUpdates, $update );
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}
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// Try to run the updates now if in CLI mode and no transaction is active.
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// This covers scripts that don't/barely use the DB but make updates to other stores.
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if ( $wgCommandLineMode ) {
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self::tryOpportunisticExecute( 'run' );
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}
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}
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/**
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* Add a callable update. In a lot of cases, we just need a callback/closure,
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* defining a new DeferrableUpdate object is not necessary
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*
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* @see MWCallableUpdate::__construct()
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*
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* @param callable $callable
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* @param int $stage DeferredUpdates constant (PRESEND or POSTSEND) (since 1.27)
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* @param IDatabase|IDatabase[]|null $dbw Abort if this DB is rolled back [optional] (since 1.28)
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*/
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public static function addCallableUpdate(
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$callable, $stage = self::POSTSEND, $dbw = null
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) {
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self::addUpdate( new MWCallableUpdate( $callable, wfGetCaller(), $dbw ), $stage );
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}
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/**
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* Do any deferred updates and clear the list
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*
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* @param string $mode Use "enqueue" to use the job queue when possible [Default: "run"]
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* @param int $stage DeferredUpdates constant (PRESEND, POSTSEND, or ALL) (since 1.27)
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*/
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public static function doUpdates( $mode = 'run', $stage = self::ALL ) {
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$stageEffective = ( $stage === self::ALL ) ? self::POSTSEND : $stage;
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// For ALL mode, make sure that any PRESEND updates added along the way get run.
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// Normally, these use the subqueue, but that isn't true for MergeableUpdate items.
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do {
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if ( $stage === self::ALL || $stage === self::PRESEND ) {
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self::execute( self::$preSendUpdates, $mode, $stageEffective );
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}
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if ( $stage === self::ALL || $stage == self::POSTSEND ) {
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self::execute( self::$postSendUpdates, $mode, $stageEffective );
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}
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} while ( $stage === self::ALL && self::$preSendUpdates );
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}
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/**
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* @param DeferrableUpdate[] $queue
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* @param DeferrableUpdate $update
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*/
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private static function push( array &$queue, DeferrableUpdate $update ) {
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if ( $update instanceof MergeableUpdate ) {
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$class = get_class( $update ); // fully-qualified class
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if ( isset( $queue[$class] ) ) {
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/** @var MergeableUpdate $existingUpdate */
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$existingUpdate = $queue[$class];
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$existingUpdate->merge( $update );
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// Move the update to the end to handle things like mergeable purge
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// updates that might depend on the prior updates in the queue running
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unset( $queue[$class] );
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$queue[$class] = $existingUpdate;
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} else {
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$queue[$class] = $update;
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}
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} else {
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$queue[] = $update;
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}
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}
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/**
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* Immediately run/queue a list of updates
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*
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* @param DeferrableUpdate[] &$queue List of DeferrableUpdate objects
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* @param string $mode Use "enqueue" to use the job queue when possible
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* @param int $stage Class constant (PRESEND, POSTSEND) (since 1.28)
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* @throws ErrorPageError Happens on top-level calls
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* @throws Exception Happens on second-level calls
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*/
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protected static function execute( array &$queue, $mode, $stage ) {
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$services = MediaWikiServices::getInstance();
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$stats = $services->getStatsdDataFactory();
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$lbFactory = $services->getDBLoadBalancerFactory();
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$method = RequestContext::getMain()->getRequest()->getMethod();
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$ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
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/** @var ErrorPageError $reportableError */
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$reportableError = null;
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/** @var DeferrableUpdate[] $updates Snapshot of queue */
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$updates = $queue;
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// Keep doing rounds of updates until none get enqueued...
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while ( $updates ) {
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$queue = []; // clear the queue
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// Order will be DataUpdate followed by generic DeferrableUpdate tasks
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$updatesByType = [ 'data' => [], 'generic' => [] ];
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foreach ( $updates as $du ) {
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if ( $du instanceof DataUpdate ) {
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$du->setTransactionTicket( $ticket );
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$updatesByType['data'][] = $du;
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} else {
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$updatesByType['generic'][] = $du;
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}
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$name = ( $du instanceof DeferrableCallback )
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? get_class( $du ) . '-' . $du->getOrigin()
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: get_class( $du );
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$stats->increment( 'deferred_updates.' . $method . '.' . $name );
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}
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// Execute all remaining tasks...
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foreach ( $updatesByType as $updatesForType ) {
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foreach ( $updatesForType as $update ) {
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self::$executeContext = [ 'stage' => $stage, 'subqueue' => [] ];
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try {
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/** @var DeferrableUpdate $update */
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$guiError = self::runUpdate( $update, $lbFactory, $mode, $stage );
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$reportableError = $reportableError ?: $guiError;
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// Do the subqueue updates for $update until there are none
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while ( self::$executeContext['subqueue'] ) {
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$subUpdate = reset( self::$executeContext['subqueue'] );
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$firstKey = key( self::$executeContext['subqueue'] );
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unset( self::$executeContext['subqueue'][$firstKey] );
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if ( $subUpdate instanceof DataUpdate ) {
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$subUpdate->setTransactionTicket( $ticket );
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}
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$guiError = self::runUpdate( $subUpdate, $lbFactory, $mode, $stage );
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$reportableError = $reportableError ?: $guiError;
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}
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} finally {
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// Make sure we always clean up the context.
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// Losing updates while rewinding the stack is acceptable,
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// losing updates that are added later is not.
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self::$executeContext = null;
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}
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}
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}
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$updates = $queue; // new snapshot of queue (check for new entries)
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}
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if ( $reportableError ) {
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throw $reportableError; // throw the first of any GUI errors
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}
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}
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/**
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* @param DeferrableUpdate $update
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* @param LBFactory $lbFactory
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* @param string $mode
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* @param int $stage
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* @return ErrorPageError|null
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*/
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private static function runUpdate(
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DeferrableUpdate $update, LBFactory $lbFactory, $mode, $stage
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) {
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$guiError = null;
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try {
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if ( $mode === 'enqueue' && $update instanceof EnqueueableDataUpdate ) {
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// Run only the job enqueue logic to complete the update later
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$spec = $update->getAsJobSpecification();
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JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
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} elseif ( $update instanceof TransactionRoundDefiningUpdate ) {
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$update->doUpdate();
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} else {
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// Run the bulk of the update now
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$fnameTrxOwner = get_class( $update ) . '::doUpdate';
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$lbFactory->beginMasterChanges( $fnameTrxOwner );
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$update->doUpdate();
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$lbFactory->commitMasterChanges( $fnameTrxOwner );
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}
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} catch ( Exception $e ) {
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// Reporting GUI exceptions does not work post-send
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if ( $e instanceof ErrorPageError && $stage === self::PRESEND ) {
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$guiError = $e;
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}
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MWExceptionHandler::rollbackMasterChangesAndLog( $e );
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// VW-style hack to work around T190178, so we can make sure
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// PageMetaDataUpdater doesn't throw exceptions.
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if ( defined( 'MW_PHPUNIT_TEST' ) ) {
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throw $e;
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}
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}
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return $guiError;
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}
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/**
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* Run all deferred updates immediately if there are no DB writes active
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*
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* If there are many deferred updates pending, $mode is 'run', and there
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* are still busy LBFactory database handles, then any EnqueueableDataUpdate
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* tasks might be enqueued as jobs to be executed later.
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*
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* @param string $mode Use "enqueue" to use the job queue when possible
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* @return bool Whether updates were allowed to run
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* @since 1.28
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*/
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public static function tryOpportunisticExecute( $mode = 'run' ) {
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// execute() loop is already running
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if ( self::$executeContext ) {
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return false;
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}
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// Avoiding running updates without them having outer scope
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if ( !self::areDatabaseTransactionsActive() ) {
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self::doUpdates( $mode );
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return true;
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}
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if ( self::pendingUpdatesCount() >= self::BIG_QUEUE_SIZE ) {
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// If we cannot run the updates with outer transaction context, try to
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// at least enqueue all the updates that support queueing to job queue
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self::$preSendUpdates = self::enqueueUpdates( self::$preSendUpdates );
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self::$postSendUpdates = self::enqueueUpdates( self::$postSendUpdates );
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}
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return !self::pendingUpdatesCount();
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}
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/**
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* Enqueue a job for each EnqueueableDataUpdate item and return the other items
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*
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* @param DeferrableUpdate[] $updates A list of deferred update instances
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* @return DeferrableUpdate[] Remaining updates that do not support being queued
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*/
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private static function enqueueUpdates( array $updates ) {
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$remaining = [];
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foreach ( $updates as $update ) {
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if ( $update instanceof EnqueueableDataUpdate ) {
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$spec = $update->getAsJobSpecification();
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JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
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} else {
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$remaining[] = $update;
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}
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}
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return $remaining;
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}
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/**
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* @return int Number of enqueued updates
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* @since 1.28
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*/
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public static function pendingUpdatesCount() {
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return count( self::$preSendUpdates ) + count( self::$postSendUpdates );
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}
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/**
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* @param int $stage DeferredUpdates constant (PRESEND, POSTSEND, or ALL)
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* @return DeferrableUpdate[]
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* @since 1.29
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*/
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public static function getPendingUpdates( $stage = self::ALL ) {
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$updates = [];
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if ( $stage === self::ALL || $stage === self::PRESEND ) {
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$updates = array_merge( $updates, self::$preSendUpdates );
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}
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if ( $stage === self::ALL || $stage === self::POSTSEND ) {
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$updates = array_merge( $updates, self::$postSendUpdates );
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}
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return $updates;
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}
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/**
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* Clear all pending updates without performing them. Generally, you don't
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* want or need to call this. Unit tests need it though.
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*/
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public static function clearPendingUpdates() {
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self::$preSendUpdates = [];
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self::$postSendUpdates = [];
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}
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/**
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* @return bool If a transaction round is active or connection is not ready for commit()
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*/
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private static function areDatabaseTransactionsActive() {
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$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
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if ( $lbFactory->hasTransactionRound() || !$lbFactory->isReadyForRoundOperations() ) {
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return true;
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}
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$connsBusy = false;
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$lbFactory->forEachLB( function ( LoadBalancer $lb ) use ( &$connsBusy ) {
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$lb->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$connsBusy ) {
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if ( $conn->writesOrCallbacksPending() || $conn->explicitTrxActive() ) {
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$connsBusy = true;
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}
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} );
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} );
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return $connsBusy;
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}
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}
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