551 lines
21 KiB
PHP
551 lines
21 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 Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
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use MediaWiki\Logger\LoggerFactory;
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use MediaWiki\MediaWikiServices;
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use Psr\Log\LoggerInterface;
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use Wikimedia\Rdbms\DBTransactionError;
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use Wikimedia\Rdbms\IDatabase;
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use Wikimedia\Rdbms\ILBFactory;
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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 deferral of updates within the scope of a PHP script invocation
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*
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* In web request mode, deferred updates run at the end of request execution, after the main
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* database transaction round ends, and either before (PRESEND) or after (POSTSEND) the HTTP
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* response has been sent. If an update runs after the HTTP response is sent, it will not block
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* clients. Otherwise, the client will not see the response until the update finishes. Use the
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* PRESEND and POSTSEND class constants to specify when an update should run. POSTSEND is the
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* default for DeferredUpdates::addUpdate() and DeferredUpdates::addCallableUpdate(). An update
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* that might need to alter the HTTP response output must use PRESEND. The control flow with
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* regard to deferred updates during a typical state changing web request is as follows:
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* - 1) Main transaction round starts
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* - 2) Various writes to RBMS/file/blob stores and deferred updates enqueued
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* - 3) Main transaction round ends
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* - 4) PRESEND pending update queue is B1...BN
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* - 5) B1 runs, resulting PRESEND updates iteratively run in FIFO order; likewise for B2..BN
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* - 6) The web response is sent out to the client
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* - 7) POSTSEND pending update queue is A1...AM
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* - 8) A1 runs, resulting updates iteratively run in FIFO order; likewise for A2..AM
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*
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* @see MediaWiki::restInPeace()
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*
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* In CLI mode, no distinction is made between PRESEND and POSTSEND deferred updates and all of
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* them will run during the following occasions:
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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) Upon the completion of Maintenance::execute() via Maintenance::shutdown()
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*
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* @see MWLBFactory::applyGlobalState()
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*
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* If DeferredUpdates::doUpdates() is currently running a deferred update, then the public
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* DeferredUpdates interface operates on the PRESEND/POSTSEND "sub"-queues that correspond to
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* the innermost in-progress deferred update. Otherwise, the public interface operates on the
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* PRESEND/POSTSEND "top"-queues. Affected methods include:
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* - DeferredUpdates::addUpdate()
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* - DeferredUpdates::addCallableUpdate()
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* - DeferredUpdates::doUpdates()
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* - DeferredUpdates::tryOpportunisticExecute()
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* - DeferredUpdates::pendingUpdatesCount()
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* - DeferredUpdates::getPendingUpdates()
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* - DeferredUpdates::clearPendingUpdates()
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*
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* Updates that work through this system will be more likely to complete by the time the
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* client makes their next request after this request than with the JobQueue system.
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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 DeferredUpdatesScopeStack|null Queue states based on recursion level */
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private static $scopeStack;
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/** @var int Process all updates; in web requests, use only after flushing output buffer */
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public const ALL = 0;
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/** @var int Specify/process updates that should run before flushing output buffer */
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public const PRESEND = 1;
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/** @var int Specify/process updates that should run after flushing output buffer */
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public const POSTSEND = 2;
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/** @var int[] List of "defer until" queue stages that can be reached */
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public const STAGES = [ self::PRESEND, self::POSTSEND ];
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/** @var int Queue size threshold for converting updates into jobs */
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private const BIG_QUEUE_SIZE = 100;
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/**
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* Add an update to the pending update queue for execution at the appropriate time
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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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* If an update is already in progress, then what happens to this update is as follows:
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* - If it has a "defer until" stage at/before the actual run stage of the innermost
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* in-progress update, then it will go into the sub-queue of that in-progress update.
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* As soon as that update completes, MergeableUpdate instances in its sub-queue will be
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* merged into the top-queues and the non-MergeableUpdate instances will be executed.
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* This is done to better isolate updates from the failures of other updates and reduce
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* the chance of race conditions caused by updates not fully seeing the intended changes
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* of previously enqueued and executed updates.
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* - If it has a "defer until" stage later than the actual run stage of the innermost
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* in-progress update, then it will go into the normal top-queue for that stage.
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*
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* @param DeferrableUpdate $update Some object that implements doUpdate()
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* @param int $stage One of (DeferredUpdates::PRESEND, DeferredUpdates::POSTSEND)
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* @since 1.28 Added the $stage parameter
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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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self::getScopeStack()->current()->addUpdate( $update, $stage );
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// If CLI mode is active and no RDBMs transaction round is in the way, then run all
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// the pending updates now. This is needed for scripts that never, or rarely, use the
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// RDBMs layer, but that do modify systems via deferred updates. This logic avoids
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// excessive pending update queue sizes when long-running scripts never trigger the
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// basic RDBMs hooks for running pending updates.
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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 an update to the pending update queue that invokes the specified callback when run
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*
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* @see DeferredUpdates::addUpdate()
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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 One of (DeferredUpdates::PRESEND, DeferredUpdates::POSTSEND)
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* @param IDatabase|IDatabase[]|null $dbw Abort if this DB is rolled back [optional]
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* @since 1.27 Added $stage parameter
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* @since 1.28 Added the $dbw parameter
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*/
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public static function addCallableUpdate( $callable, $stage = self::POSTSEND, $dbw = null ) {
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self::addUpdate( new MWCallableUpdate( $callable, wfGetCaller(), $dbw ), $stage );
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}
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/**
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* Consume and execute all pending updates
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*
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* Note that it is rarely the case that this method should be called outside of a few
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* select entry points. For simplicity, that kind of recursion is discouraged. Recursion
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* cannot happen if an explicit transaction round is active, which limits usage to updates
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* with TRX_ROUND_ABSENT that do not leave open an transactions round of their own during
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* the call to this method.
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*
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* In the less-common case of this being called within an in-progress DeferrableUpdate,
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* this will not see any top-queue updates (since they were consumed and are being run
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* inside an outer execution loop). In that case, it will instead operate on the sub-queue
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* of the innermost in-progress update on the stack.
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*
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* The $mode parameter determines how the updates are processed. Use "run" to process the
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* updates by running them. Otherwise, use "enqueue" to process the updates by converting
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* the EnqueueableDataUpdate instances to jobs and running the others.
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*
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* @param string $mode Either "run" or "enqueue" [default: "run"]
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* @param int $stage Which updates to process. One of
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* (DeferredUpdates::PRESEND, DeferredUpdates::POSTSEND, DeferredUpdates::ALL)
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* @internal For use by MediaWiki, Maintenance, JobRunner, JobExecutor
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* @since 1.27 Added $stage parameter
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*/
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public static function doUpdates( $mode = 'run', $stage = self::ALL ) {
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$services = MediaWikiServices::getInstance();
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$stats = $services->getStatsdDataFactory();
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$lbf = $services->getDBLoadBalancerFactory();
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$logger = LoggerFactory::getInstance( 'DeferredUpdates' );
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$httpMethod = $services->getMainConfig()->get( 'CommandLineMode' )
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? 'cli'
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: strtolower( RequestContext::getMain()->getRequest()->getMethod() );
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/** @var ErrorPageError $guiError First presentable client-level error thrown */
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$guiError = null;
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/** @var Throwable $exception First of any error thrown */
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$exception = null;
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$scope = self::getScopeStack()->current();
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// T249069: recursion is not possible once explicit transaction rounds are involved
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$activeUpdate = $scope->getActiveUpdate();
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if ( $activeUpdate ) {
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$class = get_class( $activeUpdate );
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if ( !( $activeUpdate instanceof TransactionRoundAwareUpdate ) ) {
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throw new LogicException(
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__METHOD__ . ": reached from $class, which is not TransactionRoundAwareUpdate"
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);
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}
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if ( $activeUpdate->getTransactionRoundRequirement() !== $activeUpdate::TRX_ROUND_ABSENT ) {
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throw new LogicException(
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__METHOD__ . ": reached from $class, which does not specify TRX_ROUND_ABSENT"
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);
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}
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}
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$scope->processUpdates(
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$stage,
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function ( DeferrableUpdate $update, $activeStage )
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use ( $mode, $lbf, $logger, $stats, $httpMethod, &$guiError, &$exception )
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{
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// If applicable, just enqueue the update as a job in the job queue system
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if ( $mode === 'enqueue' && $update instanceof EnqueueableDataUpdate ) {
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self::jobify( $update, $lbf, $logger, $stats, $httpMethod );
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return;
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}
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// Otherwise, run the update....
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$scopeStack = self::getScopeStack();
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$childScope = $scopeStack->descend( $activeStage, $update );
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try {
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$e = self::run( $update, $lbf, $logger, $stats, $httpMethod );
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$guiError = $guiError ?: ( $e instanceof ErrorPageError ? $e : null );
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$exception = $exception ?: $e;
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// Any addUpdate() calls between descend() and ascend() used the sub-queue.
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// In rare cases, DeferrableUpdate::doUpdates() will process them by calling
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// doUpdates() itself. In any case, process remaining updates in the subqueue.
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// them, enqueueing them, or transferring them to the parent scope
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// queues as appropriate...
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$childScope->processUpdates(
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$activeStage,
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function ( DeferrableUpdate $subUpdate )
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use ( $lbf, $logger, $stats, $httpMethod, &$guiError, &$exception )
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{
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$e = self::run( $subUpdate, $lbf, $logger, $stats, $httpMethod );
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$guiError = $guiError ?: ( $e instanceof ErrorPageError ? $e : null );
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$exception = $exception ?: $e;
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}
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);
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} finally {
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$scopeStack->ascend();
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}
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}
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);
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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 ( $exception && defined( 'MW_PHPUNIT_TEST' ) ) {
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throw $exception;
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}
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// Throw the first of any GUI errors as long as the context is HTTP pre-send. However,
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// callers should check permissions *before* enqueueing updates. If the main transaction
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// round actions succeed but some deferred updates fail due to permissions errors then
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// there is a risk that some secondary data was not properly updated.
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if ( $guiError && $stage === self::PRESEND && !headers_sent() ) {
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throw $guiError;
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}
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}
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/**
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* Consume and execute all pending updates unless an update is already
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* in progress or the LBFactory service instance has "busy" DB handles
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*
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* A DB handle is considered "busy" if it has an unfinished transaction that cannot safely
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* be flushed or the parent LBFactory instance has an unfinished transaction round that
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* cannot safely be flushed. If the number of pending updates reaches BIG_QUEUE_SIZE and
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* there are still busy DB handles, then EnqueueableDataUpdate updates might be enqueued
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* as jobs. This avoids excessive memory use and risk of losing updates due to failures.
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*
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* The $mode parameter determines how the updates are processed. Use "run" to process the
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* updates by running them. Otherwise, use "enqueue" to process the updates by converting
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* the EnqueueableDataUpdate instances to jobs and running the others.
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*
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* Note that this method operates on updates from all stages and thus should not be called
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* during web requests. It is only intended for long-running Maintenance scripts.
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*
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* @param string $mode Either "run" or "enqueue" [default: "run"]
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* @return bool Whether updates were allowed to run
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* @internal For use by Maintenance
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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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// Leave execution up to the current loop if an update is already in progress
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if ( self::getRecursiveExecutionStackDepth() ) {
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return false;
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}
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// Run the updates for this context if they will have outer transaction scope
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if ( !self::areDatabaseTransactionsActive() ) {
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self::doUpdates( $mode, self::ALL );
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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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// There are a large number of pending updates and none of them can run yet.
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// The odds of losing updates due to an error increase when executing long queues
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// and when large amounts of time pass while tasks are queued. Mitigate this by
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// trying to migrate updates to the job queue system (where applicable).
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self::getScopeStack()->current()->consumeMatchingUpdates(
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self::ALL,
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EnqueueableDataUpdate::class,
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static function ( EnqueueableDataUpdate $update ) {
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$spec = $update->getAsJobSpecification();
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JobQueueGroup::singleton( $spec['domain'] )->push( $spec['job'] );
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}
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);
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}
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return false;
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}
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/**
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* Get the number of pending updates for the current execution context
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*
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* If an update is in progress, then this operates on the sub-queues of the
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* innermost in-progress update. Otherwise, it acts on the top-queues.
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*
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* @return int
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* @since 1.28
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*/
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public static function pendingUpdatesCount() {
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return self::getScopeStack()->current()->pendingUpdatesCount();
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}
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/**
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* Get a list of the pending updates for the current execution context
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*
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* If an update is in progress, then this operates on the sub-queues of the
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* innermost in-progress update. Otherwise, it acts on the top-queues.
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*
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* @param int $stage Look for updates with this "defer until" stage. One of
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* (DeferredUpdates::PRESEND, DeferredUpdates::POSTSEND, DeferredUpdates::ALL)
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* @return DeferrableUpdate[]
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* @internal This method should only be used for unit tests
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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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return self::getScopeStack()->current()->getPendingUpdates( $stage );
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}
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/**
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* Cancel all pending updates for the current execution context
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*
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* If an update is in progress, then this operates on the sub-queues of the
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* innermost in-progress update. Otherwise, it acts on the top-queues.
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*
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* @internal This method should only be used for unit tests
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*/
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public static function clearPendingUpdates() {
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self::getScopeStack()->current()->clearPendingUpdates();
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}
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/**
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* Get the number of in-progress calls to DeferredUpdates::doUpdates()
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*
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* @return int
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* @internal This method should only be used for unit tests
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*/
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public static function getRecursiveExecutionStackDepth() {
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return self::getScopeStack()->getRecursiveDepth();
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}
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/**
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* Run an update, and, if an error was thrown, catch/log it and enqueue the update as
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* a job in the job queue system if possible (e.g. implements EnqueueableDataUpdate)
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*
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* @param DeferrableUpdate $update
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* @param ILBFactory $lbFactory
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* @param LoggerInterface $logger
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* @param StatsdDataFactoryInterface $stats
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* @param string $httpMethod
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* @return Throwable|null
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*/
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private static function run(
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DeferrableUpdate $update,
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ILBFactory $lbFactory,
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LoggerInterface $logger,
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StatsdDataFactoryInterface $stats,
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$httpMethod
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): ?Throwable {
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$suffix = ( $update instanceof DeferrableCallback ) ? "_{$update->getOrigin()}" : '';
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$type = get_class( $update ) . $suffix;
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$stats->increment( "deferred_updates.$httpMethod.$type" );
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$updateId = spl_object_id( $update );
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$logger->debug( __METHOD__ . ": started $type #$updateId" );
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$startTime = microtime( true );
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$e = null;
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try {
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self::attemptUpdate( $update, $lbFactory );
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return null;
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} catch ( Throwable $e ) {
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} finally {
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$executionTime = microtime( true ) - $startTime;
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$logger->debug( __METHOD__ . ": ended $type #$updateId, processing time: $executionTime" );
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}
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MWExceptionHandler::logException( $e );
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$logger->error(
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"Deferred update '{deferred_type}' failed to run.",
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[
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'deferred_type' => $type,
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'exception' => $e,
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]
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);
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$lbFactory->rollbackPrimaryChanges( __METHOD__ );
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// Try to push the update as a job so it can run later if possible
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if ( $update instanceof EnqueueableDataUpdate ) {
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$jobEx = null;
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try {
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$spec = $update->getAsJobSpecification();
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JobQueueGroup::singleton( $spec['domain'] )->push( $spec['job'] );
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return $e;
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} catch ( Throwable $jobEx ) {
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}
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MWExceptionHandler::logException( $jobEx );
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$logger->error(
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"Deferred update '{deferred_type}' failed to enqueue as a job.",
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[
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'deferred_type' => $type,
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'exception' => $jobEx,
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]
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);
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$lbFactory->rollbackPrimaryChanges( __METHOD__ );
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}
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return $e;
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}
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/**
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* Enqueue an update as a job in the job queue system and catch/log any exceptions
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*
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* @param EnqueueableDataUpdate $update
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* @param LBFactory $lbFactory
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* @param LoggerInterface $logger
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* @param StatsdDataFactoryInterface $stats
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* @param string $httpMethod
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*/
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private static function jobify(
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EnqueueableDataUpdate $update,
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LBFactory $lbFactory,
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LoggerInterface $logger,
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StatsdDataFactoryInterface $stats,
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$httpMethod
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) {
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$type = get_class( $update );
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$stats->increment( "deferred_updates.$httpMethod.$type" );
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$jobEx = null;
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try {
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$spec = $update->getAsJobSpecification();
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JobQueueGroup::singleton( $spec['domain'] )->push( $spec['job'] );
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return;
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} catch ( Throwable $jobEx ) {
|
|
}
|
|
|
|
MWExceptionHandler::logException( $jobEx );
|
|
$logger->error(
|
|
"Deferred update '$type' failed to enqueue as a job.",
|
|
[
|
|
'deferred_type' => $type,
|
|
'exception' => $jobEx,
|
|
]
|
|
);
|
|
|
|
$lbFactory->rollbackPrimaryChanges( __METHOD__ );
|
|
}
|
|
|
|
/**
|
|
* Attempt to run an update with the appropriate transaction round state it expects
|
|
*
|
|
* DeferredUpdate classes that wrap the execution of bundles of other DeferredUpdate
|
|
* instances can use this method to run the updates. Any such wrapper class should
|
|
* always use TRX_ROUND_ABSENT itself.
|
|
*
|
|
* @param DeferrableUpdate $update
|
|
* @param ILBFactory $lbFactory
|
|
* @since 1.34
|
|
*/
|
|
public static function attemptUpdate( DeferrableUpdate $update, ILBFactory $lbFactory ) {
|
|
$ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
|
|
if ( !$ticket || $lbFactory->hasTransactionRound() ) {
|
|
throw new DBTransactionError( null, "A database transaction round is pending." );
|
|
}
|
|
|
|
if ( $update instanceof DataUpdate ) {
|
|
$update->setTransactionTicket( $ticket );
|
|
}
|
|
|
|
// Designate $update::doUpdate() as the write round owner
|
|
$fnameTrxOwner = ( $update instanceof DeferrableCallback )
|
|
? $update->getOrigin()
|
|
: get_class( $update ) . '::doUpdate';
|
|
// Determine whether the write round will be explicit or implicit
|
|
$useExplicitTrxRound = !(
|
|
$update instanceof TransactionRoundAwareUpdate &&
|
|
$update->getTransactionRoundRequirement() == $update::TRX_ROUND_ABSENT
|
|
);
|
|
|
|
// Flush any pending changes left over from an implicit transaction round
|
|
if ( $useExplicitTrxRound ) {
|
|
$lbFactory->beginPrimaryChanges( $fnameTrxOwner ); // new explicit round
|
|
} else {
|
|
$lbFactory->commitPrimaryChanges( $fnameTrxOwner ); // new implicit round
|
|
}
|
|
// Run the update after any stale primary DB view snapshots have been flushed
|
|
$update->doUpdate();
|
|
// Commit any pending changes from the explicit or implicit transaction round
|
|
$lbFactory->commitPrimaryChanges( $fnameTrxOwner );
|
|
}
|
|
|
|
/**
|
|
* @return bool If a transaction round is active or connection is not ready for commit()
|
|
*/
|
|
private static function areDatabaseTransactionsActive() {
|
|
$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
|
|
if ( $lbFactory->hasTransactionRound() || !$lbFactory->isReadyForRoundOperations() ) {
|
|
return true;
|
|
}
|
|
|
|
$connsBusy = false;
|
|
$lbFactory->forEachLB( static function ( LoadBalancer $lb ) use ( &$connsBusy ) {
|
|
$lb->forEachOpenPrimaryConnection( static function ( IDatabase $conn ) use ( &$connsBusy ) {
|
|
if ( $conn->writesOrCallbacksPending() || $conn->explicitTrxActive() ) {
|
|
$connsBusy = true;
|
|
}
|
|
} );
|
|
} );
|
|
|
|
return $connsBusy;
|
|
}
|
|
|
|
/**
|
|
* @return DeferredUpdatesScopeStack
|
|
*/
|
|
private static function getScopeStack() {
|
|
if ( self::$scopeStack === null ) {
|
|
self::$scopeStack = new DeferredUpdatesScopeStack();
|
|
}
|
|
|
|
return self::$scopeStack;
|
|
}
|
|
}
|