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diff --git a/www/wiki/includes/deferred/DeferredUpdates.php b/www/wiki/includes/deferred/DeferredUpdates.php
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+<?php
+/**
+ * Interface and manager for deferred updates.
+ *
+ * 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 Wikimedia\Rdbms\IDatabase;
+use MediaWiki\MediaWikiServices;
+use Wikimedia\Rdbms\LBFactory;
+use Wikimedia\Rdbms\LoadBalancer;
+
+/**
+ * Class for managing the deferred updates
+ *
+ * In web request mode, deferred updates can be run at the end of the request, either before or
+ * after the HTTP response has been sent. In either case, they run after the DB commit step. If
+ * an update runs after the response is sent, it will not block clients. If sent before, it will
+ * run synchronously. These two modes are defined via PRESEND and POSTSEND constants, the latter
+ * being the default for addUpdate() and addCallableUpdate().
+ *
+ * Updates that work through this system will be more likely to complete by the time the client
+ * makes their next request after this one than with the JobQueue system.
+ *
+ * In CLI mode, updates run immediately if no DB writes are pending. Otherwise, they run when:
+ *   - a) Any waitForReplication() call if no writes are pending on any DB
+ *   - b) A commit happens on Maintenance::getDB( DB_MASTER ) if no writes are pending on any DB
+ *   - c) EnqueueableDataUpdate tasks may enqueue on commit of Maintenance::getDB( DB_MASTER )
+ *   - d) At the completion of Maintenance::execute()
+ *
+ * When updates are deferred, they go into one two FIFO "top-queues" (one for pre-send and one
+ * for post-send). Updates enqueued *during* doUpdate() of a "top" update go into the "sub-queue"
+ * for that update. After that method finishes, the sub-queue is run until drained. This continues
+ * for each top-queue job until the entire top queue is drained. This happens for the pre-send
+ * top-queue, and later on, the post-send top-queue, in execute().
+ *
+ * @since 1.19
+ */
+class DeferredUpdates {
+	/** @var DeferrableUpdate[] Updates to be deferred until before request end */
+	private static $preSendUpdates = [];
+	/** @var DeferrableUpdate[] Updates to be deferred until after request end */
+	private static $postSendUpdates = [];
+
+	const ALL = 0; // all updates; in web requests, use only after flushing the output buffer
+	const PRESEND = 1; // for updates that should run before flushing output buffer
+	const POSTSEND = 2; // for updates that should run after flushing output buffer
+
+	const BIG_QUEUE_SIZE = 100;
+
+	/** @var array|null Information about the current execute() call or null if not running */
+	private static $executeContext;
+
+	/**
+	 * Add an update to the deferred list to be run later by execute()
+	 *
+	 * In CLI mode, callback magic will also be used to run updates when safe
+	 *
+	 * @param DeferrableUpdate $update Some object that implements doUpdate()
+	 * @param int $stage DeferredUpdates constant (PRESEND or POSTSEND) (since 1.27)
+	 */
+	public static function addUpdate( DeferrableUpdate $update, $stage = self::POSTSEND ) {
+		global $wgCommandLineMode;
+
+		if ( self::$executeContext && self::$executeContext['stage'] >= $stage ) {
+			// This is a sub-DeferredUpdate; run it right after its parent update.
+			// Also, while post-send updates are running, push any "pre-send" jobs to the
+			// active post-send queue to make sure they get run this round (or at all).
+			self::$executeContext['subqueue'][] = $update;
+
+			return;
+		}
+
+		if ( $stage === self::PRESEND ) {
+			self::push( self::$preSendUpdates, $update );
+		} else {
+			self::push( self::$postSendUpdates, $update );
+		}
+
+		// Try to run the updates now if in CLI mode and no transaction is active.
+		// This covers scripts that don't/barely use the DB but make updates to other stores.
+		if ( $wgCommandLineMode ) {
+			self::tryOpportunisticExecute( 'run' );
+		}
+	}
+
+	/**
+	 * Add a callable update. In a lot of cases, we just need a callback/closure,
+	 * defining a new DeferrableUpdate object is not necessary
+	 *
+	 * @see MWCallableUpdate::__construct()
+	 *
+	 * @param callable $callable
+	 * @param int $stage DeferredUpdates constant (PRESEND or POSTSEND) (since 1.27)
+	 * @param IDatabase|IDatabase[]|null $dbw Abort if this DB is rolled back [optional] (since 1.28)
+	 */
+	public static function addCallableUpdate(
+		$callable, $stage = self::POSTSEND, $dbw = null
+	) {
+		self::addUpdate( new MWCallableUpdate( $callable, wfGetCaller(), $dbw ), $stage );
+	}
+
+	/**
+	 * Do any deferred updates and clear the list
+	 *
+	 * @param string $mode Use "enqueue" to use the job queue when possible [Default: "run"]
+	 * @param int $stage DeferredUpdates constant (PRESEND, POSTSEND, or ALL) (since 1.27)
+	 */
+	public static function doUpdates( $mode = 'run', $stage = self::ALL ) {
+		$stageEffective = ( $stage === self::ALL ) ? self::POSTSEND : $stage;
+
+		if ( $stage === self::ALL || $stage === self::PRESEND ) {
+			self::execute( self::$preSendUpdates, $mode, $stageEffective );
+		}
+
+		if ( $stage === self::ALL || $stage == self::POSTSEND ) {
+			self::execute( self::$postSendUpdates, $mode, $stageEffective );
+		}
+	}
+
+	/**
+	 * @param bool $value Whether to just immediately run updates in addUpdate()
+	 * @since 1.28
+	 * @deprecated 1.29 Causes issues in Web-executed jobs - see T165714 and T100085.
+	 */
+	public static function setImmediateMode( $value ) {
+		wfDeprecated( __METHOD__, '1.29' );
+	}
+
+	/**
+	 * @param DeferrableUpdate[] $queue
+	 * @param DeferrableUpdate $update
+	 */
+	private static function push( array &$queue, DeferrableUpdate $update ) {
+		if ( $update instanceof MergeableUpdate ) {
+			$class = get_class( $update ); // fully-qualified class
+			if ( isset( $queue[$class] ) ) {
+				/** @var MergeableUpdate $existingUpdate */
+				$existingUpdate = $queue[$class];
+				$existingUpdate->merge( $update );
+			} else {
+				$queue[$class] = $update;
+			}
+		} else {
+			$queue[] = $update;
+		}
+	}
+
+	/**
+	 * Immediately run/queue a list of updates
+	 *
+	 * @param DeferrableUpdate[] &$queue List of DeferrableUpdate objects
+	 * @param string $mode Use "enqueue" to use the job queue when possible
+	 * @param int $stage Class constant (PRESEND, POSTSEND) (since 1.28)
+	 * @throws ErrorPageError Happens on top-level calls
+	 * @throws Exception Happens on second-level calls
+	 */
+	protected static function execute( array &$queue, $mode, $stage ) {
+		$services = MediaWikiServices::getInstance();
+		$stats = $services->getStatsdDataFactory();
+		$lbFactory = $services->getDBLoadBalancerFactory();
+		$method = RequestContext::getMain()->getRequest()->getMethod();
+
+		$ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
+
+		/** @var ErrorPageError $reportableError */
+		$reportableError = null;
+		/** @var DeferrableUpdate[] $updates Snapshot of queue */
+		$updates = $queue;
+
+		// Keep doing rounds of updates until none get enqueued...
+		while ( $updates ) {
+			$queue = []; // clear the queue
+
+			// Order will be DataUpdate followed by generic DeferrableUpdate tasks
+			$updatesByType = [ 'data' => [], 'generic' => [] ];
+			foreach ( $updates as $du ) {
+				if ( $du instanceof DataUpdate ) {
+					$du->setTransactionTicket( $ticket );
+					$updatesByType['data'][] = $du;
+				} else {
+					$updatesByType['generic'][] = $du;
+				}
+
+				$name = ( $du instanceof DeferrableCallback )
+					? get_class( $du ) . '-' . $du->getOrigin()
+					: get_class( $du );
+				$stats->increment( 'deferred_updates.' . $method . '.' . $name );
+			}
+
+			// Execute all remaining tasks...
+			foreach ( $updatesByType as $updatesForType ) {
+				foreach ( $updatesForType as $update ) {
+					self::$executeContext = [ 'stage' => $stage, 'subqueue' => [] ];
+					/** @var DeferrableUpdate $update */
+					$guiError = self::runUpdate( $update, $lbFactory, $mode, $stage );
+					$reportableError = $reportableError ?: $guiError;
+					// Do the subqueue updates for $update until there are none
+					while ( self::$executeContext['subqueue'] ) {
+						$subUpdate = reset( self::$executeContext['subqueue'] );
+						$firstKey = key( self::$executeContext['subqueue'] );
+						unset( self::$executeContext['subqueue'][$firstKey] );
+
+						if ( $subUpdate instanceof DataUpdate ) {
+							$subUpdate->setTransactionTicket( $ticket );
+						}
+
+						$guiError = self::runUpdate( $subUpdate, $lbFactory, $mode, $stage );
+						$reportableError = $reportableError ?: $guiError;
+					}
+					self::$executeContext = null;
+				}
+			}
+
+			$updates = $queue; // new snapshot of queue (check for new entries)
+		}
+
+		if ( $reportableError ) {
+			throw $reportableError; // throw the first of any GUI errors
+		}
+	}
+
+	/**
+	 * @param DeferrableUpdate $update
+	 * @param LBFactory $lbFactory
+	 * @param string $mode
+	 * @param int $stage
+	 * @return ErrorPageError|null
+	 */
+	private static function runUpdate(
+		DeferrableUpdate $update, LBFactory $lbFactory, $mode, $stage
+	) {
+		$guiError = null;
+		try {
+			if ( $mode === 'enqueue' && $update instanceof EnqueueableDataUpdate ) {
+				// Run only the job enqueue logic to complete the update later
+				$spec = $update->getAsJobSpecification();
+				JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
+			} elseif ( $update instanceof TransactionRoundDefiningUpdate ) {
+				$update->doUpdate();
+			} else {
+				// Run the bulk of the update now
+				$fnameTrxOwner = get_class( $update ) . '::doUpdate';
+				$lbFactory->beginMasterChanges( $fnameTrxOwner );
+				$update->doUpdate();
+				$lbFactory->commitMasterChanges( $fnameTrxOwner );
+			}
+		} catch ( Exception $e ) {
+			// Reporting GUI exceptions does not work post-send
+			if ( $e instanceof ErrorPageError && $stage === self::PRESEND ) {
+				$guiError = $e;
+			}
+			MWExceptionHandler::rollbackMasterChangesAndLog( $e );
+		}
+
+		return $guiError;
+	}
+
+	/**
+	 * Run all deferred updates immediately if there are no DB writes active
+	 *
+	 * If $mode is 'run' but there are busy databates, EnqueueableDataUpdate
+	 * tasks will be enqueued anyway for the sake of progress.
+	 *
+	 * @param string $mode Use "enqueue" to use the job queue when possible
+	 * @return bool Whether updates were allowed to run
+	 * @since 1.28
+	 */
+	public static function tryOpportunisticExecute( $mode = 'run' ) {
+		// execute() loop is already running
+		if ( self::$executeContext ) {
+			return false;
+		}
+
+		// Avoiding running updates without them having outer scope
+		if ( !self::areDatabaseTransactionsActive() ) {
+			self::doUpdates( $mode );
+			return true;
+		}
+
+		if ( self::pendingUpdatesCount() >= self::BIG_QUEUE_SIZE ) {
+			// If we cannot run the updates with outer transaction context, try to
+			// at least enqueue all the updates that support queueing to job queue
+			self::$preSendUpdates = self::enqueueUpdates( self::$preSendUpdates );
+			self::$postSendUpdates = self::enqueueUpdates( self::$postSendUpdates );
+		}
+
+		return !self::pendingUpdatesCount();
+	}
+
+	/**
+	 * Enqueue a job for each EnqueueableDataUpdate item and return the other items
+	 *
+	 * @param DeferrableUpdate[] $updates A list of deferred update instances
+	 * @return DeferrableUpdate[] Remaining updates that do not support being queued
+	 */
+	private static function enqueueUpdates( array $updates ) {
+		$remaining = [];
+
+		foreach ( $updates as $update ) {
+			if ( $update instanceof EnqueueableDataUpdate ) {
+				$spec = $update->getAsJobSpecification();
+				JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
+			} else {
+				$remaining[] = $update;
+			}
+		}
+
+		return $remaining;
+	}
+
+	/**
+	 * @return int Number of enqueued updates
+	 * @since 1.28
+	 */
+	public static function pendingUpdatesCount() {
+		return count( self::$preSendUpdates ) + count( self::$postSendUpdates );
+	}
+
+	/**
+	 * @param int $stage DeferredUpdates constant (PRESEND, POSTSEND, or ALL)
+	 * @return DeferrableUpdate[]
+	 * @since 1.29
+	 */
+	public static function getPendingUpdates( $stage = self::ALL ) {
+		$updates = [];
+		if ( $stage === self::ALL || $stage === self::PRESEND ) {
+			$updates = array_merge( $updates, self::$preSendUpdates );
+		}
+		if ( $stage === self::ALL || $stage === self::POSTSEND ) {
+			$updates = array_merge( $updates, self::$postSendUpdates );
+		}
+		return $updates;
+	}
+
+	/**
+	 * Clear all pending updates without performing them. Generally, you don't
+	 * want or need to call this. Unit tests need it though.
+	 */
+	public static function clearPendingUpdates() {
+		self::$preSendUpdates = [];
+		self::$postSendUpdates = [];
+	}
+
+	/**
+	 * @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() ) {
+			return true;
+		}
+
+		$connsBusy = false;
+		$lbFactory->forEachLB( function ( LoadBalancer $lb ) use ( &$connsBusy ) {
+			$lb->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$connsBusy ) {
+				if ( $conn->writesOrCallbacksPending() || $conn->explicitTrxActive() ) {
+					$connsBusy = true;
+				}
+			} );
+		} );
+
+		return $connsBusy;
+	}
+}