X-Git-Url: https://scripts.mit.edu/gitweb/autoinstallsdev/mediawiki.git/blobdiff_plain/19e297c21b10b1b8a3acad5e73fc71dcb35db44a..6932310fd58ebef145fa01eb76edf7150284d8ea:/includes/jobqueue/utils/BacklinkJobUtils.php

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+<?php
+/**
+ * Job to update links for a given title.
+ *
+ * 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
+ * @ingroup JobQueue
+ */
+
+/**
+ * Class with Backlink related Job helper methods
+ *
+ * When an asset changes, a base job can be inserted to update all assets that depend on it.
+ * The base job splits into per-title "leaf" jobs and a "remnant" job to handle the remaining
+ * range of backlinks. This recurs until the remnant job's backlink range is small enough that
+ * only leaf jobs are created from it.
+ *
+ * For example, if templates A and B are edited (at the same time) the queue will have:
+ *     (A base, B base)
+ * When these jobs run, the queue will have per-title and remnant partition jobs:
+ *     (titleX,titleY,titleZ,...,A remnant,titleM,titleN,titleO,...,B remnant)
+ *
+ * This works best when the queue is FIFO, for several reasons:
+ *   - a) Since the remnant jobs are enqueued after the leaf jobs, the slower leaf jobs have to
+ *        get popped prior to the fast remnant jobs. This avoids flooding the queue with leaf jobs
+ *        for every single backlink of widely used assets (which can be millions).
+ *   - b) Other jobs going in the queue still get a chance to run after a widely used asset changes.
+ *        This is due to the large remnant job pushing to the end of the queue with each division.
+ *
+ * The size of the queues used in this manner depend on the number of assets changes and the
+ * number of workers. Also, with FIFO-per-partition queues, the queue size can be somewhat larger,
+ * depending on the number of queue partitions.
+ *
+ * @ingroup JobQueue
+ * @since 1.23
+ */
+class BacklinkJobUtils {
+	/**
+	 * Break down $job into approximately ($bSize/$cSize) leaf jobs and a single partition
+	 * job that covers the remaining backlink range (if needed). Jobs for the first $bSize
+	 * titles are collated ($cSize per job) into leaf jobs to do actual work. All the
+	 * resulting jobs are of the same class as $job. No partition job is returned if the
+	 * range covered by $job was less than $bSize, as the leaf jobs have full coverage.
+	 *
+	 * The leaf jobs have the 'pages' param set to a (<page ID>:(<namespace>,<DB key>),...)
+	 * map so that the run() function knows what pages to act on. The leaf jobs will keep
+	 * the same job title as the parent job (e.g. $job).
+	 *
+	 * The partition jobs have the 'range' parameter set to a map of the format
+	 * (start:<integer>, end:<integer>, batchSize:<integer>, subranges:((<start>,<end>),...)),
+	 * the 'table' parameter set to that of $job, and the 'recursive' parameter set to true.
+	 * This method can be called on the resulting job to repeat the process again.
+	 *
+	 * The job provided ($job) must have the 'recursive' parameter set to true and the 'table'
+	 * parameter must be set to a backlink table. The job title will be used as the title to
+	 * find backlinks for. Any 'range' parameter must follow the same format as mentioned above.
+	 * This should be managed by recursive calls to this method.
+	 *
+	 * The first jobs return are always the leaf jobs. This lets the caller use push() to
+	 * put them directly into the queue and works well if the queue is FIFO. In such a queue,
+	 * the leaf jobs have to get finished first before anything can resolve the next partition
+	 * job, which keeps the queue very small.
+	 *
+	 * $opts includes:
+	 *   - params : extra job parameters to include in each job
+	 *
+	 * @param Job $job
+	 * @param int $bSize BacklinkCache partition size; usually $wgUpdateRowsPerJob
+	 * @param int $cSize Max titles per leaf job; Usually 1 or a modest value
+	 * @param array $opts Optional parameter map
+	 * @return Job[] List of Job objects
+	 */
+	public static function partitionBacklinkJob( Job $job, $bSize, $cSize, $opts = [] ) {
+		$class = get_class( $job );
+		$title = $job->getTitle();
+		$params = $job->getParams();
+
+		if ( isset( $params['pages'] ) || empty( $params['recursive'] ) ) {
+			$ranges = []; // sanity; this is a leaf node
+			$realBSize = 0;
+			wfWarn( __METHOD__ . " called on {$job->getType()} leaf job (explosive recursion)." );
+		} elseif ( isset( $params['range'] ) ) {
+			// This is a range job to trigger the insertion of partitioned/title jobs...
+			$ranges = $params['range']['subranges'];
+			$realBSize = $params['range']['batchSize'];
+		} else {
+			// This is a base job to trigger the insertion of partitioned jobs...
+			$ranges = $title->getBacklinkCache()->partition( $params['table'], $bSize );
+			$realBSize = $bSize;
+		}
+
+		$extraParams = isset( $opts['params'] ) ? $opts['params'] : [];
+
+		$jobs = [];
+		// Combine the first range (of size $bSize) backlinks into leaf jobs
+		if ( isset( $ranges[0] ) ) {
+			list( $start, $end ) = $ranges[0];
+			$iter = $title->getBacklinkCache()->getLinks( $params['table'], $start, $end );
+			$titles = iterator_to_array( $iter );
+			/** @var Title[] $titleBatch */
+			foreach ( array_chunk( $titles, $cSize ) as $titleBatch ) {
+				$pages = [];
+				foreach ( $titleBatch as $tl ) {
+					$pages[$tl->getArticleID()] = [ $tl->getNamespace(), $tl->getDBkey() ];
+				}
+				$jobs[] = new $class(
+					$title, // maintain parent job title
+					[ 'pages' => $pages ] + $extraParams
+				);
+			}
+		}
+		// Take all of the remaining ranges and build a partition job from it
+		if ( isset( $ranges[1] ) ) {
+			$jobs[] = new $class(
+				$title, // maintain parent job title
+				[
+					'recursive'     => true,
+					'table'         => $params['table'],
+					'range'         => [
+						'start'     => $ranges[1][0],
+						'end'       => $ranges[count( $ranges ) - 1][1],
+						'batchSize' => $realBSize,
+						'subranges' => array_slice( $ranges, 1 )
+					],
+					// Track how many times the base job divided for debugging
+					'division'      => isset( $params['division'] )
+						? ( $params['division'] + 1 )
+						: 1
+				] + $extraParams
+			);
+		}
+
+		return $jobs;
+	}
+}