Implement extension registration from an extension.json file

[mediawiki.git] / includes / jobqueue / jobs / RefreshLinksJob.php

<?php
/**
 * Job to update link tables for pages
 *
 * 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
 */

/**
 * Job to update link tables for pages
 *
 * This job comes in a few variants:
 *   - a) Recursive jobs to update links for backlink pages for a given title.
 *        These jobs have (recursive:true,table:<table>) set.
 *   - b) Jobs to update links for a set of pages (the job title is ignored).
 *            These jobs have (pages:(<page ID>:(<namespace>,<title>),...) set.
 *   - c) Jobs to update links for a single page (the job title)
 *        These jobs need no extra fields set.
 *
 * @ingroup JobQueue
 */
class RefreshLinksJob extends Job {
        const PARSE_THRESHOLD_SEC = 1.0;

        function __construct( $title, $params = '' ) {
                parent::__construct( 'refreshLinks', $title, $params );
                // Base backlink update jobs and per-title update jobs can be de-duplicated.
                // If template A changes twice before any jobs run, a clean queue will have:
                //              (A base, A base)
                // The second job is ignored by the queue on insertion.
                // Suppose, many pages use template A, and that template itself uses template B.
                // An edit to both will first create two base jobs. A clean FIFO 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)
                // Some these jobs will be the same, and will automatically be ignored by
                // the queue upon insertion. Some title jobs will run before the duplicate is
                // inserted, so the work will still be done twice in those cases. More titles
                // can be de-duplicated as the remnant jobs continue to be broken down. This
                // works best when $wgUpdateRowsPerJob, and either the pages have few backlinks
                // and/or the backlink sets for pages A and B are almost identical.
                $this->removeDuplicates = !isset( $params['range'] )
                        && ( !isset( $params['pages'] ) || count( $params['pages'] ) == 1 );
        }

        function run() {
                global $wgUpdateRowsPerJob;

                // Job to update all (or a range of) backlink pages for a page
                if ( !empty( $this->params['recursive'] ) ) {
                        // Carry over information for de-duplication
                        $extraParams = $this->getRootJobParams();
                        // Avoid slave lag when fetching templates.
                        // When the outermost job is run, we know that the caller that enqueued it must have
                        // committed the relevant changes to the DB by now. At that point, record the master
                        // position and pass it along as the job recursively breaks into smaller range jobs.
                        // Hopefully, when leaf jobs are popped, the slaves will have reached that position.
                        if ( isset( $this->params['masterPos'] ) ) {
                                $extraParams['masterPos'] = $this->params['masterPos'];
                        } elseif ( wfGetLB()->getServerCount() > 1 ) {
                                $extraParams['masterPos'] = wfGetLB()->getMasterPos();
                        } else {
                                $extraParams['masterPos'] = false;
                        }
                        // Convert this into no more than $wgUpdateRowsPerJob RefreshLinks per-title
                        // jobs and possibly a recursive RefreshLinks job for the rest of the backlinks
                        $jobs = BacklinkJobUtils::partitionBacklinkJob(
                                $this,
                                $wgUpdateRowsPerJob,
                                1, // job-per-title
                                array( 'params' => $extraParams )
                        );
                        JobQueueGroup::singleton()->push( $jobs );
                // Job to update link tables for a set of titles
                } elseif ( isset( $this->params['pages'] ) ) {
                        foreach ( $this->params['pages'] as $pageId => $nsAndKey ) {
                                list( $ns, $dbKey ) = $nsAndKey;
                                $this->runForTitle( Title::makeTitleSafe( $ns, $dbKey ) );
                        }
                // Job to update link tables for a given title
                } else {
                        $this->runForTitle( $this->title );
                }

                return true;
        }

        protected function runForTitle( Title $title = null ) {
                $linkCache = LinkCache::singleton();
                $linkCache->clear();

                if ( is_null( $title ) ) {
                        $this->setLastError( "refreshLinks: Invalid title" );
                        return false;
                }

                // Wait for the DB of the current/next slave DB handle to catch up to the master.
                // This way, we get the correct page_latest for templates or files that just changed
                // milliseconds ago, having triggered this job to begin with.
                if ( isset( $this->params['masterPos'] ) && $this->params['masterPos'] !== false ) {
                        wfGetLB()->waitFor( $this->params['masterPos'] );
                }

                $page = WikiPage::factory( $title );

                // Fetch the current revision...
                $revision = Revision::newFromTitle( $title, false, Revision::READ_NORMAL );
                if ( !$revision ) {
                        $this->setLastError( "refreshLinks: Article not found {$title->getPrefixedDBkey()}" );
                        return false; // XXX: what if it was just deleted?
                }
                $content = $revision->getContent( Revision::RAW );
                if ( !$content ) {
                        // If there is no content, pretend the content is empty
                        $content = $revision->getContentHandler()->makeEmptyContent();
                }

                $parserOutput = false;
                $parserOptions = $page->makeParserOptions( 'canonical' );
                // If page_touched changed after this root job (with a good slave lag skew factor),
                // then it is likely that any views of the pages already resulted in re-parses which
                // are now in cache. This can be reused to avoid expensive parsing in some cases.
                if ( isset( $this->params['rootJobTimestamp'] ) ) {
                        $skewedTimestamp = wfTimestamp( TS_UNIX, $this->params['rootJobTimestamp'] ) + 5;
                        if ( $page->getLinksTimestamp() > wfTimestamp( TS_MW, $skewedTimestamp ) ) {
                                // Something already updated the backlinks since this job was made
                                return true;
                        }
                        if ( $page->getTouched() > wfTimestamp( TS_MW, $skewedTimestamp ) ) {
                                $parserOutput = ParserCache::singleton()->getDirty( $page, $parserOptions );
                                if ( $parserOutput && $parserOutput->getCacheTime() <= $skewedTimestamp ) {
                                        $parserOutput = false; // too stale
                                }
                        }
                }
                // Fetch the current revision and parse it if necessary...
                if ( $parserOutput == false ) {
                        $start = microtime( true );
                        // Revision ID must be passed to the parser output to get revision variables correct
                        $parserOutput = $content->getParserOutput(
                                $title, $revision->getId(), $parserOptions, false );
                        $ellapsed = microtime( true ) - $start;
                        // If it took a long time to render, then save this back to the cache to avoid
                        // wasted CPU by other apaches or job runners. We don't want to always save to
                        // cache as this can cause high cache I/O and LRU churn when a template changes.
                        if ( $ellapsed >= self::PARSE_THRESHOLD_SEC
                                && $page->isParserCacheUsed( $parserOptions, $revision->getId() )
                                && $parserOutput->isCacheable()
                        ) {
                                $ctime = wfTimestamp( TS_MW, (int)$start ); // cache time
                                ParserCache::singleton()->save(
                                        $parserOutput, $page, $parserOptions, $ctime, $revision->getId()
                                );
                        }
                }

                $updates = $content->getSecondaryDataUpdates( $title, null, false, $parserOutput );
                DataUpdate::runUpdates( $updates );

                InfoAction::invalidateCache( $title );

                return true;
        }

        public function getDeduplicationInfo() {
                $info = parent::getDeduplicationInfo();
                if ( is_array( $info['params'] ) ) {
                        // Don't let highly unique "masterPos" values ruin duplicate detection
                        unset( $info['params']['masterPos'] );
                        // For per-pages jobs, the job title is that of the template that changed
                        // (or similar), so remove that since it ruins duplicate detection
                        if ( isset( $info['pages'] ) ) {
                                unset( $info['namespace'] );
                                unset( $info['title'] );
                        }
                }

                return $info;
        }

        public function workItemCount() {
                return isset( $this->params['pages'] ) ? count( $this->params['pages'] ) : 1;
        }
}