RefreshLinksJob.php

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<?php
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 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 cause 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;
    }
}