RefreshLinksJob.php

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<?php
use MediaWiki\MediaWikiServices;
use Wikimedia\Rdbms\DBReplicationWaitError;
 
class RefreshLinksJob extends Job {
    const PARSE_THRESHOLD_SEC = 1.0;
    const CLOCK_FUDGE = 10;
    const LAG_WAIT_TIMEOUT = 15;
 
    function __construct( Title $title, array $params ) {
        parent::__construct( 'refreshLinks', $title, $params );
        // Avoid the overhead of de-duplication when it would be pointless
        $this->removeDuplicates = (
            // Ranges rarely will line up
            !isset( $params['range'] ) &&
            // Multiple pages per job make matches unlikely
            !( isset( $params['pages'] ) && count( $params['pages'] ) != 1 )
        );
        $this->params += [ 'causeAction' => 'unknown', 'causeAgent' => 'unknown' ];
    }
 
    public static function newPrioritized( Title $title, array $params ) {
        $job = new self( $title, $params );
        $job->command = 'refreshLinksPrioritized';
 
        return $job;
    }
 
    public static function newDynamic( Title $title, array $params ) {
        $job = new self( $title, $params );
        $job->command = 'refreshLinksDynamic';
 
        return $job;
    }
 
    function run() {
        global $wgUpdateRowsPerJob;
 
        // Job to update all (or a range of) backlink pages for a page
        if ( !empty( $this->params['recursive'] ) ) {
            // When the base job branches, wait for the replica DBs to catch up to the master.
            // From then on, we know that any template changes at the time the base job was
            // enqueued will be reflected in backlink page parses when the leaf jobs run.
            if ( !isset( $this->params['range'] ) ) {
                try {
                    $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
                    $lbFactory->waitForReplication( [
                        'wiki'    => wfWikiID(),
                        'timeout' => self::LAG_WAIT_TIMEOUT
                    ] );
                } catch ( DBReplicationWaitError $e ) { // only try so hard
                    $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
                    $stats->increment( 'refreshlinks.lag_wait_failed' );
                }
            }
            // Carry over information for de-duplication
            $extraParams = $this->getRootJobParams();
            $extraParams['triggeredRecursive'] = true;
            // Carry over cause information for logging
            $extraParams['causeAction'] = $this->params['causeAction'];
            $extraParams['causeAgent'] = $this->params['causeAgent'];
            // 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
                [ '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 $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 ) {
        $services = MediaWikiServices::getInstance();
        $stats = $services->getStatsdDataFactory();
        $lbFactory = $services->getDBLoadBalancerFactory();
        $ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
 
        $page = WikiPage::factory( $title );
        $page->loadPageData( WikiPage::READ_LATEST );
 
        // Serialize links updates by page ID so they see each others' changes
        $dbw = $lbFactory->getMainLB()->getConnection( DB_MASTER );
        $scopedLock = LinksUpdate::acquirePageLock( $dbw, $page->getId(), 'job' );
        // Get the latest ID *after* acquirePageLock() flushed the transaction.
        // This is used to detect edits/moves after loadPageData() but before the scope lock.
        // The works around the chicken/egg problem of determining the scope lock key.
        $latest = $title->getLatestRevID( Title::GAID_FOR_UPDATE );
 
        if ( !empty( $this->params['triggeringRevisionId'] ) ) {
            // Fetch the specified revision; lockAndGetLatest() below detects if the page
            // was edited since and aborts in order to avoid corrupting the link tables
            $revision = Revision::newFromId(
                $this->params['triggeringRevisionId'],
                Revision::READ_LATEST
            );
        } else {
            // Fetch current revision; READ_LATEST reduces lockAndGetLatest() check failures
            $revision = Revision::newFromTitle( $title, false, Revision::READ_LATEST );
        }
 
        if ( !$revision ) {
            $stats->increment( 'refreshlinks.rev_not_found' );
            $this->setLastError( "Revision not found for {$title->getPrefixedDBkey()}" );
            return false; // just deleted?
        } elseif ( $revision->getId() != $latest || $revision->getPage() !== $page->getId() ) {
            // Do not clobber over newer updates with older ones. If all jobs where FIFO and
            // serialized, it would be OK to update links based on older revisions since it
            // would eventually get to the latest. Since that is not the case (by design),
            // only update the link tables to a state matching the current revision's output.
            $stats->increment( 'refreshlinks.rev_not_current' );
            $this->setLastError( "Revision {$revision->getId()} is not current" );
            return false;
        }
 
        $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, then it is likely that
        // any views of the pages already resulted in re-parses which are now in
        // cache. The cache can be reused to avoid expensive parsing in some cases.
        if ( isset( $this->params['rootJobTimestamp'] ) ) {
            $opportunistic = !empty( $this->params['isOpportunistic'] );
 
            $skewedTimestamp = $this->params['rootJobTimestamp'];
            if ( $opportunistic ) {
                // Neither clock skew nor DB snapshot/replica DB lag matter much for such
                // updates; focus on reusing the (often recently updated) cache
            } else {
                // For transclusion updates, the template changes must be reflected
                $skewedTimestamp = wfTimestamp( TS_MW,
                    wfTimestamp( TS_UNIX, $skewedTimestamp ) + self::CLOCK_FUDGE
                );
            }
 
            if ( $page->getLinksTimestamp() > $skewedTimestamp ) {
                // Something already updated the backlinks since this job was made
                $stats->increment( 'refreshlinks.update_skipped' );
                return true;
            }
 
            if ( $page->getTouched() >= $this->params['rootJobTimestamp'] || $opportunistic ) {
                // Cache is suspected to be up-to-date. As long as the cache rev ID matches
                // and it reflects the job's triggering change, then it is usable.
                $parserOutput = $services->getParserCache()->getDirty( $page, $parserOptions );
                if ( !$parserOutput
                    || $parserOutput->getCacheRevisionId() != $revision->getId()
                    || $parserOutput->getCacheTime() < $skewedTimestamp
                ) {
                    $parserOutput = false; // too stale
                }
            }
        }
 
        // Fetch the current revision and parse it if necessary...
        if ( $parserOutput ) {
            $stats->increment( 'refreshlinks.parser_cached' );
        } else {
            $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 );
            $elapsed = 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 ( $elapsed >= self::PARSE_THRESHOLD_SEC
                && $page->shouldCheckParserCache( $parserOptions, $revision->getId() )
                && $parserOutput->isCacheable()
            ) {
                $ctime = wfTimestamp( TS_MW, (int)$start ); // cache time
                $services->getParserCache()->save(
                    $parserOutput, $page, $parserOptions, $ctime, $revision->getId()
                );
            }
            $stats->increment( 'refreshlinks.parser_uncached' );
        }
 
        $updates = $content->getSecondaryDataUpdates(
            $title,
            null,
            !empty( $this->params['useRecursiveLinksUpdate'] ),
            $parserOutput
        );
 
        // For legacy hook handlers doing updates via LinksUpdateConstructed, make sure
        // any pending writes they made get flushed before the doUpdate() calls below.
        // This avoids snapshot-clearing errors in LinksUpdate::acquirePageLock().
        $lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
 
        foreach ( $updates as $update ) {
            // Carry over cause in case so the update can do extra logging
            $update->setCause( $this->params['causeAction'], $this->params['causeAgent'] );
            // FIXME: This code probably shouldn't be here?
            // Needed by things like Echo notifications which need
            // to know which user caused the links update
            if ( $update instanceof LinksUpdate ) {
                $update->setRevision( $revision );
                if ( !empty( $this->params['triggeringUser'] ) ) {
                    $userInfo = $this->params['triggeringUser'];
                    if ( $userInfo['userId'] ) {
                        $user = User::newFromId( $userInfo['userId'] );
                    } else {
                        // Anonymous, use the username
                        $user = User::newFromName( $userInfo['userName'], false );
                    }
                    $update->setTriggeringUser( $user );
                }
            }
        }
 
        foreach ( $updates as $update ) {
            $update->setTransactionTicket( $ticket );
            $update->doUpdate();
        }
 
        InfoAction::invalidateCache( $title );
 
        // Commit any writes here in case this method is called in a loop.
        // In that case, the scoped lock will fail to be acquired.
        $lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
 
        return true;
    }
 
    public function getDeduplicationInfo() {
        $info = parent::getDeduplicationInfo();
        unset( $info['causeAction'] );
        unset( $info['causeAgent'] );
        if ( is_array( $info['params'] ) ) {
            // 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['params']['pages'] ) ) {
                unset( $info['namespace'] );
                unset( $info['title'] );
            }
        }
 
        return $info;
    }
 
    public function workItemCount() {
        if ( !empty( $this->params['recursive'] ) ) {
            return 0; // nothing actually refreshed
        } elseif ( isset( $this->params['pages'] ) ) {
            return count( $this->params['pages'] );
        }
 
        return 1; // one title
    }
}