RefreshLinksJob.php

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<?php
use MediaWiki\MediaWikiServices;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\RevisionRenderer;
use Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;

class RefreshLinksJob extends Job {
    const NORMAL_MAX_LAG = 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' ];
        // Tell JobRunner to not automatically wrap run() in a transaction round.
        // Each runForTitle() call will manage its own rounds in order to run DataUpdates
        // and to avoid contention as well.
        $this->executionFlags |= self::JOB_NO_EXPLICIT_TRX_ROUND;
    }

    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() {
        $ok = true;

        // Job to update all (or a range of) backlink pages for a page
        if ( !empty( $this->params['recursive'] ) ) {
            $services = MediaWikiServices::getInstance();
            // 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'] ) ) {
                $lbFactory = $services->getDBLoadBalancerFactory();
                if ( !$lbFactory->waitForReplication( [
                    'domain'  => $lbFactory->getLocalDomainID(),
                    'timeout' => self::LAG_WAIT_TIMEOUT
                ] ) ) { // only try so hard
                    $stats = $services->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,
                $services->getMainConfig()->get( 'UpdateRowsPerJob' ),
                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 list( $ns, $dbKey ) ) {
                $title = Title::makeTitleSafe( $ns, $dbKey );
                if ( $title ) {
                    $ok = $this->runForTitle( $title ) && $ok;
                } else {
                    $ok = false;
                    $this->setLastError( "Invalid title ($ns,$dbKey)." );
                }
            }
        // Job to update link tables for a given title
        } else {
            $ok = $this->runForTitle( $this->title );
        }

        return $ok;
    }

    protected function runForTitle( Title $title ) {
        $services = MediaWikiServices::getInstance();
        $stats = $services->getStatsdDataFactory();
        $renderer = $services->getRevisionRenderer();
        $parserCache = $services->getParserCache();
        $lbFactory = $services->getDBLoadBalancerFactory();
        $ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );

        // Load the page from the master DB
        $page = WikiPage::factory( $title );
        $page->loadPageData( WikiPage::READ_LATEST );

        // Serialize link update job by page ID so they see each others' changes.
        // The page ID and latest revision ID will be queried again after the lock
        // is acquired to bail if they are changed from that of loadPageData() above.
        // Serialize links updates by page ID so they see each others' changes
        $dbw = $lbFactory->getMainLB()->getConnectionRef( DB_MASTER );
        $scopedLock = LinksUpdate::acquirePageLock( $dbw, $page->getId(), 'job' );
        if ( $scopedLock === null ) {
            // Another job is already updating the page, likely for a prior revision (T170596)
            $this->setLastError( 'LinksUpdate already running for this page, try again later.' );
            $stats->increment( 'refreshlinks.lock_failure' );

            return false;
        }

        if ( $this->isAlreadyRefreshed( $page ) ) {
            $stats->increment( 'refreshlinks.update_skipped' );

            return true;
        }

        // Parse during a fresh transaction round for better read consistency
        $lbFactory->beginMasterChanges( __METHOD__ );
        $output = $this->getParserOutput( $renderer, $parserCache, $page, $stats );
        $options = $this->getDataUpdateOptions();
        $lbFactory->commitMasterChanges( __METHOD__ );

        if ( !$output ) {
            return false; // raced out?
        }

        // Tell DerivedPageDataUpdater to use this parser output
        $options['known-revision-output'] = $output;
        // Execute corresponding DataUpdates immediately
        $page->doSecondaryDataUpdates( $options );
        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;
    }

    private function isAlreadyRefreshed( WikiPage $page ) {
        // Get the timestamp of the change that triggered this job
        $rootTimestamp = $this->params['rootJobTimestamp'] ?? null;
        if ( $rootTimestamp === null ) {
            return false;
        }

        if ( !empty( $this->params['isOpportunistic'] ) ) {
            // Neither clock skew nor DB snapshot/replica DB lag matter much for
            // such updates; focus on reusing the (often recently updated) cache
            $lagAwareTimestamp = $rootTimestamp;
        } else {
            // For transclusion updates, the template changes must be reflected
            $lagAwareTimestamp = wfTimestamp(
                TS_MW,
                wfTimestamp( TS_UNIX, $rootTimestamp ) + self::NORMAL_MAX_LAG
            );
        }

        return ( $page->getLinksTimestamp() > $lagAwareTimestamp );
    }

    private function getParserOutput(
        RevisionRenderer $renderer,
        ParserCache $parserCache,
        WikiPage $page,
        StatsdDataFactoryInterface $stats
    ) {
        $revision = $this->getCurrentRevisionIfUnchanged( $page, $stats );
        if ( !$revision ) {
            return null; // race condition?
        }

        $cachedOutput = $this->getParserOutputFromCache( $parserCache, $page, $revision, $stats );
        if ( $cachedOutput ) {
            return $cachedOutput;
        }

        $renderedRevision = $renderer->getRenderedRevision(
            $revision,
            $page->makeParserOptions( 'canonical' ),
            null,
            [ 'audience' => $revision::RAW ]
        );

        $parseTimestamp = wfTimestampNow(); // timestamp that parsing started
        $output = $renderedRevision->getRevisionParserOutput( [ 'generate-html' => false ] );
        $output->setCacheTime( $parseTimestamp ); // notify LinksUpdate::doUpdate()

        return $output;
    }

    private function getCurrentRevisionIfUnchanged(
        WikiPage $page,
        StatsdDataFactoryInterface $stats
    ) {
        $title = $page->getTitle();
        // Get the latest ID since acquirePageLock() in runForTitle() 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 name
        $latest = $title->getLatestRevID( Title::READ_LATEST );

        $triggeringRevisionId = $this->params['triggeringRevisionId'] ?? null;
        if ( $triggeringRevisionId && $triggeringRevisionId !== $latest ) {
            // This job is obsolete and one for the latest revision will handle updates
            $stats->increment( 'refreshlinks.rev_not_current' );
            $this->setLastError( "Revision $triggeringRevisionId is not current" );

            return null;
        }

        // Load the current revision. Note that $page should have loaded with READ_LATEST.
        // This instance will be reused in WikiPage::doSecondaryDataUpdates() later on.
        $revision = $page->getRevisionRecord();
        if ( !$revision ) {
            $stats->increment( 'refreshlinks.rev_not_found' );
            $this->setLastError( "Revision not found for {$title->getPrefixedDBkey()}" );

            return null; // just deleted?
        } elseif ( $revision->getId() !== $latest || $revision->getPageId() !== $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 null;
        }

        return $revision;
    }

    private function getParserOutputFromCache(
        ParserCache $parserCache,
        WikiPage $page,
        RevisionRecord $currentRevision,
        StatsdDataFactoryInterface $stats
    ) {
        $cachedOutput = null;
        // 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.
        $rootTimestamp = $this->params['rootJobTimestamp'] ?? null;
        if ( $rootTimestamp !== null ) {
            $opportunistic = !empty( $this->params['isOpportunistic'] );
            if ( $opportunistic ) {
                // Neither clock skew nor DB snapshot/replica DB lag matter much for
                // such updates; focus on reusing the (often recently updated) cache
                $lagAwareTimestamp = $rootTimestamp;
            } else {
                // For transclusion updates, the template changes must be reflected
                $lagAwareTimestamp = wfTimestamp(
                    TS_MW,
                    wfTimestamp( TS_UNIX, $rootTimestamp ) + self::NORMAL_MAX_LAG
                );
            }

            if ( $page->getTouched() >= $rootTimestamp || $opportunistic ) {
                // Cache is suspected to be up-to-date so it's worth the I/O of checking.
                // As long as the cache rev ID matches the current rev ID and it reflects
                // the job's triggering change, then it is usable.
                $parserOptions = $page->makeParserOptions( 'canonical' );
                $output = $parserCache->getDirty( $page, $parserOptions );
                if (
                    $output &&
                    $output->getCacheRevisionId() == $currentRevision->getId() &&
                    $output->getCacheTime() >= $lagAwareTimestamp
                ) {
                    $cachedOutput = $output;
                }
            }
        }

        if ( $cachedOutput ) {
            $stats->increment( 'refreshlinks.parser_cached' );
        } else {
            $stats->increment( 'refreshlinks.parser_uncached' );
        }

        return $cachedOutput;
    }

    private function getDataUpdateOptions() {
        $options = [
            'recursive' => !empty( $this->params['useRecursiveLinksUpdate'] ),
            // Carry over cause so the update can do extra logging
            'causeAction' => $this->params['causeAction'],
            'causeAgent' => $this->params['causeAgent']
        ];
        if ( !empty( $this->params['triggeringUser'] ) ) {
            $userInfo = $this->params['triggeringUser'];
            if ( $userInfo['userId'] ) {
                $options['triggeringUser'] = User::newFromId( $userInfo['userId'] );
            } else {
                // Anonymous, use the username
                $options['triggeringUser'] = User::newFromName( $userInfo['userName'], false );
            }
        }

        return $options;
    }

    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
    }
}