findBadBlobs.php

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<?php
use MediaWiki\MediaWikiServices;
use MediaWiki\Revision\RevisionArchiveRecord;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\RevisionStore;
use MediaWiki\Revision\RevisionStoreRecord;
use MediaWiki\Revision\SlotRecord;
use MediaWiki\Storage\BlobStore;
use Wikimedia\Rdbms\LBFactory;
use Wikimedia\Rdbms\LoadBalancer;
 
require_once __DIR__ . '/Maintenance.php';
 
class FindBadBlobs extends Maintenance {
 
    private $revisionStore;
 
    private $blobStore;
 
    private $loadBalancer;
 
    private $lbFactory;
 
    public function __construct() {
        parent::__construct();
 
        $this->setBatchSize( 1000 );
        $this->addDescription( 'Find and mark bad content blobs. Marked blobs will be read as empty. '
            . 'Use --scan-from to find revisions with bad blobs, use --mark to mark them.' );
        $this->addOption( 'scan-from', 'Start scanning revisions at the given date. '
            . 'Format: Anything supported by MediaWiki, e.g. YYYYMMDDHHMMSS or YYYY-MM-DDTHH:MM:SS',
            false, true );
        $this->addOption( 'revisions', 'A list of revision IDs to process, separated by comma or '
            . 'colon or whitespace. Revisions belonging to deleted pages will work. '
            . 'If set to "-" IDs are read from stdin, one per line.', false, true );
        $this->addOption( 'limit', 'Maximum number of revisions for --scan-from to scan. '
            . 'Default: 1000', false, true );
        $this->addOption( 'mark', 'Mark the blob as "known bad", to avoid errors when '
            . 'attempting to read it. The value given is the reason for marking the blob as bad, '
            . 'typically a ticket ID. Requires --revisions to also be set.', false, true );
    }
 
    public function initializeServices(
        ?RevisionStore $revisionStore = null,
        ?BlobStore $blobStore = null,
        ?LoadBalancer $loadBalancer = null,
        ?LBFactory $lbFactory = null
    ) {
        $services = MediaWikiServices::getInstance();
 
        $this->revisionStore = $revisionStore ?? $this->revisionStore ?? $services->getRevisionStore();
        $this->blobStore = $blobStore ?? $this->blobStore ?? $services->getBlobStore();
        $this->loadBalancer = $loadBalancer ?? $this->loadBalancer ?? $services->getDBLoadBalancer();
        $this->lbFactory = $lbFactory ?? $this->lbFactory ?? $services->getDBLoadBalancerFactory();
    }
 
    private function getStartTimestamp() {
        $tsOpt = $this->getOption( 'scan-from' );
        if ( strlen( $tsOpt ) < 14 ) {
            $this->fatalError( 'Bad timestamp: ' . $tsOpt
                . ', please provide time and date down to the second.' );
        }
 
        $ts = wfTimestamp( TS_MW, $tsOpt );
        if ( !$ts ) {
            $this->fatalError( 'Bad timestamp: ' . $tsOpt );
        }
 
        return $ts;
    }
 
    private function getRevisionIds() {
        $opt = $this->getOption( 'revisions' );
 
        if ( $opt === '-' ) {
            $opt = stream_get_contents( STDIN );
 
            if ( !$opt ) {
                return [];
            }
        }
 
        return $this->parseIntList( $opt );
    }
 
    public function execute() {
        $this->initializeServices();
 
        if ( $this->hasOption( 'revisions' ) ) {
            if ( $this->hasOption( 'scan-from' ) ) {
                $this->fatalError( 'Cannot use --revisions together with --scan-from' );
            }
 
            $ids = $this->getRevisionIds();
 
            $count = $this->scanRevisionsById( $ids );
        } elseif ( $this->hasOption( 'scan-from' ) ) {
            if ( $this->hasOption( 'mark' ) ) {
                $this->fatalError( 'Cannot use --mark with --scan-from, '
                    . 'use --revisions to specify revisions to mark.' );
            }
 
            $fromTimestamp = $this->getStartTimestamp();
            $total = $this->getOption( 'limit', 1000 );
 
            $count = $this->scanRevisionsByTimestamp( $fromTimestamp, $total );
 
            $this->output( "The range of archive rows scanned is based on the range of revision IDs "
                . "scanned in the revision table.\n" );
        } else {
            if ( $this->hasOption( 'mark' ) ) {
                $this->fatalError( 'The --mark must be used together with --revisions' );
            } else {
                $this->fatalError( 'Must specify one of --revisions or --scan-from' );
            }
        }
 
        if ( $this->hasOption( 'mark' ) ) {
            $this->output( "Marked $count bad revisions.\n" );
        } else {
            $this->output( "Found $count bad revisions.\n" );
 
            if ( $count > 0 ) {
                $this->output( "On a unix/linux environment, you can use grep and cut to list of IDs\n" );
                $this->output( "that can then be used with the --revisions option. E.g.\n" );
                $this->output( "  grep '! Found bad blob' | cut -s -f 3\n" );
            }
        }
    }
 
    private function scanRevisionsByTimestamp( $fromTimestamp, $total ) {
        $count = 0;
        $lastRevId = 0;
        $firstRevId = 0;
        $lastTimestamp = $fromTimestamp;
        $revisionRowsScanned = 0;
        $archiveRowsScanned = 0;
 
        $this->output( "Scanning revisions table, "
            . "$total rows starting at rev_timestamp $fromTimestamp\n" );
 
        while ( $revisionRowsScanned < $total ) {
            $batchSize = min( $total - $revisionRowsScanned, $this->getBatchSize() );
            $revisions = $this->loadRevisionsByTimestamp( $lastRevId, $lastTimestamp, $batchSize );
            if ( !$revisions ) {
                break;
            }
 
            foreach ( $revisions as $rev ) {
                // we are sorting by timestamp, so we may encounter revision IDs out of sequence
                $firstRevId = $firstRevId ? min( $firstRevId, $rev->getId() ) : $rev->getId();
                $lastRevId = max( $lastRevId, $rev->getId() );
 
                $count += $this->checkRevision( $rev );
            }
 
            $lastTimestamp = $rev->getTimestamp();
            $batchSize = count( $revisions );
            $revisionRowsScanned += $batchSize;
            $this->output(
                "\t- Scanned a batch of $batchSize revisions, "
                . "up to revision $lastRevId ($lastTimestamp)\n"
            );
 
            $this->waitForReplication();
        }
 
        // NOTE: the archive table isn't indexed by timestamp, so the best we can do is use the
        // revision ID just before the first revision ID we found above as the starting point
        // of the scan, and scan up to on revision after the last revision ID we found above.
        // If $firstRevId is 0, the loop body above didn't execute,
        // so we should skip the one below as well.
        $fromArchived = $this->getNextRevision( $firstRevId, '<', 'DESC' );
        $maxArchived = $this->getNextRevision( $lastRevId, '>', 'ASC' );
        $maxArchived = $maxArchived ?: PHP_INT_MAX;
 
        $this->output( "Scanning archive table by ar_rev_id, $fromArchived to $maxArchived\n" );
        while ( $firstRevId > 0 && $fromArchived < $maxArchived ) {
            $batchSize = min( $total - $archiveRowsScanned, $this->getBatchSize() );
            $revisions = $this->loadArchiveByRevisionId( $fromArchived, $maxArchived, $batchSize );
            if ( !$revisions ) {
                break;
            }
            foreach ( $revisions as $rev ) {
                $count += $this->checkRevision( $rev );
            }
            $fromArchived = $rev->getId();
            $batchSize = count( $revisions );
            $archiveRowsScanned += $batchSize;
            $this->output(
                "\t- Scanned a batch of $batchSize archived revisions, "
                . "up to revision $fromArchived ($lastTimestamp)\n"
            );
 
            $this->waitForReplication();
        }
 
        return $count;
    }
 
    private function loadRevisionsByTimestamp( int $afterId, string $fromTimestamp, $batchSize ) {
        $db = $this->loadBalancer->getConnectionRef( DB_REPLICA );
        $queryInfo = $this->revisionStore->getQueryInfo();
        $quotedTimestamp = $db->addQuotes( $fromTimestamp );
        $rows = $db->select(
            $queryInfo['tables'],
            $queryInfo['fields'],
            "rev_timestamp > $quotedTimestamp OR "
            . "(rev_timestamp = $quotedTimestamp AND rev_id > $afterId )",
            __METHOD__,
            [
                'USE INDEX' => [ 'revision' => 'rev_timestamp' ],
                'ORDER BY' => 'rev_timestamp, rev_id',
                'LIMIT' => $batchSize,
            ],
            $queryInfo['joins']
        );
        $result = $this->revisionStore->newRevisionsFromBatch( $rows, [ 'slots' => true ] );
        $this->handleStatus( $result );
 
        $records = array_filter( $result->value );
 
        '@phan-var RevisionStoreRecord[] $records';
        return $records;
    }
 
    private function loadArchiveByRevisionId( int $afterId, int $uptoId, $batchSize ) {
        $db = $this->loadBalancer->getConnectionRef( DB_REPLICA );
        $queryInfo = $this->revisionStore->getArchiveQueryInfo();
        $rows = $db->select(
            $queryInfo['tables'],
            $queryInfo['fields'],
            [ "ar_rev_id > $afterId", "ar_rev_id <= $uptoId" ],
            __METHOD__,
            [ 'LIMIT' => $batchSize, 'ORDER BY' => 'ar_rev_id' ],
            $queryInfo['joins']
        );
        $result = $this->revisionStore->newRevisionsFromBatch(
            $rows,
            [ 'archive' => true, 'slots' => true ]
        );
        $this->handleStatus( $result );
 
        $records = array_filter( $result->value );
 
        '@phan-var RevisionArchiveRecord[] $records';
        return $records;
    }
 
    private function getNextRevision( int $revId, string $comp, string $dir ) {
        $db = $this->loadBalancer->getConnectionRef( DB_REPLICA );
        $next = $db->selectField(
            'revision',
            'rev_id',
            "rev_id $comp $revId",
            __METHOD__,
            [ 'ORDER BY' => "rev_id $dir" ]
        );
        return (int)$next;
    }
 
    private function scanRevisionsById( array $ids ) {
        $count = 0;
        $total = count( $ids );
 
        $this->output( "Scanning $total ids\n" );
 
        foreach ( array_chunk( $ids, $this->getBatchSize() ) as $batch ) {
            $revisions = $this->loadRevisionsById( $batch );
 
            if ( !$revisions ) {
                continue;
            }
 
            foreach ( $revisions as $rev ) {
                $count += $this->checkRevision( $rev );
            }
 
            $batchSize = count( $revisions );
            $this->output( "\t- Scanned a batch of $batchSize revisions\n" );
        }
 
        return $count;
    }
 
    private function loadRevisionsById( array $ids ) {
        $db = $this->loadBalancer->getConnectionRef( DB_REPLICA );
        $queryInfo = $this->revisionStore->getQueryInfo();
 
        $rows = $db->select(
            $queryInfo['tables'],
            $queryInfo['fields'],
            [
                'rev_id ' => $ids,
            ],
            __METHOD__,
            [],
            $queryInfo['joins']
        );
 
        $result = $this->revisionStore->newRevisionsFromBatch( $rows, [ 'slots' => true ] );
 
        $this->handleStatus( $result );
 
        $revisions = array_filter( $result->value );
        '@phan-var RevisionArchiveRecord[] $revisions';
 
        // if not all revisions were found, check the archive table.
        if ( count( $revisions ) < count( $ids ) ) {
            $archiveQueryInfo = $this->revisionStore->getArchiveQueryInfo();
            $remainingIds = array_diff( $ids, array_keys( $revisions ) );
 
            $rows = $db->select(
                $archiveQueryInfo['tables'],
                $archiveQueryInfo['fields'],
                [
                    'ar_rev_id ' => $remainingIds,
                ],
                __METHOD__,
                [],
                $archiveQueryInfo['joins']
            );
 
            $archiveResult = $this->revisionStore->newRevisionsFromBatch(
                $rows,
                [ 'slots' => true, 'archive' => true ]
            );
 
            $this->handleStatus( $archiveResult );
 
            // don't use array_merge, since it will re-index
            $revisions += array_filter( $archiveResult->value );
        }
 
        return $revisions;
    }
 
    private function checkRevision( RevisionRecord $rev ) {
        $count = 0;
        foreach ( $rev->getSlots()->getSlots() as $slot ) {
            $count += $this->checkSlot( $rev, $slot );
        }
 
        if ( $count === 0 && $this->hasOption( 'mark' ) ) {
            $this->output( "\t# No bad blob found on revision {$rev->getId()}, skipped!\n" );
        }
 
        return $count;
    }
 
    private function checkSlot( RevisionRecord $rev, SlotRecord $slot ) {
        $address = $slot->getAddress();
        $error = null;
        $type = null;
 
        try {
            $this->blobStore->getBlob( $address );
            // nothing to do
            return 0;
        } catch ( Exception $ex ) {
            $error = $ex->getMessage();
            $type = get_class( $ex );
        }
 
        // NOTE: output the revision ID again at the end in a separate column for easy processing
        // via the "cut" shell command.
        $this->output( "\t! Found bad blob on revision {$rev->getId()} "
            . "from {$rev->getTimestamp()} ({$slot->getRole()} slot): "
            . "content_id={$slot->getContentId()}, address=<{$slot->getAddress()}>, "
            . "error='$error', type='$type'. ID:\t{$rev->getId()}\n" );
 
        if ( $this->hasOption( 'mark' ) ) {
            $newAddress = $this->markBlob( $rev, $slot, $error );
            $this->output( "\tChanged address to <$newAddress>\n" );
        }
 
        return 1;
    }
 
    private function markBlob( RevisionRecord $rev, SlotRecord $slot, string $error = null ) {
        $args = [];
 
        if ( $this->hasOption( 'mark' ) ) {
            $args['reason'] = $this->getOption( 'mark' );
        }
 
        if ( $error ) {
            $args['error'] = $error;
        }
 
        $address = $slot->getAddress() ?: 'empty';
        $badAddress = 'bad:' . urlencode( $address );
 
        if ( $args ) {
            $badAddress .= '?' . wfArrayToCgi( $args );
        }
 
        $badAddress = substr( $badAddress, 0, 255 );
 
        $dbw = $this->loadBalancer->getConnectionRef( DB_PRIMARY );
        $dbw->update(
            'content',
            [ 'content_address' => $badAddress ],
            [ 'content_id' => $slot->getContentId() ],
            __METHOD__
        );
 
        return $badAddress;
    }
 
    private function handleStatus( StatusValue $status ) {
        if ( !$status->isOK() ) {
            $this->fatalError(
                Status::wrap( $status )->getMessage( false, false, 'en' )->text()
            );
        }
        if ( !$status->isGood() ) {
            $this->error(
                "\t! " . Status::wrap( $status )->getMessage( false, false, 'en' )->text()
            );
        }
    }
 
}
 
$maintClass = FindBadBlobs::class;
require_once RUN_MAINTENANCE_IF_MAIN;