recompressTracked.php

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<?php
use MediaWiki\Logger\LegacyLogger;
use MediaWiki\MediaWikiServices;
use MediaWiki\Shell\Shell;
use Wikimedia\Rdbms\IDatabase;

$optionsWithArgs = RecompressTracked::getOptionsWithArgs();
require __DIR__ . '/../commandLine.inc';

if ( count( $args ) < 1 ) {
    echo "Usage: php recompressTracked.php [options] <cluster> [... <cluster>...]
Moves blobs indexed by trackBlobs.php to a specified list of destination clusters,
and recompresses them in the process. Restartable.

Options:
    --procs <procs>       Set the number of child processes (default 1)
    --copy-only           Copy only, do not update the text table. Restart
                          without this option to complete.
    --debug-log <file>    Log debugging data to the specified file
    --info-log <file>     Log progress messages to the specified file
    --critical-log <file> Log error messages to the specified file
";
    exit( 1 );
}

$job = RecompressTracked::newFromCommandLine( $args, $options );
$job->execute();

class RecompressTracked {
    public $destClusters;
    public $batchSize = 1000;
    public $orphanBatchSize = 1000;
    public $reportingInterval = 10;
    public $numProcs = 1;
    public $numBatches = 0;
    public $pageBlobClass, $orphanBlobClass;
    public $replicaPipes, $replicaProcs, $prevReplicaId;
    public $copyOnly = false;
    public $isChild = false;
    public $replicaId = false;
    public $noCount = false;
    public $debugLog, $infoLog, $criticalLog;
    public $store;

    private static $optionsWithArgs = [
        'procs',
        'replica-id',
        'debug-log',
        'info-log',
        'critical-log'
    ];

    private static $cmdLineOptionMap = [
        'no-count' => 'noCount',
        'procs' => 'numProcs',
        'copy-only' => 'copyOnly',
        'child' => 'isChild',
        'replica-id' => 'replicaId',
        'debug-log' => 'debugLog',
        'info-log' => 'infoLog',
        'critical-log' => 'criticalLog',
    ];

    static function getOptionsWithArgs() {
        return self::$optionsWithArgs;
    }

    static function newFromCommandLine( $args, $options ) {
        $jobOptions = [ 'destClusters' => $args ];
        foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
            if ( isset( $options[$cmdOption] ) ) {
                $jobOptions[$classOption] = $options[$cmdOption];
            }
        }

        return new self( $jobOptions );
    }

    function __construct( $options ) {
        foreach ( $options as $name => $value ) {
            $this->$name = $value;
        }
        $this->store = new ExternalStoreDB;
        if ( !$this->isChild ) {
            $GLOBALS['wgDebugLogPrefix'] = "RCT M: ";
        } elseif ( $this->replicaId !== false ) {
            $GLOBALS['wgDebugLogPrefix'] = "RCT {$this->replicaId}: ";
        }
        $this->pageBlobClass = function_exists( 'xdiff_string_bdiff' ) ?
            DiffHistoryBlob::class : ConcatenatedGzipHistoryBlob::class;
        $this->orphanBlobClass = ConcatenatedGzipHistoryBlob::class;
    }

    function debug( $msg ) {
        wfDebug( "$msg\n" );
        if ( $this->debugLog ) {
            $this->logToFile( $msg, $this->debugLog );
        }
    }

    function info( $msg ) {
        echo "$msg\n";
        if ( $this->infoLog ) {
            $this->logToFile( $msg, $this->infoLog );
        }
    }

    function critical( $msg ) {
        echo "$msg\n";
        if ( $this->criticalLog ) {
            $this->logToFile( $msg, $this->criticalLog );
        }
    }

    function logToFile( $msg, $file ) {
        $header = '[' . date( 'd\TH:i:s' ) . '] ' . wfHostname() . ' ' . posix_getpid();
        if ( $this->replicaId !== false ) {
            $header .= "({$this->replicaId})";
        }
        $header .= ' ' . wfWikiID();
        LegacyLogger::emit( sprintf( "%-50s %s\n", $header, $msg ), $file );
    }

    function syncDBs() {
        $dbw = wfGetDB( DB_MASTER );
        $dbr = wfGetDB( DB_REPLICA );
        $pos = $dbw->getMasterPos();
        $dbr->masterPosWait( $pos, 100000 );
    }

    function execute() {
        if ( $this->isChild ) {
            $this->executeChild();
        } else {
            $this->executeParent();
        }
    }

    function executeParent() {
        if ( !$this->checkTrackingTable() ) {
            return;
        }

        $this->syncDBs();
        $this->startReplicaProcs();
        $this->doAllPages();
        $this->doAllOrphans();
        $this->killReplicaProcs();
    }

    function checkTrackingTable() {
        $dbr = wfGetDB( DB_REPLICA );
        if ( !$dbr->tableExists( 'blob_tracking' ) ) {
            $this->critical( "Error: blob_tracking table does not exist" );

            return false;
        }
        $row = $dbr->selectRow( 'blob_tracking', '*', '', __METHOD__ );
        if ( !$row ) {
            $this->info( "Warning: blob_tracking table contains no rows, skipping this wiki." );

            return false;
        }

        return true;
    }

    function startReplicaProcs() {
        $cmd = 'php ' . Shell::escape( __FILE__ );
        foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
            if ( $cmdOption == 'replica-id' ) {
                continue;
            } elseif ( in_array( $cmdOption, self::$optionsWithArgs ) && isset( $this->$classOption ) ) {
                $cmd .= " --$cmdOption " . Shell::escape( $this->$classOption );
            } elseif ( $this->$classOption ) {
                $cmd .= " --$cmdOption";
            }
        }
        $cmd .= ' --child' .
            ' --wiki ' . Shell::escape( wfWikiID() ) .
            ' ' . Shell::escape( ...$this->destClusters );

        $this->replicaPipes = $this->replicaProcs = [];
        for ( $i = 0; $i < $this->numProcs; $i++ ) {
            $pipes = [];
            $spec = [
                [ 'pipe', 'r' ],
                [ 'file', 'php://stdout', 'w' ],
                [ 'file', 'php://stderr', 'w' ]
            ];
            Wikimedia\suppressWarnings();
            $proc = proc_open( "$cmd --replica-id $i", $spec, $pipes );
            Wikimedia\restoreWarnings();
            if ( !$proc ) {
                $this->critical( "Error opening replica DB process: $cmd" );
                exit( 1 );
            }
            $this->replicaProcs[$i] = $proc;
            $this->replicaPipes[$i] = $pipes[0];
        }
        $this->prevReplicaId = -1;
    }

    function killReplicaProcs() {
        $this->info( "Waiting for replica DB processes to finish..." );
        for ( $i = 0; $i < $this->numProcs; $i++ ) {
            $this->dispatchToReplica( $i, 'quit' );
        }
        for ( $i = 0; $i < $this->numProcs; $i++ ) {
            $status = proc_close( $this->replicaProcs[$i] );
            if ( $status ) {
                $this->critical( "Warning: child #$i exited with status $status" );
            }
        }
        $this->info( "Done." );
    }

    function dispatch( ...$args ) {
        $pipes = $this->replicaPipes;
        $x = [];
        $y = [];
        $numPipes = stream_select( $x, $pipes, $y, 3600 );
        if ( !$numPipes ) {
            $this->critical( "Error waiting to write to replica DBs. Aborting" );
            exit( 1 );
        }
        for ( $i = 0; $i < $this->numProcs; $i++ ) {
            $replicaId = ( $i + $this->prevReplicaId + 1 ) % $this->numProcs;
            if ( isset( $pipes[$replicaId] ) ) {
                $this->prevReplicaId = $replicaId;
                $this->dispatchToReplica( $replicaId, $args );

                return;
            }
        }
        $this->critical( "Unreachable" );
        exit( 1 );
    }

    function dispatchToReplica( $replicaId, $args ) {
        $args = (array)$args;
        $cmd = implode( ' ', $args );
        fwrite( $this->replicaPipes[$replicaId], "$cmd\n" );
    }

    function doAllPages() {
        $dbr = wfGetDB( DB_REPLICA );
        $i = 0;
        $startId = 0;
        if ( $this->noCount ) {
            $numPages = '[unknown]';
        } else {
            $numPages = $dbr->selectField( 'blob_tracking',
                'COUNT(DISTINCT bt_page)',
                # A condition is required so that this query uses the index
                [ 'bt_moved' => 0 ],
                __METHOD__
            );
        }
        if ( $this->copyOnly ) {
            $this->info( "Copying pages..." );
        } else {
            $this->info( "Moving pages..." );
        }
        while ( true ) {
            $res = $dbr->select( 'blob_tracking',
                [ 'bt_page' ],
                [
                    'bt_moved' => 0,
                    'bt_page > ' . $dbr->addQuotes( $startId )
                ],
                __METHOD__,
                [
                    'DISTINCT',
                    'ORDER BY' => 'bt_page',
                    'LIMIT' => $this->batchSize,
                ]
            );
            if ( !$res->numRows() ) {
                break;
            }
            foreach ( $res as $row ) {
                $startId = $row->bt_page;
                $this->dispatch( 'doPage', $row->bt_page );
                $i++;
            }
            $this->report( 'pages', $i, $numPages );
        }
        $this->report( 'pages', $i, $numPages );
        if ( $this->copyOnly ) {
            $this->info( "All page copies queued." );
        } else {
            $this->info( "All page moves queued." );
        }
    }

    function report( $label, $current, $end ) {
        $this->numBatches++;
        if ( $current == $end || $this->numBatches >= $this->reportingInterval ) {
            $this->numBatches = 0;
            $this->info( "$label: $current / $end" );
            MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
        }
    }

    function doAllOrphans() {
        $dbr = wfGetDB( DB_REPLICA );
        $startId = 0;
        $i = 0;
        if ( $this->noCount ) {
            $numOrphans = '[unknown]';
        } else {
            $numOrphans = $dbr->selectField( 'blob_tracking',
                'COUNT(DISTINCT bt_text_id)',
                [ 'bt_moved' => 0, 'bt_page' => 0 ],
                __METHOD__ );
            if ( !$numOrphans ) {
                return;
            }
        }
        if ( $this->copyOnly ) {
            $this->info( "Copying orphans..." );
        } else {
            $this->info( "Moving orphans..." );
        }

        while ( true ) {
            $res = $dbr->select( 'blob_tracking',
                [ 'bt_text_id' ],
                [
                    'bt_moved' => 0,
                    'bt_page' => 0,
                    'bt_text_id > ' . $dbr->addQuotes( $startId )
                ],
                __METHOD__,
                [
                    'DISTINCT',
                    'ORDER BY' => 'bt_text_id',
                    'LIMIT' => $this->batchSize
                ]
            );
            if ( !$res->numRows() ) {
                break;
            }
            $ids = [];
            foreach ( $res as $row ) {
                $startId = $row->bt_text_id;
                $ids[] = $row->bt_text_id;
                $i++;
            }
            // Need to send enough orphan IDs to the child at a time to fill a blob,
            // so orphanBatchSize needs to be at least ~100.
            // batchSize can be smaller or larger.
            while ( count( $ids ) > $this->orphanBatchSize ) {
                $args = array_slice( $ids, 0, $this->orphanBatchSize );
                $ids = array_slice( $ids, $this->orphanBatchSize );
                array_unshift( $args, 'doOrphanList' );
                $this->dispatch( ...$args );
            }
            if ( count( $ids ) ) {
                $args = $ids;
                array_unshift( $args, 'doOrphanList' );
                $this->dispatch( ...$args );
            }

            $this->report( 'orphans', $i, $numOrphans );
        }
        $this->report( 'orphans', $i, $numOrphans );
        $this->info( "All orphans queued." );
    }

    function executeChild() {
        $this->debug( 'starting' );
        $this->syncDBs();

        while ( !feof( STDIN ) ) {
            $line = rtrim( fgets( STDIN ) );
            if ( $line == '' ) {
                continue;
            }
            $this->debug( $line );
            $args = explode( ' ', $line );
            $cmd = array_shift( $args );
            switch ( $cmd ) {
                case 'doPage':
                    $this->doPage( intval( $args[0] ) );
                    break;
                case 'doOrphanList':
                    $this->doOrphanList( array_map( 'intval', $args ) );
                    break;
                case 'quit':
                    return;
            }
            MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
        }
    }

    function doPage( $pageId ) {
        $title = Title::newFromID( $pageId );
        if ( $title ) {
            $titleText = $title->getPrefixedText();
        } else {
            $titleText = '[deleted]';
        }
        $dbr = wfGetDB( DB_REPLICA );

        // Finish any incomplete transactions
        if ( !$this->copyOnly ) {
            $this->finishIncompleteMoves( [ 'bt_page' => $pageId ] );
            $this->syncDBs();
        }

        $startId = 0;
        $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );

        $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
        while ( true ) {
            $res = $dbr->select(
                [ 'blob_tracking', 'text' ],
                '*',
                [
                    'bt_page' => $pageId,
                    'bt_text_id > ' . $dbr->addQuotes( $startId ),
                    'bt_moved' => 0,
                    'bt_new_url IS NULL',
                    'bt_text_id=old_id',
                ],
                __METHOD__,
                [
                    'ORDER BY' => 'bt_text_id',
                    'LIMIT' => $this->batchSize
                ]
            );
            if ( !$res->numRows() ) {
                break;
            }

            $lastTextId = 0;
            foreach ( $res as $row ) {
                $startId = $row->bt_text_id;
                if ( $lastTextId == $row->bt_text_id ) {
                    // Duplicate (null edit)
                    continue;
                }
                $lastTextId = $row->bt_text_id;
                // Load the text
                $text = Revision::getRevisionText( $row );
                if ( $text === false ) {
                    $this->critical( "Error loading {$row->bt_rev_id}/{$row->bt_text_id}" );
                    continue;
                }

                // Queue it
                if ( !$trx->addItem( $text, $row->bt_text_id ) ) {
                    $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
                    $trx->commit();
                    $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
                    $lbFactory->waitForReplication();
                }
            }
        }

        $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
        $trx->commit();
    }

    function moveTextRow( $textId, $url ) {
        if ( $this->copyOnly ) {
            $this->critical( "Internal error: can't call moveTextRow() in --copy-only mode" );
            exit( 1 );
        }
        $dbw = wfGetDB( DB_MASTER );
        $dbw->begin( __METHOD__ );
        $dbw->update( 'text',
            [ // set
                'old_text' => $url,
                'old_flags' => 'external,utf-8',
            ],
            [ // where
                'old_id' => $textId
            ],
            __METHOD__
        );
        $dbw->update( 'blob_tracking',
            [ 'bt_moved' => 1 ],
            [ 'bt_text_id' => $textId ],
            __METHOD__
        );
        $dbw->commit( __METHOD__ );
    }

    function finishIncompleteMoves( $conds ) {
        $dbr = wfGetDB( DB_REPLICA );
        $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();

        $startId = 0;
        $conds = array_merge( $conds, [
            'bt_moved' => 0,
            'bt_new_url IS NOT NULL'
        ] );
        while ( true ) {
            $res = $dbr->select( 'blob_tracking',
                '*',
                array_merge( $conds, [ 'bt_text_id > ' . $dbr->addQuotes( $startId ) ] ),
                __METHOD__,
                [
                    'ORDER BY' => 'bt_text_id',
                    'LIMIT' => $this->batchSize,
                ]
            );
            if ( !$res->numRows() ) {
                break;
            }
            $this->debug( 'Incomplete: ' . $res->numRows() . ' rows' );
            foreach ( $res as $row ) {
                $startId = $row->bt_text_id;
                $this->moveTextRow( $row->bt_text_id, $row->bt_new_url );
                if ( $row->bt_text_id % 10 == 0 ) {
                    $lbFactory->waitForReplication();
                }
            }
        }
    }

    function getTargetCluster() {
        $cluster = next( $this->destClusters );
        if ( $cluster === false ) {
            $cluster = reset( $this->destClusters );
        }

        return $cluster;
    }

    function getExtDB( $cluster ) {
        $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
        $lb = $lbFactory->getExternalLB( $cluster );

        return $lb->getConnection( DB_MASTER );
    }

    function doOrphanList( $textIds ) {
        // Finish incomplete moves
        if ( !$this->copyOnly ) {
            $this->finishIncompleteMoves( [ 'bt_text_id' => $textIds ] );
            $this->syncDBs();
        }

        $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );

        $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
        $res = wfGetDB( DB_REPLICA )->select(
            [ 'text', 'blob_tracking' ],
            [ 'old_id', 'old_text', 'old_flags' ],
            [
                'old_id' => $textIds,
                'bt_text_id=old_id',
                'bt_moved' => 0,
            ],
            __METHOD__,
            [ 'DISTINCT' ]
        );

        foreach ( $res as $row ) {
            $text = Revision::getRevisionText( $row );
            if ( $text === false ) {
                $this->critical( "Error: cannot load revision text for old_id={$row->old_id}" );
                continue;
            }

            if ( !$trx->addItem( $text, $row->old_id ) ) {
                $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
                $trx->commit();
                $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
                $lbFactory->waitForReplication();
            }
        }
        $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
        $trx->commit();
    }
}

class CgzCopyTransaction {
    public $parent;
    public $blobClass;
    public $cgz;
    public $referrers;

    function __construct( $parent, $blobClass ) {
        $this->blobClass = $blobClass;
        $this->cgz = false;
        $this->texts = [];
        $this->parent = $parent;
    }

    function addItem( $text, $textId ) {
        if ( !$this->cgz ) {
            $class = $this->blobClass;
            $this->cgz = new $class;
        }
        $hash = $this->cgz->addItem( $text );
        $this->referrers[$textId] = $hash;
        $this->texts[$textId] = $text;

        return $this->cgz->isHappy();
    }

    function getSize() {
        return count( $this->texts );
    }

    function recompress() {
        $class = $this->blobClass;
        $this->cgz = new $class;
        $this->referrers = [];
        foreach ( $this->texts as $textId => $text ) {
            $hash = $this->cgz->addItem( $text );
            $this->referrers[$textId] = $hash;
        }
    }

    function commit() {
        $originalCount = count( $this->texts );
        if ( !$originalCount ) {
            return;
        }

        /* Check to see if the target text_ids have been moved already.
         *
         * We originally read from the replica DB, so this can happen when a single
         * text_id is shared between multiple pages. It's rare, but possible
         * if a delete/move/undelete cycle splits up a null edit.
         *
         * We do a locking read to prevent closer-run race conditions.
         */
        $dbw = wfGetDB( DB_MASTER );
        $dbw->begin( __METHOD__ );
        $res = $dbw->select( 'blob_tracking',
            [ 'bt_text_id', 'bt_moved' ],
            [ 'bt_text_id' => array_keys( $this->referrers ) ],
            __METHOD__, [ 'FOR UPDATE' ] );
        $dirty = false;
        foreach ( $res as $row ) {
            if ( $row->bt_moved ) {
                # This row has already been moved, remove it
                $this->parent->debug( "TRX: conflict detected in old_id={$row->bt_text_id}" );
                unset( $this->texts[$row->bt_text_id] );
                $dirty = true;
            }
        }

        // Recompress the blob if necessary
        if ( $dirty ) {
            if ( !count( $this->texts ) ) {
                // All have been moved already
                if ( $originalCount > 1 ) {
                    // This is suspcious, make noise
                    $this->parent->critical(
                        "Warning: concurrent operation detected, are there two conflicting " .
                        "processes running, doing the same job?" );
                }

                return;
            }
            $this->recompress();
        }

        // Insert the data into the destination cluster
        $targetCluster = $this->parent->getTargetCluster();
        $store = $this->parent->store;
        $targetDB = $store->getMaster( $targetCluster );
        $targetDB->clearFlag( DBO_TRX ); // we manage the transactions
        $targetDB->begin( __METHOD__ );
        $baseUrl = $this->parent->store->store( $targetCluster, serialize( $this->cgz ) );

        // Write the new URLs to the blob_tracking table
        foreach ( $this->referrers as $textId => $hash ) {
            $url = $baseUrl . '/' . $hash;
            $dbw->update( 'blob_tracking',
                [ 'bt_new_url' => $url ],
                [
                    'bt_text_id' => $textId,
                    'bt_moved' => 0, # Check for concurrent conflicting update
                ],
                __METHOD__
            );
        }

        $targetDB->commit( __METHOD__ );
        // Critical section here: interruption at this point causes blob duplication
        // Reversing the order of the commits would cause data loss instead
        $dbw->commit( __METHOD__ );

        // Write the new URLs to the text table and set the moved flag
        if ( !$this->parent->copyOnly ) {
            foreach ( $this->referrers as $textId => $hash ) {
                $url = $baseUrl . '/' . $hash;
                $this->parent->moveTextRow( $textId, $url );
            }
        }
    }
}