syncFileBackend.php

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<?php
require_once __DIR__ . '/Maintenance.php';

class SyncFileBackend extends Maintenance {
    public function __construct() {
        parent::__construct();
        $this->mDescription = "Sync one file backend with another using the journal";
        $this->addOption( 'src', 'Name of backend to sync from', true, true );
        $this->addOption( 'dst', 'Name of destination backend to sync', false, true );
        $this->addOption( 'start', 'Starting journal ID', false, true );
        $this->addOption( 'end', 'Ending journal ID', false, true );
        $this->addOption( 'posdir', 'Directory to read/record journal positions', false, true );
        $this->addOption( 'posdump', 'Just dump current journal position into the position dir.' );
        $this->addOption( 'postime', 'For position dumps, get the ID at this time', false, true );
        $this->addOption( 'backoff', 'Stop at entries younger than this age (sec).', false, true );
        $this->addOption( 'verbose', 'Verbose mode', false, false, 'v' );
        $this->setBatchSize( 50 );
    }

    public function execute() {
        $src = FileBackendGroup::singleton()->get( $this->getOption( 'src' ) );

        $posDir = $this->getOption( 'posdir' );
        $posFile = $posDir ? $posDir . '/' . wfWikiID() : false;

        if ( $this->hasOption( 'posdump' ) ) {
            // Just dump the current position into the specified position dir
            if ( !$this->hasOption( 'posdir' ) ) {
                $this->error( "Param posdir required!", 1 );
            }
            if ( $this->hasOption( 'postime' ) ) {
                $id = (int)$src->getJournal()->getPositionAtTime( $this->getOption( 'postime' ) );
                $this->output( "Requested journal position is $id.\n" );
            } else {
                $id = (int)$src->getJournal()->getCurrentPosition();
                $this->output( "Current journal position is $id.\n" );
            }
            if ( file_put_contents( $posFile, $id, LOCK_EX ) !== false ) {
                $this->output( "Saved journal position file.\n" );
            } else {
                $this->output( "Could not save journal position file.\n" );
            }
            if ( $this->isQuiet() ) {
                print $id; // give a single machine-readable number
            }
            return;
        }

        if ( !$this->hasOption( 'dst' ) ) {
            $this->error( "Param dst required!", 1 );
        }
        $dst = FileBackendGroup::singleton()->get( $this->getOption( 'dst' ) );

        $start = $this->getOption( 'start', 0 );
        if ( !$start && $posFile && is_dir( $posDir ) ) {
            $start = is_file( $posFile )
                ? (int)trim( file_get_contents( $posFile ) )
                : 0;
            ++$start; // we already did this ID, start with the next one
            $startFromPosFile = true;
        } else {
            $startFromPosFile = false;
        }

        if ( $this->hasOption( 'backoff' ) ) {
            $time = time() - $this->getOption( 'backoff', 0 );
            $end = (int)$src->getJournal()->getPositionAtTime( $time );
        } else {
            $end = $this->getOption( 'end', INF );
        }

        $this->output( "Synchronizing backend '{$dst->getName()}' to '{$src->getName()}'...\n" );
        $this->output( "Starting journal position is $start.\n" );
        if ( is_finite( $end ) ) {
            $this->output( "Ending journal position is $end.\n" );
        }

        // Periodically update the position file
        $callback = function( $pos ) use ( $startFromPosFile, $posFile, $start ) {
            if ( $startFromPosFile && $pos >= $start ) { // successfully advanced
                file_put_contents( $posFile, $pos, LOCK_EX );
            }
        };

        // Actually sync the dest backend with the reference backend
        $lastOKPos = $this->syncBackends( $src, $dst, $start, $end, $callback );

        // Update the sync position file
        if ( $startFromPosFile && $lastOKPos >= $start ) { // successfully advanced
            if ( file_put_contents( $posFile, $lastOKPos, LOCK_EX ) !== false ) {
                $this->output( "Updated journal position file.\n" );
            } else {
                $this->output( "Could not update journal position file.\n" );
            }
        }

        if ( $lastOKPos === false ) {
            if ( !$start ) {
                $this->output( "No journal entries found.\n" );
            } else {
                $this->output( "No new journal entries found.\n" );
            }
        } else {
            $this->output( "Stopped synchronization at journal position $lastOKPos.\n" );
        }

        if ( $this->isQuiet() ) {
            print $lastOKPos; // give a single machine-readable number
        }
    }

    protected function syncBackends(
        FileBackend $src, FileBackend $dst, $start, $end, Closure $callback
    ) {
        $lastOKPos = 0; // failed
        $first = true; // first batch

        if ( $start > $end ) { // sanity
            $this->error( "Error: given starting ID greater than ending ID.", 1 );
        }

        do {
            $limit = min( $this->mBatchSize, $end - $start + 1 ); // don't go pass ending ID
            $this->output( "Doing id $start to " . ( $start + $limit - 1 ) . "...\n" );

            $entries = $src->getJournal()->getChangeEntries( $start, $limit, $next );
            $start = $next; // start where we left off next time
            if ( $first && !count( $entries ) ) {
                return false; // nothing to do
            }
            $first = false;

            $lastPosInBatch = 0;
            $pathsInBatch = array(); // changed paths
            foreach ( $entries as $entry ) {
                if ( $entry['op'] !== 'null' ) { // null ops are just for reference
                    $pathsInBatch[$entry['path']] = 1; // remove duplicates
                }
                $lastPosInBatch = $entry['id'];
            }

            $status = $this->syncFileBatch( array_keys( $pathsInBatch ), $src, $dst );
            if ( $status->isOK() ) {
                $lastOKPos = max( $lastOKPos, $lastPosInBatch );
                $callback( $lastOKPos ); // update position file
            } else {
                $this->error( print_r( $status->getErrorsArray(), true ) );
                break; // no gaps; everything up to $lastPos must be OK
            }

            if ( !$start ) {
                $this->output( "End of journal entries.\n" );
            }
        } while ( $start && $start <= $end );

        return $lastOKPos;
    }

    protected function syncFileBatch( array $paths, FileBackend $src, FileBackend $dst ) {
        $status = Status::newGood();
        if ( !count( $paths ) ) {
            return $status; // nothing to do
        }

        // Source: convert internal backend names (FileBackendMultiWrite) to the public one
        $sPaths = $this->replaceNamePaths( $paths, $src );
        // Destination: get corresponding path name
        $dPaths = $this->replaceNamePaths( $paths, $dst );

        // Lock the live backend paths from modification
        $sLock = $src->getScopedFileLocks( $sPaths, LockManager::LOCK_UW, $status );
        $eLock = $dst->getScopedFileLocks( $dPaths, LockManager::LOCK_EX, $status );
        if ( !$status->isOK() ) {
            return $status;
        }

        $ops = array();
        $fsFiles = array();
        foreach ( $sPaths as $i => $sPath ) {
            $dPath = $dPaths[$i]; // destination
            $sExists = $src->fileExists( array( 'src' => $sPath, 'latest' => 1 ) );
            if ( $sExists === true ) { // exists in source
                if ( $this->filesAreSame( $src, $dst, $sPath, $dPath ) ) {
                    continue; // avoid local copies for non-FS backends
                }
                // Note: getLocalReference() is fast for FS backends
                $fsFile = $src->getLocalReference( array( 'src' => $sPath, 'latest' => 1 ) );
                if ( !$fsFile ) {
                    $this->error( "Unable to sync '$dPath': could not get local copy." );
                    $status->fatal( 'backend-fail-internal', $src->getName() );
                    return $status;
                }
                $fsFiles[] = $fsFile; // keep TempFSFile objects alive as needed
                // Note: prepare() is usually fast for key/value backends
                $status->merge( $dst->prepare( array(
                    'dir' => dirname( $dPath ), 'bypassReadOnly' => 1 ) ) );
                if ( !$status->isOK() ) {
                    return $status;
                }
                $ops[] = array( 'op' => 'store',
                    'src' => $fsFile->getPath(), 'dst' => $dPath, 'overwrite' => 1 );
            } elseif ( $sExists === false ) { // does not exist in source
                $ops[] = array( 'op' => 'delete', 'src' => $dPath, 'ignoreMissingSource' => 1 );
            } else { // error
                $this->error( "Unable to sync '$dPath': could not stat file." );
                $status->fatal( 'backend-fail-internal', $src->getName() );
                return $status;
            }
        }

        $t_start = microtime( true );
        $status = $dst->doQuickOperations( $ops, array( 'bypassReadOnly' => 1 ) );
        if ( !$status->isOK() ) {
            sleep( 10 ); // wait and retry copy again
            $status = $dst->doQuickOperations( $ops, array( 'bypassReadOnly' => 1 ) );
        }
        $ellapsed_ms = floor( ( microtime( true ) - $t_start ) * 1000 );
        if ( $status->isOK() && $this->getOption( 'verbose' ) ) {
            $this->output( "Synchronized these file(s) [{$ellapsed_ms}ms]:\n" .
                implode( "\n", $dPaths ) . "\n" );
        }

        return $status;
    }

    protected function replaceNamePaths( $paths, FileBackend $backend ) {
        return preg_replace(
            '!^mwstore://([^/]+)!',
            StringUtils::escapeRegexReplacement( "mwstore://" . $backend->getName() ),
            $paths // string or array
        );
    }

    protected function filesAreSame( FileBackend $src, FileBackend $dst, $sPath, $dPath ) {
        return (
            ( $src->getFileSize( array( 'src' => $sPath ) )
                === $dst->getFileSize( array( 'src' => $dPath ) ) // short-circuit
            ) && ( $src->getFileSha1Base36( array( 'src' => $sPath ) )
                === $dst->getFileSha1Base36( array( 'src' => $dPath ) )
            )
        );
    }
}

$maintClass = "SyncFileBackend";
require_once RUN_MAINTENANCE_IF_MAIN;