wikimedia / mediawiki

maintenance/syncFileBackend.php

<?php

For compatibility and reusability of your code, PSR1 recommends that a file should introduce either new symbols (like classes, functions, etc.) or have side-effects (like outputting something, or including other files), but not both at the same time. The first symbol is defined on line 32 and the first side effect is on line 24.

/**
 * Sync one file backend to another based on the journal of later.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Maintenance
 */

require_once __DIR__ . '/Maintenance.php';

/**
 * Maintenance script that syncs one file backend to another based on
 * the journal of later.
 *
 * @ingroup Maintenance
 */
class SyncFileBackend extends Maintenance {
	public function __construct() {
		parent::__construct();
		$this->addDescription( '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 ) ) {

The expression $posFile of type string|false is loosely compared to true; this is ambiguous if the string can be empty. You might want to explicitly use !== false instead.

			$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
		}
	}

	/**
	 * Sync $dst backend to $src backend based on the $src logs given after $start.
	 * Returns the journal entry ID this advanced to and handled (inclusive).
	 *
	 * @param FileBackend $src
	 * @param FileBackend $dst
	 * @param int $start Starting journal position
	 * @param int $end Starting journal position
	 * @param Closure $callback Callback to update any position file
	 * @return int|bool Journal entry ID or false if there are none
	 */
	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 );
		}

		$next = null;
		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 = []; // 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;
	}

	/**
	 * Sync particular files of backend $src to the corresponding $dst backend files
	 *
	 * @param array $paths
	 * @param FileBackend $src
	 * @param FileBackend $dst
	 * @return Status
	 */
	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 );

$sLock is not used, you could remove the assignment.

It seems like $sPaths defined by $this->replaceNamePaths($paths, $src) on line 215 can also be of type string; however, FileBackend::getScopedFileLocks() does only seem to accept array, maybe add an additional type check?

		$eLock = $dst->getScopedFileLocks( $dPaths, LockManager::LOCK_EX, $status );

$eLock is not used, you could remove the assignment.

It seems like $dPaths defined by $this->replaceNamePaths($paths, $dst) on line 217 can also be of type string; however, FileBackend::getScopedFileLocks() does only seem to accept array, maybe add an additional type check?

		if ( !$status->isOK() ) {
			return $status;
		}

		$src->preloadFileStat( [ 'srcs' => $sPaths, 'latest' => 1 ] );
		$dst->preloadFileStat( [ 'srcs' => $dPaths, 'latest' => 1 ] );

		$ops = [];
		$fsFiles = [];
		foreach ( $sPaths as $i => $sPath ) {

The expression $sPaths of type string|array<integer,string> is not guaranteed to be traversable. How about adding an additional type check?

			$dPath = $dPaths[$i]; // destination
			$sExists = $src->fileExists( [ '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( [ '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( [
					'dir' => dirname( $dPath ), 'bypassReadOnly' => 1 ] ) );
				if ( !$status->isOK() ) {
					return $status;
				}
				$ops[] = [ 'op' => 'store',
					'src' => $fsFile->getPath(), 'dst' => $dPath, 'overwrite' => 1 ];
			} elseif ( $sExists === false ) { // does not exist in source
				$ops[] = [ '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( $ops, [ 'bypassReadOnly' => 1 ] );
		if ( !$status->isOK() ) {
			sleep( 10 ); // wait and retry copy again
			$status = $dst->doQuickOperations( $ops, [ 'bypassReadOnly' => 1 ] );
		}
		$elapsed_ms = floor( ( microtime( true ) - $t_start ) * 1000 );
		if ( $status->isOK() && $this->getOption( 'verbose' ) ) {
			$this->output( "Synchronized these file(s) [{$elapsed_ms}ms]:\n" .
				implode( "\n", $dPaths ) . "\n" );
		}

		return $status;
	}

	/**
	 * Substitute the backend name of storage paths with that of a given one
	 *
	 * @param array|string $paths List of paths or single string path
	 * @param FileBackend $backend
	 * @return array|string
	 */
	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( [ 'src' => $sPath ] )
				=== $dst->getFileSize( [ 'src' => $dPath ] ) // short-circuit
			) && ( $src->getFileSha1Base36( [ 'src' => $sPath ] )
				=== $dst->getFileSha1Base36( [ 'src' => $dPath ] )
			)
		);
	}
}

$maintClass = "SyncFileBackend";
require_once RUN_MAINTENANCE_IF_MAIN;