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Diffstat (limited to 'includes/filebackend/lockmanager/FSLockManager.php')
-rw-r--r-- | includes/filebackend/lockmanager/FSLockManager.php | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/includes/filebackend/lockmanager/FSLockManager.php b/includes/filebackend/lockmanager/FSLockManager.php new file mode 100644 index 00000000..9a6206fd --- /dev/null +++ b/includes/filebackend/lockmanager/FSLockManager.php @@ -0,0 +1,255 @@ +<?php +/** + * Simple version of LockManager based on using FS lock files. + * + * 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 LockManager + */ + +/** + * Simple version of LockManager based on using FS lock files. + * All locks are non-blocking, which avoids deadlocks. + * + * This should work fine for small sites running off one server. + * Do not use this with 'lockDirectory' set to an NFS mount unless the + * NFS client is at least version 2.6.12. Otherwise, the BSD flock() + * locks will be ignored; see http://nfs.sourceforge.net/#section_d. + * + * @ingroup LockManager + * @since 1.19 + */ +class FSLockManager extends LockManager { + /** @var Array Mapping of lock types to the type actually used */ + protected $lockTypeMap = array( + self::LOCK_SH => self::LOCK_SH, + self::LOCK_UW => self::LOCK_SH, + self::LOCK_EX => self::LOCK_EX + ); + + protected $lockDir; // global dir for all servers + + /** @var Array Map of (locked key => lock type => lock file handle) */ + protected $handles = array(); + + /** + * Construct a new instance from configuration. + * + * $config includes: + * - lockDirectory : Directory containing the lock files + * + * @param array $config + */ + function __construct( array $config ) { + parent::__construct( $config ); + + $this->lockDir = $config['lockDirectory']; + } + + /** + * @see LockManager::doLock() + * @param $paths array + * @param $type int + * @return Status + */ + protected function doLock( array $paths, $type ) { + $status = Status::newGood(); + + $lockedPaths = array(); // files locked in this attempt + foreach ( $paths as $path ) { + $status->merge( $this->doSingleLock( $path, $type ) ); + if ( $status->isOK() ) { + $lockedPaths[] = $path; + } else { + // Abort and unlock everything + $status->merge( $this->doUnlock( $lockedPaths, $type ) ); + return $status; + } + } + + return $status; + } + + /** + * @see LockManager::doUnlock() + * @param $paths array + * @param $type int + * @return Status + */ + protected function doUnlock( array $paths, $type ) { + $status = Status::newGood(); + + foreach ( $paths as $path ) { + $status->merge( $this->doSingleUnlock( $path, $type ) ); + } + + return $status; + } + + /** + * Lock a single resource key + * + * @param $path string + * @param $type integer + * @return Status + */ + protected function doSingleLock( $path, $type ) { + $status = Status::newGood(); + + if ( isset( $this->locksHeld[$path][$type] ) ) { + ++$this->locksHeld[$path][$type]; + } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) { + $this->locksHeld[$path][$type] = 1; + } else { + wfSuppressWarnings(); + $handle = fopen( $this->getLockPath( $path ), 'a+' ); + wfRestoreWarnings(); + if ( !$handle ) { // lock dir missing? + wfMkdirParents( $this->lockDir ); + $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again + } + if ( $handle ) { + // Either a shared or exclusive lock + $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX; + if ( flock( $handle, $lock | LOCK_NB ) ) { + // Record this lock as active + $this->locksHeld[$path][$type] = 1; + $this->handles[$path][$type] = $handle; + } else { + fclose( $handle ); + $status->fatal( 'lockmanager-fail-acquirelock', $path ); + } + } else { + $status->fatal( 'lockmanager-fail-openlock', $path ); + } + } + + return $status; + } + + /** + * Unlock a single resource key + * + * @param $path string + * @param $type integer + * @return Status + */ + protected function doSingleUnlock( $path, $type ) { + $status = Status::newGood(); + + if ( !isset( $this->locksHeld[$path] ) ) { + $status->warning( 'lockmanager-notlocked', $path ); + } elseif ( !isset( $this->locksHeld[$path][$type] ) ) { + $status->warning( 'lockmanager-notlocked', $path ); + } else { + $handlesToClose = array(); + --$this->locksHeld[$path][$type]; + if ( $this->locksHeld[$path][$type] <= 0 ) { + unset( $this->locksHeld[$path][$type] ); + // If a LOCK_SH comes in while we have a LOCK_EX, we don't + // actually add a handler, so check for handler existence. + if ( isset( $this->handles[$path][$type] ) ) { + if ( $type === self::LOCK_EX + && isset( $this->locksHeld[$path][self::LOCK_SH] ) + && !isset( $this->handles[$path][self::LOCK_SH] ) ) + { + // EX lock came first: move this handle to the SH one + $this->handles[$path][self::LOCK_SH] = $this->handles[$path][$type]; + } else { + // Mark this handle to be unlocked and closed + $handlesToClose[] = $this->handles[$path][$type]; + } + unset( $this->handles[$path][$type] ); + } + } + if ( !count( $this->locksHeld[$path] ) ) { + unset( $this->locksHeld[$path] ); // no locks on this path + } + // Unlock handles to release locks and delete + // any lock files that end up with no locks on them... + if ( wfIsWindows() ) { + // Windows: for any process, including this one, + // calling unlink() on a locked file will fail + $status->merge( $this->closeLockHandles( $path, $handlesToClose ) ); + $status->merge( $this->pruneKeyLockFiles( $path ) ); + } else { + // Unix: unlink() can be used on files currently open by this + // process and we must do so in order to avoid race conditions + $status->merge( $this->pruneKeyLockFiles( $path ) ); + $status->merge( $this->closeLockHandles( $path, $handlesToClose ) ); + } + } + + return $status; + } + + /** + * @param $path string + * @param $handlesToClose array + * @return Status + */ + private function closeLockHandles( $path, array $handlesToClose ) { + $status = Status::newGood(); + foreach ( $handlesToClose as $handle ) { + if ( !flock( $handle, LOCK_UN ) ) { + $status->fatal( 'lockmanager-fail-releaselock', $path ); + } + if ( !fclose( $handle ) ) { + $status->warning( 'lockmanager-fail-closelock', $path ); + } + } + return $status; + } + + /** + * @param $path string + * @return Status + */ + private function pruneKeyLockFiles( $path ) { + $status = Status::newGood(); + if ( !isset( $this->locksHeld[$path] ) ) { + # No locks are held for the lock file anymore + if ( !unlink( $this->getLockPath( $path ) ) ) { + $status->warning( 'lockmanager-fail-deletelock', $path ); + } + unset( $this->handles[$path] ); + } + return $status; + } + + /** + * Get the path to the lock file for a key + * @param $path string + * @return string + */ + protected function getLockPath( $path ) { + $hash = self::sha1Base36( $path ); + return "{$this->lockDir}/{$hash}.lock"; + } + + /** + * Make sure remaining locks get cleared for sanity + */ + function __destruct() { + while ( count( $this->locksHeld ) ) { + foreach ( $this->locksHeld as $path => $locks ) { + $this->doSingleUnlock( $path, self::LOCK_EX ); + $this->doSingleUnlock( $path, self::LOCK_SH ); + } + } + } +} |