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<?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 file handle) */
protected $handles = array();
/**
* Construct a new instance from configuration.
*
* @param array $config Includes:
* - lockDirectory : Directory containing the lock files
*/
function __construct( array $config ) {
parent::__construct( $config );
$this->lockDir = $config['lockDirectory'];
}
/**
* @see LockManager::doLock()
* @param array $paths
* @param int $type
* @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 array $paths
* @param int $type
* @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 string $path
* @param int $type
* @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 {
if ( isset( $this->handles[$path] ) ) {
$handle = $this->handles[$path];
} else {
MediaWiki\suppressWarnings();
$handle = fopen( $this->getLockPath( $path ), 'a+' );
MediaWiki\restoreWarnings();
if ( !$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] = $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 string $path
* @param int $type
* @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 ( !count( $this->locksHeld[$path] ) ) {
unset( $this->locksHeld[$path] ); // no locks on this path
if ( isset( $this->handles[$path] ) ) {
$handlesToClose[] = $this->handles[$path];
unset( $this->handles[$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 string $path
* @param array $handlesToClose
* @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 string $path
* @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 string $path
* @return string
*/
protected function getLockPath( $path ) {
return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.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 );
}
}
}
}
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