includes/libs/lockmanager/FSLockManager.php

   1 <?php
   2 /**
   3  * Simple version of LockManager based on using FS lock files.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup LockManager
  22  */
  23
  24 /**
  25  * Simple version of LockManager based on using FS lock files.
  26  * All locks are non-blocking, which avoids deadlocks.
  27  *
  28  * This should work fine for small sites running off one server.
  29  * Do not use this with 'lockDirectory' set to an NFS mount unless the
  30  * NFS client is at least version 2.6.12. Otherwise, the BSD flock()
  31  * locks will be ignored; see http://nfs.sourceforge.net/#section_d.
  32  *
  33  * @ingroup LockManager
  34  * @since 1.19
  35  */
  36 class FSLockManager extends LockManager {
  37         /** @var array Mapping of lock types to the type actually used */
  38         protected $lockTypeMap = [
  39                 self::LOCK_SH => self::LOCK_SH,
  40                 self::LOCK_UW => self::LOCK_SH,
  41                 self::LOCK_EX => self::LOCK_EX
  42         ];
  43
  44         /** @var string Global dir for all servers */
  45         protected $lockDir;
  46
  47         /** @var array Map of (locked key => lock file handle) */
  48         protected $handles = [];
  49
  50         /** @var bool */
  51         protected $isWindows;
  52
  53         /**
  54          * Construct a new instance from configuration.
  55          *
  56          * @param array $config Includes:
  57          *   - lockDirectory : Directory containing the lock files
  58          */
  59         function __construct( array $config ) {
  60                 parent::__construct( $config );
  61
  62                 $this->lockDir = $config['lockDirectory'];
  63                 $this->isWindows = ( strtoupper( substr( PHP_OS, 0, 3 ) ) === 'WIN' );
  64         }
  65
  66         /**
  67          * @see LockManager::doLock()
  68          * @param array $paths
  69          * @param int $type
  70          * @return StatusValue
  71          */
  72         protected function doLock( array $paths, $type ) {
  73                 $status = StatusValue::newGood();
  74
  75                 $lockedPaths = []; // files locked in this attempt
  76                 foreach ( $paths as $path ) {
  77                         $status->merge( $this->doSingleLock( $path, $type ) );
  78                         if ( $status->isOK() ) {
  79                                 $lockedPaths[] = $path;
  80                         } else {
  81                                 // Abort and unlock everything
  82                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
  83
  84                                 return $status;
  85                         }
  86                 }
  87
  88                 return $status;
  89         }
  90
  91         /**
  92          * @see LockManager::doUnlock()
  93          * @param array $paths
  94          * @param int $type
  95          * @return StatusValue
  96          */
  97         protected function doUnlock( array $paths, $type ) {
  98                 $status = StatusValue::newGood();
  99
 100                 foreach ( $paths as $path ) {
 101                         $status->merge( $this->doSingleUnlock( $path, $type ) );
 102                 }
 103
 104                 return $status;
 105         }
 106
 107         /**
 108          * Lock a single resource key
 109          *
 110          * @param string $path
 111          * @param int $type
 112          * @return StatusValue
 113          */
 114         protected function doSingleLock( $path, $type ) {
 115                 $status = StatusValue::newGood();
 116
 117                 if ( isset( $this->locksHeld[$path][$type] ) ) {
 118                         ++$this->locksHeld[$path][$type];
 119                 } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 120                         $this->locksHeld[$path][$type] = 1;
 121                 } else {
 122                         if ( isset( $this->handles[$path] ) ) {
 123                                 $handle = $this->handles[$path];
 124                         } else {
 125                                 MediaWiki\suppressWarnings();
 126                                 $handle = fopen( $this->getLockPath( $path ), 'a+' );
 127                                 if ( !$handle ) { // lock dir missing?
 128                                         mkdir( $this->lockDir, 0777, true );
 129                                         $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
 130                                 }
 131                                 MediaWiki\restoreWarnings();
 132                         }
 133                         if ( $handle ) {
 134                                 // Either a shared or exclusive lock
 135                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 136                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 137                                         // Record this lock as active
 138                                         $this->locksHeld[$path][$type] = 1;
 139                                         $this->handles[$path] = $handle;
 140                                 } else {
 141                                         fclose( $handle );
 142                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 143                                 }
 144                         } else {
 145                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 146                         }
 147                 }
 148
 149                 return $status;
 150         }
 151
 152         /**
 153          * Unlock a single resource key
 154          *
 155          * @param string $path
 156          * @param int $type
 157          * @return StatusValue
 158          */
 159         protected function doSingleUnlock( $path, $type ) {
 160                 $status = StatusValue::newGood();
 161
 162                 if ( !isset( $this->locksHeld[$path] ) ) {
 163                         $status->warning( 'lockmanager-notlocked', $path );
 164                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 165                         $status->warning( 'lockmanager-notlocked', $path );
 166                 } else {
 167                         $handlesToClose = [];
 168                         --$this->locksHeld[$path][$type];
 169                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 170                                 unset( $this->locksHeld[$path][$type] );
 171                         }
 172                         if ( !count( $this->locksHeld[$path] ) ) {
 173                                 unset( $this->locksHeld[$path] ); // no locks on this path
 174                                 if ( isset( $this->handles[$path] ) ) {
 175                                         $handlesToClose[] = $this->handles[$path];
 176                                         unset( $this->handles[$path] );
 177                                 }
 178                         }
 179                         // Unlock handles to release locks and delete
 180                         // any lock files that end up with no locks on them...
 181                         if ( $this->isWindows ) {
 182                                 // Windows: for any process, including this one,
 183                                 // calling unlink() on a locked file will fail
 184                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 185                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 186                         } else {
 187                                 // Unix: unlink() can be used on files currently open by this
 188                                 // process and we must do so in order to avoid race conditions
 189                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 190                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 191                         }
 192                 }
 193
 194                 return $status;
 195         }
 196
 197         /**
 198          * @param string $path
 199          * @param array $handlesToClose
 200          * @return StatusValue
 201          */
 202         private function closeLockHandles( $path, array $handlesToClose ) {
 203                 $status = StatusValue::newGood();
 204                 foreach ( $handlesToClose as $handle ) {
 205                         if ( !flock( $handle, LOCK_UN ) ) {
 206                                 $status->fatal( 'lockmanager-fail-releaselock', $path );
 207                         }
 208                         if ( !fclose( $handle ) ) {
 209                                 $status->warning( 'lockmanager-fail-closelock', $path );
 210                         }
 211                 }
 212
 213                 return $status;
 214         }
 215
 216         /**
 217          * @param string $path
 218          * @return StatusValue
 219          */
 220         private function pruneKeyLockFiles( $path ) {
 221                 $status = StatusValue::newGood();
 222                 if ( !isset( $this->locksHeld[$path] ) ) {
 223                         # No locks are held for the lock file anymore
 224                         if ( !unlink( $this->getLockPath( $path ) ) ) {
 225                                 $status->warning( 'lockmanager-fail-deletelock', $path );
 226                         }
 227                         unset( $this->handles[$path] );
 228                 }
 229
 230                 return $status;
 231         }
 232
 233         /**
 234          * Get the path to the lock file for a key
 235          * @param string $path
 236          * @return string
 237          */
 238         protected function getLockPath( $path ) {
 239                 return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.lock";
 240         }
 241
 242         /**
 243          * Make sure remaining locks get cleared for sanity
 244          */
 245         function __destruct() {
 246                 while ( count( $this->locksHeld ) ) {
 247                         foreach ( $this->locksHeld as $path => $locks ) {
 248                                 $this->doSingleUnlock( $path, self::LOCK_EX );
 249                                 $this->doSingleUnlock( $path, self::LOCK_SH );
 250                         }
 251                 }
 252         }
 253 }