includes/filebackend/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 = array(
  39                 self::LOCK_SH => self::LOCK_SH,
  40                 self::LOCK_UW => self::LOCK_SH,
  41                 self::LOCK_EX => self::LOCK_EX
  42         );
  43
  44         protected $lockDir; // global dir for all servers
  45
  46         /** @var Array Map of (locked key => lock file handle) */
  47         protected $handles = array();
  48
  49         /**
  50          * Construct a new instance from configuration.
  51          *
  52          * $config includes:
  53          *   - lockDirectory : Directory containing the lock files
  54          *
  55          * @param array $config
  56          */
  57         function __construct( array $config ) {
  58                 parent::__construct( $config );
  59
  60                 $this->lockDir = $config['lockDirectory'];
  61         }
  62
  63         /**
  64          * @see LockManager::doLock()
  65          * @param $paths array
  66          * @param $type int
  67          * @return Status
  68          */
  69         protected function doLock( array $paths, $type ) {
  70                 $status = Status::newGood();
  71
  72                 $lockedPaths = array(); // files locked in this attempt
  73                 foreach ( $paths as $path ) {
  74                         $status->merge( $this->doSingleLock( $path, $type ) );
  75                         if ( $status->isOK() ) {
  76                                 $lockedPaths[] = $path;
  77                         } else {
  78                                 // Abort and unlock everything
  79                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
  80                                 return $status;
  81                         }
  82                 }
  83
  84                 return $status;
  85         }
  86
  87         /**
  88          * @see LockManager::doUnlock()
  89          * @param $paths array
  90          * @param $type int
  91          * @return Status
  92          */
  93         protected function doUnlock( array $paths, $type ) {
  94                 $status = Status::newGood();
  95
  96                 foreach ( $paths as $path ) {
  97                         $status->merge( $this->doSingleUnlock( $path, $type ) );
  98                 }
  99
 100                 return $status;
 101         }
 102
 103         /**
 104          * Lock a single resource key
 105          *
 106          * @param $path string
 107          * @param $type integer
 108          * @return Status
 109          */
 110         protected function doSingleLock( $path, $type ) {
 111                 $status = Status::newGood();
 112
 113                 if ( isset( $this->locksHeld[$path][$type] ) ) {
 114                         ++$this->locksHeld[$path][$type];
 115                 } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 116                         $this->locksHeld[$path][$type] = 1;
 117                 } else {
 118                         if ( isset( $this->handles[$path] ) ) {
 119                                 $handle = $this->handles[$path];
 120                         } else {
 121                                 wfSuppressWarnings();
 122                                 $handle = fopen( $this->getLockPath( $path ), 'a+' );
 123                                 wfRestoreWarnings();
 124                                 if ( !$handle ) { // lock dir missing?
 125                                         wfMkdirParents( $this->lockDir );
 126                                         $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
 127                                 }
 128                         }
 129                         if ( $handle ) {
 130                                 // Either a shared or exclusive lock
 131                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 132                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 133                                         // Record this lock as active
 134                                         $this->locksHeld[$path][$type] = 1;
 135                                         $this->handles[$path] = $handle;
 136                                 } else {
 137                                         fclose( $handle );
 138                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 139                                 }
 140                         } else {
 141                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 142                         }
 143                 }
 144
 145                 return $status;
 146         }
 147
 148         /**
 149          * Unlock a single resource key
 150          *
 151          * @param $path string
 152          * @param $type integer
 153          * @return Status
 154          */
 155         protected function doSingleUnlock( $path, $type ) {
 156                 $status = Status::newGood();
 157
 158                 if ( !isset( $this->locksHeld[$path] ) ) {
 159                         $status->warning( 'lockmanager-notlocked', $path );
 160                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 161                         $status->warning( 'lockmanager-notlocked', $path );
 162                 } else {
 163                         $handlesToClose = array();
 164                         --$this->locksHeld[$path][$type];
 165                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 166                                 unset( $this->locksHeld[$path][$type] );
 167                         }
 168                         if ( !count( $this->locksHeld[$path] ) ) {
 169                                 unset( $this->locksHeld[$path] ); // no locks on this path
 170                                 if ( isset( $this->handles[$path] ) ) {
 171                                         $handlesToClose[] = $this->handles[$path];
 172                                         unset( $this->handles[$path] );
 173                                 }
 174                         }
 175                         // Unlock handles to release locks and delete
 176                         // any lock files that end up with no locks on them...
 177                         if ( wfIsWindows() ) {
 178                                 // Windows: for any process, including this one,
 179                                 // calling unlink() on a locked file will fail
 180                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 181                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 182                         } else {
 183                                 // Unix: unlink() can be used on files currently open by this
 184                                 // process and we must do so in order to avoid race conditions
 185                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 186                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 187                         }
 188                 }
 189
 190                 return $status;
 191         }
 192
 193         /**
 194          * @param $path string
 195          * @param $handlesToClose array
 196          * @return Status
 197          */
 198         private function closeLockHandles( $path, array $handlesToClose ) {
 199                 $status = Status::newGood();
 200                 foreach ( $handlesToClose as $handle ) {
 201                         if ( !flock( $handle, LOCK_UN ) ) {
 202                                 $status->fatal( 'lockmanager-fail-releaselock', $path );
 203                         }
 204                         if ( !fclose( $handle ) ) {
 205                                 $status->warning( 'lockmanager-fail-closelock', $path );
 206                         }
 207                 }
 208                 return $status;
 209         }
 210
 211         /**
 212          * @param $path string
 213          * @return Status
 214          */
 215         private function pruneKeyLockFiles( $path ) {
 216                 $status = Status::newGood();
 217                 if ( !isset( $this->locksHeld[$path] ) ) {
 218                         # No locks are held for the lock file anymore
 219                         if ( !unlink( $this->getLockPath( $path ) ) ) {
 220                                 $status->warning( 'lockmanager-fail-deletelock', $path );
 221                         }
 222                         unset( $this->handles[$path] );
 223                 }
 224                 return $status;
 225         }
 226
 227         /**
 228          * Get the path to the lock file for a key
 229          * @param $path string
 230          * @return string
 231          */
 232         protected function getLockPath( $path ) {
 233                 return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.lock";
 234         }
 235
 236         /**
 237          * Make sure remaining locks get cleared for sanity
 238          */
 239         function __destruct() {
 240                 while ( count( $this->locksHeld ) ) {
 241                         foreach ( $this->locksHeld as $path => $locks ) {
 242                                 $this->doSingleUnlock( $path, self::LOCK_EX );
 243                                 $this->doSingleUnlock( $path, self::LOCK_SH );
 244                         }
 245                 }
 246         }
 247 }