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 type => 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                         wfSuppressWarnings();
 119                         $handle = fopen( $this->getLockPath( $path ), 'a+' );
 120                         wfRestoreWarnings();
 121                         if ( !$handle ) { // lock dir missing?
 122                                 wfMkdirParents( $this->lockDir );
 123                                 $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
 124                         }
 125                         if ( $handle ) {
 126                                 // Either a shared or exclusive lock
 127                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 128                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 129                                         // Record this lock as active
 130                                         $this->locksHeld[$path][$type] = 1;
 131                                         $this->handles[$path][$type] = $handle;
 132                                 } else {
 133                                         fclose( $handle );
 134                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 135                                 }
 136                         } else {
 137                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 138                         }
 139                 }
 140
 141                 return $status;
 142         }
 143
 144         /**
 145          * Unlock a single resource key
 146          *
 147          * @param $path string
 148          * @param $type integer
 149          * @return Status
 150          */
 151         protected function doSingleUnlock( $path, $type ) {
 152                 $status = Status::newGood();
 153
 154                 if ( !isset( $this->locksHeld[$path] ) ) {
 155                         $status->warning( 'lockmanager-notlocked', $path );
 156                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 157                         $status->warning( 'lockmanager-notlocked', $path );
 158                 } else {
 159                         $handlesToClose = array();
 160                         --$this->locksHeld[$path][$type];
 161                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 162                                 unset( $this->locksHeld[$path][$type] );
 163                                 // If a LOCK_SH comes in while we have a LOCK_EX, we don't
 164                                 // actually add a handler, so check for handler existence.
 165                                 if ( isset( $this->handles[$path][$type] ) ) {
 166                                         if ( $type === self::LOCK_EX
 167                                                 && isset( $this->locksHeld[$path][self::LOCK_SH] )
 168                                                 && !isset( $this->handles[$path][self::LOCK_SH] ) )
 169                                         {
 170                                                 // EX lock came first: move this handle to the SH one
 171                                                 $this->handles[$path][self::LOCK_SH] = $this->handles[$path][$type];
 172                                         } else {
 173                                                 // Mark this handle to be unlocked and closed
 174                                                 $handlesToClose[] = $this->handles[$path][$type];
 175                                         }
 176                                         unset( $this->handles[$path][$type] );
 177                                 }
 178                         }
 179                         if ( !count( $this->locksHeld[$path] ) ) {
 180                                 unset( $this->locksHeld[$path] ); // no locks on this path
 181                         }
 182                         // Unlock handles to release locks and delete
 183                         // any lock files that end up with no locks on them...
 184                         if ( wfIsWindows() ) {
 185                                 // Windows: for any process, including this one,
 186                                 // calling unlink() on a locked file will fail
 187                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 188                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 189                         } else {
 190                                 // Unix: unlink() can be used on files currently open by this
 191                                 // process and we must do so in order to avoid race conditions
 192                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 193                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 194                         }
 195                 }
 196
 197                 return $status;
 198         }
 199
 200         /**
 201          * @param $path string
 202          * @param $handlesToClose array
 203          * @return Status
 204          */
 205         private function closeLockHandles( $path, array $handlesToClose ) {
 206                 $status = Status::newGood();
 207                 foreach ( $handlesToClose as $handle ) {
 208                         if ( !flock( $handle, LOCK_UN ) ) {
 209                                 $status->fatal( 'lockmanager-fail-releaselock', $path );
 210                         }
 211                         if ( !fclose( $handle ) ) {
 212                                 $status->warning( 'lockmanager-fail-closelock', $path );
 213                         }
 214                 }
 215                 return $status;
 216         }
 217
 218         /**
 219          * @param $path string
 220          * @return Status
 221          */
 222         private function pruneKeyLockFiles( $path ) {
 223                 $status = Status::newGood();
 224                 if ( !isset( $this->locksHeld[$path] ) ) {
 225                         # No locks are held for the lock file anymore
 226                         if ( !unlink( $this->getLockPath( $path ) ) ) {
 227                                 $status->warning( 'lockmanager-fail-deletelock', $path );
 228                         }
 229                         unset( $this->handles[$path] );
 230                 }
 231                 return $status;
 232         }
 233
 234         /**
 235          * Get the path to the lock file for a key
 236          * @param $path string
 237          * @return string
 238          */
 239         protected function getLockPath( $path ) {
 240                 return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.lock";
 241         }
 242
 243         /**
 244          * Make sure remaining locks get cleared for sanity
 245          */
 246         function __destruct() {
 247                 while ( count( $this->locksHeld ) ) {
 248                         foreach ( $this->locksHeld as $path => $locks ) {
 249                                 $this->doSingleUnlock( $path, self::LOCK_EX );
 250                                 $this->doSingleUnlock( $path, self::LOCK_SH );
 251                         }
 252                 }
 253         }
 254 }