includes/filerepo/backend/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          * @return Status
  66          */
  67         protected function doLock( array $paths, $type ) {
  68                 $status = Status::newGood();
  69
  70                 $lockedPaths = array(); // files locked in this attempt
  71                 foreach ( $paths as $path ) {
  72                         $status->merge( $this->doSingleLock( $path, $type ) );
  73                         if ( $status->isOK() ) {
  74                                 $lockedPaths[] = $path;
  75                         } else {
  76                                 // Abort and unlock everything
  77                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
  78                                 return $status;
  79                         }
  80                 }
  81
  82                 return $status;
  83         }
  84
  85         /**
  86          * @see LockManager::doUnlock()
  87          * @return Status
  88          */
  89         protected function doUnlock( array $paths, $type ) {
  90                 $status = Status::newGood();
  91
  92                 foreach ( $paths as $path ) {
  93                         $status->merge( $this->doSingleUnlock( $path, $type ) );
  94                 }
  95
  96                 return $status;
  97         }
  98
  99         /**
 100          * Lock a single resource key
 101          *
 102          * @param $path string
 103          * @param $type integer
 104          * @return Status
 105          */
 106         protected function doSingleLock( $path, $type ) {
 107                 $status = Status::newGood();
 108
 109                 if ( isset( $this->locksHeld[$path][$type] ) ) {
 110                         ++$this->locksHeld[$path][$type];
 111                 } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 112                         $this->locksHeld[$path][$type] = 1;
 113                 } else {
 114                         wfSuppressWarnings();
 115                         $handle = fopen( $this->getLockPath( $path ), 'a+' );
 116                         wfRestoreWarnings();
 117                         if ( !$handle ) { // lock dir missing?
 118                                 wfMkdirParents( $this->lockDir );
 119                                 $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
 120                         }
 121                         if ( $handle ) {
 122                                 // Either a shared or exclusive lock
 123                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 124                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 125                                         // Record this lock as active
 126                                         $this->locksHeld[$path][$type] = 1;
 127                                         $this->handles[$path][$type] = $handle;
 128                                 } else {
 129                                         fclose( $handle );
 130                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 131                                 }
 132                         } else {
 133                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 134                         }
 135                 }
 136
 137                 return $status;
 138         }
 139
 140         /**
 141          * Unlock a single resource key
 142          *
 143          * @param $path string
 144          * @param $type integer
 145          * @return Status
 146          */
 147         protected function doSingleUnlock( $path, $type ) {
 148                 $status = Status::newGood();
 149
 150                 if ( !isset( $this->locksHeld[$path] ) ) {
 151                         $status->warning( 'lockmanager-notlocked', $path );
 152                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 153                         $status->warning( 'lockmanager-notlocked', $path );
 154                 } else {
 155                         $handlesToClose = array();
 156                         --$this->locksHeld[$path][$type];
 157                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 158                                 unset( $this->locksHeld[$path][$type] );
 159                                 // If a LOCK_SH comes in while we have a LOCK_EX, we don't
 160                                 // actually add a handler, so check for handler existence.
 161                                 if ( isset( $this->handles[$path][$type] ) ) {
 162                                         if ( $type === self::LOCK_EX
 163                                                 && isset( $this->locksHeld[$path][self::LOCK_SH] )
 164                                                 && !isset( $this->handles[$path][self::LOCK_SH] ) )
 165                                         {
 166                                                 // EX lock came first: move this handle to the SH one
 167                                                 $this->handles[$path][self::LOCK_SH] = $this->handles[$path][$type];
 168                                         } else {
 169                                                 // Mark this handle to be unlocked and closed
 170                                                 $handlesToClose[] = $this->handles[$path][$type];
 171                                         }
 172                                         unset( $this->handles[$path][$type] );
 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         private function closeLockHandles( $path, array $handlesToClose ) {
 194                 $status = Status::newGood();
 195                 foreach ( $handlesToClose as $handle ) {
 196                         if ( !flock( $handle, LOCK_UN ) ) {
 197                                 $status->fatal( 'lockmanager-fail-releaselock', $path );
 198                         }
 199                         if ( !fclose( $handle ) ) {
 200                                 $status->warning( 'lockmanager-fail-closelock', $path );
 201                         }
 202                 }
 203                 return $status;
 204         }
 205
 206         private function pruneKeyLockFiles( $path ) {
 207                 $status = Status::newGood();
 208                 if ( !count( $this->locksHeld[$path] ) ) {
 209                         # No locks are held for the lock file anymore
 210                         if ( !unlink( $this->getLockPath( $path ) ) ) {
 211                                 $status->warning( 'lockmanager-fail-deletelock', $path );
 212                         }
 213                         unset( $this->locksHeld[$path] );
 214                         unset( $this->handles[$path] );
 215                 }
 216                 return $status;
 217         }
 218
 219         /**
 220          * Get the path to the lock file for a key
 221          * @param $path string
 222          * @return string
 223          */
 224         protected function getLockPath( $path ) {
 225                 $hash = self::sha1Base36( $path );
 226                 return "{$this->lockDir}/{$hash}.lock";
 227         }
 228
 229         function __destruct() {
 230                 // Make sure remaining locks get cleared for sanity
 231                 foreach ( $this->locksHeld as $path => $locks ) {
 232                         $this->doSingleUnlock( $path, self::LOCK_EX );
 233                         $this->doSingleUnlock( $path, self::LOCK_SH );
 234                 }
 235         }
 236 }