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 = [
  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 = [];
  48
  49         /**
  50          * Construct a new instance from configuration.
  51          *
  52          * @param array $config Includes:
  53          *   - lockDirectory : Directory containing the lock files
  54          */
  55         function __construct( array $config ) {
  56                 parent::__construct( $config );
  57
  58                 $this->lockDir = $config['lockDirectory'];
  59         }
  60
  61         /**
  62          * @see LockManager::doLock()
  63          * @param array $paths
  64          * @param int $type
  65          * @return Status
  66          */
  67         protected function doLock( array $paths, $type ) {
  68                 $status = Status::newGood();
  69
  70                 $lockedPaths = []; // 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
  79                                 return $status;
  80                         }
  81                 }
  82
  83                 return $status;
  84         }
  85
  86         /**
  87          * @see LockManager::doUnlock()
  88          * @param array $paths
  89          * @param int $type
  90          * @return Status
  91          */
  92         protected function doUnlock( array $paths, $type ) {
  93                 $status = Status::newGood();
  94
  95                 foreach ( $paths as $path ) {
  96                         $status->merge( $this->doSingleUnlock( $path, $type ) );
  97                 }
  98
  99                 return $status;
 100         }
 101
 102         /**
 103          * Lock a single resource key
 104          *
 105          * @param string $path
 106          * @param int $type
 107          * @return Status
 108          */
 109         protected function doSingleLock( $path, $type ) {
 110                 $status = Status::newGood();
 111
 112                 if ( isset( $this->locksHeld[$path][$type] ) ) {
 113                         ++$this->locksHeld[$path][$type];
 114                 } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 115                         $this->locksHeld[$path][$type] = 1;
 116                 } else {
 117                         if ( isset( $this->handles[$path] ) ) {
 118                                 $handle = $this->handles[$path];
 119                         } else {
 120                                 MediaWiki\suppressWarnings();
 121                                 $handle = fopen( $this->getLockPath( $path ), 'a+' );
 122                                 MediaWiki\restoreWarnings();
 123                                 if ( !$handle ) { // lock dir missing?
 124                                         wfMkdirParents( $this->lockDir );
 125                                         $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
 126                                 }
 127                         }
 128                         if ( $handle ) {
 129                                 // Either a shared or exclusive lock
 130                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 131                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 132                                         // Record this lock as active
 133                                         $this->locksHeld[$path][$type] = 1;
 134                                         $this->handles[$path] = $handle;
 135                                 } else {
 136                                         fclose( $handle );
 137                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 138                                 }
 139                         } else {
 140                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 141                         }
 142                 }
 143
 144                 return $status;
 145         }
 146
 147         /**
 148          * Unlock a single resource key
 149          *
 150          * @param string $path
 151          * @param int $type
 152          * @return Status
 153          */
 154         protected function doSingleUnlock( $path, $type ) {
 155                 $status = Status::newGood();
 156
 157                 if ( !isset( $this->locksHeld[$path] ) ) {
 158                         $status->warning( 'lockmanager-notlocked', $path );
 159                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 160                         $status->warning( 'lockmanager-notlocked', $path );
 161                 } else {
 162                         $handlesToClose = [];
 163                         --$this->locksHeld[$path][$type];
 164                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 165                                 unset( $this->locksHeld[$path][$type] );
 166                         }
 167                         if ( !count( $this->locksHeld[$path] ) ) {
 168                                 unset( $this->locksHeld[$path] ); // no locks on this path
 169                                 if ( isset( $this->handles[$path] ) ) {
 170                                         $handlesToClose[] = $this->handles[$path];
 171                                         unset( $this->handles[$path] );
 172                                 }
 173                         }
 174                         // Unlock handles to release locks and delete
 175                         // any lock files that end up with no locks on them...
 176                         if ( wfIsWindows() ) {
 177                                 // Windows: for any process, including this one,
 178                                 // calling unlink() on a locked file will fail
 179                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 180                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 181                         } else {
 182                                 // Unix: unlink() can be used on files currently open by this
 183                                 // process and we must do so in order to avoid race conditions
 184                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 185                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 186                         }
 187                 }
 188
 189                 return $status;
 190         }
 191
 192         /**
 193          * @param string $path
 194          * @param array $handlesToClose
 195          * @return Status
 196          */
 197         private function closeLockHandles( $path, array $handlesToClose ) {
 198                 $status = Status::newGood();
 199                 foreach ( $handlesToClose as $handle ) {
 200                         if ( !flock( $handle, LOCK_UN ) ) {
 201                                 $status->fatal( 'lockmanager-fail-releaselock', $path );
 202                         }
 203                         if ( !fclose( $handle ) ) {
 204                                 $status->warning( 'lockmanager-fail-closelock', $path );
 205                         }
 206                 }
 207
 208                 return $status;
 209         }
 210
 211         /**
 212          * @param string $path
 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
 225                 return $status;
 226         }
 227
 228         /**
 229          * Get the path to the lock file for a key
 230          * @param string $path
 231          * @return string
 232          */
 233         protected function getLockPath( $path ) {
 234                 return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.lock";
 235         }
 236
 237         /**
 238          * Make sure remaining locks get cleared for sanity
 239          */
 240         function __destruct() {
 241                 while ( count( $this->locksHeld ) ) {
 242                         foreach ( $this->locksHeld as $path => $locks ) {
 243                                 $this->doSingleUnlock( $path, self::LOCK_EX );
 244                                 $this->doSingleUnlock( $path, self::LOCK_SH );
 245                         }
 246                 }
 247         }
 248 }