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                                 Wikimedia\suppressWarnings();
 126                                 $handle = fopen( $this->getLockPath( $path ), 'a+' );
 127                                 if ( !$handle && !is_dir( $this->lockDir ) ) {
 128                                         // Create the lock directory in case it is missing
 129                                         if ( mkdir( $this->lockDir, 0777, true ) ) {
 130                                                 $handle = fopen( $this->getLockPath( $path ), 'a+' ); // try again
 131                                         } else {
 132                                                 $this->logger->error( "Cannot create directory '{$this->lockDir}'." );
 133                                         }
 134                                 }
 135                                 Wikimedia\restoreWarnings();
 136                         }
 137                         if ( $handle ) {
 138                                 // Either a shared or exclusive lock
 139                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 140                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 141                                         // Record this lock as active
 142                                         $this->locksHeld[$path][$type] = 1;
 143                                         $this->handles[$path] = $handle;
 144                                 } else {
 145                                         fclose( $handle );
 146                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 147                                 }
 148                         } else {
 149                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 150                         }
 151                 }
 152
 153                 return $status;
 154         }
 155
 156         /**
 157          * Unlock a single resource key
 158          *
 159          * @param string $path
 160          * @param int $type
 161          * @return StatusValue
 162          */
 163         protected function doSingleUnlock( $path, $type ) {
 164                 $status = StatusValue::newGood();
 165
 166                 if ( !isset( $this->locksHeld[$path] ) ) {
 167                         $status->warning( 'lockmanager-notlocked', $path );
 168                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 169                         $status->warning( 'lockmanager-notlocked', $path );
 170                 } else {
 171                         $handlesToClose = [];
 172                         --$this->locksHeld[$path][$type];
 173                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 174                                 unset( $this->locksHeld[$path][$type] );
 175                         }
 176                         if ( $this->locksHeld[$path] === [] ) {
 177                                 unset( $this->locksHeld[$path] ); // no locks on this path
 178                                 if ( isset( $this->handles[$path] ) ) {
 179                                         $handlesToClose[] = $this->handles[$path];
 180                                         unset( $this->handles[$path] );
 181                                 }
 182                         }
 183                         // Unlock handles to release locks and delete
 184                         // any lock files that end up with no locks on them...
 185                         if ( $this->isWindows ) {
 186                                 // Windows: for any process, including this one,
 187                                 // calling unlink() on a locked file will fail
 188                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 189                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 190                         } else {
 191                                 // Unix: unlink() can be used on files currently open by this
 192                                 // process and we must do so in order to avoid race conditions
 193                                 $status->merge( $this->pruneKeyLockFiles( $path ) );
 194                                 $status->merge( $this->closeLockHandles( $path, $handlesToClose ) );
 195                         }
 196                 }
 197
 198                 return $status;
 199         }
 200
 201         /**
 202          * @param string $path
 203          * @param array $handlesToClose
 204          * @return StatusValue
 205          */
 206         private function closeLockHandles( $path, array $handlesToClose ) {
 207                 $status = StatusValue::newGood();
 208                 foreach ( $handlesToClose as $handle ) {
 209                         if ( !flock( $handle, LOCK_UN ) ) {
 210                                 $status->fatal( 'lockmanager-fail-releaselock', $path );
 211                         }
 212                         if ( !fclose( $handle ) ) {
 213                                 $status->warning( 'lockmanager-fail-closelock', $path );
 214                         }
 215                 }
 216
 217                 return $status;
 218         }
 219
 220         /**
 221          * @param string $path
 222          * @return StatusValue
 223          */
 224         private function pruneKeyLockFiles( $path ) {
 225                 $status = StatusValue::newGood();
 226                 if ( !isset( $this->locksHeld[$path] ) ) {
 227                         # No locks are held for the lock file anymore
 228                         if ( !unlink( $this->getLockPath( $path ) ) ) {
 229                                 $status->warning( 'lockmanager-fail-deletelock', $path );
 230                         }
 231                         unset( $this->handles[$path] );
 232                 }
 233
 234                 return $status;
 235         }
 236
 237         /**
 238          * Get the path to the lock file for a key
 239          * @param string $path
 240          * @return string
 241          */
 242         protected function getLockPath( $path ) {
 243                 return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.lock";
 244         }
 245
 246         /**
 247          * Make sure remaining locks get cleared for sanity
 248          */
 249         function __destruct() {
 250                 while ( count( $this->locksHeld ) ) {
 251                         foreach ( $this->locksHeld as $path => $locks ) {
 252                                 $this->doSingleUnlock( $path, self::LOCK_EX );
 253                                 $this->doSingleUnlock( $path, self::LOCK_SH );
 254                         }
 255                 }
 256         }
 257 }