includes/libs/lockmanager/FSLockManager.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  */
  20
  21 /**
  22  * Simple lock management based on server-local temporary files.
  23  *
  24  * All locks are non-blocking, which avoids deadlocks.
  25  *
  26  * This should work fine for small sites running from a single web server.
  27  * Do not use this with 'lockDirectory' set to an NFS mount unless the
  28  * NFS client is at least version 2.6.12. Otherwise, the BSD flock()
  29  * locks will be ignored; see http://nfs.sourceforge.net/#section_d.
  30  *
  31  * @ingroup LockManager
  32  * @since 1.19
  33  */
  34 class FSLockManager extends LockManager {
  35         /** @var array Mapping of lock types to the type actually used */
  36         protected $lockTypeMap = [
  37                 self::LOCK_SH => self::LOCK_SH,
  38                 self::LOCK_UW => self::LOCK_SH,
  39                 self::LOCK_EX => self::LOCK_EX
  40         ];
  41
  42         /** @var string Global dir for all servers */
  43         protected $lockDir;
  44
  45         /** @var array Map of (locked key => lock file handle) */
  46         protected $handles = [];
  47
  48         /** @var bool */
  49         protected $isWindows;
  50
  51         /**
  52          * Construct a new instance from configuration.
  53          *
  54          * @param array $config Includes:
  55          *   - lockDirectory : Directory containing the lock files
  56          */
  57         public function __construct( array $config ) {
  58                 parent::__construct( $config );
  59
  60                 $this->lockDir = $config['lockDirectory'];
  61                 $this->isWindows = ( PHP_OS_FAMILY === 'Windows' );
  62         }
  63
  64         /**
  65          * @see LockManager::doLock()
  66          * @param array $paths
  67          * @param int $type
  68          * @return StatusValue
  69          */
  70         protected function doLock( array $paths, $type ) {
  71                 $status = StatusValue::newGood();
  72
  73                 $lockedPaths = []; // files locked in this attempt
  74                 foreach ( $paths as $path ) {
  75                         $status->merge( $this->doSingleLock( $path, $type ) );
  76                         if ( $status->isOK() ) {
  77                                 $lockedPaths[] = $path;
  78                         } else {
  79                                 // Abort and unlock everything
  80                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
  81
  82                                 return $status;
  83                         }
  84                 }
  85
  86                 return $status;
  87         }
  88
  89         /**
  90          * @see LockManager::doUnlock()
  91          * @param array $paths
  92          * @param int $type
  93          * @return StatusValue
  94          */
  95         protected function doUnlock( array $paths, $type ) {
  96                 $status = StatusValue::newGood();
  97
  98                 foreach ( $paths as $path ) {
  99                         $status->merge( $this->doSingleUnlock( $path, $type ) );
 100                 }
 101
 102                 return $status;
 103         }
 104
 105         /**
 106          * Lock a single resource key
 107          *
 108          * @param string $path
 109          * @param int $type
 110          * @return StatusValue
 111          */
 112         protected function doSingleLock( $path, $type ) {
 113                 $status = StatusValue::newGood();
 114
 115                 if ( isset( $this->locksHeld[$path][$type] ) ) {
 116                         ++$this->locksHeld[$path][$type];
 117                 } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 118                         $this->locksHeld[$path][$type] = 1;
 119                 } else {
 120                         if ( isset( $this->handles[$path] ) ) {
 121                                 $handle = $this->handles[$path];
 122                         } else {
 123                                 // phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
 124                                 $handle = @fopen( $this->getLockPath( $path ), 'a+' );
 125                                 if ( !$handle && !is_dir( $this->lockDir ) ) {
 126                                         // Create the lock directory and try again
 127                                         // phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
 128                                         if ( @mkdir( $this->lockDir, 0777, true ) ) {
 129                                                 // phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
 130                                                 $handle = @fopen( $this->getLockPath( $path ), 'a+' );
 131                                         } else {
 132                                                 $this->logger->error( "Cannot create directory '{$this->lockDir}'." );
 133                                         }
 134                                 }
 135                         }
 136                         if ( $handle ) {
 137                                 // Either a shared or exclusive lock
 138                                 $lock = ( $type == self::LOCK_SH ) ? LOCK_SH : LOCK_EX;
 139                                 if ( flock( $handle, $lock | LOCK_NB ) ) {
 140                                         // Record this lock as active
 141                                         $this->locksHeld[$path][$type] = 1;
 142                                         $this->handles[$path] = $handle;
 143                                 } else {
 144                                         fclose( $handle );
 145                                         $status->fatal( 'lockmanager-fail-conflict' );
 146                                 }
 147                         } else {
 148                                 $status->fatal( 'lockmanager-fail-openlock', $path );
 149                         }
 150                 }
 151
 152                 return $status;
 153         }
 154
 155         /**
 156          * Unlock a single resource key
 157          *
 158          * @param string $path
 159          * @param int $type
 160          * @return StatusValue
 161          */
 162         protected function doSingleUnlock( $path, $type ) {
 163                 $status = StatusValue::newGood();
 164
 165                 if ( !isset( $this->locksHeld[$path] ) ) {
 166                         $status->warning( 'lockmanager-notlocked', $path );
 167                 } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 168                         $status->warning( 'lockmanager-notlocked', $path );
 169                 } else {
 170                         $handlesToClose = [];
 171                         --$this->locksHeld[$path][$type];
 172                         if ( $this->locksHeld[$path][$type] <= 0 ) {
 173                                 unset( $this->locksHeld[$path][$type] );
 174                         }
 175                         if ( $this->locksHeld[$path] === [] ) {
 176                                 unset( $this->locksHeld[$path] ); // no locks on this path
 177                                 if ( isset( $this->handles[$path] ) ) {
 178                                         $handlesToClose[] = $this->handles[$path];
 179                                         unset( $this->handles[$path] );
 180                                 }
 181                         }
 182                         // Unlock handles to release locks and delete
 183                         // any lock files that end up with no locks on them...
 184                         if ( $this->isWindows ) {
 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 string $path
 202          * @param array $handlesToClose
 203          * @return StatusValue
 204          */
 205         private function closeLockHandles( $path, array $handlesToClose ) {
 206                 $status = StatusValue::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
 216                 return $status;
 217         }
 218
 219         /**
 220          * @param string $path
 221          * @return StatusValue
 222          */
 223         private function pruneKeyLockFiles( $path ) {
 224                 $status = StatusValue::newGood();
 225                 if ( !isset( $this->locksHeld[$path] ) ) {
 226                         # No locks are held for the lock file anymore
 227                         if ( !unlink( $this->getLockPath( $path ) ) ) {
 228                                 $status->warning( 'lockmanager-fail-deletelock', $path );
 229                         }
 230                         unset( $this->handles[$path] );
 231                 }
 232
 233                 return $status;
 234         }
 235
 236         /**
 237          * Get the path to the lock file for a key
 238          * @param string $path
 239          * @return string
 240          */
 241         protected function getLockPath( $path ) {
 242                 return "{$this->lockDir}/{$this->sha1Base36Absolute( $path )}.lock";
 243         }
 244
 245         /**
 246          * Make sure remaining locks get cleared
 247          */
 248         public function __destruct() {
 249                 while ( count( $this->locksHeld ) ) {
 250                         foreach ( $this->locksHeld as $path => $locks ) {
 251                                 $this->doSingleUnlock( $path, self::LOCK_EX );
 252                                 $this->doSingleUnlock( $path, self::LOCK_SH );
 253                         }
 254                 }
 255         }
 256 }