includes/filerepo/backend/lockmanager/LockManager.php

   1 <?php
   2 /**
   3  * @defgroup LockManager Lock management
   4  * @ingroup FileBackend
   5  */
   6
   7 /**
   8  * Resource locking handling.
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License along
  21  * with this program; if not, write to the Free Software Foundation, Inc.,
  22  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  23  * http://www.gnu.org/copyleft/gpl.html
  24  *
  25  * @file
  26  * @ingroup LockManager
  27  * @author Aaron Schulz
  28  */
  29
  30 /**
  31  * @brief Class for handling resource locking.
  32  *
  33  * Locks on resource keys can either be shared or exclusive.
  34  *
  35  * Implementations must keep track of what is locked by this proccess
  36  * in-memory and support nested locking calls (using reference counting).
  37  * At least LOCK_UW and LOCK_EX must be implemented. LOCK_SH can be a no-op.
  38  * Locks should either be non-blocking or have low wait timeouts.
  39  *
  40  * Subclasses should avoid throwing exceptions at all costs.
  41  *
  42  * @ingroup LockManager
  43  * @since 1.19
  44  */
  45 abstract class LockManager {
  46         /** @var Array Mapping of lock types to the type actually used */
  47         protected $lockTypeMap = array(
  48                 self::LOCK_SH => self::LOCK_SH,
  49                 self::LOCK_UW => self::LOCK_EX, // subclasses may use self::LOCK_SH
  50                 self::LOCK_EX => self::LOCK_EX
  51         );
  52
  53         /** @var Array Map of (resource path => lock type => count) */
  54         protected $locksHeld = array();
  55
  56         /* Lock types; stronger locks have higher values */
  57         const LOCK_SH = 1; // shared lock (for reads)
  58         const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
  59         const LOCK_EX = 3; // exclusive lock (for writes)
  60
  61         /**
  62          * Construct a new instance from configuration
  63          *
  64          * @param $config Array
  65          */
  66         public function __construct( array $config ) {}
  67
  68         /**
  69          * Lock the resources at the given abstract paths
  70          *
  71          * @param $paths Array List of resource names
  72          * @param $type integer LockManager::LOCK_* constant
  73          * @return Status
  74          */
  75         final public function lock( array $paths, $type = self::LOCK_EX ) {
  76                 wfProfileIn( __METHOD__ );
  77                 $status = $this->doLock( array_unique( $paths ), $this->lockTypeMap[$type] );
  78                 wfProfileOut( __METHOD__ );
  79                 return $status;
  80         }
  81
  82         /**
  83          * Unlock the resources at the given abstract paths
  84          *
  85          * @param $paths Array List of storage paths
  86          * @param $type integer LockManager::LOCK_* constant
  87          * @return Status
  88          */
  89         final public function unlock( array $paths, $type = self::LOCK_EX ) {
  90                 wfProfileIn( __METHOD__ );
  91                 $status = $this->doUnlock( array_unique( $paths ), $this->lockTypeMap[$type] );
  92                 wfProfileOut( __METHOD__ );
  93                 return $status;
  94         }
  95
  96         /**
  97          * Get the base 36 SHA-1 of a string, padded to 31 digits
  98          *
  99          * @param $path string
 100          * @return string
 101          */
 102         final protected static function sha1Base36( $path ) {
 103                 return wfBaseConvert( sha1( $path ), 16, 36, 31 );
 104         }
 105
 106         /**
 107          * Lock resources with the given keys and lock type
 108          *
 109          * @param $paths Array List of storage paths
 110          * @param $type integer LockManager::LOCK_* constant
 111          * @return string
 112          */
 113         abstract protected function doLock( array $paths, $type );
 114
 115         /**
 116          * Unlock resources with the given keys and lock type
 117          *
 118          * @param $paths Array List of storage paths
 119          * @param $type integer LockManager::LOCK_* constant
 120          * @return string
 121          */
 122         abstract protected function doUnlock( array $paths, $type );
 123 }
 124
 125 /**
 126  * Self releasing locks
 127  *
 128  * LockManager helper class to handle scoped locks, which
 129  * release when an object is destroyed or goes out of scope.
 130  *
 131  * @ingroup LockManager
 132  * @since 1.19
 133  */
 134 class ScopedLock {
 135         /** @var LockManager */
 136         protected $manager;
 137         /** @var Status */
 138         protected $status;
 139         /** @var Array List of resource paths*/
 140         protected $paths;
 141
 142         protected $type; // integer lock type
 143
 144         /**
 145          * @param $manager LockManager
 146          * @param $paths Array List of storage paths
 147          * @param $type integer LockManager::LOCK_* constant
 148          * @param $status Status
 149          */
 150         protected function __construct(
 151                 LockManager $manager, array $paths, $type, Status $status
 152         ) {
 153                 $this->manager = $manager;
 154                 $this->paths = $paths;
 155                 $this->status = $status;
 156                 $this->type = $type;
 157         }
 158
 159         /**
 160          * Get a ScopedLock object representing a lock on resource paths.
 161          * Any locks are released once this object goes out of scope.
 162          * The status object is updated with any errors or warnings.
 163          *
 164          * @param $manager LockManager
 165          * @param $paths Array List of storage paths
 166          * @param $type integer LockManager::LOCK_* constant
 167          * @param $status Status
 168          * @return ScopedLock|null Returns null on failure
 169          */
 170         public static function factory(
 171                 LockManager $manager, array $paths, $type, Status $status
 172         ) {
 173                 $lockStatus = $manager->lock( $paths, $type );
 174                 $status->merge( $lockStatus );
 175                 if ( $lockStatus->isOK() ) {
 176                         return new self( $manager, $paths, $type, $status );
 177                 }
 178                 return null;
 179         }
 180
 181         function __destruct() {
 182                 $wasOk = $this->status->isOK();
 183                 $this->status->merge( $this->manager->unlock( $this->paths, $this->type ) );
 184                 if ( $wasOk ) {
 185                         // Make sure status is OK, despite any unlockFiles() fatals
 186                         $this->status->setResult( true, $this->status->value );
 187                 }
 188         }
 189 }
 190
 191 /**
 192  * Simple version of LockManager that does nothing
 193  * @since 1.19
 194  */
 195 class NullLockManager extends LockManager {
 196         /**
 197          * @see LockManager::doLock()
 198          * @param $paths array
 199          * @param $type int
 200          * @return Status
 201          */
 202         protected function doLock( array $paths, $type ) {
 203                 return Status::newGood();
 204         }
 205
 206         /**
 207          * @see LockManager::doUnlock()
 208          * @param $paths array
 209          * @param $type int
 210          * @return Status
 211          */
 212         protected function doUnlock( array $paths, $type ) {
 213                 return Status::newGood();
 214         }
 215 }