includes/filebackend/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         protected $domain; // string; domain (usually wiki ID)
  57         protected $lockTTL; // integer; maximum time locks can be held
  58
  59         /* Lock types; stronger locks have higher values */
  60         const LOCK_SH = 1; // shared lock (for reads)
  61         const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
  62         const LOCK_EX = 3; // exclusive lock (for writes)
  63
  64         /**
  65          * Construct a new instance from configuration
  66          *
  67          * $config paramaters include:
  68          *   - domain  : Domain (usually wiki ID) that all resources are relative to [optional]
  69          *   - lockTTL : Age (in seconds) at which resource locks should expire.
  70          *               This only applies if locks are not tied to a connection/process.
  71          *
  72          * @param $config Array
  73          */
  74         public function __construct( array $config ) {
  75                 $this->domain = isset( $config['domain'] ) ? $config['domain'] : wfWikiID();
  76                 if ( isset( $config['lockTTL'] ) ) {
  77                         $this->lockTTL = max( 1, $config['lockTTL'] );
  78                 } elseif ( PHP_SAPI === 'cli' ) {
  79                         $this->lockTTL = 2*3600;
  80                 } else {
  81                         $met = ini_get( 'max_execution_time' ); // this is 0 in CLI mode
  82                         $this->lockTTL = max( 5*60, 2*(int)$met );
  83                 }
  84         }
  85
  86         /**
  87          * Lock the resources at the given abstract paths
  88          *
  89          * @param array $paths List of resource names
  90          * @param $type integer LockManager::LOCK_* constant
  91          * @return Status
  92          */
  93         final public function lock( array $paths, $type = self::LOCK_EX ) {
  94                 wfProfileIn( __METHOD__ );
  95                 $status = $this->doLock( array_unique( $paths ), $this->lockTypeMap[$type] );
  96                 wfProfileOut( __METHOD__ );
  97                 return $status;
  98         }
  99
 100         /**
 101          * Unlock the resources at the given abstract paths
 102          *
 103          * @param array $paths List of storage paths
 104          * @param $type integer LockManager::LOCK_* constant
 105          * @return Status
 106          */
 107         final public function unlock( array $paths, $type = self::LOCK_EX ) {
 108                 wfProfileIn( __METHOD__ );
 109                 $status = $this->doUnlock( array_unique( $paths ), $this->lockTypeMap[$type] );
 110                 wfProfileOut( __METHOD__ );
 111                 return $status;
 112         }
 113
 114         /**
 115          * Get the base 36 SHA-1 of a string, padded to 31 digits.
 116          * Before hashing, the path will be prefixed with the domain ID.
 117          * This should be used interally for lock key or file names.
 118          *
 119          * @param $path string
 120          * @return string
 121          */
 122         final protected function sha1Base36Absolute( $path ) {
 123                 return wfBaseConvert( sha1( "{$this->domain}:{$path}" ), 16, 36, 31 );
 124         }
 125
 126         /**
 127          * Get the base 16 SHA-1 of a string, padded to 31 digits.
 128          * Before hashing, the path will be prefixed with the domain ID.
 129          * This should be used interally for lock key or file names.
 130          *
 131          * @param $path string
 132          * @return string
 133          */
 134         final protected function sha1Base16Absolute( $path ) {
 135                 return sha1( "{$this->domain}:{$path}" );
 136         }
 137
 138         /**
 139          * Lock resources with the given keys and lock type
 140          *
 141          * @param array $paths List of storage paths
 142          * @param $type integer LockManager::LOCK_* constant
 143          * @return string
 144          */
 145         abstract protected function doLock( array $paths, $type );
 146
 147         /**
 148          * Unlock resources with the given keys and lock type
 149          *
 150          * @param array $paths List of storage paths
 151          * @param $type integer LockManager::LOCK_* constant
 152          * @return string
 153          */
 154         abstract protected function doUnlock( array $paths, $type );
 155 }
 156
 157 /**
 158  * Simple version of LockManager that does nothing
 159  * @since 1.19
 160  */
 161 class NullLockManager extends LockManager {
 162         /**
 163          * @see LockManager::doLock()
 164          * @param $paths array
 165          * @param $type int
 166          * @return Status
 167          */
 168         protected function doLock( array $paths, $type ) {
 169                 return Status::newGood();
 170         }
 171
 172         /**
 173          * @see LockManager::doUnlock()
 174          * @param $paths array
 175          * @param $type int
 176          * @return Status
 177          */
 178         protected function doUnlock( array $paths, $type ) {
 179                 return Status::newGood();
 180         }
 181 }