includes/objectcache/ObjectCacheSessionHandler.php

   1 <?php
   2 /**
   3  * Session storage in object cache.
   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 Cache
  22  */
  23
  24 /**
  25  * Session storage in object cache.
  26  * Used if $wgSessionsInObjectCache is true.
  27  *
  28  * @ingroup Cache
  29  */
  30 class ObjectCacheSessionHandler {
  31         /** @var array Map of (session ID => SHA-1 of the data) */
  32         protected static $hashCache = array();
  33
  34         /**
  35          * Install a session handler for the current web request
  36          */
  37         static function install() {
  38                 session_set_save_handler(
  39                         array( __CLASS__, 'open' ),
  40                         array( __CLASS__, 'close' ),
  41                         array( __CLASS__, 'read' ),
  42                         array( __CLASS__, 'write' ),
  43                         array( __CLASS__, 'destroy' ),
  44                         array( __CLASS__, 'gc' ) );
  45
  46                 // It's necessary to register a shutdown function to call session_write_close(),
  47                 // because by the time the request shutdown function for the session module is
  48                 // called, $wgMemc has already been destroyed. Shutdown functions registered
  49                 // this way are called before object destruction.
  50                 register_shutdown_function( array( __CLASS__, 'handleShutdown' ) );
  51         }
  52
  53         /**
  54          * Get the cache storage object to use for session storage
  55          * @return BagOStuff
  56          */
  57         protected static function getCache() {
  58                 global $wgSessionCacheType;
  59
  60                 return ObjectCache::getInstance( $wgSessionCacheType );
  61         }
  62
  63         /**
  64          * Get a cache key for the given session id.
  65          *
  66          * @param string $id Session id
  67          * @return string Cache key
  68          */
  69         protected static function getKey( $id ) {
  70                 return wfMemcKey( 'session', $id );
  71         }
  72
  73         /**
  74          * @param mixed $data
  75          * @return string
  76          */
  77         protected static function getHash( $data ) {
  78                 return sha1( serialize( $data ) );
  79         }
  80
  81         /**
  82          * Callback when opening a session.
  83          *
  84          * @param string $save_path Path used to store session files, unused
  85          * @param string $session_name Session name
  86          * @return bool Success
  87          */
  88         static function open( $save_path, $session_name ) {
  89                 return true;
  90         }
  91
  92         /**
  93          * Callback when closing a session.
  94          * NOP.
  95          *
  96          * @return bool Success
  97          */
  98         static function close() {
  99                 return true;
 100         }
 101
 102         /**
 103          * Callback when reading session data.
 104          *
 105          * @param string $id Session id
 106          * @return mixed Session data
 107          */
 108         static function read( $id ) {
 109                 $data = self::getCache()->get( self::getKey( $id ) );
 110
 111                 self::$hashCache = array( $id => self::getHash( $data ) );
 112
 113                 return ( $data === false ) ? '' : $data;
 114         }
 115
 116         /**
 117          * Callback when writing session data.
 118          *
 119          * @param string $id Session id
 120          * @param string $data Session data
 121          * @return bool Success
 122          */
 123         static function write( $id, $data ) {
 124                 global $wgObjectCacheSessionExpiry;
 125
 126                 // Only issue a write if anything changed (PHP 5.6 already does this)
 127                 if ( !isset( self::$hashCache[$id] )
 128                         || self::getHash( $data ) !== self::$hashCache[$id]
 129                 ) {
 130                         self::getCache()->set( self::getKey( $id ), $data, $wgObjectCacheSessionExpiry );
 131                 }
 132
 133                 return true;
 134         }
 135
 136         /**
 137          * Callback to destroy a session when calling session_destroy().
 138          *
 139          * @param string $id Session id
 140          * @return bool Success
 141          */
 142         static function destroy( $id ) {
 143                 self::getCache()->delete( self::getKey( $id ) );
 144
 145                 return true;
 146         }
 147
 148         /**
 149          * Callback to execute garbage collection.
 150          * NOP: Object caches perform garbage collection implicitly
 151          *
 152          * @param int $maxlifetime Maximum session life time
 153          * @return bool Success
 154          */
 155         static function gc( $maxlifetime ) {
 156                 return true;
 157         }
 158
 159         /**
 160          * Shutdown function. See the comment inside ObjectCacheSessionHandler::install
 161          * for rationale.
 162          */
 163         static function handleShutdown() {
 164                 session_write_close();
 165         }
 166 }