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
  32         const TTL_REFRESH_WINDOW = 600; // refresh if expiring in 10 minutes
  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                 return ObjectCache::getInstance( $wgSessionCacheType );
  60         }
  61
  62         /**
  63          * Get a cache key for the given session id.
  64          *
  65          * @param string $id Session id
  66          * @return string Cache key
  67          */
  68         protected static function getKey( $id ) {
  69                 return wfMemcKey( 'session', $id );
  70         }
  71
  72         /**
  73          * Callback when opening a session.
  74          *
  75          * @param string $save_path Path used to store session files, unused
  76          * @param string $session_name Session name
  77          * @return bool Success
  78          */
  79         static function open( $save_path, $session_name ) {
  80                 return true;
  81         }
  82
  83         /**
  84          * Callback when closing a session.
  85          * NOP.
  86          *
  87          * @return bool Success
  88          */
  89         static function close() {
  90                 return true;
  91         }
  92
  93         /**
  94          * Callback when reading session data.
  95          *
  96          * @param string $id Session id
  97          * @return mixed Session data
  98          */
  99         static function read( $id ) {
 100                 $data = self::getCache()->get( self::getKey( $id ) );
 101                 if ( $data === false ) {
 102                         return '';
 103                 }
 104                 return $data;
 105         }
 106
 107         /**
 108          * Callback when writing session data.
 109          *
 110          * @param string $id Session id
 111          * @param string $data Session data
 112          * @return bool Success
 113          */
 114         static function write( $id, $data ) {
 115                 global $wgObjectCacheSessionExpiry;
 116                 self::getCache()->set( self::getKey( $id ), $data, $wgObjectCacheSessionExpiry );
 117                 return true;
 118         }
 119
 120         /**
 121          * Callback to destroy a session when calling session_destroy().
 122          *
 123          * @param string $id Session id
 124          * @return bool Success
 125          */
 126         static function destroy( $id ) {
 127                 self::getCache()->delete( self::getKey( $id ) );
 128
 129                 return true;
 130         }
 131
 132         /**
 133          * Callback to execute garbage collection.
 134          * NOP: Object caches perform garbage collection implicitly
 135          *
 136          * @param int $maxlifetime Maximum session life time
 137          * @return bool Success
 138          */
 139         static function gc( $maxlifetime ) {
 140                 return true;
 141         }
 142
 143         /**
 144          * Shutdown function.
 145          * See the comment inside ObjectCacheSessionHandler::install for rationale.
 146          */
 147         static function handleShutdown() {
 148                 global $wgObjectCacheSessionExpiry;
 149
 150                 $now = microtime( true );
 151                 // Session are only written in object stores when $_SESSION changes,
 152                 // which also renews the TTL ($wgObjectCacheSessionExpiry). If a user
 153                 // is active but not causing session data changes, it may suddenly
 154                 // as they view a form, blocking the first submission.
 155                 // Make a dummy change every so often to avoid this.
 156                 if ( !isset( $_SESSION['wsExpiresUnix'] )
 157                         || ( $now + self::TTL_REFRESH_WINDOW ) > isset( $_SESSION['wsExpiresUnix'] )
 158                 ) {
 159                         $_SESSION['wsExpiresUnix'] = $now + $wgObjectCacheSessionExpiry;
 160                 }
 161
 162                 session_write_close();
 163         }
 164 }