includes/objectcache/ObjectCache.php

   1 <?php
   2 /**
   3  * Functions to get cache objects.
   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 use MediaWiki\Logger\LoggerFactory;
  25
  26 /**
  27  * Functions to get cache objects
  28  *
  29  * The word "cache" has two main dictionary meanings, and both
  30  * are used in this factory class. They are:
  31  *   - a) A place to store copies or computations on existing data
  32  *     for higher access speeds (the computer science definition)
  33  *   - b) A place to store lightweight data that is not canonically
  34  *     stored anywhere else (e.g. a "hoard" of objects)
  35  *
  36  * @ingroup Cache
  37  */
  38 class ObjectCache {
  39         /** @var Array Map of (id => BagOStuff) */
  40         public static $instances = array();
  41
  42         /** @var Array Map of (id => WANObjectCache) */
  43         public static $wanInstances = array();
  44
  45         /**
  46          * Get a cached instance of the specified type of cache object.
  47          *
  48          * @param string $id
  49          * @return BagOStuff
  50          */
  51         static function getInstance( $id ) {
  52                 if ( !isset( self::$instances[$id] ) ) {
  53                         self::$instances[$id] = self::newFromId( $id );
  54                 }
  55
  56                 return self::$instances[$id];
  57         }
  58
  59         /**
  60          * Get a cached instance of the specified type of cache object.
  61          *
  62          * @since 1.26
  63          * @param string $id
  64          * @return WANObjectCache
  65          */
  66         static function getWANInstance( $id ) {
  67                 if ( !isset( self::$wanInstances[$id] ) ) {
  68                         self::$wanInstances[$id] = self::newWANCacheFromId( $id );
  69                 }
  70
  71                 return self::$wanInstances[$id];
  72         }
  73
  74         /**
  75          * Clear all the cached instances.
  76          */
  77         static function clear() {
  78                 self::$instances = array();
  79                 self::$wanInstances = array();
  80         }
  81
  82         /**
  83          * Create a new cache object of the specified type.
  84          *
  85          * @param string $id
  86          * @return BagOStuff
  87          * @throws MWException
  88          */
  89         static function newFromId( $id ) {
  90                 global $wgObjectCaches;
  91
  92                 if ( !isset( $wgObjectCaches[$id] ) ) {
  93                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
  94                                 "It is not present in \$wgObjectCaches." );
  95                 }
  96
  97                 return self::newFromParams( $wgObjectCaches[$id] );
  98         }
  99
 100         /**
 101          * Create a new cache object from parameters
 102          *
 103          * @param array $params
 104          * @return BagOStuff
 105          * @throws MWException
 106          */
 107         static function newFromParams( $params ) {
 108                 if ( isset( $params['loggroup'] ) ) {
 109                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 110                 } else {
 111                         // For backwards-compatability with custom parameters, lets not
 112                         // have all logging suddenly disappear
 113                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 114                 }
 115                 if ( isset( $params['factory'] ) ) {
 116                         return call_user_func( $params['factory'], $params );
 117                 } elseif ( isset( $params['class'] ) ) {
 118                         $class = $params['class'];
 119                         return new $class( $params );
 120                 } else {
 121                         throw new MWException( "The definition of cache type \""
 122                                 . print_r( $params, true ) . "\" lacks both "
 123                                 . "factory and class parameters." );
 124                 }
 125         }
 126
 127         /**
 128          * Factory function referenced from DefaultSettings.php for CACHE_ANYTHING
 129          *
 130          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 131          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 132          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 133          * be an alias to the configured cache choice for that.
 134          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 135          * then CACHE_ANYTHING will forward to CACHE_DB.
 136          *
 137          * @param array $params
 138          * @return BagOStuff
 139          */
 140         static function newAnything( $params ) {
 141                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 142                 $candidates = array( $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType );
 143                 foreach ( $candidates as $candidate ) {
 144                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 145                                 return self::getInstance( $candidate );
 146                         }
 147                 }
 148                 return self::getInstance( CACHE_DB );
 149         }
 150
 151         /**
 152          * Factory function referenced from DefaultSettings.php for CACHE_ACCEL.
 153          *
 154          * This will look for any APC style server-local cache.
 155          * A fallback cache can be specified if none is found.
 156          *
 157          * @param array $params
 158          * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24)
 159          * @return BagOStuff
 160          * @throws MWException
 161          */
 162         static function newAccelerator( $params, $fallback = null ) {
 163                 if ( function_exists( 'apc_fetch' ) ) {
 164                         $id = 'apc';
 165                 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
 166                         $id = 'xcache';
 167                 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
 168                         $id = 'wincache';
 169                 } else {
 170                         if ( $fallback === null ) {
 171                                 throw new MWException( 'CACHE_ACCEL requested but no suitable object ' .
 172                                         'cache is present. You may want to install APC.' );
 173                         }
 174                         $id = $fallback;
 175                 }
 176                 return self::newFromId( $id );
 177         }
 178
 179         /**
 180          * Factory function that creates a memcached client object.
 181          *
 182          * This always uses the PHP client, since the PECL client has a different
 183          * hashing scheme and a different interpretation of the flags bitfield, so
 184          * switching between the two clients randomly would be disastrous.
 185          *
 186          * @param array $params
 187          * @return MemcachedPhpBagOStuff
 188          */
 189         static function newMemcached( $params ) {
 190                 return new MemcachedPhpBagOStuff( $params );
 191         }
 192
 193         /**
 194          * Create a new cache object of the specified type
 195          *
 196          * @since 1.26
 197          * @param string $id
 198          * @return WANObjectCache
 199          * @throws MWException
 200          */
 201         static function newWANCacheFromId( $id ) {
 202                 global $wgWANObjectCaches;
 203
 204                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 205                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 206                                 "It is not present in \$wgWANObjectCaches." );
 207                 }
 208
 209                 $params = $wgWANObjectCaches[$id];
 210                 $class = $params['relayerConfig']['class'];
 211                 $params['relayer'] = new $class( $params['relayerConfig'] );
 212                 $params['cache'] = self::newFromId( $params['cacheId'] );
 213                 $class = $params['class'];
 214
 215                 return new $class( $params );
 216         }
 217
 218         /**
 219          * Get the main WAN cache object
 220          *
 221          * @since 1.26
 222          * @return WANObjectCache
 223          */
 224         static function getMainWANInstance() {
 225                 global $wgMainWANCache;
 226
 227                 return self::getWANInstance( $wgMainWANCache );
 228         }
 229
 230         /**
 231          * Stash objects are BagOStuff instances suitable for storing light
 232          * weight data that is not canonically stored elsewhere (such as RDBMS).
 233          * Stashes should be configured to propagate changes to all data-centers.
 234          *
 235          * Callers should be prepared for:
 236          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 237          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 238          * In general, this means avoiding updates on idempotent HTTP requests and
 239          * avoiding an assumption of perfect serializability (or accepting anomalies).
 240          * Reads may be eventually consistent or data might rollback as nodes flap.
 241          *
 242          * @since 1.26
 243          * @return BagOStuff
 244          */
 245         static function getMainStashInstance() {
 246                 global $wgMainStash;
 247
 248                 return self::getInstance( $wgMainStash );
 249         }
 250 }