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         /** @var Array Map of (id => WANObjectCache) */
  42         public static $wanInstances = array();
  43
  44         /**
  45          * Get a cached instance of the specified type of cache object.
  46          *
  47          * @param string $id
  48          *
  49          * @return BagOStuff
  50          */
  51         static function getInstance( $id ) {
  52                 if ( isset( self::$instances[$id] ) ) {
  53                         return self::$instances[$id];
  54                 }
  55
  56                 $object = self::newFromId( $id );
  57                 self::$instances[$id] = $object;
  58                 return $object;
  59         }
  60
  61         /**
  62          * Get a cached instance of the specified type of cache object.
  63          *
  64          * @param string $id
  65          *
  66          * @return WANObjectCache
  67          * @since 1.26
  68          */
  69         static function getWANInstance( $id ) {
  70                 if ( isset( self::$wanInstances[$id] ) ) {
  71                         return self::$wanInstances[$id];
  72                 }
  73
  74                 $object = self::newWANCacheFromId( $id );
  75                 self::$wanInstances[$id] = $object;
  76                 return $object;
  77         }
  78
  79         /**
  80          * Clear all the cached instances.
  81          */
  82         static function clear() {
  83                 self::$instances = array();
  84                 self::$wanInstances = array();
  85         }
  86
  87         /**
  88          * Create a new cache object of the specified type.
  89          *
  90          * @param string $id
  91          *
  92          * @throws MWException
  93          * @return BagOStuff
  94          */
  95         static function newFromId( $id ) {
  96                 global $wgObjectCaches;
  97
  98                 if ( !isset( $wgObjectCaches[$id] ) ) {
  99                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 100                                 "It is not present in \$wgObjectCaches." );
 101                 }
 102
 103                 return self::newFromParams( $wgObjectCaches[$id] );
 104         }
 105
 106         /**
 107          * Create a new cache object from parameters
 108          *
 109          * @param array $params
 110          *
 111          * @throws MWException
 112          * @return BagOStuff
 113          */
 114         static function newFromParams( $params ) {
 115                 if ( isset( $params['loggroup'] ) ) {
 116                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 117                 } else {
 118                         // For backwards-compatability with custom parameters, lets not
 119                         // have all logging suddenly disappear
 120                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 121                 }
 122                 if ( isset( $params['factory'] ) ) {
 123                         return call_user_func( $params['factory'], $params );
 124                 } elseif ( isset( $params['class'] ) ) {
 125                         $class = $params['class'];
 126                         return new $class( $params );
 127                 } else {
 128                         throw new MWException( "The definition of cache type \""
 129                                 . print_r( $params, true ) . "\" lacks both "
 130                                 . "factory and class parameters." );
 131                 }
 132         }
 133
 134         /**
 135          * Factory function referenced from DefaultSettings.php for CACHE_ANYTHING
 136          *
 137          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 138          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 139          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 140          * be an alias to the configured cache choice for that.
 141          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 142          * then CACHE_ANYTHING will forward to CACHE_DB.
 143          * @param array $params
 144          * @return BagOStuff
 145          */
 146         static function newAnything( $params ) {
 147                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 148                 $candidates = array( $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType );
 149                 foreach ( $candidates as $candidate ) {
 150                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 151                                 return self::getInstance( $candidate );
 152                         }
 153                 }
 154                 return self::getInstance( CACHE_DB );
 155         }
 156
 157         /**
 158          * Factory function referenced from DefaultSettings.php for CACHE_ACCEL.
 159          *
 160          * This will look for any APC style server-local cache.
 161          * A fallback cache can be specified if none is found.
 162          *
 163          * @param array $params
 164          * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24)
 165          * @throws MWException
 166          * @return BagOStuff
 167          */
 168         static function newAccelerator( $params, $fallback = null ) {
 169                 if ( function_exists( 'apc_fetch' ) ) {
 170                         $id = 'apc';
 171                 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
 172                         $id = 'xcache';
 173                 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
 174                         $id = 'wincache';
 175                 } else {
 176                         if ( $fallback !== null ) {
 177                                 return self::newFromId( $fallback );
 178                         }
 179                         throw new MWException( "CACHE_ACCEL requested but no suitable object " .
 180                                 "cache is present. You may want to install APC." );
 181                 }
 182                 return self::newFromId( $id );
 183         }
 184
 185         /**
 186          * Factory function that creates a memcached client object.
 187          *
 188          * This always uses the PHP client, since the PECL client has a different
 189          * hashing scheme and a different interpretation of the flags bitfield, so
 190          * switching between the two clients randomly would be disastrous.
 191          *
 192          * @param array $params
 193          *
 194          * @return MemcachedPhpBagOStuff
 195          */
 196         static function newMemcached( $params ) {
 197                 return new MemcachedPhpBagOStuff( $params );
 198         }
 199
 200         /**
 201          * Create a new cache object of the specified type
 202          *
 203          * @param string $id
 204          *
 205          * @throws MWException
 206          * @return WANObjectCache
 207          * @since 1.26
 208          */
 209         static function newWANCacheFromId( $id ) {
 210                 global $wgWANObjectCaches;
 211
 212                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 213                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 214                                 "It is not present in \$wgWANObjectCaches." );
 215                 }
 216
 217                 $params = $wgWANObjectCaches[$id];
 218                 $class = $params['relayerConfig']['class'];
 219                 $params['relayer'] = new $class( $params['relayerConfig'] );
 220                 $params['cache'] = self::newFromId( $params['cacheId'] );
 221                 $class = $params['class'];
 222
 223                 return new $class( $params );
 224         }
 225
 226         /**
 227          * Get the main WAN cache object
 228          *
 229          * @return WANObjectCache
 230          * @since 1.26
 231          */
 232         static function getMainWANInstance() {
 233                 global $wgMainWANCache;
 234
 235                 return self::getWANInstance( $wgMainWANCache );
 236         }
 237
 238         /**
 239          * Stash objects are BagOStuff instances suitable for storing light
 240          * weight data that is not canonically stored elsewhere (such as RDBMS).
 241          * Stashes should be configured to propagate changes to all data-centers.
 242          *
 243          * Callers should be prepared for:
 244          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 245          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 246          * In general, this means avoiding updates on idempotent HTTP requests and
 247          * avoiding an assumption of perfect serializability (or accepting anomalies).
 248          * Reads may be eventually consistent or data might rollback as nodes flap.
 249          *
 250          *
 251          * @return BagOStuff
 252          * @since 1.26
 253          */
 254         static function getMainStashInstance() {
 255                 global $wgMainStash;
 256
 257                 return self::getInstance( $wgMainStash );
 258         }
 259 }