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  * The former should always use strongly consistent stores, so callers don't
  37  * have to deal with stale reads. The later may be eventually consistent, but
  38  * callers can use BagOStuff:READ_LATEST to see the latest available data.
  39  *
  40  * @ingroup Cache
  41  */
  42 class ObjectCache {
  43         /** @var Array Map of (id => BagOStuff) */
  44         public static $instances = array();
  45
  46         /** @var Array Map of (id => WANObjectCache) */
  47         public static $wanInstances = array();
  48
  49         /**
  50          * Get a cached instance of the specified type of cache object.
  51          *
  52          * @param string $id
  53          * @return BagOStuff
  54          */
  55         static function getInstance( $id ) {
  56                 if ( !isset( self::$instances[$id] ) ) {
  57                         self::$instances[$id] = self::newFromId( $id );
  58                 }
  59
  60                 return self::$instances[$id];
  61         }
  62
  63         /**
  64          * Get a cached instance of the specified type of cache object.
  65          *
  66          * @since 1.26
  67          * @param string $id
  68          * @return WANObjectCache
  69          */
  70         static function getWANInstance( $id ) {
  71                 if ( !isset( self::$wanInstances[$id] ) ) {
  72                         self::$wanInstances[$id] = self::newWANCacheFromId( $id );
  73                 }
  74
  75                 return self::$wanInstances[$id];
  76         }
  77
  78         /**
  79          * Clear all the cached instances.
  80          */
  81         static function clear() {
  82                 self::$instances = array();
  83                 self::$wanInstances = array();
  84         }
  85
  86         /**
  87          * Create a new cache object of the specified type.
  88          *
  89          * @param string $id
  90          * @return BagOStuff
  91          * @throws MWException
  92          */
  93         static function newFromId( $id ) {
  94                 global $wgObjectCaches;
  95
  96                 if ( !isset( $wgObjectCaches[$id] ) ) {
  97                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
  98                                 "It is not present in \$wgObjectCaches." );
  99                 }
 100
 101                 return self::newFromParams( $wgObjectCaches[$id] );
 102         }
 103
 104         /**
 105          * Create a new cache object from parameters
 106          *
 107          * @param array $params
 108          * @return BagOStuff
 109          * @throws MWException
 110          */
 111         static function newFromParams( $params ) {
 112                 if ( isset( $params['loggroup'] ) ) {
 113                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 114                 } else {
 115                         // For backwards-compatability with custom parameters, lets not
 116                         // have all logging suddenly disappear
 117                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 118                 }
 119                 if ( isset( $params['factory'] ) ) {
 120                         return call_user_func( $params['factory'], $params );
 121                 } elseif ( isset( $params['class'] ) ) {
 122                         $class = $params['class'];
 123                         return new $class( $params );
 124                 } else {
 125                         throw new MWException( "The definition of cache type \""
 126                                 . print_r( $params, true ) . "\" lacks both "
 127                                 . "factory and class parameters." );
 128                 }
 129         }
 130
 131         /**
 132          * Factory function referenced from DefaultSettings.php for CACHE_ANYTHING
 133          *
 134          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 135          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 136          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 137          * be an alias to the configured cache choice for that.
 138          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 139          * then CACHE_ANYTHING will forward to CACHE_DB.
 140          *
 141          * @param array $params
 142          * @return BagOStuff
 143          */
 144         static function newAnything( $params ) {
 145                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 146                 $candidates = array( $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType );
 147                 foreach ( $candidates as $candidate ) {
 148                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 149                                 return self::getInstance( $candidate );
 150                         }
 151                 }
 152                 return self::getInstance( CACHE_DB );
 153         }
 154
 155         /**
 156          * Factory function referenced from DefaultSettings.php for CACHE_ACCEL.
 157          *
 158          * This will look for any APC style server-local cache.
 159          * A fallback cache can be specified if none is found.
 160          *
 161          * @param array $params
 162          * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24)
 163          * @return BagOStuff
 164          * @throws MWException
 165          */
 166         static function newAccelerator( $params, $fallback = null ) {
 167                 if ( function_exists( 'apc_fetch' ) ) {
 168                         $id = 'apc';
 169                 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
 170                         $id = 'xcache';
 171                 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
 172                         $id = 'wincache';
 173                 } else {
 174                         if ( $fallback === null ) {
 175                                 throw new MWException( 'CACHE_ACCEL requested but no suitable object ' .
 176                                         'cache is present. You may want to install APC.' );
 177                         }
 178                         $id = $fallback;
 179                 }
 180                 return self::newFromId( $id );
 181         }
 182
 183         /**
 184          * Factory function that creates a memcached client object.
 185          *
 186          * This always uses the PHP client, since the PECL client has a different
 187          * hashing scheme and a different interpretation of the flags bitfield, so
 188          * switching between the two clients randomly would be disastrous.
 189          *
 190          * @param array $params
 191          * @return MemcachedPhpBagOStuff
 192          */
 193         static function newMemcached( $params ) {
 194                 return new MemcachedPhpBagOStuff( $params );
 195         }
 196
 197         /**
 198          * Create a new cache object of the specified type
 199          *
 200          * @since 1.26
 201          * @param string $id
 202          * @return WANObjectCache
 203          * @throws MWException
 204          */
 205         static function newWANCacheFromId( $id ) {
 206                 global $wgWANObjectCaches;
 207
 208                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 209                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 210                                 "It is not present in \$wgWANObjectCaches." );
 211                 }
 212
 213                 $params = $wgWANObjectCaches[$id];
 214                 $class = $params['relayerConfig']['class'];
 215                 $params['relayer'] = new $class( $params['relayerConfig'] );
 216                 $params['cache'] = self::newFromId( $params['cacheId'] );
 217                 $class = $params['class'];
 218
 219                 return new $class( $params );
 220         }
 221
 222         /**
 223          * Get the main WAN cache object
 224          *
 225          * @since 1.26
 226          * @return WANObjectCache
 227          */
 228         static function getMainWANInstance() {
 229                 global $wgMainWANCache;
 230
 231                 return self::getWANInstance( $wgMainWANCache );
 232         }
 233
 234         /**
 235          * Stash objects are BagOStuff instances suitable for storing light
 236          * weight data that is not canonically stored elsewhere (such as RDBMS).
 237          * Stashes should be configured to propagate changes to all data-centers.
 238          *
 239          * Callers should be prepared for:
 240          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 241          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 242          * In general, this means avoiding updates on idempotent HTTP requests and
 243          * avoiding an assumption of perfect serializability (or accepting anomalies).
 244          * Reads may be eventually consistent or data might rollback as nodes flap.
 245          * Callers can use BagOStuff:READ_LATEST to see the latest available data.
 246          *
 247          * @return BagOStuff
 248          * @since 1.26
 249          */
 250         static function getMainStashInstance() {
 251                 global $wgMainStash;
 252
 253                 return self::getInstance( $wgMainStash );
 254         }
 255 }