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  *
  32  *   - a) Cache (the computer science definition).
  33  *        A place to store copies or computations on existing data for
  34  *        higher access speeds.
  35  *   - b) Storage.
  36  *        A place to store lightweight data that is not canonically
  37  *        stored anywhere else (e.g. a "hoard" of objects).
  38  *
  39  * The former should always use strongly consistent stores, so callers don't
  40  * have to deal with stale reads. The later may be eventually consistent, but
  41  * callers can use BagOStuff:READ_LATEST to see the latest available data.
  42  *
  43  * Primary entry points:
  44  *
  45  * - ObjectCache::getMainWANInstance()
  46  *   Purpose: Memory cache.
  47  *   Stored in the local data-center's main cache (keyspace different from local-cluster cache).
  48  *   Delete events are broadcasted to other DCs main cache. See WANObjectCache for details.
  49  *
  50  * - ObjectCache::getLocalServerInstance( $fallbackType )
  51  *   Purpose: Memory cache for very hot keys.
  52  *   Stored only on the individual web server (typically APC for web requests,
  53  *   and EmptyBagOStuff in CLI mode).
  54  *   Not replicated to the other servers.
  55  *
  56  * - ObjectCache::getLocalClusterInstance()
  57  *   Purpose: Memory storage for per-cluster coordination and tracking.
  58  *   A typical use case would be a rate limit counter or cache regeneration mutex.
  59  *   Stored centrally within the local data-center. Not replicated to other DCs.
  60  *   Configured by $wgMainCacheType.
  61  *
  62  * - ObjectCache::getMainStashInstance()
  63  *   Purpose: Ephemeral global storage.
  64  *   Stored centrally within the primary data-center.
  65  *   Changes are applied there first and replicated to other DCs (best-effort).
  66  *   To retrieve the latest value (e.g. not from a slave), use BagOStuff::READ_LATEST.
  67  *   This store may be subject to LRU style evictions.
  68  *
  69  * - ObjectCache::getInstance( $cacheType )
  70  *   Purpose: Special cases (like tiered memory/disk caches).
  71  *   Get a specific cache type by key in $wgObjectCaches.
  72  *
  73  * All the above cache instances (BagOStuff and WANObjectCache) have their makeKey()
  74  * method scoped to the *current* wiki ID. Use makeGlobalKey() to avoid this scoping
  75  * when using keys that need to be shared amongst wikis.
  76  *
  77  * @ingroup Cache
  78  */
  79 class ObjectCache {
  80         /** @var BagOStuff[] Map of (id => BagOStuff) */
  81         public static $instances = [];
  82         /** @var WANObjectCache[] Map of (id => WANObjectCache) */
  83         public static $wanInstances = [];
  84
  85         /**
  86          * Get a cached instance of the specified type of cache object.
  87          *
  88          * @param string $id A key in $wgObjectCaches.
  89          * @return BagOStuff
  90          */
  91         public static function getInstance( $id ) {
  92                 if ( !isset( self::$instances[$id] ) ) {
  93                         self::$instances[$id] = self::newFromId( $id );
  94                 }
  95
  96                 return self::$instances[$id];
  97         }
  98
  99         /**
 100          * Get a cached instance of the specified type of WAN cache object.
 101          *
 102          * @since 1.26
 103          * @param string $id A key in $wgWANObjectCaches.
 104          * @return WANObjectCache
 105          */
 106         public static function getWANInstance( $id ) {
 107                 if ( !isset( self::$wanInstances[$id] ) ) {
 108                         self::$wanInstances[$id] = self::newWANCacheFromId( $id );
 109                 }
 110
 111                 return self::$wanInstances[$id];
 112         }
 113
 114         /**
 115          * Create a new cache object of the specified type.
 116          *
 117          * @param string $id A key in $wgObjectCaches.
 118          * @return BagOStuff
 119          * @throws MWException
 120          */
 121         public static function newFromId( $id ) {
 122                 global $wgObjectCaches;
 123
 124                 if ( !isset( $wgObjectCaches[$id] ) ) {
 125                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 126                                 "It is not present in \$wgObjectCaches." );
 127                 }
 128
 129                 return self::newFromParams( $wgObjectCaches[$id] );
 130         }
 131
 132         /**
 133          * Get the default keyspace for this wiki.
 134          *
 135          * This is either the value of the `CachePrefix` configuration variable,
 136          * or (if the former is unset) the `DBname` configuration variable, with
 137          * `DBprefix` (if defined).
 138          *
 139          * @return string
 140          */
 141         public static function getDefaultKeyspace() {
 142                 global $wgCachePrefix;
 143
 144                 $keyspace = $wgCachePrefix;
 145                 if ( is_string( $keyspace ) && $keyspace !== '' ) {
 146                         return $keyspace;
 147                 }
 148
 149                 return wfWikiID();
 150         }
 151
 152         /**
 153          * Create a new cache object from parameters.
 154          *
 155          * @param array $params Must have 'factory' or 'class' property.
 156          *  - factory: Callback passed $params that returns BagOStuff.
 157          *  - class: BagOStuff subclass constructed with $params.
 158          *  - loggroup: Alias to set 'logger' key with LoggerFactory group.
 159          *  - .. Other parameters passed to factory or class.
 160          * @return BagOStuff
 161          * @throws MWException
 162          */
 163         public static function newFromParams( $params ) {
 164                 if ( isset( $params['loggroup'] ) ) {
 165                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 166                 } else {
 167                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 168                 }
 169                 if ( !isset( $params['keyspace'] ) ) {
 170                         $params['keyspace'] = self::getDefaultKeyspace();
 171                 }
 172                 if ( isset( $params['factory'] ) ) {
 173                         return call_user_func( $params['factory'], $params );
 174                 } elseif ( isset( $params['class'] ) ) {
 175                         $class = $params['class'];
 176                         // Automatically set the 'async' update handler
 177                         if ( $class === 'MultiWriteBagOStuff' ) {
 178                                 $params['asyncHandler'] = isset( $params['asyncHandler'] )
 179                                         ? $params['asyncHandler']
 180                                         : 'DeferredUpdates::addCallableUpdate';
 181                         }
 182                         // Do b/c logic for MemcachedBagOStuff
 183                         if ( is_subclass_of( $class, 'MemcachedBagOStuff' ) ) {
 184                                 if ( !isset( $params['servers'] ) ) {
 185                                         $params['servers'] = $GLOBALS['wgMemCachedServers'];
 186                                 }
 187                                 if ( !isset( $params['debug'] ) ) {
 188                                         $params['debug'] = $GLOBALS['wgMemCachedDebug'];
 189                                 }
 190                                 if ( !isset( $params['persistent'] ) ) {
 191                                         $params['persistent'] = $GLOBALS['wgMemCachedPersistent'];
 192                                 }
 193                                 if ( !isset( $params['timeout'] ) ) {
 194                                         $params['timeout'] = $GLOBALS['wgMemCachedTimeout'];
 195                                 }
 196                         }
 197                         return new $class( $params );
 198                 } else {
 199                         throw new MWException( "The definition of cache type \""
 200                                 . print_r( $params, true ) . "\" lacks both "
 201                                 . "factory and class parameters." );
 202                 }
 203         }
 204
 205         /**
 206          * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php)
 207          *
 208          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 209          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 210          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 211          * be an alias to the configured cache choice for that.
 212          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 213          * then CACHE_ANYTHING will forward to CACHE_DB.
 214          *
 215          * @param array $params
 216          * @return BagOStuff
 217          */
 218         public static function newAnything( $params ) {
 219                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 220                 $candidates = [ $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType ];
 221                 foreach ( $candidates as $candidate ) {
 222                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 223                                 return self::getInstance( $candidate );
 224                         }
 225                 }
 226                 return self::getInstance( CACHE_DB );
 227         }
 228
 229         /**
 230          * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php)
 231          *
 232          * This will look for any APC style server-local cache.
 233          * A fallback cache can be specified if none is found.
 234          *
 235          *     // Direct calls
 236          *     ObjectCache::getLocalServerInstance( $fallbackType );
 237          *
 238          *     // From $wgObjectCaches via newFromParams()
 239          *     ObjectCache::getLocalServerInstance( array( 'fallback' => $fallbackType ) );
 240          *
 241          * @param int|string|array $fallback Fallback cache or parameter map with 'fallback'
 242          * @return BagOStuff
 243          * @throws MWException
 244          * @since 1.27
 245          */
 246         public static function getLocalServerInstance( $fallback = CACHE_NONE ) {
 247                 if ( function_exists( 'apc_fetch' ) ) {
 248                         $id = 'apc';
 249                 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
 250                         $id = 'xcache';
 251                 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
 252                         $id = 'wincache';
 253                 } else {
 254                         if ( is_array( $fallback ) ) {
 255                                 $id = isset( $fallback['fallback'] ) ? $fallback['fallback'] : CACHE_NONE;
 256                         } else {
 257                                 $id = $fallback;
 258                         }
 259                 }
 260
 261                 return self::getInstance( $id );
 262         }
 263
 264         /**
 265          * @param array $params [optional] Array key 'fallback' for $fallback.
 266          * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24)
 267          * @return BagOStuff
 268          * @deprecated 1.27
 269          */
 270         public static function newAccelerator( $params = [], $fallback = null ) {
 271                 if ( $fallback === null ) {
 272                         if ( is_array( $params ) && isset( $params['fallback'] ) ) {
 273                                 $fallback = $params['fallback'];
 274                         } elseif ( !is_array( $params ) ) {
 275                                 $fallback = $params;
 276                         }
 277                 }
 278
 279                 return self::getLocalServerInstance( $fallback );
 280         }
 281
 282         /**
 283          * Create a new cache object of the specified type.
 284          *
 285          * @since 1.26
 286          * @param string $id A key in $wgWANObjectCaches.
 287          * @return WANObjectCache
 288          * @throws MWException
 289          */
 290         public static function newWANCacheFromId( $id ) {
 291                 global $wgWANObjectCaches;
 292
 293                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 294                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 295                                 "It is not present in \$wgWANObjectCaches." );
 296                 }
 297
 298                 $params = $wgWANObjectCaches[$id];
 299                 $class = $params['relayerConfig']['class'];
 300                 $params['relayer'] = new $class( $params['relayerConfig'] );
 301                 $params['cache'] = self::newFromId( $params['cacheId'] );
 302                 if ( isset( $params['loggroup'] ) ) {
 303                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 304                 } else {
 305                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 306                 }
 307                 $class = $params['class'];
 308
 309                 return new $class( $params );
 310         }
 311
 312         /**
 313          * Get the main cluster-local cache object.
 314          *
 315          * @since 1.27
 316          * @return BagOStuff
 317          */
 318         public static function getLocalClusterInstance() {
 319                 global $wgMainCacheType;
 320
 321                 return self::getInstance( $wgMainCacheType );
 322         }
 323
 324         /**
 325          * Get the main WAN cache object.
 326          *
 327          * @since 1.26
 328          * @return WANObjectCache
 329          */
 330         public static function getMainWANInstance() {
 331                 global $wgMainWANCache;
 332
 333                 return self::getWANInstance( $wgMainWANCache );
 334         }
 335
 336         /**
 337          * Get the cache object for the main stash.
 338          *
 339          * Stash objects are BagOStuff instances suitable for storing light
 340          * weight data that is not canonically stored elsewhere (such as RDBMS).
 341          * Stashes should be configured to propagate changes to all data-centers.
 342          *
 343          * Callers should be prepared for:
 344          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 345          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 346          * In general, this means avoiding updates on idempotent HTTP requests and
 347          * avoiding an assumption of perfect serializability (or accepting anomalies).
 348          * Reads may be eventually consistent or data might rollback as nodes flap.
 349          * Callers can use BagOStuff:READ_LATEST to see the latest available data.
 350          *
 351          * @return BagOStuff
 352          * @since 1.26
 353          */
 354         public static function getMainStashInstance() {
 355                 global $wgMainStash;
 356
 357                 return self::getInstance( $wgMainStash );
 358         }
 359
 360         /**
 361          * Clear all the cached instances.
 362          */
 363         public static function clear() {
 364                 self::$instances = [];
 365                 self::$wanInstances = [];
 366         }
 367 }