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 use MediaWiki\MediaWikiServices;
  26
  27 /**
  28  * Functions to get cache objects
  29  *
  30  * The word "cache" has two main dictionary meanings, and both
  31  * are used in this factory class. They are:
  32  *
  33  *   - a) Cache (the computer science definition).
  34  *        A place to store copies or computations on existing data for
  35  *        higher access speeds.
  36  *   - b) Storage.
  37  *        A place to store lightweight data that is not canonically
  38  *        stored anywhere else (e.g. a "hoard" of objects).
  39  *
  40  * The former should always use strongly consistent stores, so callers don't
  41  * have to deal with stale reads. The later may be eventually consistent, but
  42  * callers can use BagOStuff:READ_LATEST to see the latest available data.
  43  *
  44  * Primary entry points:
  45  *
  46  * - ObjectCache::getMainWANInstance()
  47  *   Purpose: Memory cache.
  48  *   Stored in the local data-center's main cache (keyspace different from local-cluster cache).
  49  *   Delete events are broadcasted to other DCs main cache. See WANObjectCache for details.
  50  *
  51  * - ObjectCache::getLocalServerInstance( $fallbackType )
  52  *   Purpose: Memory cache for very hot keys.
  53  *   Stored only on the individual web server (typically APC for web requests,
  54  *   and EmptyBagOStuff in CLI mode).
  55  *   Not replicated to the other servers.
  56  *
  57  * - ObjectCache::getLocalClusterInstance()
  58  *   Purpose: Memory storage for per-cluster coordination and tracking.
  59  *   A typical use case would be a rate limit counter or cache regeneration mutex.
  60  *   Stored centrally within the local data-center. Not replicated to other DCs.
  61  *   Configured by $wgMainCacheType.
  62  *
  63  * - ObjectCache::getMainStashInstance()
  64  *   Purpose: Ephemeral global storage.
  65  *   Stored centrally within the primary data-center.
  66  *   Changes are applied there first and replicated to other DCs (best-effort).
  67  *   To retrieve the latest value (e.g. not from a slave), use BagOStuff::READ_LATEST.
  68  *   This store may be subject to LRU style evictions.
  69  *
  70  * - ObjectCache::getInstance( $cacheType )
  71  *   Purpose: Special cases (like tiered memory/disk caches).
  72  *   Get a specific cache type by key in $wgObjectCaches.
  73  *
  74  * All the above cache instances (BagOStuff and WANObjectCache) have their makeKey()
  75  * method scoped to the *current* wiki ID. Use makeGlobalKey() to avoid this scoping
  76  * when using keys that need to be shared amongst wikis.
  77  *
  78  * @ingroup Cache
  79  */
  80 class ObjectCache {
  81         /** @var BagOStuff[] Map of (id => BagOStuff) */
  82         public static $instances = [];
  83         /** @var WANObjectCache[] Map of (id => WANObjectCache) */
  84         public static $wanInstances = [];
  85
  86         /**
  87          * Get a cached instance of the specified type of cache object.
  88          *
  89          * @param string $id A key in $wgObjectCaches.
  90          * @return BagOStuff
  91          */
  92         public static function getInstance( $id ) {
  93                 if ( !isset( self::$instances[$id] ) ) {
  94                         self::$instances[$id] = self::newFromId( $id );
  95                 }
  96
  97                 return self::$instances[$id];
  98         }
  99
 100         /**
 101          * Get a cached instance of the specified type of WAN cache object.
 102          *
 103          * @since 1.26
 104          * @param string $id A key in $wgWANObjectCaches.
 105          * @return WANObjectCache
 106          */
 107         public static function getWANInstance( $id ) {
 108                 if ( !isset( self::$wanInstances[$id] ) ) {
 109                         self::$wanInstances[$id] = self::newWANCacheFromId( $id );
 110                 }
 111
 112                 return self::$wanInstances[$id];
 113         }
 114
 115         /**
 116          * Create a new cache object of the specified type.
 117          *
 118          * @param string $id A key in $wgObjectCaches.
 119          * @return BagOStuff
 120          * @throws MWException
 121          */
 122         public static function newFromId( $id ) {
 123                 global $wgObjectCaches;
 124
 125                 if ( !isset( $wgObjectCaches[$id] ) ) {
 126                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 127                                 "It is not present in \$wgObjectCaches." );
 128                 }
 129
 130                 return self::newFromParams( $wgObjectCaches[$id] );
 131         }
 132
 133         /**
 134          * Get the default keyspace for this wiki.
 135          *
 136          * This is either the value of the `CachePrefix` configuration variable,
 137          * or (if the former is unset) the `DBname` configuration variable, with
 138          * `DBprefix` (if defined).
 139          *
 140          * @return string
 141          */
 142         public static function getDefaultKeyspace() {
 143                 global $wgCachePrefix;
 144
 145                 $keyspace = $wgCachePrefix;
 146                 if ( is_string( $keyspace ) && $keyspace !== '' ) {
 147                         return $keyspace;
 148                 }
 149
 150                 return wfWikiID();
 151         }
 152
 153         /**
 154          * Create a new cache object from parameters.
 155          *
 156          * @param array $params Must have 'factory' or 'class' property.
 157          *  - factory: Callback passed $params that returns BagOStuff.
 158          *  - class: BagOStuff subclass constructed with $params.
 159          *  - loggroup: Alias to set 'logger' key with LoggerFactory group.
 160          *  - .. Other parameters passed to factory or class.
 161          * @return BagOStuff
 162          * @throws MWException
 163          */
 164         public static function newFromParams( $params ) {
 165                 if ( isset( $params['loggroup'] ) ) {
 166                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 167                 } else {
 168                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 169                 }
 170                 if ( !isset( $params['keyspace'] ) ) {
 171                         $params['keyspace'] = self::getDefaultKeyspace();
 172                 }
 173                 if ( isset( $params['factory'] ) ) {
 174                         return call_user_func( $params['factory'], $params );
 175                 } elseif ( isset( $params['class'] ) ) {
 176                         $class = $params['class'];
 177                         // Automatically set the 'async' update handler
 178                         $params['asyncHandler'] = isset( $params['asyncHandler'] )
 179                                 ? $params['asyncHandler']
 180                                 : 'DeferredUpdates::addCallableUpdate';
 181                         // Enable reportDupes by default
 182                         $params['reportDupes'] = isset( $params['reportDupes'] )
 183                                 ? $params['reportDupes']
 184                                 : true;
 185                         // Do b/c logic for MemcachedBagOStuff
 186                         if ( is_subclass_of( $class, 'MemcachedBagOStuff' ) ) {
 187                                 if ( !isset( $params['servers'] ) ) {
 188                                         $params['servers'] = $GLOBALS['wgMemCachedServers'];
 189                                 }
 190                                 if ( !isset( $params['debug'] ) ) {
 191                                         $params['debug'] = $GLOBALS['wgMemCachedDebug'];
 192                                 }
 193                                 if ( !isset( $params['persistent'] ) ) {
 194                                         $params['persistent'] = $GLOBALS['wgMemCachedPersistent'];
 195                                 }
 196                                 if ( !isset( $params['timeout'] ) ) {
 197                                         $params['timeout'] = $GLOBALS['wgMemCachedTimeout'];
 198                                 }
 199                         }
 200                         return new $class( $params );
 201                 } else {
 202                         throw new MWException( "The definition of cache type \""
 203                                 . print_r( $params, true ) . "\" lacks both "
 204                                 . "factory and class parameters." );
 205                 }
 206         }
 207
 208         /**
 209          * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php)
 210          *
 211          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 212          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 213          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 214          * be an alias to the configured cache choice for that.
 215          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 216          * then CACHE_ANYTHING will forward to CACHE_DB.
 217          *
 218          * @param array $params
 219          * @return BagOStuff
 220          */
 221         public static function newAnything( $params ) {
 222                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 223                 $candidates = [ $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType ];
 224                 foreach ( $candidates as $candidate ) {
 225                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 226                                 return self::getInstance( $candidate );
 227                         }
 228                 }
 229                 return self::getInstance( CACHE_DB );
 230         }
 231
 232         /**
 233          * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php)
 234          *
 235          * This will look for any APC style server-local cache.
 236          * A fallback cache can be specified if none is found.
 237          *
 238          *     // Direct calls
 239          *     ObjectCache::getLocalServerInstance( $fallbackType );
 240          *
 241          *     // From $wgObjectCaches via newFromParams()
 242          *     ObjectCache::getLocalServerInstance( array( 'fallback' => $fallbackType ) );
 243          *
 244          * @param int|string|array $fallback Fallback cache or parameter map with 'fallback'
 245          * @return BagOStuff
 246          * @throws MWException
 247          * @since 1.27
 248          */
 249         public static function getLocalServerInstance( $fallback = CACHE_NONE ) {
 250                 if ( function_exists( 'apc_fetch' ) ) {
 251                         $id = 'apc';
 252                 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
 253                         $id = 'xcache';
 254                 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
 255                         $id = 'wincache';
 256                 } else {
 257                         if ( is_array( $fallback ) ) {
 258                                 $id = isset( $fallback['fallback'] ) ? $fallback['fallback'] : CACHE_NONE;
 259                         } else {
 260                                 $id = $fallback;
 261                         }
 262                 }
 263
 264                 return self::getInstance( $id );
 265         }
 266
 267         /**
 268          * @param array $params [optional] Array key 'fallback' for $fallback.
 269          * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24)
 270          * @return BagOStuff
 271          * @deprecated 1.27
 272          */
 273         public static function newAccelerator( $params = [], $fallback = null ) {
 274                 if ( $fallback === null ) {
 275                         if ( is_array( $params ) && isset( $params['fallback'] ) ) {
 276                                 $fallback = $params['fallback'];
 277                         } elseif ( !is_array( $params ) ) {
 278                                 $fallback = $params;
 279                         }
 280                 }
 281
 282                 return self::getLocalServerInstance( $fallback );
 283         }
 284
 285         /**
 286          * Create a new cache object of the specified type.
 287          *
 288          * @since 1.26
 289          * @param string $id A key in $wgWANObjectCaches.
 290          * @return WANObjectCache
 291          * @throws MWException
 292          */
 293         public static function newWANCacheFromId( $id ) {
 294                 global $wgWANObjectCaches;
 295
 296                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 297                         throw new MWException( "Invalid object cache type \"$id\" requested. " .
 298                                 "It is not present in \$wgWANObjectCaches." );
 299                 }
 300
 301                 $params = $wgWANObjectCaches[$id];
 302                 foreach ( $params['channels'] as $action => $channel ) {
 303                         $params['relayers'][$action] = MediaWikiServices::getInstance()->getEventRelayerGroup()
 304                                 ->getRelayer( $channel );
 305                         $params['channels'][$action] = $channel;
 306                 }
 307                 $params['cache'] = self::newFromId( $params['cacheId'] );
 308                 if ( isset( $params['loggroup'] ) ) {
 309                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 310                 } else {
 311                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 312                 }
 313                 $class = $params['class'];
 314
 315                 return new $class( $params );
 316         }
 317
 318         /**
 319          * Get the main cluster-local cache object.
 320          *
 321          * @since 1.27
 322          * @return BagOStuff
 323          */
 324         public static function getLocalClusterInstance() {
 325                 global $wgMainCacheType;
 326
 327                 return self::getInstance( $wgMainCacheType );
 328         }
 329
 330         /**
 331          * Get the main WAN cache object.
 332          *
 333          * @since 1.26
 334          * @return WANObjectCache
 335          */
 336         public static function getMainWANInstance() {
 337                 global $wgMainWANCache;
 338
 339                 return self::getWANInstance( $wgMainWANCache );
 340         }
 341
 342         /**
 343          * Get the cache object for the main stash.
 344          *
 345          * Stash objects are BagOStuff instances suitable for storing light
 346          * weight data that is not canonically stored elsewhere (such as RDBMS).
 347          * Stashes should be configured to propagate changes to all data-centers.
 348          *
 349          * Callers should be prepared for:
 350          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 351          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 352          * In general, this means avoiding updates on idempotent HTTP requests and
 353          * avoiding an assumption of perfect serializability (or accepting anomalies).
 354          * Reads may be eventually consistent or data might rollback as nodes flap.
 355          * Callers can use BagOStuff:READ_LATEST to see the latest available data.
 356          *
 357          * @return BagOStuff
 358          * @since 1.26
 359          */
 360         public static function getMainStashInstance() {
 361                 global $wgMainStash;
 362
 363                 return self::getInstance( $wgMainStash );
 364         }
 365
 366         /**
 367          * Clear all the cached instances.
 368          */
 369         public static function clear() {
 370                 self::$instances = [];
 371                 self::$wanInstances = [];
 372         }
 373 }