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 latter 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 or APCu 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 replica DB), 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 InvalidArgumentException
 121          */
 122         public static function newFromId( $id ) {
 123                 global $wgObjectCaches;
 124
 125                 if ( !isset( $wgObjectCaches[$id] ) ) {
 126                         // Always recognize these ones
 127                         if ( $id === CACHE_NONE ) {
 128                                 return new EmptyBagOStuff();
 129                         } elseif ( $id === 'hash' ) {
 130                                 return new HashBagOStuff();
 131                         }
 132
 133                         throw new InvalidArgumentException( "Invalid object cache type \"$id\" requested. " .
 134                                 "It is not present in \$wgObjectCaches." );
 135                 }
 136
 137                 return self::newFromParams( $wgObjectCaches[$id] );
 138         }
 139
 140         /**
 141          * Get the default keyspace for this wiki.
 142          *
 143          * This is either the value of the `CachePrefix` configuration variable,
 144          * or (if the former is unset) the `DBname` configuration variable, with
 145          * `DBprefix` (if defined).
 146          *
 147          * @return string
 148          */
 149         public static function getDefaultKeyspace() {
 150                 global $wgCachePrefix;
 151
 152                 $keyspace = $wgCachePrefix;
 153                 if ( is_string( $keyspace ) && $keyspace !== '' ) {
 154                         return $keyspace;
 155                 }
 156
 157                 return wfWikiID();
 158         }
 159
 160         /**
 161          * Create a new cache object from parameters.
 162          *
 163          * @param array $params Must have 'factory' or 'class' property.
 164          *  - factory: Callback passed $params that returns BagOStuff.
 165          *  - class: BagOStuff subclass constructed with $params.
 166          *  - loggroup: Alias to set 'logger' key with LoggerFactory group.
 167          *  - .. Other parameters passed to factory or class.
 168          * @return BagOStuff
 169          * @throws InvalidArgumentException
 170          */
 171         public static function newFromParams( $params ) {
 172                 if ( isset( $params['loggroup'] ) ) {
 173                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 174                 } else {
 175                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 176                 }
 177                 if ( !isset( $params['keyspace'] ) ) {
 178                         $params['keyspace'] = self::getDefaultKeyspace();
 179                 }
 180                 if ( isset( $params['factory'] ) ) {
 181                         return call_user_func( $params['factory'], $params );
 182                 } elseif ( isset( $params['class'] ) ) {
 183                         $class = $params['class'];
 184                         // Automatically set the 'async' update handler
 185                         $params['asyncHandler'] = isset( $params['asyncHandler'] )
 186                                 ? $params['asyncHandler']
 187                                 : 'DeferredUpdates::addCallableUpdate';
 188                         // Enable reportDupes by default
 189                         $params['reportDupes'] = isset( $params['reportDupes'] )
 190                                 ? $params['reportDupes']
 191                                 : true;
 192                         // Do b/c logic for SqlBagOStuff
 193                         if ( is_a( $class, SqlBagOStuff::class, true ) ) {
 194                                 if ( isset( $params['server'] ) && !isset( $params['servers'] ) ) {
 195                                         $params['servers'] = [ $params['server'] ];
 196                                         unset( $params['server'] );
 197                                 }
 198                                 // In the past it was not required to set 'dbDirectory' in $wgObjectCaches
 199                                 if ( isset( $params['servers'] ) ) {
 200                                         foreach ( $params['servers'] as &$server ) {
 201                                                 if ( $server['type'] === 'sqlite' && !isset( $server['dbDirectory'] ) ) {
 202                                                         $server['dbDirectory'] = MediaWikiServices::getInstance()
 203                                                                 ->getMainConfig()->get( 'SQLiteDataDir' );
 204                                                 }
 205                                         }
 206                                 }
 207                         }
 208
 209                         // Do b/c logic for MemcachedBagOStuff
 210                         if ( is_subclass_of( $class, MemcachedBagOStuff::class ) ) {
 211                                 if ( !isset( $params['servers'] ) ) {
 212                                         $params['servers'] = $GLOBALS['wgMemCachedServers'];
 213                                 }
 214                                 if ( !isset( $params['debug'] ) ) {
 215                                         $params['debug'] = $GLOBALS['wgMemCachedDebug'];
 216                                 }
 217                                 if ( !isset( $params['persistent'] ) ) {
 218                                         $params['persistent'] = $GLOBALS['wgMemCachedPersistent'];
 219                                 }
 220                                 if ( !isset( $params['timeout'] ) ) {
 221                                         $params['timeout'] = $GLOBALS['wgMemCachedTimeout'];
 222                                 }
 223                         }
 224                         return new $class( $params );
 225                 } else {
 226                         throw new InvalidArgumentException( "The definition of cache type \""
 227                                 . print_r( $params, true ) . "\" lacks both "
 228                                 . "factory and class parameters." );
 229                 }
 230         }
 231
 232         /**
 233          * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php)
 234          *
 235          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 236          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 237          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 238          * be an alias to the configured cache choice for that.
 239          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 240          * then CACHE_ANYTHING will forward to CACHE_DB.
 241          *
 242          * @param array $params
 243          * @return BagOStuff
 244          */
 245         public static function newAnything( $params ) {
 246                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 247                 $candidates = [ $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType ];
 248                 foreach ( $candidates as $candidate ) {
 249                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 250                                 return self::getInstance( $candidate );
 251                         }
 252                 }
 253
 254                 if ( MediaWikiServices::getInstance()->isServiceDisabled( 'DBLoadBalancer' ) ) {
 255                         // The LoadBalancer is disabled, probably because
 256                         // MediaWikiServices::disableStorageBackend was called.
 257                         $candidate = CACHE_NONE;
 258                 } else {
 259                         $candidate = CACHE_DB;
 260                 }
 261
 262                 return self::getInstance( $candidate );
 263         }
 264
 265         /**
 266          * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php)
 267          *
 268          * This will look for any APC or APCu style server-local cache.
 269          * A fallback cache can be specified if none is found.
 270          *
 271          *     // Direct calls
 272          *     ObjectCache::getLocalServerInstance( $fallbackType );
 273          *
 274          *     // From $wgObjectCaches via newFromParams()
 275          *     ObjectCache::getLocalServerInstance( [ 'fallback' => $fallbackType ] );
 276          *
 277          * @param int|string|array $fallback Fallback cache or parameter map with 'fallback'
 278          * @return BagOStuff
 279          * @throws InvalidArgumentException
 280          * @since 1.27
 281          */
 282         public static function getLocalServerInstance( $fallback = CACHE_NONE ) {
 283                 $cache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
 284                 if ( $cache instanceof EmptyBagOStuff ) {
 285                         if ( is_array( $fallback ) ) {
 286                                 $fallback = isset( $fallback['fallback'] ) ? $fallback['fallback'] : CACHE_NONE;
 287                         }
 288                         $cache = self::getInstance( $fallback );
 289                 }
 290
 291                 return $cache;
 292         }
 293
 294         /**
 295          * Create a new cache object of the specified type.
 296          *
 297          * @since 1.26
 298          * @param string $id A key in $wgWANObjectCaches.
 299          * @return WANObjectCache
 300          * @throws UnexpectedValueException
 301          */
 302         public static function newWANCacheFromId( $id ) {
 303                 global $wgWANObjectCaches, $wgObjectCaches;
 304
 305                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 306                         throw new UnexpectedValueException(
 307                                 "Cache type \"$id\" requested is not present in \$wgWANObjectCaches." );
 308                 }
 309
 310                 $params = $wgWANObjectCaches[$id];
 311                 if ( !isset( $wgObjectCaches[$params['cacheId']] ) ) {
 312                         throw new UnexpectedValueException(
 313                                 "Cache type \"{$params['cacheId']}\" is not present in \$wgObjectCaches." );
 314                 }
 315                 $params['store'] = $wgObjectCaches[$params['cacheId']];
 316
 317                 return self::newWANCacheFromParams( $params );
 318         }
 319
 320         /**
 321          * Create a new cache object of the specified type.
 322          *
 323          * @since 1.28
 324          * @param array $params
 325          * @return WANObjectCache
 326          * @throws UnexpectedValueException
 327          */
 328         public static function newWANCacheFromParams( array $params ) {
 329                 foreach ( $params['channels'] as $action => $channel ) {
 330                         $params['relayers'][$action] = MediaWikiServices::getInstance()->getEventRelayerGroup()
 331                                 ->getRelayer( $channel );
 332                         $params['channels'][$action] = $channel;
 333                 }
 334                 $params['cache'] = self::newFromParams( $params['store'] );
 335                 if ( isset( $params['loggroup'] ) ) {
 336                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 337                 } else {
 338                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 339                 }
 340                 $class = $params['class'];
 341
 342                 return new $class( $params );
 343         }
 344
 345         /**
 346          * Get the main cluster-local cache object.
 347          *
 348          * @since 1.27
 349          * @return BagOStuff
 350          */
 351         public static function getLocalClusterInstance() {
 352                 global $wgMainCacheType;
 353
 354                 return self::getInstance( $wgMainCacheType );
 355         }
 356
 357         /**
 358          * Get the main WAN cache object.
 359          *
 360          * @since 1.26
 361          * @return WANObjectCache
 362          * @deprecated Since 1.28 Use MediaWikiServices::getMainWANCache()
 363          */
 364         public static function getMainWANInstance() {
 365                 return MediaWikiServices::getInstance()->getMainWANObjectCache();
 366         }
 367
 368         /**
 369          * Get the cache object for the main stash.
 370          *
 371          * Stash objects are BagOStuff instances suitable for storing light
 372          * weight data that is not canonically stored elsewhere (such as RDBMS).
 373          * Stashes should be configured to propagate changes to all data-centers.
 374          *
 375          * Callers should be prepared for:
 376          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 377          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 378          * In general, this means avoiding updates on idempotent HTTP requests and
 379          * avoiding an assumption of perfect serializability (or accepting anomalies).
 380          * Reads may be eventually consistent or data might rollback as nodes flap.
 381          * Callers can use BagOStuff:READ_LATEST to see the latest available data.
 382          *
 383          * @return BagOStuff
 384          * @since 1.26
 385          * @deprecated Since 1.28 Use MediaWikiServices::getMainObjectStash
 386          */
 387         public static function getMainStashInstance() {
 388                 return MediaWikiServices::getInstance()->getMainObjectStash();
 389         }
 390
 391         /**
 392          * Clear all the cached instances.
 393          */
 394         public static function clear() {
 395                 self::$instances = [];
 396                 self::$wanInstances = [];
 397         }
 398 }