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'] = $params['asyncHandler'] ?? 'DeferredUpdates::addCallableUpdate';
 186                         // Enable reportDupes by default
 187                         $params['reportDupes'] = $params['reportDupes'] ?? true;
 188                         // Do b/c logic for SqlBagOStuff
 189                         if ( is_a( $class, SqlBagOStuff::class, true ) ) {
 190                                 if ( isset( $params['server'] ) && !isset( $params['servers'] ) ) {
 191                                         $params['servers'] = [ $params['server'] ];
 192                                         unset( $params['server'] );
 193                                 }
 194                                 // In the past it was not required to set 'dbDirectory' in $wgObjectCaches
 195                                 if ( isset( $params['servers'] ) ) {
 196                                         foreach ( $params['servers'] as &$server ) {
 197                                                 if ( $server['type'] === 'sqlite' && !isset( $server['dbDirectory'] ) ) {
 198                                                         $server['dbDirectory'] = MediaWikiServices::getInstance()
 199                                                                 ->getMainConfig()->get( 'SQLiteDataDir' );
 200                                                 }
 201                                         }
 202                                 }
 203                         }
 204
 205                         // Do b/c logic for MemcachedBagOStuff
 206                         if ( is_subclass_of( $class, MemcachedBagOStuff::class ) ) {
 207                                 if ( !isset( $params['servers'] ) ) {
 208                                         $params['servers'] = $GLOBALS['wgMemCachedServers'];
 209                                 }
 210                                 if ( !isset( $params['debug'] ) ) {
 211                                         $params['debug'] = $GLOBALS['wgMemCachedDebug'];
 212                                 }
 213                                 if ( !isset( $params['persistent'] ) ) {
 214                                         $params['persistent'] = $GLOBALS['wgMemCachedPersistent'];
 215                                 }
 216                                 if ( !isset( $params['timeout'] ) ) {
 217                                         $params['timeout'] = $GLOBALS['wgMemCachedTimeout'];
 218                                 }
 219                         }
 220                         return new $class( $params );
 221                 } else {
 222                         throw new InvalidArgumentException( "The definition of cache type \""
 223                                 . print_r( $params, true ) . "\" lacks both "
 224                                 . "factory and class parameters." );
 225                 }
 226         }
 227
 228         /**
 229          * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php)
 230          *
 231          * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
 232          * If a caching method is configured for any of the main caches ($wgMainCacheType,
 233          * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
 234          * be an alias to the configured cache choice for that.
 235          * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
 236          * then CACHE_ANYTHING will forward to CACHE_DB.
 237          *
 238          * @param array $params
 239          * @return BagOStuff
 240          */
 241         public static function newAnything( $params ) {
 242                 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
 243                 $candidates = [ $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType ];
 244                 foreach ( $candidates as $candidate ) {
 245                         $cache = false;
 246                         if ( $candidate !== CACHE_NONE && $candidate !== CACHE_ANYTHING ) {
 247                                 $cache = self::getInstance( $candidate );
 248                                 // CACHE_ACCEL might default to nothing if no APCu
 249                                 // See includes/ServiceWiring.php
 250                                 if ( !( $cache instanceof EmptyBagOStuff ) ) {
 251                                         return $cache;
 252                                 }
 253                         }
 254                 }
 255
 256                 if ( MediaWikiServices::getInstance()->isServiceDisabled( 'DBLoadBalancer' ) ) {
 257                         // The LoadBalancer is disabled, probably because
 258                         // MediaWikiServices::disableStorageBackend was called.
 259                         $candidate = CACHE_NONE;
 260                 } else {
 261                         $candidate = CACHE_DB;
 262                 }
 263
 264                 return self::getInstance( $candidate );
 265         }
 266
 267         /**
 268          * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php)
 269          *
 270          * This will look for any APC or APCu style server-local cache.
 271          * A fallback cache can be specified if none is found.
 272          *
 273          *     // Direct calls
 274          *     ObjectCache::getLocalServerInstance( $fallbackType );
 275          *
 276          *     // From $wgObjectCaches via newFromParams()
 277          *     ObjectCache::getLocalServerInstance( [ 'fallback' => $fallbackType ] );
 278          *
 279          * @param int|string|array $fallback Fallback cache or parameter map with 'fallback'
 280          * @return BagOStuff
 281          * @throws InvalidArgumentException
 282          * @since 1.27
 283          */
 284         public static function getLocalServerInstance( $fallback = CACHE_NONE ) {
 285                 $cache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
 286                 if ( $cache instanceof EmptyBagOStuff ) {
 287                         if ( is_array( $fallback ) ) {
 288                                 $fallback = $fallback['fallback'] ?? CACHE_NONE;
 289                         }
 290                         $cache = self::getInstance( $fallback );
 291                 }
 292
 293                 return $cache;
 294         }
 295
 296         /**
 297          * Create a new cache object of the specified type.
 298          *
 299          * @since 1.26
 300          * @param string $id A key in $wgWANObjectCaches.
 301          * @return WANObjectCache
 302          * @throws UnexpectedValueException
 303          */
 304         public static function newWANCacheFromId( $id ) {
 305                 global $wgWANObjectCaches, $wgObjectCaches;
 306
 307                 if ( !isset( $wgWANObjectCaches[$id] ) ) {
 308                         throw new UnexpectedValueException(
 309                                 "Cache type \"$id\" requested is not present in \$wgWANObjectCaches." );
 310                 }
 311
 312                 $params = $wgWANObjectCaches[$id];
 313                 if ( !isset( $wgObjectCaches[$params['cacheId']] ) ) {
 314                         throw new UnexpectedValueException(
 315                                 "Cache type \"{$params['cacheId']}\" is not present in \$wgObjectCaches." );
 316                 }
 317                 $params['store'] = $wgObjectCaches[$params['cacheId']];
 318
 319                 return self::newWANCacheFromParams( $params );
 320         }
 321
 322         /**
 323          * Create a new cache object of the specified type.
 324          *
 325          * @since 1.28
 326          * @param array $params
 327          * @return WANObjectCache
 328          * @throws UnexpectedValueException
 329          */
 330         public static function newWANCacheFromParams( array $params ) {
 331                 global $wgCommandLineMode;
 332
 333                 $services = MediaWikiServices::getInstance();
 334
 335                 $erGroup = $services->getEventRelayerGroup();
 336                 if ( isset( $params['channels'] ) ) {
 337                         foreach ( $params['channels'] as $action => $channel ) {
 338                                 $params['relayers'][$action] = $erGroup->getRelayer( $channel );
 339                                 $params['channels'][$action] = $channel;
 340                         }
 341                 }
 342                 $params['cache'] = self::newFromParams( $params['store'] );
 343                 if ( isset( $params['loggroup'] ) ) {
 344                         $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] );
 345                 } else {
 346                         $params['logger'] = LoggerFactory::getInstance( 'objectcache' );
 347                 }
 348                 if ( !$wgCommandLineMode ) {
 349                         // Send the statsd data post-send on HTTP requests; avoid in CLI mode (T181385)
 350                         $params['stats'] = $services->getStatsdDataFactory();
 351                         // Let pre-emptive refreshes happen post-send on HTTP requests
 352                         $params['asyncHandler'] = [ DeferredUpdates::class, 'addCallableUpdate' ];
 353                 }
 354                 $class = $params['class'];
 355
 356                 return new $class( $params );
 357         }
 358
 359         /**
 360          * Get the main cluster-local cache object.
 361          *
 362          * @since 1.27
 363          * @return BagOStuff
 364          */
 365         public static function getLocalClusterInstance() {
 366                 global $wgMainCacheType;
 367
 368                 return self::getInstance( $wgMainCacheType );
 369         }
 370
 371         /**
 372          * Get the main WAN cache object.
 373          *
 374          * @since 1.26
 375          * @return WANObjectCache
 376          * @deprecated Since 1.28 Use MediaWikiServices::getMainWANObjectCache()
 377          */
 378         public static function getMainWANInstance() {
 379                 return MediaWikiServices::getInstance()->getMainWANObjectCache();
 380         }
 381
 382         /**
 383          * Get the cache object for the main stash.
 384          *
 385          * Stash objects are BagOStuff instances suitable for storing light
 386          * weight data that is not canonically stored elsewhere (such as RDBMS).
 387          * Stashes should be configured to propagate changes to all data-centers.
 388          *
 389          * Callers should be prepared for:
 390          *   - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
 391          *   - b) Reads to be eventually consistent, e.g. for get()/getMulti()
 392          * In general, this means avoiding updates on idempotent HTTP requests and
 393          * avoiding an assumption of perfect serializability (or accepting anomalies).
 394          * Reads may be eventually consistent or data might rollback as nodes flap.
 395          * Callers can use BagOStuff:READ_LATEST to see the latest available data.
 396          *
 397          * @return BagOStuff
 398          * @since 1.26
 399          * @deprecated Since 1.28 Use MediaWikiServices::getMainObjectStash
 400          */
 401         public static function getMainStashInstance() {
 402                 return MediaWikiServices::getInstance()->getMainObjectStash();
 403         }
 404
 405         /**
 406          * Clear all the cached instances.
 407          */
 408         public static function clear() {
 409                 self::$instances = [];
 410                 self::$wanInstances = [];
 411         }
 412
 413         /**
 414          * Detects which local server cache library is present and returns a configuration for it
 415          * @since 1.32
 416          *
 417          * @return int|string Index to cache in $wgObjectCaches
 418          */
 419         public static function detectLocalServerCache() {
 420                 if ( function_exists( 'apc_fetch' ) ) {
 421                         return 'apc';
 422                 } elseif ( function_exists( 'apcu_fetch' ) ) {
 423                         return 'apcu';
 424                 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
 425                         return 'wincache';
 426                 }
 427                 return CACHE_NONE;
 428         }
 429 }