diff options
Diffstat (limited to 'includes/objectcache/ObjectCache.php')
| -rw-r--r-- | includes/objectcache/ObjectCache.php | 189 |
1 files changed, 157 insertions, 32 deletions
diff --git a/includes/objectcache/ObjectCache.php b/includes/objectcache/ObjectCache.php index 2e47e24a..60191057 100644 --- a/includes/objectcache/ObjectCache.php +++ b/includes/objectcache/ObjectCache.php @@ -26,44 +26,94 @@ use MediaWiki\Logger\LoggerFactory; /** * Functions to get cache objects * + * The word "cache" has two main dictionary meanings, and both + * are used in this factory class. They are: + * + * - a) Cache (the computer science definition). + * A place to store copies or computations on existing data for + * higher access speeds. + * - b) Storage. + * A place to store lightweight data that is not canonically + * stored anywhere else (e.g. a "hoard" of objects). + * + * The former should always use strongly consistent stores, so callers don't + * have to deal with stale reads. The later may be eventually consistent, but + * callers can use BagOStuff:READ_LATEST to see the latest available data. + * + * Primary entry points: + * + * - ObjectCache::newAccelerator( $fallbackType ) + * Purpose: Cache. + * Stored only on the individual web server. + * Not associated with other servers. + * + * - wfGetMainCache() + * Purpose: Cache. + * Stored centrally within the local data-center. + * Not replicated to other DCs. + * Also known as $wgMemc. Configured by $wgMainCacheType. + * + * - ObjectCache::getMainWANInstance() + * Purpose: Cache. + * Stored in the local data-center's main cache (uses different cache keys). + * Delete events are broadcasted to other DCs. See WANObjectCache for details. + * + * - ObjectCache::getMainStashInstance() + * Purpose: Ephemeral storage. + * Stored centrally within the local data-center. + * Changes are replicated to other DCs (eventually consistent). + * To retrieve the latest value (e.g. not from a slave), use BagOStuff:READ_LATEST. + * This store may be subject to LRU style evictions. + * + * - wfGetCache( $cacheType ) + * Get a specific cache type by key in $wgObjectCaches. + * * @ingroup Cache */ class ObjectCache { + /** @var Array Map of (id => BagOStuff) */ public static $instances = array(); + /** @var Array Map of (id => WANObjectCache) */ + public static $wanInstances = array(); + /** * Get a cached instance of the specified type of cache object. * - * @param string $id - * + * @param string $id A key in $wgObjectCaches. * @return BagOStuff */ - static function getInstance( $id ) { - if ( isset( self::$instances[$id] ) ) { - return self::$instances[$id]; + public static function getInstance( $id ) { + if ( !isset( self::$instances[$id] ) ) { + self::$instances[$id] = self::newFromId( $id ); } - $object = self::newFromId( $id ); - self::$instances[$id] = $object; - return $object; + return self::$instances[$id]; } /** - * Clear all the cached instances. + * Get a cached instance of the specified type of WAN cache object. + * + * @since 1.26 + * @param string $id A key in $wgWANObjectCaches. + * @return WANObjectCache */ - static function clear() { - self::$instances = array(); + public static function getWANInstance( $id ) { + if ( !isset( self::$wanInstances[$id] ) ) { + self::$wanInstances[$id] = self::newWANCacheFromId( $id ); + } + + return self::$wanInstances[$id]; } /** * Create a new cache object of the specified type. * - * @param string $id - * - * @throws MWException + * @param string $id A key in $wgObjectCaches. * @return BagOStuff + * @throws MWException */ - static function newFromId( $id ) { + public static function newFromId( $id ) { global $wgObjectCaches; if ( !isset( $wgObjectCaches[$id] ) ) { @@ -75,14 +125,17 @@ class ObjectCache { } /** - * Create a new cache object from parameters - * - * @param array $params + * Create a new cache object from parameters. * - * @throws MWException + * @param array $params Must have 'factory' or 'class' property. + * - factory: Callback passed $params that returns BagOStuff. + * - class: BagOStuff subclass constructed with $params. + * - loggroup: Alias to set 'logger' key with LoggerFactory group. + * - .. Other parameters passed to factory or class. * @return BagOStuff + * @throws MWException */ - static function newFromParams( $params ) { + public static function newFromParams( $params ) { if ( isset( $params['loggroup'] ) ) { $params['logger'] = LoggerFactory::getInstance( $params['loggroup'] ); } else { @@ -103,7 +156,7 @@ class ObjectCache { } /** - * Factory function referenced from DefaultSettings.php for CACHE_ANYTHING + * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php) * * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option. * If a caching method is configured for any of the main caches ($wgMainCacheType, @@ -111,10 +164,11 @@ class ObjectCache { * be an alias to the configured cache choice for that. * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE), * then CACHE_ANYTHING will forward to CACHE_DB. + * * @param array $params * @return BagOStuff */ - static function newAnything( $params ) { + public static function newAnything( $params ) { global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType; $candidates = array( $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType ); foreach ( $candidates as $candidate ) { @@ -126,17 +180,20 @@ class ObjectCache { } /** - * Factory function referenced from DefaultSettings.php for CACHE_ACCEL. + * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php) * * This will look for any APC style server-local cache. * A fallback cache can be specified if none is found. * - * @param array $params + * @param array $params [optional] * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24) - * @throws MWException * @return BagOStuff + * @throws MWException */ - static function newAccelerator( $params, $fallback = null ) { + public static function newAccelerator( $params = array(), $fallback = null ) { + if ( !is_array( $params ) && $fallback === null ) { + $fallback = $params; + } if ( function_exists( 'apc_fetch' ) ) { $id = 'apc'; } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) { @@ -144,11 +201,11 @@ class ObjectCache { } elseif ( function_exists( 'wincache_ucache_get' ) ) { $id = 'wincache'; } else { - if ( $fallback !== null ) { - return self::newFromId( $fallback ); + if ( $fallback === null ) { + throw new MWException( 'CACHE_ACCEL requested but no suitable object ' . + 'cache is present. You may want to install APC.' ); } - throw new MWException( "CACHE_ACCEL requested but no suitable object " . - "cache is present. You may want to install APC." ); + $id = $fallback; } return self::newFromId( $id ); } @@ -161,10 +218,78 @@ class ObjectCache { * switching between the two clients randomly would be disastrous. * * @param array $params - * * @return MemcachedPhpBagOStuff */ - static function newMemcached( $params ) { + public static function newMemcached( $params ) { return new MemcachedPhpBagOStuff( $params ); } + + /** + * Create a new cache object of the specified type. + * + * @since 1.26 + * @param string $id A key in $wgWANObjectCaches. + * @return WANObjectCache + * @throws MWException + */ + public static function newWANCacheFromId( $id ) { + global $wgWANObjectCaches; + + if ( !isset( $wgWANObjectCaches[$id] ) ) { + throw new MWException( "Invalid object cache type \"$id\" requested. " . + "It is not present in \$wgWANObjectCaches." ); + } + + $params = $wgWANObjectCaches[$id]; + $class = $params['relayerConfig']['class']; + $params['relayer'] = new $class( $params['relayerConfig'] ); + $params['cache'] = self::newFromId( $params['cacheId'] ); + $class = $params['class']; + + return new $class( $params ); + } + + /** + * Get the main WAN cache object. + * + * @since 1.26 + * @return WANObjectCache + */ + public static function getMainWANInstance() { + global $wgMainWANCache; + + return self::getWANInstance( $wgMainWANCache ); + } + + /** + * Get the cache object for the main stash. + * + * Stash objects are BagOStuff instances suitable for storing light + * weight data that is not canonically stored elsewhere (such as RDBMS). + * Stashes should be configured to propagate changes to all data-centers. + * + * Callers should be prepared for: + * - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs + * - b) Reads to be eventually consistent, e.g. for get()/getMulti() + * In general, this means avoiding updates on idempotent HTTP requests and + * avoiding an assumption of perfect serializability (or accepting anomalies). + * Reads may be eventually consistent or data might rollback as nodes flap. + * Callers can use BagOStuff:READ_LATEST to see the latest available data. + * + * @return BagOStuff + * @since 1.26 + */ + public static function getMainStashInstance() { + global $wgMainStash; + + return self::getInstance( $wgMainStash ); + } + + /** + * Clear all the cached instances. + */ + public static function clear() { + self::$instances = array(); + self::$wanInstances = array(); + } } |