3 * Functions to get cache objects.
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24 use MediaWiki\Logger\LoggerFactory
;
27 * Functions to get cache objects
29 * The word "cache" has two main dictionary meanings, and both
30 * are used in this factory class. They are:
32 * - a) Cache (the computer science definition).
33 * A place to store copies or computations on existing data for
34 * higher access speeds.
36 * A place to store lightweight data that is not canonically
37 * stored anywhere else (e.g. a "hoard" of objects).
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.
43 * Primary entry points:
45 * - ObjectCache::newAccelerator( $fallbackType )
47 * Stored only on the individual web server.
48 * Not associated with other servers.
52 * Stored centrally within the local data-center.
53 * Not replicated to other DCs.
54 * Also known as $wgMemc. Configured by $wgMainCacheType.
56 * - ObjectCache::getMainWANInstance()
58 * Stored in the local data-center's main cache (uses different cache keys).
59 * Delete events are broadcasted to other DCs. See WANObjectCache for details.
61 * - ObjectCache::getMainStashInstance()
62 * Purpose: Ephemeral storage.
63 * Stored centrally within the local data-center.
64 * Changes are replicated to other DCs (eventually consistent).
65 * To retrieve the latest value (e.g. not from a slave), use BagOStuff:READ_LATEST.
66 * This store may be subject to LRU style evictions.
68 * - wfGetCache( $cacheType )
69 * Get a specific cache type by key in $wgObjectCaches.
74 /** @var Array Map of (id => BagOStuff) */
75 public static $instances = array();
77 /** @var Array Map of (id => WANObjectCache) */
78 public static $wanInstances = array();
81 * Get a cached instance of the specified type of cache object.
83 * @param string $id A key in $wgObjectCaches.
86 public static function getInstance( $id ) {
87 if ( !isset( self
::$instances[$id] ) ) {
88 self
::$instances[$id] = self
::newFromId( $id );
91 return self
::$instances[$id];
95 * Get a cached instance of the specified type of WAN cache object.
98 * @param string $id A key in $wgWANObjectCaches.
99 * @return WANObjectCache
101 public static function getWANInstance( $id ) {
102 if ( !isset( self
::$wanInstances[$id] ) ) {
103 self
::$wanInstances[$id] = self
::newWANCacheFromId( $id );
106 return self
::$wanInstances[$id];
110 * Create a new cache object of the specified type.
112 * @param string $id A key in $wgObjectCaches.
114 * @throws MWException
116 public static function newFromId( $id ) {
117 global $wgObjectCaches;
119 if ( !isset( $wgObjectCaches[$id] ) ) {
120 throw new MWException( "Invalid object cache type \"$id\" requested. " .
121 "It is not present in \$wgObjectCaches." );
124 return self
::newFromParams( $wgObjectCaches[$id] );
128 * Create a new cache object from parameters.
130 * @param array $params Must have 'factory' or 'class' property.
131 * - factory: Callback passed $params that returns BagOStuff.
132 * - class: BagOStuff subclass constructed with $params.
133 * - loggroup: Alias to set 'logger' key with LoggerFactory group.
134 * - .. Other parameters passed to factory or class.
136 * @throws MWException
138 public static function newFromParams( $params ) {
139 if ( isset( $params['loggroup'] ) ) {
140 $params['logger'] = LoggerFactory
::getInstance( $params['loggroup'] );
142 // For backwards-compatability with custom parameters, lets not
143 // have all logging suddenly disappear
144 $params['logger'] = LoggerFactory
::getInstance( 'objectcache' );
146 if ( isset( $params['factory'] ) ) {
147 return call_user_func( $params['factory'], $params );
148 } elseif ( isset( $params['class'] ) ) {
149 $class = $params['class'];
150 return new $class( $params );
152 throw new MWException( "The definition of cache type \""
153 . print_r( $params, true ) . "\" lacks both "
154 . "factory and class parameters." );
159 * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php)
161 * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
162 * If a caching method is configured for any of the main caches ($wgMainCacheType,
163 * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively
164 * be an alias to the configured cache choice for that.
165 * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE),
166 * then CACHE_ANYTHING will forward to CACHE_DB.
168 * @param array $params
171 public static function newAnything( $params ) {
172 global $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType;
173 $candidates = array( $wgMainCacheType, $wgMessageCacheType, $wgParserCacheType );
174 foreach ( $candidates as $candidate ) {
175 if ( $candidate !== CACHE_NONE
&& $candidate !== CACHE_ANYTHING
) {
176 return self
::getInstance( $candidate );
179 return self
::getInstance( CACHE_DB
);
183 * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php)
185 * This will look for any APC style server-local cache.
186 * A fallback cache can be specified if none is found.
188 * @param array $params [optional]
189 * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24)
191 * @throws MWException
193 public static function newAccelerator( $params = array(), $fallback = null ) {
194 if ( !is_array( $params ) && $fallback === null ) {
197 if ( function_exists( 'apc_fetch' ) ) {
199 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
201 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
204 if ( $fallback === null ) {
205 throw new MWException( 'CACHE_ACCEL requested but no suitable object ' .
206 'cache is present. You may want to install APC.' );
210 return self
::newFromId( $id );
214 * Factory function that creates a memcached client object.
216 * This always uses the PHP client, since the PECL client has a different
217 * hashing scheme and a different interpretation of the flags bitfield, so
218 * switching between the two clients randomly would be disastrous.
220 * @param array $params
221 * @return MemcachedPhpBagOStuff
223 public static function newMemcached( $params ) {
224 return new MemcachedPhpBagOStuff( $params );
228 * Create a new cache object of the specified type.
231 * @param string $id A key in $wgWANObjectCaches.
232 * @return WANObjectCache
233 * @throws MWException
235 public static function newWANCacheFromId( $id ) {
236 global $wgWANObjectCaches;
238 if ( !isset( $wgWANObjectCaches[$id] ) ) {
239 throw new MWException( "Invalid object cache type \"$id\" requested. " .
240 "It is not present in \$wgWANObjectCaches." );
243 $params = $wgWANObjectCaches[$id];
244 $class = $params['relayerConfig']['class'];
245 $params['relayer'] = new $class( $params['relayerConfig'] );
246 $params['cache'] = self
::newFromId( $params['cacheId'] );
247 $class = $params['class'];
249 return new $class( $params );
253 * Get the main WAN cache object.
256 * @return WANObjectCache
258 public static function getMainWANInstance() {
259 global $wgMainWANCache;
261 return self
::getWANInstance( $wgMainWANCache );
265 * Get the cache object for the main stash.
267 * Stash objects are BagOStuff instances suitable for storing light
268 * weight data that is not canonically stored elsewhere (such as RDBMS).
269 * Stashes should be configured to propagate changes to all data-centers.
271 * Callers should be prepared for:
272 * - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs
273 * - b) Reads to be eventually consistent, e.g. for get()/getMulti()
274 * In general, this means avoiding updates on idempotent HTTP requests and
275 * avoiding an assumption of perfect serializability (or accepting anomalies).
276 * Reads may be eventually consistent or data might rollback as nodes flap.
277 * Callers can use BagOStuff:READ_LATEST to see the latest available data.
282 public static function getMainStashInstance() {
285 return self
::getInstance( $wgMainStash );
289 * Clear all the cached instances.
291 public static function clear() {
292 self
::$instances = array();
293 self
::$wanInstances = array();