3 * Functions to get cache objects.
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24 use MediaWiki\Logger\LoggerFactory
;
25 use MediaWiki\MediaWikiServices
;
28 * Functions to get cache objects
30 * The word "cache" has two main dictionary meanings, and both
31 * are used in this factory class. They are:
33 * - a) Cache (the computer science definition).
34 * A place to store copies or computations on existing data for
35 * higher access speeds.
37 * A place to store lightweight data that is not canonically
38 * stored anywhere else (e.g. a "hoard" of objects).
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.
44 * Primary entry points:
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.
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.
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.
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.
70 * - ObjectCache::getInstance( $cacheType )
71 * Purpose: Special cases (like tiered memory/disk caches).
72 * Get a specific cache type by key in $wgObjectCaches.
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.
81 /** @var BagOStuff[] Map of (id => BagOStuff) */
82 public static $instances = [];
83 /** @var WANObjectCache[] Map of (id => WANObjectCache) */
84 public static $wanInstances = [];
87 * Get a cached instance of the specified type of cache object.
89 * @param string $id A key in $wgObjectCaches.
92 public static function getInstance( $id ) {
93 if ( !isset( self
::$instances[$id] ) ) {
94 self
::$instances[$id] = self
::newFromId( $id );
97 return self
::$instances[$id];
101 * Get a cached instance of the specified type of WAN cache object.
104 * @param string $id A key in $wgWANObjectCaches.
105 * @return WANObjectCache
107 public static function getWANInstance( $id ) {
108 if ( !isset( self
::$wanInstances[$id] ) ) {
109 self
::$wanInstances[$id] = self
::newWANCacheFromId( $id );
112 return self
::$wanInstances[$id];
116 * Create a new cache object of the specified type.
118 * @param string $id A key in $wgObjectCaches.
120 * @throws MWException
122 public static function newFromId( $id ) {
123 global $wgObjectCaches;
125 if ( !isset( $wgObjectCaches[$id] ) ) {
126 throw new MWException( "Invalid object cache type \"$id\" requested. " .
127 "It is not present in \$wgObjectCaches." );
130 return self
::newFromParams( $wgObjectCaches[$id] );
134 * Get the default keyspace for this wiki.
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).
142 public static function getDefaultKeyspace() {
143 global $wgCachePrefix;
145 $keyspace = $wgCachePrefix;
146 if ( is_string( $keyspace ) && $keyspace !== '' ) {
154 * Create a new cache object from parameters.
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.
162 * @throws MWException
164 public static function newFromParams( $params ) {
165 if ( isset( $params['loggroup'] ) ) {
166 $params['logger'] = LoggerFactory
::getInstance( $params['loggroup'] );
168 $params['logger'] = LoggerFactory
::getInstance( 'objectcache' );
170 if ( !isset( $params['keyspace'] ) ) {
171 $params['keyspace'] = self
::getDefaultKeyspace();
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']
185 // Do b/c logic for MemcachedBagOStuff
186 if ( is_subclass_of( $class, 'MemcachedBagOStuff' ) ) {
187 if ( !isset( $params['servers'] ) ) {
188 $params['servers'] = $GLOBALS['wgMemCachedServers'];
190 if ( !isset( $params['debug'] ) ) {
191 $params['debug'] = $GLOBALS['wgMemCachedDebug'];
193 if ( !isset( $params['persistent'] ) ) {
194 $params['persistent'] = $GLOBALS['wgMemCachedPersistent'];
196 if ( !isset( $params['timeout'] ) ) {
197 $params['timeout'] = $GLOBALS['wgMemCachedTimeout'];
200 return new $class( $params );
202 throw new MWException( "The definition of cache type \""
203 . print_r( $params, true ) . "\" lacks both "
204 . "factory and class parameters." );
209 * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php)
211 * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option.
212 * If a caching method is configured for any of the main caches ($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.
218 * @param array $params
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 );
229 return self
::getInstance( CACHE_DB
);
233 * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php)
235 * This will look for any APC style server-local cache.
236 * A fallback cache can be specified if none is found.
239 * ObjectCache::getLocalServerInstance( $fallbackType );
241 * // From $wgObjectCaches via newFromParams()
242 * ObjectCache::getLocalServerInstance( array( 'fallback' => $fallbackType ) );
244 * @param int|string|array $fallback Fallback cache or parameter map with 'fallback'
246 * @throws MWException
249 public static function getLocalServerInstance( $fallback = CACHE_NONE
) {
250 if ( function_exists( 'apc_fetch' ) ) {
252 } elseif ( function_exists( 'xcache_get' ) && wfIniGetBool( 'xcache.var_size' ) ) {
254 } elseif ( function_exists( 'wincache_ucache_get' ) ) {
257 if ( is_array( $fallback ) ) {
258 $id = isset( $fallback['fallback'] ) ?
$fallback['fallback'] : CACHE_NONE
;
264 return self
::getInstance( $id );
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)
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 ) ) {
282 return self
::getLocalServerInstance( $fallback );
286 * Create a new cache object of the specified type.
289 * @param string $id A key in $wgWANObjectCaches.
290 * @return WANObjectCache
291 * @throws MWException
293 public static function newWANCacheFromId( $id ) {
294 global $wgWANObjectCaches;
296 if ( !isset( $wgWANObjectCaches[$id] ) ) {
297 throw new MWException( "Invalid object cache type \"$id\" requested. " .
298 "It is not present in \$wgWANObjectCaches." );
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;
307 $params['cache'] = self
::newFromId( $params['cacheId'] );
308 if ( isset( $params['loggroup'] ) ) {
309 $params['logger'] = LoggerFactory
::getInstance( $params['loggroup'] );
311 $params['logger'] = LoggerFactory
::getInstance( 'objectcache' );
313 $class = $params['class'];
315 return new $class( $params );
319 * Get the main cluster-local cache object.
324 public static function getLocalClusterInstance() {
325 global $wgMainCacheType;
327 return self
::getInstance( $wgMainCacheType );
331 * Get the main WAN cache object.
334 * @return WANObjectCache
336 public static function getMainWANInstance() {
337 global $wgMainWANCache;
339 return self
::getWANInstance( $wgMainWANCache );
343 * Get the cache object for the main stash.
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.
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.
360 public static function getMainStashInstance() {
363 return self
::getInstance( $wgMainStash );
367 * Clear all the cached instances.
369 public static function clear() {
370 self
::$instances = [];
371 self
::$wanInstances = [];