wikimedia /
mediawiki
Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
Complex classes like ObjectCache often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use ObjectCache, and based on these observations, apply Extract Interface, too.
| 1 | <?php |
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| 80 | class ObjectCache { |
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| 81 | /** @var BagOStuff[] Map of (id => BagOStuff) */ |
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| 82 | public static $instances = []; |
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| 83 | /** @var WANObjectCache[] Map of (id => WANObjectCache) */ |
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| 84 | public static $wanInstances = []; |
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| 85 | |||
| 86 | /** |
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| 87 | * Get a cached instance of the specified type of cache object. |
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| 88 | * |
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| 89 | * @param string $id A key in $wgObjectCaches. |
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| 90 | * @return BagOStuff |
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| 91 | */ |
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| 92 | public static function getInstance( $id ) { |
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| 99 | |||
| 100 | /** |
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| 101 | * Get a cached instance of the specified type of WAN cache object. |
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| 102 | * |
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| 103 | * @since 1.26 |
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| 104 | * @param string $id A key in $wgWANObjectCaches. |
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| 105 | * @return WANObjectCache |
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| 106 | */ |
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| 107 | public static function getWANInstance( $id ) { |
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| 114 | |||
| 115 | /** |
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| 116 | * Create a new cache object of the specified type. |
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| 117 | * |
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| 118 | * @param string $id A key in $wgObjectCaches. |
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| 119 | * @return BagOStuff |
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| 120 | * @throws MWException |
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| 121 | */ |
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| 122 | public static function newFromId( $id ) { |
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| 132 | |||
| 133 | /** |
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| 134 | * Get the default keyspace for this wiki. |
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| 135 | * |
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| 136 | * This is either the value of the `CachePrefix` configuration variable, |
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| 137 | * or (if the former is unset) the `DBname` configuration variable, with |
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| 138 | * `DBprefix` (if defined). |
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| 139 | * |
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| 140 | * @return string |
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| 141 | */ |
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| 142 | public static function getDefaultKeyspace() { |
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| 152 | |||
| 153 | /** |
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| 154 | * Create a new cache object from parameters. |
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| 155 | * |
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| 156 | * @param array $params Must have 'factory' or 'class' property. |
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| 157 | * - factory: Callback passed $params that returns BagOStuff. |
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| 158 | * - class: BagOStuff subclass constructed with $params. |
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| 159 | * - loggroup: Alias to set 'logger' key with LoggerFactory group. |
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| 160 | * - .. Other parameters passed to factory or class. |
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| 161 | * @return BagOStuff |
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| 162 | * @throws MWException |
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| 163 | */ |
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| 164 | public static function newFromParams( $params ) { |
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| 207 | |||
| 208 | /** |
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| 209 | * Factory function for CACHE_ANYTHING (referenced from DefaultSettings.php) |
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| 210 | * |
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| 211 | * CACHE_ANYTHING means that stuff has to be cached, not caching is not an option. |
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| 212 | * If a caching method is configured for any of the main caches ($wgMainCacheType, |
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| 213 | * $wgMessageCacheType, $wgParserCacheType), then CACHE_ANYTHING will effectively |
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| 214 | * be an alias to the configured cache choice for that. |
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| 215 | * If no cache choice is configured (by default $wgMainCacheType is CACHE_NONE), |
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| 216 | * then CACHE_ANYTHING will forward to CACHE_DB. |
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| 217 | * |
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| 218 | * @param array $params |
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| 219 | * @return BagOStuff |
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| 220 | */ |
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| 221 | public static function newAnything( $params ) { |
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| 231 | |||
| 232 | /** |
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| 233 | * Factory function for CACHE_ACCEL (referenced from DefaultSettings.php) |
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| 234 | * |
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| 235 | * This will look for any APC style server-local cache. |
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| 236 | * A fallback cache can be specified if none is found. |
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| 237 | * |
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| 238 | * // Direct calls |
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| 239 | * ObjectCache::getLocalServerInstance( $fallbackType ); |
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| 240 | * |
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| 241 | * // From $wgObjectCaches via newFromParams() |
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| 242 | * ObjectCache::getLocalServerInstance( array( 'fallback' => $fallbackType ) ); |
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| 243 | * |
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| 244 | * @param int|string|array $fallback Fallback cache or parameter map with 'fallback' |
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| 245 | * @return BagOStuff |
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| 246 | * @throws MWException |
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| 247 | * @since 1.27 |
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| 248 | */ |
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| 249 | public static function getLocalServerInstance( $fallback = CACHE_NONE ) { |
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| 266 | |||
| 267 | /** |
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| 268 | * @param array $params [optional] Array key 'fallback' for $fallback. |
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| 269 | * @param int|string $fallback Fallback cache, e.g. (CACHE_NONE, "hash") (since 1.24) |
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| 270 | * @return BagOStuff |
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| 271 | * @deprecated 1.27 |
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| 272 | */ |
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| 273 | public static function newAccelerator( $params = [], $fallback = null ) { |
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| 284 | |||
| 285 | /** |
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| 286 | * Create a new cache object of the specified type. |
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| 287 | * |
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| 288 | * @since 1.26 |
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| 289 | * @param string $id A key in $wgWANObjectCaches. |
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| 290 | * @return WANObjectCache |
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| 291 | * @throws MWException |
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| 292 | */ |
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| 293 | public static function newWANCacheFromId( $id ) { |
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| 317 | |||
| 318 | /** |
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| 319 | * Get the main cluster-local cache object. |
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| 320 | * |
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| 321 | * @since 1.27 |
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| 322 | * @return BagOStuff |
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| 323 | */ |
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| 324 | public static function getLocalClusterInstance() { |
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| 329 | |||
| 330 | /** |
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| 331 | * Get the main WAN cache object. |
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| 332 | * |
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| 333 | * @since 1.26 |
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| 334 | * @return WANObjectCache |
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| 335 | */ |
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| 336 | public static function getMainWANInstance() { |
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| 341 | |||
| 342 | /** |
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| 343 | * Get the cache object for the main stash. |
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| 344 | * |
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| 345 | * Stash objects are BagOStuff instances suitable for storing light |
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| 346 | * weight data that is not canonically stored elsewhere (such as RDBMS). |
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| 347 | * Stashes should be configured to propagate changes to all data-centers. |
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| 348 | * |
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| 349 | * Callers should be prepared for: |
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| 350 | * - a) Writes to be slower in non-"primary" (e.g. HTTP GET/HEAD only) DCs |
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| 351 | * - b) Reads to be eventually consistent, e.g. for get()/getMulti() |
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| 352 | * In general, this means avoiding updates on idempotent HTTP requests and |
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| 353 | * avoiding an assumption of perfect serializability (or accepting anomalies). |
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| 354 | * Reads may be eventually consistent or data might rollback as nodes flap. |
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| 355 | * Callers can use BagOStuff:READ_LATEST to see the latest available data. |
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| 356 | * |
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| 357 | * @return BagOStuff |
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| 358 | * @since 1.26 |
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| 359 | */ |
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| 360 | public static function getMainStashInstance() { |
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| 365 | |||
| 366 | /** |
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| 367 | * Clear all the cached instances. |
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| 368 | */ |
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| 369 | public static function clear() { |
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| 373 | } |
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| 374 |
Instead of super-globals, we recommend to explicitly inject the dependencies of your class. This makes your code less dependent on global state and it becomes generally more testable: