includes/cache/CacheHelper.php

   1 <?php
   2 /**
   3  * Cache of various elements in a single cache entry.
   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  * @license GNU GPL v2 or later
  22  * @author Jeroen De Dauw < jeroendedauw@gmail.com >
  23  */
  24
  25 /**
  26  * Interface for all classes implementing CacheHelper functionality.
  27  *
  28  * @since 1.20
  29  */
  30 interface ICacheHelper {
  31         /**
  32          * Sets if the cache should be enabled or not.
  33          *
  34          * @since 1.20
  35          * @param bool $cacheEnabled
  36          */
  37         function setCacheEnabled( $cacheEnabled );
  38
  39         /**
  40          * Initializes the caching.
  41          * Should be called before the first time anything is added via addCachedHTML.
  42          *
  43          * @since 1.20
  44          *
  45          * @param int|null $cacheExpiry Sets the cache expiry, either ttl in seconds or unix timestamp.
  46          * @param bool|null $cacheEnabled Sets if the cache should be enabled or not.
  47          */
  48         function startCache( $cacheExpiry = null, $cacheEnabled = null );
  49
  50         /**
  51          * Get a cached value if available or compute it if not and then cache it if possible.
  52          * The provided $computeFunction is only called when the computation needs to happen
  53          * and should return a result value. $args are arguments that will be passed to the
  54          * compute function when called.
  55          *
  56          * @since 1.20
  57          *
  58          * @param callable $computeFunction
  59          * @param array|mixed $args
  60          * @param string|null $key
  61          *
  62          * @return mixed
  63          */
  64         function getCachedValue( $computeFunction, $args = [], $key = null );
  65
  66         /**
  67          * Saves the HTML to the cache in case it got recomputed.
  68          * Should be called after the last time anything is added via addCachedHTML.
  69          *
  70          * @since 1.20
  71          */
  72         function saveCache();
  73
  74         /**
  75          * Sets the time to live for the cache, in seconds or a unix timestamp
  76          * indicating the point of expiry...
  77          *
  78          * @since 1.20
  79          *
  80          * @param int $cacheExpiry
  81          */
  82         function setExpiry( $cacheExpiry );
  83 }
  84
  85 use MediaWiki\MediaWikiServices;
  86
  87 /**
  88  * Helper class for caching various elements in a single cache entry.
  89  *
  90  * To get a cached value or compute it, use getCachedValue like this:
  91  * $this->getCachedValue( $callback );
  92  *
  93  * To add HTML that should be cached, use addCachedHTML like this:
  94  * $this->addCachedHTML( $callback );
  95  *
  96  * The callback function is only called when needed, so do all your expensive
  97  * computations here. This function should returns the HTML to be cached.
  98  * It should not add anything to the PageOutput object!
  99  *
 100  * Before the first addCachedHTML call, you should call $this->startCache();
 101  * After adding the last HTML that should be cached, call $this->saveCache();
 102  *
 103  * @since 1.20
 104  */
 105 class CacheHelper implements ICacheHelper {
 106         /**
 107          * The time to live for the cache, in seconds or a unix timestamp indicating the point of expiry.
 108          *
 109          * @since 1.20
 110          * @var int
 111          */
 112         protected $cacheExpiry = 3600;
 113
 114         /**
 115          * List of HTML chunks to be cached (if !hasCached) or that where cached (of hasCached).
 116          * If not cached already, then the newly computed chunks are added here,
 117          * if it as cached already, chunks are removed from this list as they are needed.
 118          *
 119          * @since 1.20
 120          * @var array
 121          */
 122         protected $cachedChunks;
 123
 124         /**
 125          * Indicates if the to be cached content was already cached.
 126          * Null if this information is not available yet.
 127          *
 128          * @since 1.20
 129          * @var bool|null
 130          */
 131         protected $hasCached = null;
 132
 133         /**
 134          * If the cache is enabled or not.
 135          *
 136          * @since 1.20
 137          * @var bool
 138          */
 139         protected $cacheEnabled = true;
 140
 141         /**
 142          * Function that gets called when initialization is done.
 143          *
 144          * @since 1.20
 145          * @var callable
 146          */
 147         protected $onInitHandler = false;
 148
 149         /**
 150          * Elements to build a cache key with.
 151          *
 152          * @since 1.20
 153          * @var array
 154          */
 155         protected $cacheKey = [];
 156
 157         /**
 158          * Sets if the cache should be enabled or not.
 159          *
 160          * @since 1.20
 161          * @param bool $cacheEnabled
 162          */
 163         public function setCacheEnabled( $cacheEnabled ) {
 164                 $this->cacheEnabled = $cacheEnabled;
 165         }
 166
 167         /**
 168          * Initializes the caching.
 169          * Should be called before the first time anything is added via addCachedHTML.
 170          *
 171          * @since 1.20
 172          *
 173          * @param int|null $cacheExpiry Sets the cache expiry, either ttl in seconds or unix timestamp.
 174          * @param bool|null $cacheEnabled Sets if the cache should be enabled or not.
 175          */
 176         public function startCache( $cacheExpiry = null, $cacheEnabled = null ) {
 177                 if ( is_null( $this->hasCached ) ) {
 178                         if ( !is_null( $cacheExpiry ) ) {
 179                                 $this->cacheExpiry = $cacheExpiry;
 180                         }
 181
 182                         if ( !is_null( $cacheEnabled ) ) {
 183                                 $this->setCacheEnabled( $cacheEnabled );
 184                         }
 185
 186                         $this->initCaching();
 187                 }
 188         }
 189
 190         /**
 191          * Returns a message that notifies the user he/she is looking at
 192          * a cached version of the page, including a refresh link.
 193          *
 194          * @since 1.20
 195          *
 196          * @param IContextSource $context
 197          * @param bool $includePurgeLink
 198          *
 199          * @return string
 200          */
 201         public function getCachedNotice( IContextSource $context, $includePurgeLink = true ) {
 202                 if ( $this->cacheExpiry < 86400 * 3650 ) {
 203                         $message = $context->msg(
 204                                 'cachedspecial-viewing-cached-ttl',
 205                                 $context->getLanguage()->formatDuration( $this->cacheExpiry )
 206                         )->escaped();
 207                 } else {
 208                         $message = $context->msg(
 209                                 'cachedspecial-viewing-cached-ts'
 210                         )->escaped();
 211                 }
 212
 213                 if ( $includePurgeLink ) {
 214                         $refreshArgs = $context->getRequest()->getQueryValues();
 215                         unset( $refreshArgs['title'] );
 216                         $refreshArgs['action'] = 'purge';
 217
 218                         $subPage = $context->getTitle()->getFullText();
 219                         $subPage = explode( '/', $subPage, 2 );
 220                         $subPage = count( $subPage ) > 1 ? $subPage[1] : false;
 221
 222                         $message .= ' ' . MediaWikiServices::getInstance()->getLinkRenderer()->makeLink(
 223                                 $context->getTitle( $subPage ),
 224                                 $context->msg( 'cachedspecial-refresh-now' )->text(),
 225                                 [],
 226                                 $refreshArgs
 227                         );
 228                 }
 229
 230                 return $message;
 231         }
 232
 233         /**
 234          * Initializes the caching if not already done so.
 235          * Should be called before any of the caching functionality is used.
 236          *
 237          * @since 1.20
 238          */
 239         protected function initCaching() {
 240                 if ( $this->cacheEnabled && is_null( $this->hasCached ) ) {
 241                         $cachedChunks = wfGetCache( CACHE_ANYTHING )->get( $this->getCacheKeyString() );
 242
 243                         $this->hasCached = is_array( $cachedChunks );
 244                         $this->cachedChunks = $this->hasCached ? $cachedChunks : [];
 245
 246                         if ( $this->onInitHandler !== false ) {
 247                                 call_user_func( $this->onInitHandler, $this->hasCached );
 248                         }
 249                 }
 250         }
 251
 252         /**
 253          * Get a cached value if available or compute it if not and then cache it if possible.
 254          * The provided $computeFunction is only called when the computation needs to happen
 255          * and should return a result value. $args are arguments that will be passed to the
 256          * compute function when called.
 257          *
 258          * @since 1.20
 259          *
 260          * @param callable $computeFunction
 261          * @param array|mixed $args
 262          * @param string|null $key
 263          *
 264          * @return mixed
 265          */
 266         public function getCachedValue( $computeFunction, $args = [], $key = null ) {
 267                 $this->initCaching();
 268
 269                 if ( $this->cacheEnabled && $this->hasCached ) {
 270                         $value = null;
 271
 272                         if ( is_null( $key ) ) {
 273                                 $itemKey = array_keys( array_slice( $this->cachedChunks, 0, 1 ) );
 274                                 $itemKey = array_shift( $itemKey );
 275
 276                                 if ( !is_int( $itemKey ) ) {
 277                                         wfWarn( "Attempted to get item with non-numeric key while " .
 278                                                 "the next item in the queue has a key ($itemKey) in " . __METHOD__ );
 279                                 } elseif ( is_null( $itemKey ) ) {
 280                                         wfWarn( "Attempted to get an item while the queue is empty in " . __METHOD__ );
 281                                 } else {
 282                                         $value = array_shift( $this->cachedChunks );
 283                                 }
 284                         } else {
 285                                 if ( array_key_exists( $key, $this->cachedChunks ) ) {
 286                                         $value = $this->cachedChunks[$key];
 287                                         unset( $this->cachedChunks[$key] );
 288                                 } else {
 289                                         wfWarn( "There is no item with key '$key' in this->cachedChunks in " . __METHOD__ );
 290                                 }
 291                         }
 292                 } else {
 293                         if ( !is_array( $args ) ) {
 294                                 $args = [ $args ];
 295                         }
 296
 297                         $value = call_user_func_array( $computeFunction, $args );
 298
 299                         if ( $this->cacheEnabled ) {
 300                                 if ( is_null( $key ) ) {
 301                                         $this->cachedChunks[] = $value;
 302                                 } else {
 303                                         $this->cachedChunks[$key] = $value;
 304                                 }
 305                         }
 306                 }
 307
 308                 return $value;
 309         }
 310
 311         /**
 312          * Saves the HTML to the cache in case it got recomputed.
 313          * Should be called after the last time anything is added via addCachedHTML.
 314          *
 315          * @since 1.20
 316          */
 317         public function saveCache() {
 318                 if ( $this->cacheEnabled && $this->hasCached === false && !empty( $this->cachedChunks ) ) {
 319                         wfGetCache( CACHE_ANYTHING )->set(
 320                                 $this->getCacheKeyString(),
 321                                 $this->cachedChunks,
 322                                 $this->cacheExpiry
 323                         );
 324                 }
 325         }
 326
 327         /**
 328          * Sets the time to live for the cache, in seconds or a unix timestamp
 329          * indicating the point of expiry...
 330          *
 331          * @since 1.20
 332          *
 333          * @param int $cacheExpiry
 334          */
 335         public function setExpiry( $cacheExpiry ) {
 336                 $this->cacheExpiry = $cacheExpiry;
 337         }
 338
 339         /**
 340          * Returns the cache key to use to cache this page's HTML output.
 341          * Is constructed from the special page name and language code.
 342          *
 343          * @since 1.20
 344          *
 345          * @return string
 346          * @throws MWException
 347          */
 348         protected function getCacheKeyString() {
 349                 if ( $this->cacheKey === [] ) {
 350                         throw new MWException( 'No cache key set, so cannot obtain or save the CacheHelper values.' );
 351                 }
 352
 353                 return call_user_func_array( 'wfMemcKey', $this->cacheKey );
 354         }
 355
 356         /**
 357          * Sets the cache key that should be used.
 358          *
 359          * @since 1.20
 360          *
 361          * @param array $cacheKey
 362          */
 363         public function setCacheKey( array $cacheKey ) {
 364                 $this->cacheKey = $cacheKey;
 365         }
 366
 367         /**
 368          * Rebuild the content, even if it's already cached.
 369          * This effectively has the same effect as purging the cache,
 370          * since it will be overridden with the new value on the next request.
 371          *
 372          * @since 1.20
 373          */
 374         public function rebuildOnDemand() {
 375                 $this->hasCached = false;
 376         }
 377
 378         /**
 379          * Sets a function that gets called when initialization of the cache is done.
 380          *
 381          * @since 1.20
 382          *
 383          * @param callable $handlerFunction
 384          */
 385         public function setOnInitializedHandler( $handlerFunction ) {
 386                 $this->onInitHandler = $handlerFunction;
 387         }
 388 }