includes/specials/SpecialCachedPage.php

   1 <?php
   2
   3 /**
   4  * Abstract special page class with scaffolding for caching the HTML output.
   5  *
   6  * To add HTML that should be cached, use addCachedHTML like this:
   7  * $this->addCachedHTML( $callback );
   8  *
   9  * The callback function is only called when needed, so do all your expensive
  10  * computations here. This function should returns the HTML to be cached.
  11  * It should not add anything to the PageOutput object!
  12  *
  13  * Before the first addCachedHTML call, you should call $this->startCache();
  14  * After adding the last HTML that should be cached, call $this->saveCache();
  15  *
  16  * @since 1.20
  17  *
  18  * @file SpecialCachedPage.php
  19  * @ingroup SpecialPage
  20  *
  21  * @licence GNU GPL v2 or later
  22  * @author Jeroen De Dauw < jeroendedauw@gmail.com >
  23  */
  24 abstract class SpecialCachedPage extends SpecialPage {
  25
  26         /**
  27          * The time to live for the cache, in seconds or a unix timestamp indicating the point of expiry.
  28          *
  29          * @since 1.20
  30          * @var integer
  31          */
  32         protected $cacheExpiry = 3600;
  33
  34         /**
  35          * List of HTML chunks to be cached (if !hasCached) or that where cashed (of hasCached).
  36          * If no cached already, then the newly computed chunks are added here,
  37          * if it as cached already, chunks are removed from this list as they are needed.
  38          *
  39          * @since 1.20
  40          * @var array
  41          */
  42         protected $cachedChunks;
  43
  44         /**
  45          * Indicates if the to be cached content was already cached.
  46          * Null if this information is not available yet.
  47          *
  48          * @since 1.20
  49          * @var boolean|null
  50          */
  51         protected $hasCached = null;
  52
  53         /**
  54          * If the cache is enabled or not.
  55          *
  56          * @since 1.20
  57          * @var boolean
  58          */
  59         protected $cacheEnabled = true;
  60
  61         /**
  62          * Sets if the cache should be enabled or not.
  63          *
  64          * @since 1.20
  65          * @param boolean $cacheEnabled
  66          */
  67         public function setCacheEnabled( $cacheEnabled ) {
  68                 $this->cacheEnabled = $cacheEnabled;
  69         }
  70
  71         /**
  72          * Initializes the caching.
  73          * Should be called before the first time anything is added via addCachedHTML.
  74          *
  75          * @since 1.20
  76          *
  77          * @param integer|null $cacheExpiry Sets the cache expirty, either ttl in seconds or unix timestamp.
  78          * @param boolean|null $cacheEnabled Sets if the cache should be enabled or not.
  79          */
  80         public function startCache( $cacheExpiry = null, $cacheEnabled = null ) {
  81                 if ( !is_null( $cacheExpiry ) ) {
  82                         $this->cacheExpiry = $cacheExpiry;
  83                 }
  84
  85                 if ( !is_null( $cacheEnabled ) ) {
  86                         $this->setCacheEnabled( $cacheEnabled );
  87                 }
  88
  89                 if ( $this->getRequest()->getText( 'action' ) === 'purge' ) {
  90                         $this->hasCached = false;
  91                 }
  92
  93                 $this->initCaching();
  94         }
  95
  96         /**
  97          * Returns a message that notifies the user he/she is looking at
  98          * a cached version of the page, including a refresh link.
  99          *
 100          * @since 1.20
 101          *
 102          * @return string
 103          */
 104         protected function getCachedNotice() {
 105                 $refreshArgs = $this->getRequest()->getQueryValues();
 106                 unset( $refreshArgs['title'] );
 107                 $refreshArgs['action'] = 'purge';
 108
 109                 $refreshLink = Linker::link(
 110                         $this->getTitle( $this->getTitle()->getSubpageText() ),
 111                         $this->msg( 'cachedspecial-refresh-now' )->escaped(),
 112                         array(),
 113                         $refreshArgs
 114                 );
 115
 116                 if ( $this->cacheExpiry < 86400 * 3650 ) {
 117                         $message = $this->msg(
 118                                 'cachedspecial-viewing-cached-ttl',
 119                                 $this->getLanguage()->formatDuration( $this->cacheExpiry )
 120                         )->escaped();
 121                 }
 122                 else {
 123                         $message = $this->msg(
 124                                 'cachedspecial-viewing-cached-ts'
 125                         )->escaped();
 126                 }
 127
 128                 return $message . ' ' . $refreshLink;
 129         }
 130
 131         /**
 132          * Initializes the caching if not already done so.
 133          * Should be called before any of the caching functionality is used.
 134          *
 135          * @since 1.20
 136          */
 137         protected function initCaching() {
 138                 if ( $this->cacheEnabled && is_null( $this->hasCached ) ) {
 139                         $cachedChunks = wfGetCache( CACHE_ANYTHING )->get( $this->getCacheKeyString() );
 140
 141                         $this->hasCached = is_array( $cachedChunks );
 142                         $this->cachedChunks = $this->hasCached ? $cachedChunks : array();
 143
 144                         $this->onCacheInitialized();
 145                 }
 146         }
 147
 148         /**
 149          * Gets called after the cache got initialized.
 150          *
 151          * @since 1.20
 152          */
 153         protected function onCacheInitialized() {
 154                 if ( $this->hasCached ) {
 155                         $this->getOutput()->setSubtitle( $this->getCachedNotice() );
 156                 }
 157         }
 158
 159         /**
 160          * Add some HTML to be cached.
 161          * This is done by providing a callback function that should
 162          * return the HTML to be added. It will only be called if the
 163          * item is not in the cache yet or when the cache has been invalidated.
 164          *
 165          * @since 1.20
 166          *
 167          * @param {function} $computeFunction
 168          * @param array $args
 169          * @param string|null $key
 170          */
 171         public function addCachedHTML( $computeFunction, $args = array(), $key = null ) {
 172                 $this->getOutput()->addHTML( $this->getCachedValue( $computeFunction, $args, $key ) );
 173         }
 174
 175         /**
 176          * Get a cached value if available or compute it if not and then cache it if possible.
 177          * The provided $computeFunction is only called when the computation needs to happen
 178          * and should return a result value. $args are arguments that will be passed to the
 179          * compute function when called.
 180          *
 181          * @since 1.20
 182          *
 183          * @param {function} $computeFunction
 184          * @param array|mixed $args
 185          * @param string|null $key
 186          *
 187          * @return mixed
 188          */
 189         protected function getCachedValue( $computeFunction, $args = array(), $key = null ) {
 190                 $this->initCaching();
 191
 192                 if ( $this->cacheEnabled && $this->hasCached ) {
 193                         $value = null;
 194
 195                         if ( is_null( $key ) ) {
 196                                 $itemKey = array_keys( array_slice( $this->cachedChunks, 0, 1 ) );
 197                                 $itemKey = array_shift( $itemKey );
 198
 199                                 if ( !is_integer( $itemKey ) ) {
 200                                         wfWarn( "Attempted to get item with non-numeric key while the next item in the queue has a key ($itemKey) in " . __METHOD__ );
 201                                 }
 202                                 elseif ( is_null( $itemKey ) ) {
 203                                         wfWarn( "Attempted to get an item while the queue is empty in " . __METHOD__ );
 204                                 }
 205                                 else {
 206                                         $value = array_shift( $this->cachedChunks );
 207                                 }
 208                         }
 209                         else {
 210                                 if ( array_key_exists( $key, $this->cachedChunks ) ) {
 211                                         $value = $this->cachedChunks[$key];
 212                                         unset( $this->cachedChunks[$key] );
 213                                 }
 214                                 else {
 215                                         wfWarn( "There is no item with key '$key' in this->cachedChunks in " . __METHOD__ );
 216                                 }
 217                         }
 218                 }
 219                 else {
 220                         if ( !is_array( $args ) ) {
 221                                 $args = array( $args );
 222                         }
 223
 224                         $value = call_user_func_array( $computeFunction, $args );
 225
 226                         if ( $this->cacheEnabled ) {
 227                                 if ( is_null( $key ) ) {
 228                                         $this->cachedChunks[] = $value;
 229                                 }
 230                                 else {
 231                                         $this->cachedChunks[$key] = $value;
 232                                 }
 233                         }
 234                 }
 235
 236                 return $value;
 237         }
 238
 239         /**
 240          * Saves the HTML to the cache in case it got recomputed.
 241          * Should be called after the last time anything is added via addCachedHTML.
 242          *
 243          * @since 1.20
 244          */
 245         public function saveCache() {
 246                 if ( $this->cacheEnabled && $this->hasCached === false && !empty( $this->cachedChunks ) ) {
 247                         wfGetCache( CACHE_ANYTHING )->set( $this->getCacheKeyString(), $this->cachedChunks, $this->cacheExpiry );
 248                 }
 249         }
 250
 251         /**
 252          * Sets the time to live for the cache, in seconds or a unix timestamp indicating the point of expiry..
 253          *
 254          * @since 1.20
 255          *
 256          * @param integer $cacheExpiry
 257          */
 258         protected function setExpirey( $cacheExpiry ) {
 259                 $this->cacheExpiry = $cacheExpiry;
 260         }
 261
 262         /**
 263          * Returns the cache key to use to cache this page's HTML output.
 264          * Is constructed from the special page name and language code.
 265          *
 266          * @since 1.20
 267          *
 268          * @return string
 269          */
 270         protected function getCacheKeyString() {
 271                 $keyArgs = $this->getCacheKey();
 272
 273                 if ( array_key_exists( 'action', $keyArgs ) && $keyArgs['action'] === 'purge' ) {
 274                         unset( $keyArgs['action'] );
 275                 }
 276
 277                 return call_user_func_array( 'wfMemcKey', $keyArgs );
 278         }
 279
 280         /**
 281          * Returns the variables used to constructed the cache key in an array.
 282          *
 283          * @since 1.20
 284          *
 285          * @return array
 286          */
 287         protected function getCacheKey() {
 288                 return array(
 289                         $this->mName,
 290                         $this->getLanguage()->getCode()
 291                 );
 292         }
 293
 294 }