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} $callback
 168          * @param array $args
 169          * @param string|null $key
 170          */
 171         public function addCachedHTML( $callback, $args = array(), $key = null ) {
 172                 $this->initCaching();
 173
 174                 if ( $this->cacheEnabled && $this->hasCached ) {
 175                         $html = '';
 176
 177                         if ( is_null( $key ) ) {
 178                                 $itemKey = array_keys( array_slice( $this->cachedChunks, 0, 1 ) );
 179                                 $itemKey = array_shift( $itemKey );
 180
 181                                 if ( !is_integer( $itemKey ) ) {
 182                                         wfWarn( "Attempted to get item with non-numeric key while the next item in the queue has a key ($itemKey) in " . __METHOD__ );
 183                                 }
 184                                 elseif ( is_null( $itemKey ) ) {
 185                                         wfWarn( "Attempted to get an item while the queue is empty in " . __METHOD__ );
 186                                 }
 187                                 else {
 188                                         $html = array_shift( $this->cachedChunks );
 189                                 }
 190                         }
 191                         else {
 192                                 if ( array_key_exists( $key, $this->cachedChunks ) ) {
 193                                         $html = $this->cachedChunks[$key];
 194                                         unset( $this->cachedChunks[$key] );
 195                                 }
 196                                 else {
 197                                         wfWarn( "There is no item with key '$key' in this->cachedChunks in " . __METHOD__ );
 198                                 }
 199                         }
 200                 }
 201                 else {
 202                         $html = call_user_func_array( $callback, $args );
 203
 204                         if ( $this->cacheEnabled ) {
 205                                 if ( is_null( $key ) ) {
 206                                         $this->cachedChunks[] = $html;
 207                                 }
 208                                 else {
 209                                         $this->cachedChunks[$key] = $html;
 210                                 }
 211                         }
 212                 }
 213
 214                 $this->getOutput()->addHTML( $html );
 215         }
 216
 217         /**
 218          * Saves the HTML to the cache in case it got recomputed.
 219          * Should be called after the last time anything is added via addCachedHTML.
 220          *
 221          * @since 1.20
 222          */
 223         public function saveCache() {
 224                 if ( $this->cacheEnabled && $this->hasCached === false && !empty( $this->cachedChunks ) ) {
 225                         wfGetCache( CACHE_ANYTHING )->set( $this->getCacheKeyString(), $this->cachedChunks, $this->cacheExpiry );
 226                 }
 227         }
 228
 229         /**
 230          * Sets the time to live for the cache, in seconds or a unix timestamp indicating the point of expiry..
 231          *
 232          * @since 1.20
 233          *
 234          * @param integer $cacheExpiry
 235          */
 236         protected function setExpirey( $cacheExpiry ) {
 237                 $this->cacheExpiry = $cacheExpiry;
 238         }
 239
 240         /**
 241          * Returns the cache key to use to cache this page's HTML output.
 242          * Is constructed from the special page name and language code.
 243          *
 244          * @since 1.20
 245          *
 246          * @return string
 247          */
 248         protected function getCacheKeyString() {
 249                 return call_user_func_array( 'wfMemcKey', $this->getCacheKey() );
 250         }
 251
 252         /**
 253          * Returns the variables used to constructed the cache key in an array.
 254          *
 255          * @since 1.20
 256          *
 257          * @return array
 258          */
 259         protected function getCacheKey() {
 260                 return array(
 261                         $this->mName,
 262                         $this->getLanguage()->getCode()
 263                 );
 264         }
 265
 266 }