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( $this->hasCached ) ) {
  82                         if ( !is_null( $cacheExpiry ) ) {
  83                                 $this->cacheExpiry = $cacheExpiry;
  84                         }
  85
  86                         if ( !is_null( $cacheEnabled ) ) {
  87                                 $this->setCacheEnabled( $cacheEnabled );
  88                         }
  89
  90                         if ( $this->getRequest()->getText( 'action' ) === 'purge' ) {
  91                                 $this->hasCached = false;
  92                         }
  93
  94                         $this->initCaching();
  95                 }
  96         }
  97
  98         /**
  99          * Returns a message that notifies the user he/she is looking at
 100          * a cached version of the page, including a refresh link.
 101          *
 102          * @since 1.20
 103          *
 104          * @return string
 105          */
 106         protected function getCachedNotice() {
 107                 $refreshArgs = $this->getRequest()->getQueryValues();
 108                 unset( $refreshArgs['title'] );
 109                 $refreshArgs['action'] = 'purge';
 110
 111                 $refreshLink = Linker::link(
 112                         $this->getTitle( $this->getTitle()->getSubpageText() ),
 113                         $this->msg( 'cachedspecial-refresh-now' )->escaped(),
 114                         array(),
 115                         $refreshArgs
 116                 );
 117
 118                 if ( $this->cacheExpiry < 86400 * 3650 ) {
 119                         $message = $this->msg(
 120                                 'cachedspecial-viewing-cached-ttl',
 121                                 $this->getLanguage()->formatDuration( $this->cacheExpiry )
 122                         )->escaped();
 123                 }
 124                 else {
 125                         $message = $this->msg(
 126                                 'cachedspecial-viewing-cached-ts'
 127                         )->escaped();
 128                 }
 129
 130                 return $message . ' ' . $refreshLink;
 131         }
 132
 133         /**
 134          * Initializes the caching if not already done so.
 135          * Should be called before any of the caching functionality is used.
 136          *
 137          * @since 1.20
 138          */
 139         protected function initCaching() {
 140                 if ( $this->cacheEnabled && is_null( $this->hasCached ) ) {
 141                         $cachedChunks = wfGetCache( CACHE_ANYTHING )->get( $this->getCacheKeyString() );
 142
 143                         $this->hasCached = is_array( $cachedChunks );
 144                         $this->cachedChunks = $this->hasCached ? $cachedChunks : array();
 145
 146                         $this->onCacheInitialized();
 147                 }
 148         }
 149
 150         /**
 151          * Gets called after the cache got initialized.
 152          *
 153          * @since 1.20
 154          */
 155         protected function onCacheInitialized() {
 156                 if ( $this->hasCached ) {
 157                         $this->getOutput()->setSubtitle( $this->getCachedNotice() );
 158                 }
 159         }
 160
 161         /**
 162          * Add some HTML to be cached.
 163          * This is done by providing a callback function that should
 164          * return the HTML to be added. It will only be called if the
 165          * item is not in the cache yet or when the cache has been invalidated.
 166          *
 167          * @since 1.20
 168          *
 169          * @param {function} $computeFunction
 170          * @param array $args
 171          * @param string|null $key
 172          */
 173         public function addCachedHTML( $computeFunction, $args = array(), $key = null ) {
 174                 $this->getOutput()->addHTML( $this->getCachedValue( $computeFunction, $args, $key ) );
 175         }
 176
 177         /**
 178          * Get a cached value if available or compute it if not and then cache it if possible.
 179          * The provided $computeFunction is only called when the computation needs to happen
 180          * and should return a result value. $args are arguments that will be passed to the
 181          * compute function when called.
 182          *
 183          * @since 1.20
 184          *
 185          * @param {function} $computeFunction
 186          * @param array|mixed $args
 187          * @param string|null $key
 188          *
 189          * @return mixed
 190          */
 191         protected function getCachedValue( $computeFunction, $args = array(), $key = null ) {
 192                 $this->initCaching();
 193
 194                 if ( $this->cacheEnabled && $this->hasCached ) {
 195                         $value = null;
 196
 197                         if ( is_null( $key ) ) {
 198                                 $itemKey = array_keys( array_slice( $this->cachedChunks, 0, 1 ) );
 199                                 $itemKey = array_shift( $itemKey );
 200
 201                                 if ( !is_integer( $itemKey ) ) {
 202                                         wfWarn( "Attempted to get item with non-numeric key while the next item in the queue has a key ($itemKey) in " . __METHOD__ );
 203                                 }
 204                                 elseif ( is_null( $itemKey ) ) {
 205                                         wfWarn( "Attempted to get an item while the queue is empty in " . __METHOD__ );
 206                                 }
 207                                 else {
 208                                         $value = array_shift( $this->cachedChunks );
 209                                 }
 210                         }
 211                         else {
 212                                 if ( array_key_exists( $key, $this->cachedChunks ) ) {
 213                                         $value = $this->cachedChunks[$key];
 214                                         unset( $this->cachedChunks[$key] );
 215                                 }
 216                                 else {
 217                                         wfWarn( "There is no item with key '$key' in this->cachedChunks in " . __METHOD__ );
 218                                 }
 219                         }
 220                 }
 221                 else {
 222                         if ( !is_array( $args ) ) {
 223                                 $args = array( $args );
 224                         }
 225
 226                         $value = call_user_func_array( $computeFunction, $args );
 227
 228                         if ( $this->cacheEnabled ) {
 229                                 if ( is_null( $key ) ) {
 230                                         $this->cachedChunks[] = $value;
 231                                 }
 232                                 else {
 233                                         $this->cachedChunks[$key] = $value;
 234                                 }
 235                         }
 236                 }
 237
 238                 return $value;
 239         }
 240
 241         /**
 242          * Saves the HTML to the cache in case it got recomputed.
 243          * Should be called after the last time anything is added via addCachedHTML.
 244          *
 245          * @since 1.20
 246          */
 247         public function saveCache() {
 248                 if ( $this->cacheEnabled && $this->hasCached === false && !empty( $this->cachedChunks ) ) {
 249                         wfGetCache( CACHE_ANYTHING )->set( $this->getCacheKeyString(), $this->cachedChunks, $this->cacheExpiry );
 250                 }
 251         }
 252
 253         /**
 254          * Sets the time to live for the cache, in seconds or a unix timestamp indicating the point of expiry..
 255          *
 256          * @since 1.20
 257          *
 258          * @param integer $cacheExpiry
 259          */
 260         protected function setExpirey( $cacheExpiry ) {
 261                 $this->cacheExpiry = $cacheExpiry;
 262         }
 263
 264         /**
 265          * Returns the cache key to use to cache this page's HTML output.
 266          * Is constructed from the special page name and language code.
 267          *
 268          * @since 1.20
 269          *
 270          * @return string
 271          */
 272         protected function getCacheKeyString() {
 273                 $keyArgs = $this->getCacheKey();
 274
 275                 if ( array_key_exists( 'action', $keyArgs ) && $keyArgs['action'] === 'purge' ) {
 276                         unset( $keyArgs['action'] );
 277                 }
 278
 279                 return call_user_func_array( 'wfMemcKey', $keyArgs );
 280         }
 281
 282         /**
 283          * Returns the variables used to constructed the cache key in an array.
 284          *
 285          * @since 1.20
 286          *
 287          * @return array
 288          */
 289         protected function getCacheKey() {
 290                 return array(
 291                         $this->mName,
 292                         $this->getLanguage()->getCode()
 293                 );
 294         }
 295
 296 }