includes/parser/ParserCache.php

   1 <?php
   2 /**
   3  * Cache for outputs of the PHP parser
   4  *
   5  * @file
   6  */
   7
   8 /**
   9  * @ingroup Cache Parser
  10  * @todo document
  11  */
  12 class ParserCache {
  13         private $mMemc;
  14         const try116cache = false; /* Only useful $wgParserCacheExpireTime after updating to 1.17 */
  15
  16         /**
  17          * Get an instance of this object
  18          *
  19          * @return ParserCache
  20          */
  21         public static function singleton() {
  22                 static $instance;
  23                 if ( !isset( $instance ) ) {
  24                         global $parserMemc;
  25                         $instance = new ParserCache( $parserMemc );
  26                 }
  27                 return $instance;
  28         }
  29
  30         /**
  31          * Setup a cache pathway with a given back-end storage mechanism.
  32          * May be a memcached client or a BagOStuff derivative.
  33          *
  34          * @param $memCached Object
  35          */
  36         protected function __construct( $memCached ) {
  37                 if ( !$memCached ) {
  38                         throw new MWException( "Tried to create a ParserCache with an invalid memcached" );
  39                 }
  40                 $this->mMemc = $memCached;
  41         }
  42
  43         /**
  44          * @param $article Article
  45          * @param $hash string
  46          * @return mixed|string
  47          */
  48         protected function getParserOutputKey( $article, $hash ) {
  49                 global $wgRequest;
  50
  51                 // idhash seem to mean 'page id' + 'rendering hash' (r3710)
  52                 $pageid = $article->getID();
  53                 $renderkey = (int)($wgRequest->getVal('action') == 'render');
  54
  55                 $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
  56                 return $key;
  57         }
  58
  59         /**
  60          * @param $article Article
  61          * @return mixed|string
  62          */
  63         protected function getOptionsKey( $article ) {
  64                 $pageid = $article->getID();
  65                 return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
  66         }
  67
  68         /**
  69          * Provides an E-Tag suitable for the whole page. Note that $article
  70          * is just the main wikitext. The E-Tag has to be unique to the whole
  71          * page, even if the article itself is the same, so it uses the
  72          * complete set of user options. We don't want to use the preference
  73          * of a different user on a message just because it wasn't used in
  74          * $article. For example give a Chinese interface to a user with
  75          * English preferences. That's why we take into account *all* user
  76          * options. (r70809 CR)
  77          *
  78          * @param $article Article
  79          * @param $popts ParserOptions
  80          * @return string
  81          */
  82         function getETag( $article, $popts ) {
  83                 return 'W/"' . $this->getParserOutputKey( $article,
  84                         $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) ) .
  85                                 "--" . $article->getTouched() . '"';
  86         }
  87
  88         /**
  89          * Retrieve the ParserOutput from ParserCache, even if it's outdated.
  90          * @param $article Article
  91          * @param $popts ParserOptions
  92          * @return ParserOutput|bool False on failure
  93          */
  94         public function getDirty( $article, $popts ) {
  95                 $value = $this->get( $article, $popts, true );
  96                 return is_object( $value ) ? $value : false;
  97         }
  98
  99         /**
 100          * Used to provide a unique id for the PoolCounter.
 101          * It would be preferable to have this code in get()
 102          * instead of having Article looking in our internals.
 103          *
 104          * @todo Document parameter $useOutdated
 105          *
 106          * @param $article Article
 107          * @param $popts ParserOptions
 108          * @return bool|mixed|string
 109          */
 110         public function getKey( $article, $popts, $useOutdated = true ) {
 111                 global $wgCacheEpoch;
 112
 113                 if( $popts instanceof User ) {
 114                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
 115                         $popts = ParserOptions::newFromUser( $popts );
 116                 }
 117
 118                 // Determine the options which affect this article
 119                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
 120                 if ( $optionsKey != false ) {
 121                         if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
 122                                 wfIncrStats( "pcache_miss_expired" );
 123                                 $cacheTime = $optionsKey->getCacheTime();
 124                                 wfDebug( "Parser options key expired, touched " . $article->getTouched() . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
 125                                 return false;
 126                         }
 127
 128                         $usedOptions = $optionsKey->mUsedOptions;
 129                         wfDebug( "Parser cache options found.\n" );
 130                 } else {
 131                         if ( !$useOutdated && !self::try116cache ) {
 132                                 return false;
 133                         }
 134                         $usedOptions = ParserOptions::legacyOptions();
 135                 }
 136
 137                 return $this->getParserOutputKey( $article, $popts->optionsHash( $usedOptions, $article->getTitle() ) );
 138         }
 139
 140         /**
 141          * Retrieve the ParserOutput from ParserCache.
 142          * false if not found or outdated.
 143          *
 144          * @param $article Article
 145          * @param $popts ParserOptions
 146          * @param $useOutdated
 147          *
 148          * @return ParserOutput|bool False on failure
 149          */
 150         public function get( $article, $popts, $useOutdated = false ) {
 151                 global $wgCacheEpoch;
 152                 wfProfileIn( __METHOD__ );
 153
 154                 $canCache = $article->checkTouched();
 155                 if ( !$canCache ) {
 156                         // It's a redirect now
 157                         wfProfileOut( __METHOD__ );
 158                         return false;
 159                 }
 160
 161                 $touched = $article->getTouched();
 162
 163                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 164                 if ( $parserOutputKey === false ) {
 165                         wfIncrStats( 'pcache_miss_absent' );
 166                         wfProfileOut( __METHOD__ );
 167                         return false;
 168                 }
 169
 170                 $value = $this->mMemc->get( $parserOutputKey );
 171                 if ( self::try116cache && !$value && strpos( $value, '*' ) !== -1 ) {
 172                         wfDebug( "New format parser cache miss.\n" );
 173                         $parserOutputKey = $this->getParserOutputKey( $article,
 174                                 $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) );
 175                         $value = $this->mMemc->get( $parserOutputKey );
 176                 }
 177                 if ( !$value ) {
 178                         wfDebug( "ParserOutput cache miss.\n" );
 179                         wfIncrStats( "pcache_miss_absent" );
 180                         wfProfileOut( __METHOD__ );
 181                         return false;
 182                 }
 183
 184                 wfDebug( "ParserOutput cache found.\n" );
 185
 186                 // The edit section preference may not be the appropiate one in
 187                 // the ParserOutput, as we are not storing it in the parsercache
 188                 // key. Force it here. See bug 31445.
 189                 $value->setEditSectionTokens( $popts->getEditSection() );
 190
 191                 if ( !$useOutdated && $value->expired( $touched ) ) {
 192                         wfIncrStats( "pcache_miss_expired" );
 193                         $cacheTime = $value->getCacheTime();
 194                         wfDebug( "ParserOutput key expired, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 195                         $value = false;
 196                 } else {
 197                         wfIncrStats( "pcache_hit" );
 198                 }
 199
 200                 wfProfileOut( __METHOD__ );
 201                 return $value;
 202         }
 203
 204         /**
 205          * @param $parserOutput ParserOutput
 206          * @param $article Article
 207          * @param $popts ParserOptions
 208          */
 209         public function save( $parserOutput, $article, $popts ) {
 210                 $expire = $parserOutput->getCacheExpiry();
 211
 212                 if( $expire > 0 ) {
 213                         $now = wfTimestampNow();
 214
 215                         $optionsKey = new CacheTime;
 216                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 217                         $optionsKey->updateCacheExpiry( $expire );
 218
 219                         $optionsKey->setCacheTime( $now );
 220                         $parserOutput->setCacheTime( $now );
 221
 222                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 223
 224                         $parserOutputKey = $this->getParserOutputKey( $article,
 225                                 $popts->optionsHash( $optionsKey->mUsedOptions, $article->getTitle() ) );
 226
 227                         // Save the timestamp so that we don't have to load the revision row on view
 228                         $parserOutput->setTimestamp( $article->getTimestamp() );
 229
 230                         $parserOutput->mText .= "\n<!-- Saved in parser cache with key $parserOutputKey and timestamp $now -->\n";
 231                         wfDebug( "Saved in parser cache with key $parserOutputKey and timestamp $now\n" );
 232
 233                         // Save the parser output
 234                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 235
 236                         // ...and its pointer
 237                         $this->mMemc->set( $this->getOptionsKey( $article ), $optionsKey, $expire );
 238                 } else {
 239                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 240                 }
 241         }
 242 }