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