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  74          * Retrieve the ParserOutput from ParserCache, even if it's outdated.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