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
  15         /**
  16          * Get an instance of this object
  17          */
  18         public static function singleton() {
  19                 static $instance;
  20                 if ( !isset( $instance ) ) {
  21                         global $parserMemc;
  22                         $instance = new ParserCache( $parserMemc );
  23                 }
  24                 return $instance;
  25         }
  26
  27         /**
  28          * Setup a cache pathway with a given back-end storage mechanism.
  29          * May be a memcached client or a BagOStuff derivative.
  30          *
  31          * @param $memCached Object
  32          */
  33         function __construct( $memCached ) {
  34                 if ( !$memCached ) {
  35                         throw new MWException( "Tried to create a ParserCache with an invalid memcached" );
  36                 }
  37                 $this->mMemc = $memCached;
  38         }
  39
  40         protected function getParserOutputKey( $article, $hash ) {
  41                 global $wgRequest;
  42
  43                 // idhash seem to mean 'page id' + 'rendering hash' (r3710)
  44                 $pageid = $article->getID();
  45                 $renderkey = (int)($wgRequest->getVal('action') == 'render');
  46
  47                 $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
  48                 return $key;
  49         }
  50
  51         protected function getOptionsKey( $article ) {
  52                 $pageid = $article->getID();
  53                 return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
  54         }
  55
  56         /**
  57          * Provides an E-Tag suitable for the whole page. Note that $article
  58          * is just the main wikitext. The E-Tag has to be unique to the whole
  59          * page, even if the article itself is the same, so it uses the
  60          * complete set of user options. We don't want to use the preference
  61          * of a different user on a message just because it wasn't used in
  62          * $article. For example give a Chinese interface to a user with
  63          * English preferences. That's why we take into account *all* user
  64          * options. (r70809 CR)
  65          */
  66         function getETag( $article, $popts ) {
  67                 return 'W/"' . $this->getParserOutputKey( $article,
  68                         $popts->optionsHash( ParserOptions::legacyOptions() ) ) .
  69                                 "--" . $article->getTouched() . '"';
  70         }
  71
  72         /**
  73          * Retrieve the ParserOutput from ParserCache, even if it's outdated.
  74          */
  75         public function getDirty( $article, $popts ) {
  76                 $value = $this->get( $article, $popts, true );
  77                 return is_object( $value ) ? $value : false;
  78         }
  79
  80         /**
  81          * Used to provide a unique id for the PoolCounter.
  82          * It would be preferable to have this code in get()
  83          * instead of having Article looking in our internals.
  84          */
  85         public function getKey( $article, $popts, $useOutdated = true ) {
  86                 global $wgCacheEpoch;
  87
  88                 if( $popts instanceof User ) {
  89                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
  90                         $popts = ParserOptions::newFromUser( $popts );
  91                 }
  92
  93                 // Determine the options which affect this article
  94                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
  95                 if ( $optionsKey != false ) {
  96                         if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
  97                                 wfIncrStats( "pcache_miss_expired" );
  98                                 $cacheTime = $optionsKey->getCacheTime();
  99                                 wfDebug( "Parser options key expired, touched " . $article->getTouched() . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
 100                                 return false;
 101                         }
 102
 103                         $usedOptions = $optionsKey->mUsedOptions;
 104                         wfDebug( "Parser cache options found.\n" );
 105                 } else {
 106                         # TODO: Fail here $wgParserCacheExpireTime after deployment unless $useOutdated
 107
 108                         $usedOptions = ParserOptions::legacyOptions();
 109                 }
 110
 111                 return $this->getParserOutputKey( $article, $popts->optionsHash( $usedOptions ) );
 112         }
 113
 114         /**
 115          * Retrieve the ParserOutput from ParserCache.
 116          * false if not found or outdated.
 117          */
 118         public function get( $article, $popts, $useOutdated = false ) {
 119                 global $wgCacheEpoch;
 120                 wfProfileIn( __METHOD__ );
 121
 122                 $canCache = $article->checkTouched();
 123                 if ( !$canCache ) {
 124                         // It's a redirect now
 125                         wfProfileOut( __METHOD__ );
 126                         return false;
 127                 }
 128
 129                 $touched = $article->getTouched();
 130
 131                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 132                 if ( $parserOutputKey === false ) {
 133                         wfProfileOut( __METHOD__ );
 134                         return false;
 135                 }
 136
 137                 $value = $this->mMemc->get( $parserOutputKey );
 138                 if ( !$value ) {
 139                         wfDebug( "Parser cache miss.\n" );
 140                         wfIncrStats( "pcache_miss_absent" );
 141                         wfProfileOut( __METHOD__ );
 142                         return false;
 143                 }
 144
 145                 wfDebug( "Found.\n" );
 146
 147                 if ( !$useOutdated && $value->expired( $touched ) ) {
 148                         wfIncrStats( "pcache_miss_expired" );
 149                         $cacheTime = $value->getCacheTime();
 150                         wfDebug( "ParserOutput key expired, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 151                         $value = false;
 152                 } else {
 153                         if ( isset( $value->mTimestamp ) ) {
 154                                 $article->mTimestamp = $value->mTimestamp;
 155                         }
 156                         wfIncrStats( "pcache_hit" );
 157                 }
 158
 159                 wfProfileOut( __METHOD__ );
 160                 return $value;
 161         }
 162
 163
 164         public function save( $parserOutput, $article, $popts ) {
 165                 $expire = $parserOutput->getCacheExpiry();
 166
 167                 if( $expire > 0 ) {
 168                         $now = wfTimestampNow();
 169
 170                         $optionsKey = new CacheTime;
 171                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 172                         $optionsKey->updateCacheExpiry( $expire );
 173
 174                         $optionsKey->setCacheTime( $now );
 175                         $parserOutput->setCacheTime( $now );
 176
 177                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 178
 179                         $parserOutputKey = $this->getParserOutputKey( $article, $popts->optionsHash( $optionsKey->mUsedOptions ) );
 180
 181                         // Save the timestamp so that we don't have to load the revision row on view
 182                         $parserOutput->mTimestamp = $article->getTimestamp();
 183
 184                         $parserOutput->mText .= "\n<!-- Saved in parser cache with key $parserOutputKey and timestamp $now -->\n";
 185                         wfDebug( "Saved in parser cache with key $parserOutputKey and timestamp $now\n" );
 186
 187                         // Save the parser output
 188                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 189
 190                         // ...and its pointer
 191                         $this->mMemc->set( $this->getOptionsKey( $article ), $optionsKey, $expire );
 192                 } else {
 193                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 194                 }
 195         }
 196 }