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                         global $parserMemc;
  36                         $parserMemc = $memCached = wfGetParserCacheStorage();
  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->mTouched . '"';
  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          * Precondition: $article->checkTouched() has been called.
  87          */
  88         public function getKey( $article, $popts, $useOutdated = true ) {
  89                 global $wgCacheEpoch;
  90
  91                 if( $popts instanceof User ) {
  92                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
  93                         $popts = ParserOptions::newFromUser( $popts );
  94                 }
  95
  96                 // Determine the options which affect this article
  97                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
  98                 if ( $optionsKey != false ) {
  99                         if ( !$useOutdated && $optionsKey->expired( $article->mTouched ) ) {
 100                                 wfIncrStats( "pcache_miss_expired" );
 101                                 $cacheTime = $optionsKey->getCacheTime();
 102                                 wfDebug( "Parser options key expired, touched {$article->mTouched}, epoch $wgCacheEpoch, cached $cacheTime\n" );
 103                                 return false;
 104                         }
 105
 106                         $usedOptions = $optionsKey->mUsedOptions;
 107                         wfDebug( "Parser cache options found.\n" );
 108                 } else {
 109                         # TODO: Fail here $wgParserCacheExpireTime after deployment unless $useOutdated
 110
 111                         $usedOptions = ParserOptions::legacyOptions();
 112                 }
 113
 114                 return $this->getParserOutputKey( $article, $popts->optionsHash( $usedOptions ) );
 115         }
 116
 117         /**
 118          * Retrieve the ParserOutput from ParserCache.
 119          * false if not found or outdated.
 120          */
 121         public function get( $article, $popts, $useOutdated = false ) {
 122                 global $wgCacheEpoch;
 123                 wfProfileIn( __METHOD__ );
 124
 125                 $canCache = $article->checkTouched();
 126                 if ( !$canCache ) {
 127                         // It's a redirect now
 128                         wfProfileOut( __METHOD__ );
 129                         return false;
 130                 }
 131
 132                 // Having called checkTouched() ensures this will be loaded
 133                 $touched = $article->mTouched;
 134
 135                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 136                 if ( $parserOutputKey === false ) {
 137                         wfProfileOut( __METHOD__ );
 138                         return false;
 139                 }
 140
 141                 $value = $this->mMemc->get( $parserOutputKey );
 142                 if ( !$value ) {
 143                         wfDebug( "Parser cache miss.\n" );
 144                         wfIncrStats( "pcache_miss_absent" );
 145                         wfProfileOut( __METHOD__ );
 146                         return false;
 147                 }
 148
 149                 wfDebug( "Found.\n" );
 150
 151                 if ( !$useOutdated && $value->expired( $touched ) ) {
 152                         wfIncrStats( "pcache_miss_expired" );
 153                         $cacheTime = $value->getCacheTime();
 154                         wfDebug( "ParserOutput key expired, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 155                         $value = false;
 156                 } else {
 157                         if ( isset( $value->mTimestamp ) ) {
 158                                 $article->mTimestamp = $value->mTimestamp;
 159                         }
 160                         wfIncrStats( "pcache_hit" );
 161                 }
 162
 163                 wfProfileOut( __METHOD__ );
 164                 return $value;
 165         }
 166
 167
 168         public function save( $parserOutput, $article, $popts ) {
 169                 $expire = $parserOutput->getCacheExpiry();
 170
 171                 if( $expire > 0 ) {
 172                         $now = wfTimestampNow();
 173
 174                         $optionsKey = new CacheTime;
 175                         $optionsKey->mUsedOptions = $popts->usedOptions();
 176                         $optionsKey->updateCacheExpiry( $expire );
 177
 178                         $optionsKey->setCacheTime( $now );
 179                         $parserOutput->setCacheTime( $now );
 180
 181                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 182
 183                         $parserOutputKey = $this->getParserOutputKey( $article, $popts->optionsHash( $optionsKey->mUsedOptions ) );
 184
 185                         // Save the timestamp so that we don't have to load the revision row on view
 186                         $parserOutput->mTimestamp = $article->getTimestamp();
 187
 188                         $parserOutput->mText .= "\n<!-- Saved in parser cache with key $parserOutputKey and timestamp $now -->\n";
 189                         wfDebug( "Saved in parser cache with key $parserOutputKey and timestamp $now\n" );
 190
 191                         // Save the parser output
 192                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 193
 194                         // ...and its pointer
 195                         $this->mMemc->set( $this->getOptionsKey( $article ), $optionsKey, $expire );
 196                 } else {
 197                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 198                 }
 199         }
 200 }