includes/parser/ParserCache.php

   1 <?php
   2 /**
   3  * @ingroup Cache Parser
   4  * @todo document
   5  */
   6 class ParserCache {
   7         private $mMemc;
   8
   9         /**
  10          * Get an instance of this object
  11          */
  12         public static function singleton() {
  13                 static $instance;
  14                 if ( !isset( $instance ) ) {
  15                         global $parserMemc;
  16                         $instance = new ParserCache( $parserMemc );
  17                 }
  18                 return $instance;
  19         }
  20
  21         /**
  22          * Setup a cache pathway with a given back-end storage mechanism.
  23          * May be a memcached client or a BagOStuff derivative.
  24          *
  25          * @param $memCached Object
  26          */
  27         function __construct( $memCached ) {
  28                 if ( !$memCached ) {
  29                         global $parserMemc;
  30                         $parserMemc = $memCached = wfGetParserCacheStorage();
  31                 }
  32                 $this->mMemc = $memCached;
  33         }
  34
  35         protected function getParserOutputKey( $article, $hash ) {
  36                 global $wgRequest;
  37
  38                 // idhash seem to mean 'page id' + 'rendering hash' (r3710)
  39                 $pageid = $article->getID();
  40                 $renderkey = (int)($wgRequest->getVal('action') == 'render');
  41
  42                 $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
  43                 return $key;
  44         }
  45
  46         protected function getOptionsKey( $article ) {
  47                 $pageid = $article->getID();
  48                 return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
  49         }
  50
  51         function getETag( $article, $popts ) {
  52                 return 'W/"' . $this->getParserOutputKey( $article,
  53                         $popts->optionsHash( ParserOptions::legacyOptions() ) ) .
  54                                 "--" . $article->mTouched . '"';
  55         }
  56
  57         /**
  58          * Retrieve the ParserOutput from ParserCache, even if it's outdated.
  59          */
  60         public function getDirty( $article, $popts ) {
  61                 $value = $this->mMemc->get( $article, $popts, true );
  62                 return is_object( $value ) ? $value : false;
  63         }
  64
  65         /**
  66          * Used to provide a unique id for the PoolCounter.
  67          * It would be preferable to have this code in get()
  68          * instead of having Article looking in our internals.
  69          *
  70          * Precondition: $article->checkTouched() has been called.
  71          */
  72         public function getKey( $article, $popts, $useOutdated = true ) {
  73                 global $wgCacheEpoch;
  74
  75                 // Determine the options which affect this article
  76                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
  77                 if ( $optionsKey !== false ) {
  78                         if ( !$useOutdated && $optionsKey->expired( $article->mTouched ) ) {
  79                                 wfIncrStats( "pcache_miss_expired" );
  80                                 $cacheTime = $optionsKey->getCacheTime();
  81                                 wfDebug( "Parser options key expired, touched {$article->mTouched}, epoch $wgCacheEpoch, cached $cacheTime\n" );
  82                                 return false;
  83                         }
  84
  85                         $usedOptions = $optionsKey->mUsedOptions;
  86                         wfDebug( "Parser cache options found.\n" );
  87                 } else {
  88                         # TODO: Fail here $wgParserCacheExpireTime after deployment unless $useOutdated
  89
  90                         $usedOptions = ParserOptions::legacyOptions();
  91                 }
  92
  93                 return $this->getParserOutputKey( $article, $popts->optionsHash( $usedOptions ) );
  94         }
  95
  96         /**
  97          * Retrieve the ParserOutput from ParserCache.
  98          * false if not found or outdated.
  99          */
 100         public function get( $article, $popts, $useOutdated = false ) {
 101                 global $wgCacheEpoch;
 102                 wfProfileIn( __METHOD__ );
 103
 104                 $canCache = $article->checkTouched();
 105                 if ( !$canCache ) {
 106                         // It's a redirect now
 107                         wfProfileOut( __METHOD__ );
 108                         return false;
 109                 }
 110
 111                 // Having called checkTouched() ensures this will be loaded
 112                 $touched = $article->mTouched;
 113
 114                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 115                 if ( $parserOutputKey === false ) {
 116                         wfProfileOut( __METHOD__ );
 117                         return false;
 118                 }
 119
 120                 $value = $this->mMemc->get( $parserOutputKey );
 121                 if ( !$value ) {
 122                         wfDebug( "Parser cache miss.\n" );
 123                         wfIncrStats( "pcache_miss_absent" );
 124                         wfProfileOut( __METHOD__ );
 125                         return false;
 126                 }
 127
 128                 wfDebug( "Found.\n" );
 129
 130                 if ( !$useOutdated && $value->expired( $touched ) ) {
 131                         wfIncrStats( "pcache_miss_expired" );
 132                         wfDebug( "ParserOutput key expired, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 133                         $value = false;
 134                 } else {
 135                         if ( isset( $value->mTimestamp ) ) {
 136                                 $article->mTimestamp = $value->mTimestamp;
 137                         }
 138                         wfIncrStats( "pcache_hit" );
 139                 }
 140
 141                 wfProfileOut( __METHOD__ );
 142                 return $value;
 143         }
 144
 145
 146         public function save( $parserOutput, $article, $popts ) {
 147                 $expire = $parserOutput->getCacheExpiry();
 148
 149                 if( $expire > 0 ) {
 150                         $now = wfTimestampNow();
 151
 152                         $optionsKey = new CacheTime;
 153                         $optionsKey->mUsedOptions = $popts->usedOptions();
 154                         $optionsKey->updateCacheExpiry( $expire );
 155
 156                         $optionsKey->setCacheTime( $now );
 157                         $parserOutput->setCacheTime( $now );
 158
 159                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 160
 161                         $parserOutputKey = $this->getParserOutputKey( $article, $popts->optionsHash( $optionsKey->mUsedOptions ) );
 162
 163                         // Save the timestamp so that we don't have to load the revision row on view
 164                         $parserOutput->mTimestamp = $article->getTimestamp();
 165
 166                         $parserOutput->mText .= "\n<!-- Saved in parser cache with key $parserOutputKey and timestamp $now -->\n";
 167                         wfDebug( "Saved in parser cache with key $parserOutputKey and timestamp $now\n" );
 168
 169                         // Save the parser output
 170                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 171
 172                         // ...and its pointer
 173                         $this->mMemc->set( $this->getOptionsKey( $article ), $optionsKey, $expire );
 174                 } else {
 175                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 176                 }
 177         }
 178 }