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  85          * Retrieve the ParserOutput from ParserCache, even if it's outdated.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