includes/parser/ParserCache.php

   1 <?php
   2 /**
   3  * Cache for outputs of the PHP parser
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache Parser
  22  */
  23
  24 /**
  25  * @ingroup Cache Parser
  26  * @todo document
  27  */
  28 class ParserCache {
  29         private $mMemc;
  30
  31         /**
  32          * Get an instance of this object
  33          *
  34          * @return ParserCache
  35          */
  36         public static function singleton() {
  37                 static $instance;
  38                 if ( !isset( $instance ) ) {
  39                         global $parserMemc;
  40                         $instance = new ParserCache( $parserMemc );
  41                 }
  42                 return $instance;
  43         }
  44
  45         /**
  46          * Setup a cache pathway with a given back-end storage mechanism.
  47          * May be a memcached client or a BagOStuff derivative.
  48          *
  49          * @param $memCached Object
  50          * @throws MWException
  51          */
  52         protected function __construct( $memCached ) {
  53                 if ( !$memCached ) {
  54                         throw new MWException( "Tried to create a ParserCache with an invalid memcached" );
  55                 }
  56                 $this->mMemc = $memCached;
  57         }
  58
  59         /**
  60          * @param $article Article
  61          * @param $hash string
  62          * @return mixed|string
  63          */
  64         protected function getParserOutputKey( $article, $hash ) {
  65                 global $wgRequest;
  66
  67                 // idhash seem to mean 'page id' + 'rendering hash' (r3710)
  68                 $pageid = $article->getID();
  69                 $renderkey = (int)( $wgRequest->getVal( 'action' ) == 'render' );
  70
  71                 $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
  72                 return $key;
  73         }
  74
  75         /**
  76          * @param $article Article
  77          * @return mixed|string
  78          */
  79         protected function getOptionsKey( $article ) {
  80                 $pageid = $article->getID();
  81                 return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
  82         }
  83
  84         /**
  85          * Provides an E-Tag suitable for the whole page. Note that $article
  86          * is just the main wikitext. The E-Tag has to be unique to the whole
  87          * page, even if the article itself is the same, so it uses the
  88          * complete set of user options. We don't want to use the preference
  89          * of a different user on a message just because it wasn't used in
  90          * $article. For example give a Chinese interface to a user with
  91          * English preferences. That's why we take into account *all* user
  92          * options. (r70809 CR)
  93          *
  94          * @param $article Article
  95          * @param $popts ParserOptions
  96          * @return string
  97          */
  98         function getETag( $article, $popts ) {
  99                 return 'W/"' . $this->getParserOutputKey( $article,
 100                         $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) ) .
 101                                 "--" . $article->getTouched() . '"';
 102         }
 103
 104         /**
 105          * Retrieve the ParserOutput from ParserCache, even if it's outdated.
 106          * @param $article Article
 107          * @param $popts ParserOptions
 108          * @return ParserOutput|bool False on failure
 109          */
 110         public function getDirty( $article, $popts ) {
 111                 $value = $this->get( $article, $popts, true );
 112                 return is_object( $value ) ? $value : false;
 113         }
 114
 115         /**
 116          * Used to provide a unique id for the PoolCounter.
 117          * It would be preferable to have this code in get()
 118          * instead of having Article looking in our internals.
 119          *
 120          * @todo Document parameter $useOutdated
 121          *
 122          * @param $article     Article
 123          * @param $popts       ParserOptions
 124          * @param $useOutdated Boolean (default true)
 125          * @return bool|mixed|string
 126          */
 127         public function getKey( $article, $popts, $useOutdated = true ) {
 128                 global $wgCacheEpoch;
 129
 130                 if ( $popts instanceof User ) {
 131                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
 132                         $popts = ParserOptions::newFromUser( $popts );
 133                 }
 134
 135                 // Determine the options which affect this article
 136                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
 137                 if ( $optionsKey != false ) {
 138                         if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
 139                                 wfIncrStats( "pcache_miss_expired" );
 140                                 $cacheTime = $optionsKey->getCacheTime();
 141                                 wfDebug( "Parser options key expired, touched " . $article->getTouched() . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
 142                                 return false;
 143                         }
 144
 145                         $usedOptions = $optionsKey->mUsedOptions;
 146                         wfDebug( "Parser cache options found.\n" );
 147                 } else {
 148                         if ( !$useOutdated ) {
 149                                 return false;
 150                         }
 151                         $usedOptions = ParserOptions::legacyOptions();
 152                 }
 153
 154                 return $this->getParserOutputKey( $article, $popts->optionsHash( $usedOptions, $article->getTitle() ) );
 155         }
 156
 157         /**
 158          * Retrieve the ParserOutput from ParserCache.
 159          * false if not found or outdated.
 160          *
 161          * @param $article     Article
 162          * @param $popts       ParserOptions
 163          * @param $useOutdated Boolean (default false)
 164          *
 165          * @return ParserOutput|bool False on failure
 166          */
 167         public function get( $article, $popts, $useOutdated = false ) {
 168                 global $wgCacheEpoch;
 169                 wfProfileIn( __METHOD__ );
 170
 171                 $canCache = $article->checkTouched();
 172                 if ( !$canCache ) {
 173                         // It's a redirect now
 174                         wfProfileOut( __METHOD__ );
 175                         return false;
 176                 }
 177
 178                 $touched = $article->getTouched();
 179
 180                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 181                 if ( $parserOutputKey === false ) {
 182                         wfIncrStats( 'pcache_miss_absent' );
 183                         wfProfileOut( __METHOD__ );
 184                         return false;
 185                 }
 186
 187                 $value = $this->mMemc->get( $parserOutputKey );
 188                 if ( !$value ) {
 189                         wfDebug( "ParserOutput cache miss.\n" );
 190                         wfIncrStats( "pcache_miss_absent" );
 191                         wfProfileOut( __METHOD__ );
 192                         return false;
 193                 }
 194
 195                 wfDebug( "ParserOutput cache found.\n" );
 196
 197                 // The edit section preference may not be the appropiate one in
 198                 // the ParserOutput, as we are not storing it in the parsercache
 199                 // key. Force it here. See bug 31445.
 200                 $value->setEditSectionTokens( $popts->getEditSection() );
 201
 202                 if ( !$useOutdated && $value->expired( $touched ) ) {
 203                         wfIncrStats( "pcache_miss_expired" );
 204                         $cacheTime = $value->getCacheTime();
 205                         wfDebug( "ParserOutput key expired, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 206                         $value = false;
 207                 } else {
 208                         wfIncrStats( "pcache_hit" );
 209                 }
 210
 211                 wfProfileOut( __METHOD__ );
 212                 return $value;
 213         }
 214
 215         /**
 216          * @param ParserOutput $parserOutput
 217          * @param Article $article
 218          * @param ParserOptions $popts
 219          * @param string $cacheTime Time when the cache was generated
 220          */
 221         public function save( $parserOutput, $article, $popts, $cacheTime = null ) {
 222                 $expire = $parserOutput->getCacheExpiry();
 223                 if ( $expire > 0 ) {
 224                         $cacheTime = $cacheTime ?: wfTimestampNow();
 225
 226                         $optionsKey = new CacheTime;
 227                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 228                         $optionsKey->updateCacheExpiry( $expire );
 229
 230                         $optionsKey->setCacheTime( $cacheTime );
 231                         $parserOutput->setCacheTime( $cacheTime );
 232
 233                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 234
 235                         $parserOutputKey = $this->getParserOutputKey( $article,
 236                                 $popts->optionsHash( $optionsKey->mUsedOptions, $article->getTitle() ) );
 237
 238                         // Save the timestamp so that we don't have to load the revision row on view
 239                         $parserOutput->setTimestamp( $article->getTimestamp() );
 240
 241                         $parserOutput->mText .= "\n<!-- Saved in parser cache with key $parserOutputKey and timestamp $cacheTime\n -->\n";
 242                         wfDebug( "Saved in parser cache with key $parserOutputKey and timestamp $cacheTime\n" );
 243
 244                         // Save the parser output
 245                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 246
 247                         // ...and its pointer
 248                         $this->mMemc->set( $this->getOptionsKey( $article ), $optionsKey, $expire );
 249                 } else {
 250                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 251                 }
 252         }
 253 }