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         const try116cache = false; /* Only useful $wgParserCacheExpireTime after updating to 1.17 */
  31
  32         /**
  33          * Get an instance of this object
  34          *
  35          * @return ParserCache
  36          */
  37         public static function singleton() {
  38                 static $instance;
  39                 if ( !isset( $instance ) ) {
  40                         global $parserMemc;
  41                         $instance = new ParserCache( $parserMemc );
  42                 }
  43                 return $instance;
  44         }
  45
  46         /**
  47          * Setup a cache pathway with a given back-end storage mechanism.
  48          * May be a memcached client or a BagOStuff derivative.
  49          *
  50          * @param $memCached Object
  51          * @throws MWException
  52          */
  53         protected function __construct( $memCached ) {
  54                 if ( !$memCached ) {
  55                         throw new MWException( "Tried to create a ParserCache with an invalid memcached" );
  56                 }
  57                 $this->mMemc = $memCached;
  58         }
  59
  60         /**
  61          * @param $article Article
  62          * @param $hash string
  63          * @return mixed|string
  64          */
  65         protected function getParserOutputKey( $article, $hash ) {
  66                 global $wgRequest;
  67
  68                 // idhash seem to mean 'page id' + 'rendering hash' (r3710)
  69                 $pageid = $article->getID();
  70                 $renderkey = (int)( $wgRequest->getVal( 'action' ) == 'render' );
  71
  72                 $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
  73                 return $key;
  74         }
  75
  76         /**
  77          * @param $article Article
  78          * @return mixed|string
  79          */
  80         protected function getOptionsKey( $article ) {
  81                 $pageid = $article->getID();
  82                 return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
  83         }
  84
  85         /**
  86          * Provides an E-Tag suitable for the whole page. Note that $article
  87          * is just the main wikitext. The E-Tag has to be unique to the whole
  88          * page, even if the article itself is the same, so it uses the
  89          * complete set of user options. We don't want to use the preference
  90          * of a different user on a message just because it wasn't used in
  91          * $article. For example give a Chinese interface to a user with
  92          * English preferences. That's why we take into account *all* user
  93          * options. (r70809 CR)
  94          *
  95          * @param $article Article
  96          * @param $popts ParserOptions
  97          * @return string
  98          */
  99         function getETag( $article, $popts ) {
 100                 return 'W/"' . $this->getParserOutputKey( $article,
 101                         $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) ) .
 102                                 "--" . $article->getTouched() . '"';
 103         }
 104
 105         /**
 106          * Retrieve the ParserOutput from ParserCache, even if it's outdated.
 107          * @param $article Article
 108          * @param $popts ParserOptions
 109          * @return ParserOutput|bool False on failure
 110          */
 111         public function getDirty( $article, $popts ) {
 112                 $value = $this->get( $article, $popts, true );
 113                 return is_object( $value ) ? $value : false;
 114         }
 115
 116         /**
 117          * Used to provide a unique id for the PoolCounter.
 118          * It would be preferable to have this code in get()
 119          * instead of having Article looking in our internals.
 120          *
 121          * @todo Document parameter $useOutdated
 122          *
 123          * @param $article     Article
 124          * @param $popts       ParserOptions
 125          * @param $useOutdated Boolean (default true)
 126          * @return bool|mixed|string
 127          */
 128         public function getKey( $article, $popts, $useOutdated = true ) {
 129                 global $wgCacheEpoch;
 130
 131                 if ( $popts instanceof User ) {
 132                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
 133                         $popts = ParserOptions::newFromUser( $popts );
 134                 }
 135
 136                 // Determine the options which affect this article
 137                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
 138                 if ( $optionsKey != false ) {
 139                         if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
 140                                 wfIncrStats( "pcache_miss_expired" );
 141                                 $cacheTime = $optionsKey->getCacheTime();
 142                                 wfDebug( "Parser options key expired, touched " . $article->getTouched() . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
 143                                 return false;
 144                         }
 145
 146                         $usedOptions = $optionsKey->mUsedOptions;
 147                         wfDebug( "Parser cache options found.\n" );
 148                 } else {
 149                         if ( !$useOutdated && !self::try116cache ) {
 150                                 return false;
 151                         }
 152                         $usedOptions = ParserOptions::legacyOptions();
 153                 }
 154
 155                 return $this->getParserOutputKey( $article, $popts->optionsHash( $usedOptions, $article->getTitle() ) );
 156         }
 157
 158         /**
 159          * Retrieve the ParserOutput from ParserCache.
 160          * false if not found or outdated.
 161          *
 162          * @param $article     Article
 163          * @param $popts       ParserOptions
 164          * @param $useOutdated Boolean (default false)
 165          *
 166          * @return ParserOutput|bool False on failure
 167          */
 168         public function get( $article, $popts, $useOutdated = false ) {
 169                 global $wgCacheEpoch;
 170                 wfProfileIn( __METHOD__ );
 171
 172                 $canCache = $article->checkTouched();
 173                 if ( !$canCache ) {
 174                         // It's a redirect now
 175                         wfProfileOut( __METHOD__ );
 176                         return false;
 177                 }
 178
 179                 $touched = $article->getTouched();
 180
 181                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 182                 if ( $parserOutputKey === false ) {
 183                         wfIncrStats( 'pcache_miss_absent' );
 184                         wfProfileOut( __METHOD__ );
 185                         return false;
 186                 }
 187
 188                 $value = $this->mMemc->get( $parserOutputKey );
 189                 if ( self::try116cache && !$value && strpos( $value, '*' ) !== -1 ) {
 190                         wfDebug( "New format parser cache miss.\n" );
 191                         $parserOutputKey = $this->getParserOutputKey( $article,
 192                                 $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) );
 193                         $value = $this->mMemc->get( $parserOutputKey );
 194                 }
 195                 if ( !$value ) {
 196                         wfDebug( "ParserOutput cache miss.\n" );
 197                         wfIncrStats( "pcache_miss_absent" );
 198                         wfProfileOut( __METHOD__ );
 199                         return false;
 200                 }
 201
 202                 wfDebug( "ParserOutput cache found.\n" );
 203
 204                 // The edit section preference may not be the appropiate one in
 205                 // the ParserOutput, as we are not storing it in the parsercache
 206                 // key. Force it here. See bug 31445.
 207                 $value->setEditSectionTokens( $popts->getEditSection() );
 208
 209                 if ( !$useOutdated && $value->expired( $touched ) ) {
 210                         wfIncrStats( "pcache_miss_expired" );
 211                         $cacheTime = $value->getCacheTime();
 212                         wfDebug( "ParserOutput key expired, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 213                         $value = false;
 214                 } else {
 215                         wfIncrStats( "pcache_hit" );
 216                 }
 217
 218                 wfProfileOut( __METHOD__ );
 219                 return $value;
 220         }
 221
 222         /**
 223          * @param $parserOutput ParserOutput
 224          * @param $article Article
 225          * @param $popts ParserOptions
 226          */
 227         public function save( $parserOutput, $article, $popts ) {
 228                 $expire = $parserOutput->getCacheExpiry();
 229
 230                 if ( $expire > 0 ) {
 231                         $now = wfTimestampNow();
 232
 233                         $optionsKey = new CacheTime;
 234                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 235                         $optionsKey->updateCacheExpiry( $expire );
 236
 237                         $optionsKey->setCacheTime( $now );
 238                         $parserOutput->setCacheTime( $now );
 239
 240                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 241
 242                         $parserOutputKey = $this->getParserOutputKey( $article,
 243                                 $popts->optionsHash( $optionsKey->mUsedOptions, $article->getTitle() ) );
 244
 245                         // Save the timestamp so that we don't have to load the revision row on view
 246                         $parserOutput->setTimestamp( $article->getTimestamp() );
 247
 248                         $parserOutput->mText .= "\n<!-- Saved in parser cache with key $parserOutputKey and timestamp $now -->\n";
 249                         wfDebug( "Saved in parser cache with key $parserOutputKey and timestamp $now\n" );
 250
 251                         // Save the parser output
 252                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 253
 254                         // ...and its pointer
 255                         $this->mMemc->set( $this->getOptionsKey( $article ), $optionsKey, $expire );
 256                 } else {
 257                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 258                 }
 259         }
 260 }