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         /** @var MWMemcached  */
  30         private $mMemc;
  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 MWMemcached $memCached
  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 string $hash
  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 ParserOptions $popts
  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 ParserOptions $popts
 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          * Generates a key for caching the given article considering
 117          * the given parser options.
 118          *
 119          * @note Which parser options influence the cache key
 120          * is controlled via ParserOutput::recordOption() or
 121          * ParserOptions::addExtraKey().
 122          *
 123          * @note Used by Article to provide a unique id for the PoolCounter.
 124          * It would be preferable to have this code in get()
 125          * instead of having Article looking in our internals.
 126          *
 127          * @todo Document parameter $useOutdated
 128          *
 129          * @param Article $article
 130          * @param ParserOptions $popts
 131          * @param bool $useOutdated (default true)
 132          * @return bool|mixed|string
 133          */
 134         public function getKey( $article, $popts, $useOutdated = true ) {
 135                 global $wgCacheEpoch;
 136
 137                 if ( $popts instanceof User ) {
 138                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
 139                         $popts = ParserOptions::newFromUser( $popts );
 140                 }
 141
 142                 // Determine the options which affect this article
 143                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
 144                 if ( $optionsKey != false ) {
 145                         if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
 146                                 wfIncrStats( "pcache_miss_expired" );
 147                                 $cacheTime = $optionsKey->getCacheTime();
 148                                 wfDebug( "Parser options key expired, touched " . $article->getTouched()
 149                                         . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
 150                                 return false;
 151                         } elseif ( $optionsKey->isDifferentRevision( $article->getLatest() ) ) {
 152                                 wfIncrStats( "pcache_miss_revid" );
 153                                 $revId = $article->getLatest();
 154                                 $cachedRevId = $optionsKey->getCacheRevisionId();
 155                                 wfDebug( "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n" );
 156                                 return false;
 157                         }
 158
 159                         // $optionsKey->mUsedOptions is set by save() by calling ParserOutput::getUsedOptions()
 160                         $usedOptions = $optionsKey->mUsedOptions;
 161                         wfDebug( "Parser cache options found.\n" );
 162                 } else {
 163                         if ( !$useOutdated ) {
 164                                 return false;
 165                         }
 166                         $usedOptions = ParserOptions::legacyOptions();
 167                 }
 168
 169                 return $this->getParserOutputKey(
 170                         $article,
 171                         $popts->optionsHash( $usedOptions, $article->getTitle() )
 172                 );
 173         }
 174
 175         /**
 176          * Retrieve the ParserOutput from ParserCache.
 177          * false if not found or outdated.
 178          *
 179          * @param Article $article
 180          * @param ParserOptions $popts
 181          * @param bool $useOutdated (default false)
 182          *
 183          * @return ParserOutput|bool False on failure
 184          */
 185         public function get( $article, $popts, $useOutdated = false ) {
 186                 global $wgCacheEpoch;
 187                 wfProfileIn( __METHOD__ );
 188
 189                 $canCache = $article->checkTouched();
 190                 if ( !$canCache ) {
 191                         // It's a redirect now
 192                         wfProfileOut( __METHOD__ );
 193                         return false;
 194                 }
 195
 196                 $touched = $article->getTouched();
 197
 198                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 199                 if ( $parserOutputKey === false ) {
 200                         wfIncrStats( 'pcache_miss_absent' );
 201                         wfProfileOut( __METHOD__ );
 202                         return false;
 203                 }
 204
 205                 $value = $this->mMemc->get( $parserOutputKey );
 206                 if ( !$value ) {
 207                         wfDebug( "ParserOutput cache miss.\n" );
 208                         wfIncrStats( "pcache_miss_absent" );
 209                         wfProfileOut( __METHOD__ );
 210                         return false;
 211                 }
 212
 213                 wfDebug( "ParserOutput cache found.\n" );
 214
 215                 // The edit section preference may not be the appropiate one in
 216                 // the ParserOutput, as we are not storing it in the parsercache
 217                 // key. Force it here. See bug 31445.
 218                 $value->setEditSectionTokens( $popts->getEditSection() );
 219
 220                 if ( !$useOutdated && $value->expired( $touched ) ) {
 221                         wfIncrStats( "pcache_miss_expired" );
 222                         $cacheTime = $value->getCacheTime();
 223                         wfDebug( "ParserOutput key expired, touched $touched, "
 224                                 . "epoch $wgCacheEpoch, cached $cacheTime\n" );
 225                         $value = false;
 226                 } elseif ( $value->isDifferentRevision( $article->getLatest() ) ) {
 227                         wfIncrStats( "pcache_miss_revid" );
 228                         $revId = $article->getLatest();
 229                         $cachedRevId = $value->getCacheRevisionId();
 230                         wfDebug( "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n" );
 231                         $value = false;
 232                 } else {
 233                         wfIncrStats( "pcache_hit" );
 234                 }
 235
 236                 wfProfileOut( __METHOD__ );
 237                 return $value;
 238         }
 239
 240         /**
 241          * @param ParserOutput $parserOutput
 242          * @param WikiPage $page
 243          * @param ParserOptions $popts
 244          * @param string $cacheTime Time when the cache was generated
 245          * @param int $revId Revision ID that was parsed
 246          */
 247         public function save( $parserOutput, $page, $popts, $cacheTime = null, $revId = null ) {
 248                 $expire = $parserOutput->getCacheExpiry();
 249                 if ( $expire > 0 ) {
 250                         $cacheTime = $cacheTime ?: wfTimestampNow();
 251                         if ( !$revId ) {
 252                                 $revision = $page->getRevision();
 253                                 $revId = $revision ? $revision->getId() : null;
 254                         }
 255
 256                         $optionsKey = new CacheTime;
 257                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 258                         $optionsKey->updateCacheExpiry( $expire );
 259
 260                         $optionsKey->setCacheTime( $cacheTime );
 261                         $parserOutput->setCacheTime( $cacheTime );
 262                         $optionsKey->setCacheRevisionId( $revId );
 263                         $parserOutput->setCacheRevisionId( $revId );
 264
 265                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 266
 267                         $parserOutputKey = $this->getParserOutputKey( $page,
 268                                 $popts->optionsHash( $optionsKey->mUsedOptions, $page->getTitle() ) );
 269
 270                         // Save the timestamp so that we don't have to load the revision row on view
 271                         $parserOutput->setTimestamp( $page->getTimestamp() );
 272
 273                         $msg = "Saved in parser cache with key $parserOutputKey" .
 274                                 " and timestamp $cacheTime" .
 275                                 " and revision id $revId" .
 276                                 "\n";
 277
 278                         $parserOutput->mText .= "\n<!-- $msg -->\n";
 279                         wfDebug( $msg );
 280
 281                         // Save the parser output
 282                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 283
 284                         // ...and its pointer
 285                         $this->mMemc->set( $this->getOptionsKey( $page ), $optionsKey, $expire );
 286                 } else {
 287                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 288                 }
 289         }
 290 }