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          * Get an instance of this object
  32          *
  33          * @return ParserCache
  34          */
  35         public static function singleton() {
  36                 static $instance;
  37                 if ( !isset( $instance ) ) {
  38                         global $parserMemc;
  39                         $instance = new ParserCache( $parserMemc );
  40                 }
  41                 return $instance;
  42         }
  43
  44         /**
  45          * Setup a cache pathway with a given back-end storage mechanism.
  46          * May be a memcached client or a BagOStuff derivative.
  47          *
  48          * @param MWMemcached $memCached
  49          * @throws MWException
  50          */
  51         protected function __construct( $memCached ) {
  52                 if ( !$memCached ) {
  53                         throw new MWException( "Tried to create a ParserCache with an invalid memcached" );
  54                 }
  55                 $this->mMemc = $memCached;
  56         }
  57
  58         /**
  59          * @param Article $article
  60          * @param string $hash
  61          * @return mixed|string
  62          */
  63         protected function getParserOutputKey( $article, $hash ) {
  64                 global $wgRequest;
  65
  66                 // idhash seem to mean 'page id' + 'rendering hash' (r3710)
  67                 $pageid = $article->getID();
  68                 $renderkey = (int)( $wgRequest->getVal( 'action' ) == 'render' );
  69
  70                 $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
  71                 return $key;
  72         }
  73
  74         /**
  75          * @param Article $article
  76          * @return mixed|string
  77          */
  78         protected function getOptionsKey( $article ) {
  79                 $pageid = $article->getID();
  80                 return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
  81         }
  82
  83         /**
  84          * Provides an E-Tag suitable for the whole page. Note that $article
  85          * is just the main wikitext. The E-Tag has to be unique to the whole
  86          * page, even if the article itself is the same, so it uses the
  87          * complete set of user options. We don't want to use the preference
  88          * of a different user on a message just because it wasn't used in
  89          * $article. For example give a Chinese interface to a user with
  90          * English preferences. That's why we take into account *all* user
  91          * options. (r70809 CR)
  92          *
  93          * @param Article $article
  94          * @param ParserOptions $popts
  95          * @return string
  96          */
  97         function getETag( $article, $popts ) {
  98                 return 'W/"' . $this->getParserOutputKey( $article,
  99                         $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) ) .
 100                                 "--" . $article->getTouched() . '"';
 101         }
 102
 103         /**
 104          * Retrieve the ParserOutput from ParserCache, even if it's outdated.
 105          * @param Article $article
 106          * @param ParserOptions $popts
 107          * @return ParserOutput|bool False on failure
 108          */
 109         public function getDirty( $article, $popts ) {
 110                 $value = $this->get( $article, $popts, true );
 111                 return is_object( $value ) ? $value : false;
 112         }
 113
 114         /**
 115          * Generates a key for caching the given article considering
 116          * the given parser options.
 117          *
 118          * @note Which parser options influence the cache key
 119          * is controlled via ParserOutput::recordOption() or
 120          * ParserOptions::addExtraKey().
 121          *
 122          * @note Used by Article to provide a unique id for the PoolCounter.
 123          * It would be preferable to have this code in get()
 124          * instead of having Article looking in our internals.
 125          *
 126          * @todo Document parameter $useOutdated
 127          *
 128          * @param Article $article
 129          * @param ParserOptions $popts
 130          * @param bool $useOutdated (default true)
 131          * @return bool|mixed|string
 132          */
 133         public function getKey( $article, $popts, $useOutdated = true ) {
 134                 global $wgCacheEpoch;
 135
 136                 if ( $popts instanceof User ) {
 137                         wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
 138                         $popts = ParserOptions::newFromUser( $popts );
 139                 }
 140
 141                 // Determine the options which affect this article
 142                 $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
 143                 if ( $optionsKey != false ) {
 144                         if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
 145                                 wfIncrStats( "pcache_miss_expired" );
 146                                 $cacheTime = $optionsKey->getCacheTime();
 147                                 wfDebug( "Parser options key expired, touched " . $article->getTouched()
 148                                         . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
 149                                 return false;
 150                         } elseif ( $optionsKey->isDifferentRevision( $article->getLatest() ) ) {
 151                                 wfIncrStats( "pcache_miss_revid" );
 152                                 $revId = $article->getLatest();
 153                                 $cachedRevId = $optionsKey->getCacheRevisionId();
 154                                 wfDebug( "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n" );
 155                                 return false;
 156                         }
 157
 158                         // $optionsKey->mUsedOptions is set by save() by calling ParserOutput::getUsedOptions()
 159                         $usedOptions = $optionsKey->mUsedOptions;
 160                         wfDebug( "Parser cache options found.\n" );
 161                 } else {
 162                         if ( !$useOutdated ) {
 163                                 return false;
 164                         }
 165                         $usedOptions = ParserOptions::legacyOptions();
 166                 }
 167
 168                 return $this->getParserOutputKey(
 169                         $article,
 170                         $popts->optionsHash( $usedOptions, $article->getTitle() )
 171                 );
 172         }
 173
 174         /**
 175          * Retrieve the ParserOutput from ParserCache.
 176          * false if not found or outdated.
 177          *
 178          * @param Article $article
 179          * @param ParserOptions $popts
 180          * @param bool $useOutdated (default false)
 181          *
 182          * @return ParserOutput|bool False on failure
 183          */
 184         public function get( $article, $popts, $useOutdated = false ) {
 185                 global $wgCacheEpoch;
 186                 wfProfileIn( __METHOD__ );
 187
 188                 $canCache = $article->checkTouched();
 189                 if ( !$canCache ) {
 190                         // It's a redirect now
 191                         wfProfileOut( __METHOD__ );
 192                         return false;
 193                 }
 194
 195                 $touched = $article->getTouched();
 196
 197                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 198                 if ( $parserOutputKey === false ) {
 199                         wfIncrStats( 'pcache_miss_absent' );
 200                         wfProfileOut( __METHOD__ );
 201                         return false;
 202                 }
 203
 204                 $value = $this->mMemc->get( $parserOutputKey );
 205                 if ( !$value ) {
 206                         wfDebug( "ParserOutput cache miss.\n" );
 207                         wfIncrStats( "pcache_miss_absent" );
 208                         wfProfileOut( __METHOD__ );
 209                         return false;
 210                 }
 211
 212                 wfDebug( "ParserOutput cache found.\n" );
 213
 214                 // The edit section preference may not be the appropiate one in
 215                 // the ParserOutput, as we are not storing it in the parsercache
 216                 // key. Force it here. See bug 31445.
 217                 $value->setEditSectionTokens( $popts->getEditSection() );
 218
 219                 if ( !$useOutdated && $value->expired( $touched ) ) {
 220                         wfIncrStats( "pcache_miss_expired" );
 221                         $cacheTime = $value->getCacheTime();
 222                         wfDebug( "ParserOutput key expired, touched $touched, "
 223                                 . "epoch $wgCacheEpoch, cached $cacheTime\n" );
 224                         $value = false;
 225                 } elseif ( $value->isDifferentRevision( $article->getLatest() ) ) {
 226                         wfIncrStats( "pcache_miss_revid" );
 227                         $revId = $article->getLatest();
 228                         $cachedRevId = $value->getCacheRevisionId();
 229                         wfDebug( "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n" );
 230                         $value = false;
 231                 } else {
 232                         wfIncrStats( "pcache_hit" );
 233                 }
 234
 235                 wfProfileOut( __METHOD__ );
 236                 return $value;
 237         }
 238
 239         /**
 240          * @param ParserOutput $parserOutput
 241          * @param WikiPage $page
 242          * @param ParserOptions $popts
 243          * @param string $cacheTime Time when the cache was generated
 244          * @param int $revId Revision ID that was parsed
 245          */
 246         public function save( $parserOutput, $page, $popts, $cacheTime = null, $revId = null ) {
 247                 $expire = $parserOutput->getCacheExpiry();
 248                 if ( $expire > 0 ) {
 249                         $cacheTime = $cacheTime ?: wfTimestampNow();
 250                         if ( !$revId ) {
 251                                 $revision = $page->getRevision();
 252                                 $revId = $revision ? $revision->getId() : null;
 253                         }
 254
 255                         $optionsKey = new CacheTime;
 256                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 257                         $optionsKey->updateCacheExpiry( $expire );
 258
 259                         $optionsKey->setCacheTime( $cacheTime );
 260                         $parserOutput->setCacheTime( $cacheTime );
 261                         $optionsKey->setCacheRevisionId( $revId );
 262                         $parserOutput->setCacheRevisionId( $revId );
 263
 264                         $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );
 265
 266                         $parserOutputKey = $this->getParserOutputKey( $page,
 267                                 $popts->optionsHash( $optionsKey->mUsedOptions, $page->getTitle() ) );
 268
 269                         // Save the timestamp so that we don't have to load the revision row on view
 270                         $parserOutput->setTimestamp( $page->getTimestamp() );
 271
 272                         $msg = "Saved in parser cache with key $parserOutputKey" .
 273                                 " and timestamp $cacheTime" .
 274                                 " and revision id $revId" .
 275                                 "\n";
 276
 277                         $parserOutput->mText .= "\n<!-- $msg -->\n";
 278                         wfDebug( $msg );
 279
 280                         // Save the parser output
 281                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 282
 283                         // ...and its pointer
 284                         $this->mMemc->set( $this->getOptionsKey( $page ), $optionsKey, $expire );
 285                 } else {
 286                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 287                 }
 288         }
 289 }