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 BagOStuff */
  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          *
  48          * This class use an invalidation strategy that is compatible with
  49          * MultiWriteBagOStuff in async replication mode.
  50          *
  51          * @param BagOStuff $memCached
  52          * @throws MWException
  53          */
  54         protected function __construct( BagOStuff $memCached ) {
  55                 $this->mMemc = $memCached;
  56         }
  57
  58         /**
  59          * @param WikiPage $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 WikiPage $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 WikiPage $article
  94          * @param ParserOptions $popts
  95          * @return string
  96          */
  97         public 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 WikiPage $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 WikiPage $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 ( $optionsKey instanceof CacheTime ) {
 144                         if ( !$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 WikiPage|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
 187                 $canCache = $article->checkTouched();
 188                 if ( !$canCache ) {
 189                         // It's a redirect now
 190                         return false;
 191                 }
 192
 193                 $touched = $article->getTouched();
 194
 195                 $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
 196                 if ( $parserOutputKey === false ) {
 197                         wfIncrStats( 'pcache.miss.absent' );
 198                         return false;
 199                 }
 200
 201                 $value = $this->mMemc->get( $parserOutputKey );
 202                 if ( !$value ) {
 203                         wfDebug( "ParserOutput cache miss.\n" );
 204                         wfIncrStats( "pcache.miss.absent" );
 205                         return false;
 206                 }
 207
 208                 wfDebug( "ParserOutput cache found.\n" );
 209
 210                 // The edit section preference may not be the appropiate one in
 211                 // the ParserOutput, as we are not storing it in the parsercache
 212                 // key. Force it here. See bug 31445.
 213                 $value->setEditSectionTokens( $popts->getEditSection() );
 214
 215                 $wikiPage = method_exists( $article, 'getPage' )
 216                         ? $article->getPage()
 217                         : $article;
 218
 219                 if ( !$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(
 230                                 "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n"
 231                         );
 232                         $value = false;
 233                 } elseif (
 234                         Hooks::run( 'RejectParserCacheValue', array( $value, $wikiPage, $popts ) ) === false
 235                 ) {
 236                         wfIncrStats( 'pcache.miss.rejected' );
 237                         wfDebug(
 238                                 "ParserOutput key valid, but rejected by RejectParserCacheValue hook handler.\n"
 239                         );
 240                         $value = false;
 241                 } else {
 242                         wfIncrStats( "pcache.hit" );
 243                 }
 244
 245                 return $value;
 246         }
 247
 248         /**
 249          * @param ParserOutput $parserOutput
 250          * @param WikiPage $page
 251          * @param ParserOptions $popts
 252          * @param string $cacheTime Time when the cache was generated
 253          * @param int $revId Revision ID that was parsed
 254          */
 255         public function save( $parserOutput, $page, $popts, $cacheTime = null, $revId = null ) {
 256                 $expire = $parserOutput->getCacheExpiry();
 257                 if ( $expire > 0 ) {
 258                         $cacheTime = $cacheTime ?: wfTimestampNow();
 259                         if ( !$revId ) {
 260                                 $revision = $page->getRevision();
 261                                 $revId = $revision ? $revision->getId() : null;
 262                         }
 263
 264                         $optionsKey = new CacheTime;
 265                         $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
 266                         $optionsKey->updateCacheExpiry( $expire );
 267
 268                         $optionsKey->setCacheTime( $cacheTime );
 269                         $parserOutput->setCacheTime( $cacheTime );
 270                         $optionsKey->setCacheRevisionId( $revId );
 271                         $parserOutput->setCacheRevisionId( $revId );
 272
 273                         $parserOutputKey = $this->getParserOutputKey( $page,
 274                                 $popts->optionsHash( $optionsKey->mUsedOptions, $page->getTitle() ) );
 275
 276                         // Save the timestamp so that we don't have to load the revision row on view
 277                         $parserOutput->setTimestamp( $page->getTimestamp() );
 278
 279                         $msg = "Saved in parser cache with key $parserOutputKey" .
 280                                 " and timestamp $cacheTime" .
 281                                 " and revision id $revId" .
 282                                 "\n";
 283
 284                         $parserOutput->mText .= "\n<!-- $msg -->\n";
 285                         wfDebug( $msg );
 286
 287                         // Save the parser output
 288                         $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );
 289
 290                         // ...and its pointer
 291                         $this->mMemc->set( $this->getOptionsKey( $page ), $optionsKey, $expire );
 292
 293                         Hooks::run(
 294                                 'ParserCacheSaveComplete',
 295                                 array( $this, $parserOutput, $page->getTitle(), $popts, $revId )
 296                         );
 297                 } else {
 298                         wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
 299                 }
 300         }
 301 }