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[mediawiki.git] / includes / parser / ParserCache.php

<?php
/**
 * Cache for outputs of the PHP parser
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Cache Parser
 */

/**
 * @ingroup Cache Parser
 * @todo document
 */
class ParserCache {
        /** @var MWMemcached */
        private $mMemc;
        /**
         * Get an instance of this object
         *
         * @return ParserCache
         */
        public static function singleton() {
                static $instance;
                if ( !isset( $instance ) ) {
                        global $parserMemc;
                        $instance = new ParserCache( $parserMemc );
                }
                return $instance;
        }

        /**
         * Setup a cache pathway with a given back-end storage mechanism.
         * May be a memcached client or a BagOStuff derivative.
         *
         * @param MWMemcached $memCached
         * @throws MWException
         */
        protected function __construct( $memCached ) {
                if ( !$memCached ) {
                        throw new MWException( "Tried to create a ParserCache with an invalid memcached" );
                }
                $this->mMemc = $memCached;
        }

        /**
         * @param Article $article
         * @param string $hash
         * @return mixed|string
         */
        protected function getParserOutputKey( $article, $hash ) {
                global $wgRequest;

                // idhash seem to mean 'page id' + 'rendering hash' (r3710)
                $pageid = $article->getID();
                $renderkey = (int)( $wgRequest->getVal( 'action' ) == 'render' );

                $key = wfMemcKey( 'pcache', 'idhash', "{$pageid}-{$renderkey}!{$hash}" );
                return $key;
        }

        /**
         * @param Article $article
         * @return mixed|string
         */
        protected function getOptionsKey( $article ) {
                $pageid = $article->getID();
                return wfMemcKey( 'pcache', 'idoptions', "{$pageid}" );
        }

        /**
         * Provides an E-Tag suitable for the whole page. Note that $article
         * is just the main wikitext. The E-Tag has to be unique to the whole
         * page, even if the article itself is the same, so it uses the
         * complete set of user options. We don't want to use the preference
         * of a different user on a message just because it wasn't used in
         * $article. For example give a Chinese interface to a user with
         * English preferences. That's why we take into account *all* user
         * options. (r70809 CR)
         *
         * @param Article $article
         * @param ParserOptions $popts
         * @return string
         */
        public function getETag( $article, $popts ) {
                return 'W/"' . $this->getParserOutputKey( $article,
                        $popts->optionsHash( ParserOptions::legacyOptions(), $article->getTitle() ) ) .
                                "--" . $article->getTouched() . '"';
        }

        /**
         * Retrieve the ParserOutput from ParserCache, even if it's outdated.
         * @param Article $article
         * @param ParserOptions $popts
         * @return ParserOutput|bool False on failure
         */
        public function getDirty( $article, $popts ) {
                $value = $this->get( $article, $popts, true );
                return is_object( $value ) ? $value : false;
        }

        /**
         * Generates a key for caching the given article considering
         * the given parser options.
         *
         * @note Which parser options influence the cache key
         * is controlled via ParserOutput::recordOption() or
         * ParserOptions::addExtraKey().
         *
         * @note Used by Article to provide a unique id for the PoolCounter.
         * It would be preferable to have this code in get()
         * instead of having Article looking in our internals.
         *
         * @todo Document parameter $useOutdated
         *
         * @param Article $article
         * @param ParserOptions $popts
         * @param bool $useOutdated (default true)
         * @return bool|mixed|string
         */
        public function getKey( $article, $popts, $useOutdated = true ) {
                global $wgCacheEpoch;

                if ( $popts instanceof User ) {
                        wfWarn( "Use of outdated prototype ParserCache::getKey( &\$article, &\$user )\n" );
                        $popts = ParserOptions::newFromUser( $popts );
                }

                // Determine the options which affect this article
                $optionsKey = $this->mMemc->get( $this->getOptionsKey( $article ) );
                if ( $optionsKey != false ) {
                        if ( !$useOutdated && $optionsKey->expired( $article->getTouched() ) ) {
                                wfIncrStats( "pcache_miss_expired" );
                                $cacheTime = $optionsKey->getCacheTime();
                                wfDebug( "Parser options key expired, touched " . $article->getTouched()
                                        . ", epoch $wgCacheEpoch, cached $cacheTime\n" );
                                return false;
                        } elseif ( $optionsKey->isDifferentRevision( $article->getLatest() ) ) {
                                wfIncrStats( "pcache_miss_revid" );
                                $revId = $article->getLatest();
                                $cachedRevId = $optionsKey->getCacheRevisionId();
                                wfDebug( "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n" );
                                return false;
                        }

                        // $optionsKey->mUsedOptions is set by save() by calling ParserOutput::getUsedOptions()
                        $usedOptions = $optionsKey->mUsedOptions;
                        wfDebug( "Parser cache options found.\n" );
                } else {
                        if ( !$useOutdated ) {
                                return false;
                        }
                        $usedOptions = ParserOptions::legacyOptions();
                }

                return $this->getParserOutputKey(
                        $article,
                        $popts->optionsHash( $usedOptions, $article->getTitle() )
                );
        }

        /**
         * Retrieve the ParserOutput from ParserCache.
         * false if not found or outdated.
         *
         * @param Article $article
         * @param ParserOptions $popts
         * @param bool $useOutdated (default false)
         *
         * @return ParserOutput|bool False on failure
         */
        public function get( $article, $popts, $useOutdated = false ) {
                global $wgCacheEpoch;

                $canCache = $article->checkTouched();
                if ( !$canCache ) {
                        // It's a redirect now
                        return false;
                }

                $touched = $article->getTouched();

                $parserOutputKey = $this->getKey( $article, $popts, $useOutdated );
                if ( $parserOutputKey === false ) {
                        wfIncrStats( 'pcache_miss_absent' );
                        return false;
                }

                $value = $this->mMemc->get( $parserOutputKey );
                if ( !$value ) {
                        wfDebug( "ParserOutput cache miss.\n" );
                        wfIncrStats( "pcache_miss_absent" );
                        return false;
                }

                wfDebug( "ParserOutput cache found.\n" );

                // The edit section preference may not be the appropiate one in
                // the ParserOutput, as we are not storing it in the parsercache
                // key. Force it here. See bug 31445.
                $value->setEditSectionTokens( $popts->getEditSection() );

                if ( !$useOutdated && $value->expired( $touched ) ) {
                        wfIncrStats( "pcache_miss_expired" );
                        $cacheTime = $value->getCacheTime();
                        wfDebug( "ParserOutput key expired, touched $touched, "
                                . "epoch $wgCacheEpoch, cached $cacheTime\n" );
                        $value = false;
                } elseif ( $value->isDifferentRevision( $article->getLatest() ) ) {
                        wfIncrStats( "pcache_miss_revid" );
                        $revId = $article->getLatest();
                        $cachedRevId = $value->getCacheRevisionId();
                        wfDebug( "ParserOutput key is for an old revision, latest $revId, cached $cachedRevId\n" );
                        $value = false;
                } else {
                        wfIncrStats( "pcache_hit" );
                }

                return $value;
        }

        /**
         * @param ParserOutput $parserOutput
         * @param WikiPage $page
         * @param ParserOptions $popts
         * @param string $cacheTime Time when the cache was generated
         * @param int $revId Revision ID that was parsed
         */
        public function save( $parserOutput, $page, $popts, $cacheTime = null, $revId = null ) {
                $expire = $parserOutput->getCacheExpiry();
                if ( $expire > 0 ) {
                        $cacheTime = $cacheTime ?: wfTimestampNow();
                        if ( !$revId ) {
                                $revision = $page->getRevision();
                                $revId = $revision ? $revision->getId() : null;
                        }

                        $optionsKey = new CacheTime;
                        $optionsKey->mUsedOptions = $parserOutput->getUsedOptions();
                        $optionsKey->updateCacheExpiry( $expire );

                        $optionsKey->setCacheTime( $cacheTime );
                        $parserOutput->setCacheTime( $cacheTime );
                        $optionsKey->setCacheRevisionId( $revId );
                        $parserOutput->setCacheRevisionId( $revId );

                        $optionsKey->setContainsOldMagic( $parserOutput->containsOldMagic() );

                        $parserOutputKey = $this->getParserOutputKey( $page,
                                $popts->optionsHash( $optionsKey->mUsedOptions, $page->getTitle() ) );

                        // Save the timestamp so that we don't have to load the revision row on view
                        $parserOutput->setTimestamp( $page->getTimestamp() );

                        $msg = "Saved in parser cache with key $parserOutputKey" .
                                " and timestamp $cacheTime" .
                                " and revision id $revId" .
                                "\n";

                        $parserOutput->mText .= "\n<!-- $msg -->\n";
                        wfDebug( $msg );

                        // Save the parser output
                        $this->mMemc->set( $parserOutputKey, $parserOutput, $expire );

                        // ...and its pointer
                        $this->mMemc->set( $this->getOptionsKey( $page ), $optionsKey, $expire );
                } else {
                        wfDebug( "Parser output was marked as uncacheable and has not been saved.\n" );
                }
        }
}