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[mediawiki.git] / includes / cache / FileCacheBase.php

<?php
/**
 * Data storage in the file system.
 *
 * 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
 */

/**
 * Base class for data storage in the file system.
 *
 * @ingroup Cache
 */
abstract class FileCacheBase {
        protected $mKey;
        protected $mType = 'object';
        protected $mExt = 'cache';
        protected $mFilePath;
        protected $mUseGzip;
        /* lazy loaded */
        protected $mCached;

        /* @todo configurable? */
        const MISS_FACTOR = 15; // log 1 every MISS_FACTOR cache misses
        const MISS_TTL_SEC = 3600; // how many seconds ago is "recent"

        protected function __construct() {
                global $wgUseGzip;

                $this->mUseGzip = (bool)$wgUseGzip;
        }

        /**
         * Get the base file cache directory
         * @return string
         */
        final protected function baseCacheDirectory() {
                global $wgFileCacheDirectory;

                return $wgFileCacheDirectory;
        }

        /**
         * Get the base cache directory (not specific to this file)
         * @return string
         */
        abstract protected function cacheDirectory();

        /**
         * Get the path to the cache file
         * @return string
         */
        protected function cachePath() {
                if ( $this->mFilePath !== null ) {
                        return $this->mFilePath;
                }

                $dir = $this->cacheDirectory();
                # Build directories (methods include the trailing "/")
                $subDirs = $this->typeSubdirectory() . $this->hashSubdirectory();
                # Avoid extension confusion
                $key = str_replace( '.', '%2E', urlencode( $this->mKey ) );
                # Build the full file path
                $this->mFilePath = "{$dir}/{$subDirs}{$key}.{$this->mExt}";
                if ( $this->useGzip() ) {
                        $this->mFilePath .= '.gz';
                }

                return $this->mFilePath;
        }

        /**
         * Check if the cache file exists
         * @return bool
         */
        public function isCached() {
                if ( $this->mCached === null ) {
                        $this->mCached = file_exists( $this->cachePath() );
                }

                return $this->mCached;
        }

        /**
         * Get the last-modified timestamp of the cache file
         * @return string|bool TS_MW timestamp
         */
        public function cacheTimestamp() {
                $timestamp = filemtime( $this->cachePath() );

                return ( $timestamp !== false )
                        ? wfTimestamp( TS_MW, $timestamp )
                        : false;
        }

        /**
         * Check if up to date cache file exists
         * @param string $timestamp MW_TS timestamp
         *
         * @return bool
         */
        public function isCacheGood( $timestamp = '' ) {
                global $wgCacheEpoch;

                if ( !$this->isCached() ) {
                        return false;
                }

                $cachetime = $this->cacheTimestamp();
                $good = ( $timestamp <= $cachetime && $wgCacheEpoch <= $cachetime );
                wfDebug( __METHOD__ .
                        ": cachetime $cachetime, touched '{$timestamp}' epoch {$wgCacheEpoch}, good $good\n" );

                return $good;
        }

        /**
         * Check if the cache is gzipped
         * @return bool
         */
        protected function useGzip() {
                return $this->mUseGzip;
        }

        /**
         * Get the uncompressed text from the cache
         * @return string
         */
        public function fetchText() {
                if ( $this->useGzip() ) {
                        $fh = gzopen( $this->cachePath(), 'rb' );

                        return stream_get_contents( $fh );
                } else {
                        return file_get_contents( $this->cachePath() );
                }
        }

        /**
         * Save and compress text to the cache
         * @param string $text
         * @return string|false Compressed text
         */
        public function saveText( $text ) {
                if ( $this->useGzip() ) {
                        $text = gzencode( $text );
                }

                $this->checkCacheDirs(); // build parent dir
                if ( !file_put_contents( $this->cachePath(), $text, LOCK_EX ) ) {
                        wfDebug( __METHOD__ . "() failed saving " . $this->cachePath() . "\n" );
                        $this->mCached = null;

                        return false;
                }

                $this->mCached = true;

                return $text;
        }

        /**
         * Clear the cache for this page
         * @return void
         */
        public function clearCache() {
                MediaWiki\suppressWarnings();
                unlink( $this->cachePath() );
                MediaWiki\restoreWarnings();
                $this->mCached = false;
        }

        /**
         * Create parent directors of $this->cachePath()
         * @return void
         */
        protected function checkCacheDirs() {
                wfMkdirParents( dirname( $this->cachePath() ), null, __METHOD__ );
        }

        /**
         * Get the cache type subdirectory (with trailing slash)
         * An extending class could use that method to alter the type -> directory
         * mapping. @see HTMLFileCache::typeSubdirectory() for an example.
         *
         * @return string
         */
        protected function typeSubdirectory() {
                return $this->mType . '/';
        }

        /**
         * Return relative multi-level hash subdirectory (with trailing slash)
         * or the empty string if not $wgFileCacheDepth
         * @return string
         */
        protected function hashSubdirectory() {
                global $wgFileCacheDepth;

                $subdir = '';
                if ( $wgFileCacheDepth > 0 ) {
                        $hash = md5( $this->mKey );
                        for ( $i = 1; $i <= $wgFileCacheDepth; $i++ ) {
                                $subdir .= substr( $hash, 0, $i ) . '/';
                        }
                }

                return $subdir;
        }

        /**
         * Roughly increments the cache misses in the last hour by unique visitors
         * @param WebRequest $request
         * @return void
         */
        public function incrMissesRecent( WebRequest $request ) {
                if ( mt_rand( 0, self::MISS_FACTOR - 1 ) == 0 ) {
                        $cache = ObjectCache::getLocalClusterInstance();
                        # Get a large IP range that should include the user  even if that
                        # person's IP address changes
                        $ip = $request->getIP();
                        if ( !IP::isValid( $ip ) ) {
                                return;
                        }
                        $ip = IP::isIPv6( $ip )
                                ? IP::sanitizeRange( "$ip/32" )
                                : IP::sanitizeRange( "$ip/16" );

                        # Bail out if a request already came from this range...
                        $key = wfMemcKey( get_class( $this ), 'attempt', $this->mType, $this->mKey, $ip );
                        if ( $cache->get( $key ) ) {
                                return; // possibly the same user
                        }
                        $cache->set( $key, 1, self::MISS_TTL_SEC );

                        # Increment the number of cache misses...
                        $key = $this->cacheMissKey();
                        if ( $cache->get( $key ) === false ) {
                                $cache->set( $key, 1, self::MISS_TTL_SEC );
                        } else {
                                $cache->incr( $key );
                        }
                }
        }

        /**
         * Roughly gets the cache misses in the last hour by unique visitors
         * @return int
         */
        public function getMissesRecent() {
                $cache = ObjectCache::getLocalClusterInstance();

                return self::MISS_FACTOR * $cache->get( $this->cacheMissKey() );
        }

        /**
         * @return string
         */
        protected function cacheMissKey() {
                return wfMemcKey( get_class( $this ), 'misses', $this->mType, $this->mKey );
        }
}