FileCacheBase.php

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<?php
use Wikimedia\IPUtils;
 
abstract class FileCacheBase {
    protected $mKey;
    protected $mType = 'object';
    protected $mExt = 'cache';
    protected $mFilePath;
    protected $mUseGzip;
    /* lazy loaded */
    protected $mCached;
 
    /* @todo configurable? */
    private const MISS_FACTOR = 15; // log 1 every MISS_FACTOR cache misses
    private const MISS_TTL_SEC = 3600; // how many seconds ago is "recent"
 
    protected function __construct() {
        global $wgUseGzip;
 
        $this->mUseGzip = (bool)$wgUseGzip;
    }
 
    final protected function baseCacheDirectory() {
        global $wgFileCacheDirectory;
 
        return $wgFileCacheDirectory;
    }
 
    abstract protected function cacheDirectory();
 
    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;
    }
 
    public function isCached() {
        if ( $this->mCached === null ) {
            $this->mCached = file_exists( $this->cachePath() );
        }
 
        return $this->mCached;
    }
 
    public function cacheTimestamp() {
        $timestamp = filemtime( $this->cachePath() );
 
        return ( $timestamp !== false )
            ? wfTimestamp( TS_MW, $timestamp )
            : false;
    }
 
    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" );
 
        return $good;
    }
 
    protected function useGzip() {
        return $this->mUseGzip;
    }
 
    public function fetchText() {
        if ( $this->useGzip() ) {
            $fh = gzopen( $this->cachePath(), 'rb' );
 
            return stream_get_contents( $fh );
        } else {
            return file_get_contents( $this->cachePath() );
        }
    }
 
    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() );
            $this->mCached = null;
 
            return false;
        }
 
        $this->mCached = true;
 
        return $text;
    }
 
    public function clearCache() {
        Wikimedia\suppressWarnings();
        unlink( $this->cachePath() );
        Wikimedia\restoreWarnings();
        $this->mCached = false;
    }
 
    protected function checkCacheDirs() {
        wfMkdirParents( dirname( $this->cachePath() ), null, __METHOD__ );
    }
 
    protected function typeSubdirectory() {
        return $this->mType . '/';
    }
 
    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;
    }
 
    public function incrMissesRecent( WebRequest $request ) {
        if ( mt_rand( 0, self::MISS_FACTOR - 1 ) == 0 ) {
            # Get a large IP range that should include the user  even if that
            # person's IP address changes
            $ip = $request->getIP();
            if ( !IPUtils::isValid( $ip ) ) {
                return;
            }
 
            $ip = IPUtils::isIPv6( $ip )
                ? IPUtils::sanitizeRange( "$ip/32" )
                : IPUtils::sanitizeRange( "$ip/16" );
 
            # Bail out if a request already came from this range...
            $cache = ObjectCache::getLocalClusterInstance();
            $key = $cache->makeKey( static::class, 'attempt', $this->mType, $this->mKey, $ip );
            if ( !$cache->add( $key, 1, self::MISS_TTL_SEC ) ) {
                return; // possibly the same user
            }
 
            # Increment the number of cache misses...
            $cache->incrWithInit( $this->cacheMissKey( $cache ), self::MISS_TTL_SEC );
        }
    }
 
    public function getMissesRecent() {
        $cache = ObjectCache::getLocalClusterInstance();
 
        return self::MISS_FACTOR * $cache->get( $this->cacheMissKey( $cache ) );
    }
 
    protected function cacheMissKey( BagOStuff $cache ) {
        return $cache->makeKey( static::class, 'misses', $this->mType, $this->mKey );
    }
}