private void touchFileSafely(File cacheFile) {
        try {
            config.diskUsage.touch(cacheFile);
        } catch (IOException e) {
            Logger.error("Error touching file " + cacheFile);
        }
    }
Checks is cache contains fully cached file for particular url.

@param url an url cache file will be checked for.
@return {@code true} if cache contains fully cached file for passed in parameters url.
VideoCache/src/main/java/com/yc/videocache/HttpProxyCacheServer.java