}
    }

    public static UrlQueueService<UrlQueue<?>> getUrlQueueService() {
        return URL_QUEUE_SERVICE_THREAD_LOCAL.get();
    }

    public static void setUrlQueueService(final UrlQueueService<UrlQueue<?>> urlQueueService) {
        if (urlQueueService == null) {
            URL_QUEUE_SERVICE_THREAD_LOCAL.remove();
        } else {