def start_server(self, addr='', port=8000):
        """
        Expose /metrics endpoint on a new server that will
        be launched on `<addr>:<port>`.

        This may be useful if you want to restrict access to
        metrics data with firewall rules.
        NOTE: can not be used in multiprocessing mode
        """
        if self._multiprocess_on:
            raise SanicPrometheusError(
                "start_server can not be used when multiprocessing " +
                "is turned on")
        start_http_server(addr=addr, port=port)