Obtain a list of nodes from the cluster and create a new connection
        pool using the information retrieved.

        To extract the node connection parameters use the ``nodes_to_host_callback``.

        :arg initial: flag indicating if this is during startup
            (``sniff_on_start``), ignore the ``sniff_timeout`` if ``True``

def sniff_hosts(self, initial=False):
        """
        Obtain a list of nodes from the cluster and create a new connection
        pool using the information retrieved.

        To extract the node connection parameters use the ``nodes_to_host_callback``.

        :arg initial: flag indicating if this is during startup
            (``sniff_on_start``), ignore the ``sniff_timeout`` if ``True``
        """
        node_info = self._get_sniff_data(initial)

        hosts = list(filter(None, (self._get_host_info(n) for n in node_info)))

        # we weren't able to get any nodes or host_info_callback blocked all -
        # raise error.
        if not hosts:
            raise TransportError("N/A", "Unable to sniff hosts - no viable hosts found.")

        self.set_connections(hosts)