'Used to mitigate refreshes for nodes that are already known.
Some versions of the server send superfluous NEW_NODE messages in addition to UP events.'

def _refresh_nodes_if_not_up(self, addr):

    host = self._cluster.metadata.get_host(addr)
    if ((not host) or (not host.is_up)):
        self.refresh_node_list_and_token_map()
