def barrier(self):
        """Barrier for all client nodes.

        This API will be blocked untill all the clients invoke this API.
        """
        request = BarrierRequest(self._role)
        rpc.send_request(0, request)
        response = rpc.recv_response()
        assert response.msg == BARRIER_MSG
Barrier for all client nodes.

        This API will be blocked untill all the clients invoke this API.
        
python/dgl/distributed/kvstore.py