I am trying to run example from gRPC Seldon example for gRPC on google cloud kubernetes cluster. I am able to get access_token but gRPC query waits indefinitely. Finally I get following error :

Traceback (most recent call last):
File "test_request.py", line 53, in 
grpc_request()
File "test_request.py", line 50, in grpc_request
response = stub.Predict(request=request,metadata=metadata)
File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line 487, in call
return _end_unary_response_blocking(state, call, False, deadline)
File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line 437, in _end_unary_response_blocking
raise _Rendezvous(state, None, None, deadline)
grpc._channel._Rendezvous: <_Rendezvous of RPC that terminated with (StatusCode.UNAVAILABLE, OS Error)>

Whats the issue?