(gdb) py-bt
#4 Waiting for a lock (e.g. GIL)
#11 Frame 0x30654e0, for file /usr/local/lib/python2.7/site-packages/grpc/_channel.py, line 475,
in _blocking (self=<_UnaryUnaryMultiCallable(_managed_call=<function at remote 0x3080320>, _request_serializer=<met
hod_descriptor at remote 0x2f40ab8>, _channel=<grpc._cython.cygrpc.Channel at remote 0x2ffde10>, _response_deseriali
zer=<built-in method FromString of GeneratedProtocolMessageType object at remote 0x2eec1c0>, _method='/
Service/Retrieve') at remote 0x307cbd0>, request=<RetrieveRequest at remote 0x3080230>, ti
meout=None, metadata=None, credentials=None, state=<_RPCState(code=None, due=set([0, 1, 2, 4, 5, 6]), callbacks=[],
trailing_metadata=None, cancelled=False, initial_metadata=None, response=None, condition=<_Condition(_Condition__loc
k=<_RLock(_Verbose__verbose=False, _RLock__owner=None, _RLock__block=<thread.lock at remote 0x2f68930>, _RLock__coun
t=0) at remote 0x307cc90>, acquire=<instancemethod at remote 0x2f64780>, _is_owned=<instancemethod a...(truncated)
self._method, None, deadline)