Hello grpc users,
I am new to grpc, and I cannot get asyncronous RPC calls to work as
expected.
The example below defines a RPC call with name "delayed", which should
return the value 42 after "time.sleep(1)".
I get this "StatusCode.CANCELLED" error when invoking the client (after
having started the server):
$ python client.py
Exception in thread Thread-2:
Traceback (most recent call last):
File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
self.run()
File "/usr/lib/python2.7/threading.py", line 754, in run
self.__target(*self.__args, **self.__kwargs)
File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line 716,
in channel_spin
completed_call = event.tag(event)
File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line 172,
in handle_event
callback()
File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line 313,
in <lambda>
self._state.callbacks.append(lambda: fn(self))
File "client.py", line 9, in cb
print("Test client received: " + str(future.result().value))
File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line 279,
in result
raise self
_Rendezvous: <_Rendezvous of RPC that terminated with
(StatusCode.CANCELLED, Cancelled)>
If I reduce the delay from 1 second to 0.05 seconds, most of the RPC
attempts succeed, and only a few fail. What am I missing to make this
example work, such that the future notifies its callback method even if the
server needs more than a second to reply?
Thank you
Gerold
These are the files required to reproduce the problem:
+++ test.proto:
syntax="proto3";
service Test {
rpc delayed(Empty) returns (Result) {};
}
message Empty{
}
message Result{
int32 value = 1;
}
+++ server.py:
from concurrent import futures
import time
import grpc
import test_pb2
import test_pb2_grpc
class Test(test_pb2_grpc.TestServicer):
def delayed(self, request, context):
time.sleep(0.5)
return test_pb2.Result(value=42)
def serve():
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
test_pb2_grpc.add_TestServicer_to_server(Test(), server)
server.add_insecure_port('[::]:50051')
server.start()
try:
while True:
time.sleep(10)
except KeyboardInterrupt:
server.stop(0)
if __name__ == '__main__':
serve()
+++ client.py:
from __future__ import print_function
import grpc
import test_pb2
import test_pb2_grpc
def cb(future):
print("Test client received: " + str(future.result().value))
def run():
channel = grpc.insecure_channel('localhost:50051')
stub = test_pb2_grpc.TestStub(channel)
fut = stub.delayed.future(test_pb2.Empty())
fut.add_done_callback(cb)
if __name__ == '__main__':
run()
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