grpc: Python client get stuck if stub is not created inside a function

Hello again 😃

I don’t know if is a bug or a feature but there is an unexpected behavior: If the stub is created in the __main__ namespace, the process will be stuck in atexit() routines when quitting.

Example with greeter_server.py running:

This client is ok, returns immediately:

$ cat greeter_client_ok.py
from grpc.beta import implementations
import helloworld_pb2

def run():
  channel = implementations.insecure_channel('localhost', 50051)
  stub = helloworld_pb2.beta_create_Greeter_stub(channel)
if __name__ == '__main__':
  run()

This one will never exit:

$ cat greeter_client_ko.py
from grpc.beta import implementations
import helloworld_pb2

channel = implementations.insecure_channel('localhost', 50051)
stub = helloworld_pb2.beta_create_Greeter_stub(channel)

When running it, now, it is stuck, so pressing ^C gives the following backtrace:

$ python greeter_client_ko.py
^C
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/home/foo/.local/lib/python2.7/site-packages/concurrent/futures/thread.py", line 39, in _python_exit
    t.join(sys.maxint)
  File "/usr/lib/python2.7/threading.py", line 960, in join
    self.__block.wait(delay)
  File "/usr/lib/python2.7/threading.py", line 359, in wait
    _sleep(delay)
KeyboardInterrupt
Error in sys.exitfunc:
Traceback (most recent call last):
  File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/home/foo/.local/lib/python2.7/site-packages/concurrent/futures/thread.py", line 39, in _python_exit
    t.join(sys.maxint)
  File "/usr/lib/python2.7/threading.py", line 960, in join
    self.__block.wait(delay)
  File "/usr/lib/python2.7/threading.py", line 359, in wait
    _sleep(delay)
KeyboardInterrupt

PS: I am running Debian Jessie on amd64, and grpc from the git master branch