Exception while interrupting (ctrl+c) asyncio client example

[khelkun]

I'm a non regular user of python, and use Python 3.8 on Windows 10 in Visual studio code terminal (powershell).

I use the asyncio client example to connect to a (NodeJS) socket.io WSS server using a self-signed certificate (e.g ssl_verify option is set to False). When I interrupt the example with CTRL+C (after the "connection established" print), I get the following error output :

PS G:\myProject> pipenv run python src/main.py
connection established
packet queue is empty, aborting
Traceback (most recent call last):
  File "G:\VIZUA\github\vizua3d\corpusIA-camera-service\src\main.py", line 39, in <module>
    asyncio.run(main())
  File "C:\Program Files\Python310\lib\asyncio\runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 628, in run_until_complete
    self.run_forever()
  File "C:\Program Files\Python310\lib\asyncio\windows_events.py", line 321, in run_forever
    super().run_forever()
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 595, in run_forever
    self._run_once()
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 1845, in _run_once
    event_list = self._selector.select(timeout)
  File "C:\Program Files\Python310\lib\asyncio\windows_events.py", line 439, in select
    self._poll(timeout)
  File "C:\Program Files\Python310\lib\asyncio\windows_events.py", line 788, in _poll
    status = _overlapped.GetQueuedCompletionStatus(self._iocp, ms)
  File "C:\Users\sebtr\.virtualenvs\corpusIA-camera-service-T66FKxf2\lib\site-packages\engineio\client.py", line 36, in signal_handler
    return original_signal_handler(sig, frame)
  File "C:\Users\sebtr\.virtualenvs\myProject-T66FKxf2\lib\site-packages\socketio\client.py", line 26, in signal_handler
    return original_signal_handler(sig, frame)
KeyboardInterrupt
Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x000001A4F8A09EA0>
Unclosed connector
connections: ['[(<aiohttp.client_proto.ResponseHandler object at 0x000001A4F8A21DE0>, 774578.828)]']
connector: <aiohttp.connector.TCPConnector object at 0x000001A4F8A09F60>
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0x000001A4F8A0B010>
transport: <_ProactorSocketTransport fd=756 read=<_OverlappedFuture cancelled>>
Traceback (most recent call last):
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 684, in _process_write_backlog
    self._transport.write(chunk)
  File "C:\Program Files\Python310\lib\asyncio\proactor_events.py", line 361, in write
    self._loop_writing(data=bytes(data))
  File "C:\Program Files\Python310\lib\asyncio\proactor_events.py", line 397, in _loop_writing
    self._write_fut = self._loop._proactor.send(self._sock, data)
AttributeError: 'NoneType' object has no attribute 'send'
Exception ignored in: <function _SSLProtocolTransport.__del__ at 0x000001A4F7E13400>
Traceback (most recent call last):
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 321, in __del__
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 316, in close
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 593, in _start_shutdown
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 598, in _write_appdata
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 706, in _process_write_backlog
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 720, in _fatal_error
  File "C:\Program Files\Python310\lib\asyncio\proactor_events.py", line 151, in _force_close
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 745, in call_soon
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 510, in _check_closed
RuntimeError: Event loop is closed
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0x000001A4F8A0A350>
transport: <_ProactorSocketTransport fd=608 read=<_OverlappedFuture cancelled>>
Traceback (most recent call last):
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 684, in _process_write_backlog
    self._transport.write(chunk)
  File "C:\Program Files\Python310\lib\asyncio\proactor_events.py", line 361, in write
    self._loop_writing(data=bytes(data))
  File "C:\Program Files\Python310\lib\asyncio\proactor_events.py", line 397, in _loop_writing
    self._write_fut = self._loop._proactor.send(self._sock, data)
AttributeError: 'NoneType' object has no attribute 'send'
Exception ignored in: <function _SSLProtocolTransport.__del__ at 0x000001A4F7E13400>
Traceback (most recent call last):
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 321, in __del__
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 593, in _start_shutdown
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 598, in _write_appdata
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 706, in _process_write_backlog
  File "C:\Program Files\Python310\lib\asyncio\sslproto.py", line 720, in _fatal_error
  File "C:\Program Files\Python310\lib\asyncio\proactor_events.py", line 151, in _force_close
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 745, in call_soon
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 510, in _check_closed
RuntimeError: Event loop is closed

Aborted!

The AttributeError: 'NoneType' object has no attribute 'send' from asyncio\proactor_events.py disappointed me, so I stumbled on this similar issue, from where I picked this advice to change the IOCP policy in asyncio.
This made disappear the AttributeError: 'NoneType' object has no attribute 'send' exception.

However the following Traceback remains:

PS G:\myProject> pipenv run python src/main.py
connection established
packet queue is empty, aborting
Traceback (most recent call last):
  File "G:\VIZUA\github\vizua3d\myProject\src\main.py", line 42, in <module>
    asyncio.run(main())
  File "C:\Program Files\Python310\lib\asyncio\runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 628, in run_until_complete
    self.run_forever()
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 595, in run_forever
    self._run_once()
  File "C:\Program Files\Python310\lib\asyncio\base_events.py", line 1845, in _run_once
    event_list = self._selector.select(timeout)
  File "C:\Program Files\Python310\lib\selectors.py", line 324, in select
    r, w, _ = self._select(self._readers, self._writers, [], timeout)
  File "C:\Program Files\Python310\lib\selectors.py", line 315, in _select
    r, w, x = select.select(r, w, w, timeout)
  File "C:\Users\sebtr\.virtualenvs\myProject-T66FKxf2\lib\site-packages\engineio\client.py", line 36, in signal_handler
    return original_signal_handler(sig, frame)
  File "C:\Users\sebtr\.virtualenvs\myProject-T66FKxf2\lib\site-packages\socketio\client.py", line 26, in signal_handler
    return original_signal_handler(sig, frame)
KeyboardInterrupt
Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x0000023336CE9F00>
Unclosed connector
connections: ['[(<aiohttp.client_proto.ResponseHandler object at 0x0000023336D01420>, 776820.765)]']
connector: <aiohttp.connector.TCPConnector object at 0x0000023336CE9FC0>

Aborted!

3 questions:

1. Why is this Traceback printed when I interrupt the example with CTRL+C?
2. What about the IOCP policy in asyncio? Is my policy change right? May be this should be somewhere in python-socketio.
3. Why the simple client example without asyncio cannot be interrupted with CTRL+C?

[miguelgrinberg]

1. The KeyboardInterrupt exception is standard for Python programs when they are interrupted. You can catch it in your application if you want to silence it. The "Unclosed" errors come from aiohttp, which is a dependency of this package. Make sure you are using the latest versions of python-engineio and python-socketio and let me know if these errors persist.

2. I have very little knowledge of Windows related issues with asyncio. Changing the policy just configures the method that asyncio uses to achieve concurrency. My personal opinion is that changing the policy just to avoid some error on exit is probably not the correct way to think about the problem, but once again, I'm not familiar with this specific problem and/or if there are any alternative solutions. If at all possible, do try the application under WSL and see if it works better (you will still get the KeyboardInterrupt exception, which as I said, is standard after a Ctrl-C in Python).

3. In general the implementation of interrupt signals in the Windows port of Python is subpar, and I don't have a Windows system that I use routinely, so I haven't really prioritized working on Ctrl-C issues on Windows. See KeyboardInterrupt ignored on Windows #570.