[docs] asyncio on windows: WinError 995 spew in logs during load tests

Erik Aronesty erik at q32.com
Wed Oct 18 11:44:06 EDT 2017

This error intermittently occurs when I close a server and wait for it to
be closed.   I seem to get all of the messages I expect in my tests, and my
server seems to work fine on windows or linux otherwise, so it's not urgent
for me.

It seems (to me) that there is no way to catch an exception during
accept().   The coroutine is coming directly from windows a overlapped i/o
call: (ov = _overlapped.Overlapped(NULL))
Again, this exception only occurs intermittently and usually during my "1K
connections tests" and similar load tests.

DEBUG:root:waiting....<generator object WebSocketServer.wait_closed at
DEBUG:asyncio:taking long time to close proactor
ERROR:asyncio:Task exception was never retrieved
future: <Task finished coro=<IocpProactor.accept.<locals>.accept_coro()
done, defined at C:\Python36\lib\asyncio\windows_events.py:485>
exception=OSError(22, 'The I/O operation has been aborted because of either
a thread exit or an application request', None, 995, None)>
Traceback (most recent call last):
  File "C:\Python36\lib\asyncio\windows_events.py", line 489, in accept_coro
    yield from future
  File "C:\Python36\lib\asyncio\proactor_events.py", line 504, in loop
    conn, addr = f.result()
  File "C:\Python36\lib\asyncio\windows_events.py", line 702, in _poll
    value = callback(transferred, key, ov)
  File "C:\Python36\lib\asyncio\windows_events.py", line 477, in
OSError: [WinError 995] The I/O operation has been aborted because of
either a thread exit or an application request
DEBUG:root:finished....<generator object WebSocketServer.wait_closed at
DEBUG:root:loop dropped out
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