Using Proactor event loop on Windows results in random test fails

[ichorid]

https://jenkins-ci.tribler.org/job/GH_Tribler_PR_Tests/job/PR_win64_pytest/2145/console

[gw7] [ 94%] PASSED src/tribler-core/tribler_core/components/metadata_store/restapi/tests/test_metadata_endpoint.py::test_check_torrent_query 
src/tribler-core/tribler_core/components/metadata_store/restapi/tests/test_metadata_endpoint.py::test_update_entry_missing_json Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x0000000003F1D310>
Traceback (most recent call last):
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 719, in call_soon
    self._check_closed()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 508, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

[gw7] [ 94%] PASSED src/tribler-core/tribler_core/components/metadata_store/restapi/tests/test_metadata_endpoint.py::test_update_entry_missing_json Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x0000000003F1D310>
Traceback (most recent call last):
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 719, in call_soon
    self._check_closed()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 508, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x0000000003FCE310>
Traceback (most recent call last):
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 719, in call_soon
    self._check_closed()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 508, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x0000000003FCE310>
Traceback (most recent call last):
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 719, in call_soon
    self._check_closed()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 508, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x0000000003FCE310>
Traceback (most recent call last):
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 719, in call_soon
    self._check_closed()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 508, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x0000000003FCE310>
Traceback (most recent call last):
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 719, in call_soon
    self._check_closed()
  File "c:\users\tribler\appdata\local\programs\python\python38\lib\asyncio\base_events.py", line 508, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

[ichorid]

We're not the first to experience this:
encode/httpx#914

In short, related to Windows Proactor event loop implementation. The solution is to either force usage of Selector event loop for Windows test (which makes sense, since we're already forcing it for Core running on Windows), or add some asyncio.sleep() at the end of every test.

[devos50]

The solution is to either force usage of Selector event loop for Windows test

I guess this is the best approach then since we're already running the Selector event loop in the wild.