Test usage of proactor event loop

[blink1073]

Research for discuss.python.org/t/removing-the-asyncio-policy-system-asyncio-set-event-loop-policy-in-python-3-15/37553/26

[blink1073]

@ccordoba12 do you have any concerns about this?

[blink1073]

For context, the ability to set an event loop policy might be going away.

[ccordoba12]

I thought this was necessary on Windows for Python 3.8+. How did it get fix?

[blink1073]

Hey @ccordoba12, tornado 6.1 added support for the proactor loop, by starting a thread. The jupyter_server test suite runs in about 10 min with the selector loop, and 15 min with the proactor loop.

Guido suggested that if we can switch from ioloop.start() to calling asyncio.run(loop_factory=...) ourselves, we could retain the selector loop.

[ccordoba12]

@blink1073, thanks for the explanation. I must confess my ignorance about most asyncio related stuff because I haven't had time to learn about it.

So, if you consider this is no longer necessary then I'm ok with removing it.

[blink1073]

So, if you consider this is no longer necessary then I'm ok with removing it.

I still need to do more testing to make sure we're future-proof (if they take away set_event_loop_policy), but thanks!