bpo-35998: Avoid TimeoutError in test_asyncio: test_start_tls_server_1()

[asvetlov]

The test was not robust because it used to rely on sock.shutdown(socket.SHUT_RDWR) before sock.close().

Actually, sometimes these socket state changes are merged into the just transition into the socket-closed state on the peer side. I don't want to add sleep(N) between calls, it is the easiest way to add new test flakiness.

The start_tls test doesn't need to check proto.eof_received() callback receiving, there are other explicit tests for it.

The test is changed to receive TSL encrypted data and send an acknowledgment back before client socket closing.

Now everything works smoothly, I don't see any timeout exceptions even under very heavy testing.

https://bugs.python.org/issue35998

[vstinner]

LGTM, I just have a minor comment.

On Fedora 30, reproducing the take takes me 5 seconds using (the test hangs for a few minutes and then fail):

./python -m test test_asyncio -m test_start_tls_server_1 -F

With this change, the test no longer hangs.

I can ./python -m test test_asyncio -m test_start_tls_server_1 -F 6 times in parallel for 5 minutes, my system load is around 7.0 (the system is very busy), and the test still doesn't hang. So I can confirm that this change fix the issue for me.

[vstinner]

LGTM.

[miss-islington]

Thanks @asvetlov for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.7, 3.8.
🐍🍒⛏🤖

[bedevere-bot]

GH-14084 is a backport of this pull request to the 3.8 branch.

[miss-islington]

Sorry, @asvetlov and @vstinner, I could not cleanly backport this to 3.7 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker f0749da9a535375f05a2015e8960e8ae54877349 3.7

[asvetlov]

I'll make backport myself

[bedevere-bot]

GH-14086 is a backport of this pull request to the 3.7 branch.

[vstinner]

@asvetlov: I just made it :-) I really want this bug to go away, it annoy me on buildbots for 6 months at least. It was a stupid conflict on additional "loop=self.loop" in 3.7.

[asvetlov]

Yes, I see.
Thank you!