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gh-79033: Try to fix asyncio.Server.wait_closed() again #111336

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merged 2 commits into from
Oct 28, 2023

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@gvanrossum gvanrossum commented Oct 25, 2023

I identified the condition that wait_closed() is intended to wait for: the server is closed and there are no more active connections.

When this condition first becomes true, _wakeup() is called (either from close() or from _detach()) and it sets _waiters to None. So we just check for self._waiters is None; if it's not None, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly tested that wait_closed() returns immediately when the server is not closed but there are currently no active connections. This was a mistake (probably a misunderstanding of the intended semantics). I've fixed the test, and added a separate test that checks exactly for this scenario.

I also fixed an oddity where in _wakeup() the result of the waiter was set to the waiter itself. This result is not used anywhere and I changed this to None, to avoid a GC cycle.


📚 Documentation preview 📚: https://cpython-previews--111336.org.readthedocs.build/

I identified the condition that `wait_closed()` is intended
to wait for: the server is closed *and* there are no more
active connections.

When this condition first becomes true, `_wakeup()` is called
(either from `close()` or from `_detach()`) and it sets `_waiters`
to `None`. So we just check for `self._waiters is None`; if it's
not `None`, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly
tested that `wait_closed()` returns immediately when the server
is *not* closed but there are currently no active connections.
This was a mistake (probably a misunderstanding of the intended
semantics). I've fixed the test, and added a separate test that
checks exactly for this scenario.

I also fixed an oddity where in `_wakeup()` the result of the
waiter was set to the waiter itself. This result is not used
anywhere and I changed this to `None`, to avoid a GC cycle.
@gvanrossum
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Maybe @graingert has some time to review? (I'll trade you -- I'm reviewing #110728 right now.)

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Thanks @gvanrossum for the additional comments and clarification. I'm making one small docstring clarification and then will merge.

Lib/asyncio/base_events.py Show resolved Hide resolved
@willingc willingc enabled auto-merge (squash) October 28, 2023 17:36
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Thanks!

@willingc willingc merged commit 2655369 into python:main Oct 28, 2023
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@miss-islington-app
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Thanks @gvanrossum for the PR, and @willingc for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Oct 28, 2023
…GH-111336)

* Try to fix asyncio.Server.wait_closed() again

I identified the condition that `wait_closed()` is intended
to wait for: the server is closed *and* there are no more
active connections.

When this condition first becomes true, `_wakeup()` is called
(either from `close()` or from `_detach()`) and it sets `_waiters`
to `None`. So we just check for `self._waiters is None`; if it's
not `None`, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly
tested that `wait_closed()` returns immediately when the server
is *not* closed but there are currently no active connections.
This was a mistake (probably a misunderstanding of the intended
semantics). I've fixed the test, and added a separate test that
checks exactly for this scenario.

I also fixed an oddity where in `_wakeup()` the result of the
waiter was set to the waiter itself. This result is not used
anywhere and I changed this to `None`, to avoid a GC cycle.

* Update Lib/asyncio/base_events.py

---------

(cherry picked from commit 2655369)

Co-authored-by: Guido van Rossum <guido@python.org>
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
@bedevere-app
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bedevere-app bot commented Oct 28, 2023

GH-111424 is a backport of this pull request to the 3.12 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.12 bug and security fixes label Oct 28, 2023
willingc added a commit that referenced this pull request Oct 28, 2023
…1336) (#111424)

gh-79033: Try to fix asyncio.Server.wait_closed() again (GH-111336)

* Try to fix asyncio.Server.wait_closed() again

I identified the condition that `wait_closed()` is intended
to wait for: the server is closed *and* there are no more
active connections.

When this condition first becomes true, `_wakeup()` is called
(either from `close()` or from `_detach()`) and it sets `_waiters`
to `None`. So we just check for `self._waiters is None`; if it's
not `None`, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly
tested that `wait_closed()` returns immediately when the server
is *not* closed but there are currently no active connections.
This was a mistake (probably a misunderstanding of the intended
semantics). I've fixed the test, and added a separate test that
checks exactly for this scenario.

I also fixed an oddity where in `_wakeup()` the result of the
waiter was set to the waiter itself. This result is not used
anywhere and I changed this to `None`, to avoid a GC cycle.

* Update Lib/asyncio/base_events.py

---------

(cherry picked from commit 2655369)

Co-authored-by: Guido van Rossum <guido@python.org>
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
iritkatriel pushed a commit to iritkatriel/cpython that referenced this pull request Oct 29, 2023
…GH-111336)

* Try to fix asyncio.Server.wait_closed() again

I identified the condition that `wait_closed()` is intended
to wait for: the server is closed *and* there are no more
active connections.

When this condition first becomes true, `_wakeup()` is called
(either from `close()` or from `_detach()`) and it sets `_waiters`
to `None`. So we just check for `self._waiters is None`; if it's
not `None`, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly
tested that `wait_closed()` returns immediately when the server
is *not* closed but there are currently no active connections.
This was a mistake (probably a misunderstanding of the intended
semantics). I've fixed the test, and added a separate test that
checks exactly for this scenario.

I also fixed an oddity where in `_wakeup()` the result of the
waiter was set to the waiter itself. This result is not used
anywhere and I changed this to `None`, to avoid a GC cycle.

* Update Lib/asyncio/base_events.py

---------

Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
@gvanrossum gvanrossum deleted the fix-wait-closed branch November 1, 2023 15:48
aisk pushed a commit to aisk/cpython that referenced this pull request Feb 11, 2024
…GH-111336)

* Try to fix asyncio.Server.wait_closed() again

I identified the condition that `wait_closed()` is intended
to wait for: the server is closed *and* there are no more
active connections.

When this condition first becomes true, `_wakeup()` is called
(either from `close()` or from `_detach()`) and it sets `_waiters`
to `None`. So we just check for `self._waiters is None`; if it's
not `None`, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly
tested that `wait_closed()` returns immediately when the server
is *not* closed but there are currently no active connections.
This was a mistake (probably a misunderstanding of the intended
semantics). I've fixed the test, and added a separate test that
checks exactly for this scenario.

I also fixed an oddity where in `_wakeup()` the result of the
waiter was set to the waiter itself. This result is not used
anywhere and I changed this to `None`, to avoid a GC cycle.

* Update Lib/asyncio/base_events.py

---------

Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
Glyphack pushed a commit to Glyphack/cpython that referenced this pull request Sep 2, 2024
…GH-111336)

* Try to fix asyncio.Server.wait_closed() again

I identified the condition that `wait_closed()` is intended
to wait for: the server is closed *and* there are no more
active connections.

When this condition first becomes true, `_wakeup()` is called
(either from `close()` or from `_detach()`) and it sets `_waiters`
to `None`. So we just check for `self._waiters is None`; if it's
not `None`, we know we have to wait, and do so.

A problem was that the new test introduced in 3.12 explicitly
tested that `wait_closed()` returns immediately when the server
is *not* closed but there are currently no active connections.
This was a mistake (probably a misunderstanding of the intended
semantics). I've fixed the test, and added a separate test that
checks exactly for this scenario.

I also fixed an oddity where in `_wakeup()` the result of the
waiter was set to the waiter itself. This result is not used
anywhere and I changed this to `None`, to avoid a GC cycle.

* Update Lib/asyncio/base_events.py

---------

Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
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3 participants