[issue22875] asyncio: call_soon() documentation unclear on timing

[STINNER Victor]

STINNER Victor added the comment:

FYI I added a new test to the aiotest project (test suite for asyncio), for 
this issue:
https://bitbucket.org/haypo/aiotest/commits/17dd11fc2f4bafad623f940b1a33a3b8b0d39ccd

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[STINNER Victor]

STINNER Victor added the comment:

Oops, I forgot to mention the issue number in my commit.

changeset:   93893:a59fed8c710b
branch:  3.4
parent:  93891:1da9e9eaeae8
user:Victor Stinner 
date:Mon Dec 15 17:50:55 2014 +0100
files:   Doc/library/asyncio-eventloop.rst
description:
asyncio doc: call_soon() does not call immediatly the callback. Patch written
by Martin Panter.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[STINNER Victor]

STINNER Victor added the comment:

Thanks Martin for your change, I commited it.

--
resolution:  -> fixed
status: open -> closed

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[Guido van Rossum]

Guido van Rossum added the comment:

Docfix LGTM.

On Fri, Dec 12, 2014 at 10:53 PM, Martin Panter 
wrote:
>
>
> Martin Panter added the comment:
>
> I have been bitten by this when attempting to implement my own event
> loops. Parts of the “asyncio” code itself expects that the callback is not
> invoked directly after call_soon() returns. Here is a simple patch.
>
> --
> keywords: +patch
> nosy: +vadmium
> versions: +Python 3.4
> Added file: http://bugs.python.org/file37437/call_soon.patch
>
> ___
> Python tracker 
> 
> ___
>

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[Martin Panter]

Martin Panter added the comment:

I have been bitten by this when attempting to implement my own event loops. 
Parts of the “asyncio” code itself expects that the callback is not invoked 
directly after call_soon() returns. Here is a simple patch.

--
keywords: +patch
nosy: +vadmium
versions: +Python 3.4
Added file: http://bugs.python.org/file37437/call_soon.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[R. David Murray]

R. David Murray added the comment:

Personally, when I read that I thought "arrange for" made it pretty clear it 
was when control returned to the event loop, but I agree that if it can be made 
clearer it should be.

--
nosy: +r.david.murray

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[Guido van Rossum]

Guido van Rossum added the comment:

"As soon as possible" is constrained by "all callbacks are called from the 
event loop".

Feel free to suggest a doc patch (asyncio docs are in dire need of more help!)

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue22875] asyncio: call_soon() documentation unclear on timing

[Corbin Simpson]

New submission from Corbin Simpson:

Hi there!

While assisting somebody on #python (where manners go to die), I was consulting 
asyncio's documentation. Given my unfamiliarity with asyncio, I was surprised 
to read BaseEventLoop.call_soon()'s documented behavior: "Arrange for a 
callback to be called as soon as possible." [1]

The question in mind is whether call_soon() waits for control to return to the 
event loop before calling the first callback in the queue. After all, given the 
documented behavior, it would not be unreasonable for call_soon() to always 
call callbacks immediately if no other callbacks were enqueued. I can imagine 
scenarios where a previous queued callback from e.g. call_soon_threadsafe() 
creates a callback that causes queueing behavior, but otherwise I would expect 
"as soon as possible" to mean "immediately".

It's true that in other event loops, this kind of callback registration waits 
for control to return to the event loop before running callbacks. However, many 
event loops that I've worked with indicate that call_later() is the correct API 
for adding callbacks that respect the event loop. In fact, call_later(0, 
callback, args) looks quite a bit like the familiar Twisted callLater(0, 
callback, args) pattern!

Additionally, there is no indication as to whether call_later() and call_soon() 
use the same queue.

I'd like clarification on these points in the Python 3 documentation, please. 
I'd like to know whether call_soon() can be immediate, and whether call_soon() 
preempts or interleaves with call_later().

(Yes, I know that Twisted's documentation is missing this too [2] [3]. I'll get 
to that soon enough.)

Thanks!
~ C.

[1]: 
https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.BaseEventLoop.call_soon
[2]: http://twistedmatrix.com/documents/current/core/howto/time.html
[3]: 
http://twistedmatrix.com/documents/current/api/twisted.internet.interfaces.IReactorTime.html#callLater

--
assignee: docs@python
components: Documentation, asyncio
messages: 231180
nosy: Corbin.Simpson, docs@python, gvanrossum, haypo, yselivanov
priority: normal
severity: normal
status: open
title: asyncio: call_soon() documentation unclear on timing

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com