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On 07/07/14 08:28, Mark McLoughlin wrote:
> On Mon, 2014-07-07 at 18:11 +0000, Angus Salkeld wrote:
>> On 03/07/14 05:30, Mark McLoughlin wrote:
>>> Hey
>>>
>>> This is an attempt to summarize a really useful discussion that Victor,
>>> Flavio and I have been having today. At the bottom are some background
>>> links - basically what I have open in my browser right now thinking
>>> through all of this.
>>>
>>> We're attempting to take baby-steps towards moving completely from
>>> eventlet to asyncio/trollius. The thinking is for Ceilometer to be the
>>> first victim.
>>
>> Has this been widely agreed on? It seems to me like we are mixing two
>> issues:
>> 1) we need to move to py3
>> 2) some people want to move from eventlet (I am not convinced that the
>>    volume of code changes warrants the end goal - and review load)
>>
>> To achieve "1)" in a lower risk change, shouldn't we rather run eventlet
>> on top of asyncio? - i.e. not require widespread code changes.
>>
>> So we can maintain the main loop API but move to py3. I am not sure on
>> the feasibility, but seems to me like a more contained change.
> 
> Right - it's important that we see these orthogonal questions,
> particularly now that it appears eventlet is likely to be available for
> Python 3 soon.

Awesome (I didn't know that), how about we just use that?
Relax and enjoy py3:-)

Can we afford the code churn that the move to asyncio requires?
In terms of:
1) introduced bugs from the large code changes
2) redirected developers (that could be solving more pressing issues)
3) the problem of not been able to easily backport patches to stable
   (the code has diverged)
4) retraining of OpenStack developers/reviews to understand the new
   event loop. (eventlet has warts, but a lot of devs know about them).

> 
> For example, if it was generally agreed that we all want to end up on
> Python 3 with asyncio in the long term, you could imagine deploying

I am questioning whether we should be using asyncio directly (yield).
instead we keep using eventlet (the new one with py3 support) and it
runs the appropriate main loop depending on py2/3.

I don't want to derail this effort, I just want to suggest what I see
as an obvious alternative that requires a fraction of the work (or none).

The question is: "is the effort worth the outcome"?

Once we are in "asyncio heaven", would we look back and say "it
would have been more valuable to focus on X", where X could have
been say ease-of-upgrades or general-stability?


- -Angus

> (picking random examples) Glance with Python 3 and eventlet, but
> Ceilometer with Python 2 and asyncio/trollius.
> 
> However, I don't have a good handle on how your suggestion of switching
> to the asyncio event loop without widespread code changes would work?
> 
> Mark.
> 
> 
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