Le 20/08/2014 15:13, Daniel P. Berrange a écrit :
On Wed, Aug 20, 2014 at 08:33:31AM -0400, Jay Pipes wrote:
On 08/20/2014 04:48 AM, Nikola Đipanov wrote:
On 08/20/2014 08:27 AM, Joe Gordon wrote:
On Aug 19, 2014 10:45 AM, "Day, Phil" <philip....@hp.com
<mailto:philip....@hp.com>> wrote:
-----Original Message-----
From: Nikola Đipanov [mailto:ndipa...@redhat.com
Sent: 19 August 2014 17:50
To: openstack-dev@lists.openstack.org
Subject: Re: [openstack-dev] [Nova] Scheduler split wrt Extensible

On 08/19/2014 06:39 PM, Sylvain Bauza wrote:
On the other hand, ERT discussion is decoupled from the scheduler
split discussion and will be delayed until Extensible Resource Tracker
owner (Paul Murray) is back from vacation.
In the mean time, we're considering new patches using ERT as
non-acceptable, at least until a decision is made about ERT.

Even though this was not officially agreed I think this is the least
we can do
under the circumstances.

A reminder that a revert proposal is up for review still, and I
consider it fair
game to approve, although it would be great if we could hear from
Paul first:
Given the general consensus seemed to be to wait some before deciding
what to do here, isn't putting the revert patch up for approval a tad
premature ?
There was a recent discussion about reverting patches, and from that
(but not only) my understanding is that we should revert whenever in doubt.


Putting the patch back in is easy, and if proven wrong I'd be the first
to +2 it. As scary as they sound - I don't think reverts are a big deal.
Neither do I. I think it's more appropriate to revert quickly and then add
it back after any discussions, per the above revert policy.

The RT may be not able to cope with all of the new and more complex
resource types we're now trying to schedule, and so it's not surprising
that the ERT can't fix that.  It does however address some specific use
cases that the current RT can't cope with,  the spec had a pretty
through review under the new process, and was discussed during the last
2 design summits.   It worries me that we're continually failing to make
even small and useful progress in this area.
Sylvain's approach of leaving the ERT in place so it can be used for
the use cases it was designed for while holding back on doing some of
the more complex things than might need either further work in the ERT,
or some more fundamental work in the RT (which feels like as L or M
timescales based on current progress) seemed pretty pragmatic to me.

++, I really don't like the idea of rushing the revert of a feature that
went through significant design discussion especially when the author is
away and cannot defend it.
Fair enough - I will WIP the revert until Phil is back. It's the right
thing to do seeing that he is away.
Well, it's as much (or more?) Paul Murray and Andrea Rosa :)

However - I don't agree with using the length of discussion around the
feature as a valid argument against reverting.
Neither do I.

I've supplied several technical arguments on the original thread to why
I think we should revert it, and would expect a discussion that either
refutes them, or provides alternative ways forward.

Saying 'but we talked about it at length' is the ultimate appeal to
imaginary authority and frankly not helping at all.
Agreed. Perhaps it's just my provocative nature, but I hear a lot of "we've
already decided/discussed this" talk especially around the scheduler and RT
stuff, and I don't think the argument holds much water. We should all be
willing to reconsider design decisions and discussions when appropriate, and
in the case of the RT, this discussion is timely and appropriate due to the
push to split the scheduler out of Nova (prematurely IMO).
Yes, this is absolutely right. Even if we have approved a spec / blueprint
we *always* reserve the right to change our minds at a later date if new
information or points of view come to light. Hopefully this will be fairly
infrequent and we won't do it lightly, but it is a key thing we accept as
a possible outcome of the process we follow.

While I totally understand the possibility to change our minds about an approved spec, I'm a bit worried about the timeline and how it can possibly impact deliveries. In our case, the problem was raised in between 2 and 3 months after the design session occurred, and more importantly, 1 week before Feature Proposal Freeze. As a consequence, it freezes the specification and we loose the possibility to split the Scheduler by Juno.

I know there are discussions about how Nova should handle feature delivery, I just want to make sure that this corner case is part of the talks. IMHO, we need to make sure at least all cores validate a spec (either explicitely or implicitely - by not giving -1 in less than 2 weeks once the spec validated, for example) or this situation could occur more than infrequently.

My 2 cents,


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