[openstack-dev] [Glance][All] Pecan migration strategies

Oleg Anufriev oanufriev at mirantis.com
Wed Jan 15 17:16:29 UTC 2014


Implementing API on Pecan is a subthread of unification of openstack
In this context we have to do the job in any case.
I totally agree with cases Roman Prykhodchenko described.
If we swap versions now we'll have this part of work done. At that moment,
we'll need new API versions we'll have to implement just controllers, not
WSGI application.
In addition, when v3 will be provided and v1 deleted whole API service will
on Pecan.
It is still a question if v3 ever been required... So, seems wrong to delay
unification until v3.
Finally, it will be difficult to implement v3 and migrate v2 to Pecan same

Oleh Anufriiev.

This time, with content!

On Fri, Jan 10, 2014 at 4:51 AM, Flavio Percoco <flavio at redhat.com> wrote:

> Greetings,
> More discussions around the adoption of Pecan.
> I'd like to know what is the feeling of other folks about migrating
> existing APIs to Pecan as opposed to waiting for a new API version as
> an excuse to migrate the API implementation to Pecan?
> We discussed this in one of the sessions at the summit, I'd like to
> get a final consensus on what the desired migration path is for the
> overall community.
> IIRC, Cinder has a working version of the API with Pecan but there's
> not a real motivation to release a new version of it that will use
> the new implementation. Am I right?
> Nova, instead, will start migrating some parts but not all of them and
> it'll happen as part of the API v3. AFAIU.
> Recently a new patch was proposed in glance[0] and it contains a base
> implementation for the existing API v2. I love that patch and the fact
> that Oleh Anufriiev is working on it. What worries me, is that the
> patch re-implements an existing API and I don't think we should just
> swap them.

Yes, I'm a bit worried about just swapping in a new implementation, too,
much as I think the approach using Pecan is superior to the way we
initially went. At this time I don't see a really compelling reason to
switch. It would be neat however if there are any people who actually want
to run the Pecan implementation of the v2 API--if so it might be worth
taking it on into upstream. But unless we actually think there is some
future development in v2.0 that will be substantially eased by using Pecan
I think we should probably not switch implementations until there is a
major version bump.

> Yes, we have tests (unit and functional) and that should be enough to
> make sure the new implementation works as the old one - Should it?
> Should it? - but...
> This most likely has to be evaluated in a per-project basis. But:
>    - What are the thoughts of other folks on this matter?
> Cheers,
> FF
> [0] https://review.openstack.org/#/c/62911/
> --
> @flaper87
> Flavio Percoco
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