Ok, looked into this a little today, apologies for replying to my own
thread:
On Mon, Dec 21, 2015 at 01:35:54PM +, Steven Hardy wrote:
> Hi all,
>
> So I've recently had several discussions related to $subject.
>
> In summary - there's a requirement to enable underclouds to support
> deploying/updating previous versions of OpenStack overclouds.
>
> So, say I upgrade my liberty undercloud to master/mitaka, I'd like to
> ensure the following is possible:
>
> 1. Maintain any existing (liberty) overcloud without being forced to
> immediately upgrade to Mitaka (updating the undercloud can pull in features
> required to enable this upgrade however).
>
> 2. Deploy a new overcloud, with the choice between either liberty or mitaka
>
> This has some implications related to distributing tripleo-heat-templates
> (need to allow for packaging to either install both versions of t-h-t, or
> always install all versions via one package), and then there are related
> requirements related to tripleoclient (and potentially tripleo-common), so
> we maintain backwards compatiblity wrt overcloud deployment/update.
>
> So, some questions:
>
> - Do we actually want stable branches for tripleoclient (or even
> tripleo-common?) if we have to maintain backwards compatibility?
>
> - Can we add features to tripleoclient now, to make it easier to
> pre-configure known locations for specific releases (this should be
> configurable via a config file IMO, not hard-coded)?
>
> - How might we effectively test this in CI? Have a job which deploys e.g
> a stable/liberty overcloud with a master undercloud?
>
> - How hard would it be to wire in image-building for a previous release
> (Mitaka/master undercloud building liberty overcloud-full) - would it be
> reasonable to assume existing images and say the undercloud only supports
> building images for one release version?
Turns out this is pretty easy:
https://review.openstack.org/#/c/260144/
This shows how to build a liberty overcloud-full (on a master/mitaka
undercloud), then deploy a stable/liberty overcloud.
I've not heavily tested, but basically it seems to work OK, I had to apply
this pending stable/liberty backport:
https://review.openstack.org/#/c/258640/
I think the tripleo.sh patch (and steps outlined in the commit message) may
serve as a starting point for CI of this, and I do think we need to remove
the stable/liberty branch at least for tripleoclient.
Steve
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