TL;DR version:

We are going to fix Bionic simplestreams package and provide this Bionic simplestreams package in Ubuntu Cloud Archive for Xenial. With that, we are fixing Xenial simplestreams behavior (to work with keystone v3) only if end-user enables Ubuntu Cloud Archive.

Conversation about this merge request SRU:

<rbasak> rafaeldtinoco: reviewing your simplestreams Xenial SRU, I'm not sure I follow why an SRU is necessary for about half of these bugs - relating to v3 support
<rbasak> I'm not aware that we usually backport new features to old LTSes due to new features/deprecations in future OpenStack releases - that's what I thought the cloud archive was for.
<rbasak> Am I wrong, or is this case exceptional somehow?
<rafaeldtinoco> rbasak: it was a seg request
<rafaeldtinoco> because of a charm
<rafaeldtinoco> let me open the lps
<rbasak> So a statement like "The OpenStack Keystone charm supports v3 only since Queens and later" doesn't help me - why doesn't the charm support the older version?
<rafaeldtinoco> ok.. so, with xenial, the keystone charm has to use simplestreams from a ppa in order to make it work whenever updating openstack
<rafaeldtinoco> the upgrade procedure needs v3 support for not to brake
<rafaeldtinoco> because of the ordering (services) 
<rafaeldtinoco> but i must confess Im relying mostly on freyes feedback
<rafaeldtinoco> freyes: ^ do you have something else to add for rbasak  ?
<freyes> rbasak, >=Queens OpenStack dropped support for Keystone v2
<rbasak> freyes: and the cloud archive provides Queens against Xenial as a backport, correct?
<freyes> rbasak, correct
<rbasak> OK, so shouldn't this simplestreams v3 support to into the cloud archive, and not the Ubuntu Xenial archive, to solve that problem?
<rbasak> go
<freyes> rbasak, the cloud archive doesn't carry the simplestreams package, and if there is an intention to do it for newer releases it won't help with this bug
<rbasak> I don't think that "doesn't carry the simplestreams package" automatically means that an SRU is justified, though the SRU team might conclude that it's OK if no other solution makes sense.
<rbasak> But I don't understand why the package couldn't just be added to the cloud archive
<rbasak> Just because it's not there right now doesn't mean it can't be added right now.
<rbasak> It'd bump users up, but that's what you'd be doing with the SRU anyway.
<freyes> another reason why we may want to fix the package in distro is because simplestreams being a client, it could be that someone just wants to talk to a cloud that runs keystone v3, so in the case you propose, they would need to add a cloud archive repo (pulling a lot of new packages)
<freyes> I see pros and cons on both ways
<rbasak> That's the same situation for any network protocol client in Xenial though, OpenStack or not.
<rafaeldtinoco> a question that triggers me is..
<rafaeldtinoco> instead of a SRU to cloud archive
<rbasak> We expect such clients to use a newer release, or a snap, or some backport PPA, etc.
<rafaeldtinoco> we would have to have the backport instead
<rafaeldtinoco> so there is a 1:1 relation with newer fixes
<rbasak> (or run in a container of a newer release; the list goes on)
<freyes> rbasak, true, disregard my last thought
<rbasak> rafaeldtinoco: yes - that's a decision for the cloud archive maintainers, but I agree that a backport would make more sense.
<rbasak> However, the downside is that it's quite late to be doing such a backport - it might be more than you want to bump existing stable users (same concern as an SRU backport).
<rafaeldtinoco> jamespage: ^ can we have simplestreams included in cloud-archive ? this way the following SRU is not needed and, instead, the resolution would be to add the cloud-archive in order for xenial glance (>= queens) to support keystone v3 ? 
<rafaeldtinoco> i would document that in all those LPs and end user would have a place where to look if ever facing this need.
<freyes> it would be add the simplestreams in bionic to the xenial-queens archive
<jamespage> simplestreams in bionic does not work with keystone in bionic outside of any charm context due to the drop of the v2 API at queens release, which is what's in bionic
<jamespage> tl;dr its broken in distro
<jamespage> rafaeldtinoco, rbasak: ^^
<rbasak> jamespage: that might just mean that we need to fix Bionic in an SRU first though - I don't think it affects my proposal for a resolution in Xenial?
<rafaeldtinoco> fixing simplestreams in Bionic and having it available in cloud-archive for xenial (this is current suggest, right ?)
<rbasak> That's what I'm suggesting, yes
<jamespage> oh right - sorry i missed that context - yeah fix it in bionic, and we will include it in the UCA for xenial/queens
<rafaeldtinoco> good. 
<rafaeldtinoco> freyes: i can backport same patches to bionic and have u reviewing them if you're ok
<rafaeldtinoco> and then we ask jamespage (tks) to include it in cloud-archive
<freyes> rafaeldtinoco, I'm cool with that ;-)
<rbasak> OK, thanks!
<rafaeldtinoco> tku all!
<freyes> rafaeldtinoco, appreciated for chasing this