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[nova] Stance on trivial features for driver configs without integration testing


On Thu, 2019-10-17 at 12:32 -0700, Clark Boylan wrote:
> On Thu, Oct 17, 2019, at 9:33 AM, melanie witt wrote:
> > On 10/17/19 08:39, Matt Riedemann wrote:
> > > This was brought up in the nova meeting today [1] as:
> > > 
> > > "Do we have a particular stance on features to the libvirt driver for 
> > > non-integration tested configurations, e.g. lxc [2] and xen [3], meaning 
> > > if they are trivial enough do we just say the driver's quality warning 
> > > on startup is sufficient to let them land since these are changes from 
> > > casual contributors scratching an itch?"
> > > 
> > > We agreed to move this to the mailing list.
> > > 
> > > We don't have tempest jobs for the libvirt+lxc or libvirt+xen 
> > > configurations (Citrix used to host 3rd party CI for the latter) and for 
> > > the changes referenced they are from part-time contributors, minor and 
> > > self-contained, and therefore I wouldn't expect them to build CI jobs 
> > > for those configurations or stand up 3rd party CI.
> > > 
> > > There are cases in the past where we've held features out due to lack of 
> > > CI, e.g. live migration support in the vSphere driver. That's quite a 
> > > bit different in my opinion because (1) it's a much more complicated 
> > > feature, (2) there already was 3rd party CI for the vSphere driver and 
> > > (3) there is a big rich corporation maintaining the driver so I figured 
> > > they could pony up the resources to make that testing happen (and it 
> > > eventually did).
> > > 
> > > For these other small changes are we OK with letting them in knowing 
> > > that the libvirt driver already logs a quality warning on startup for 
> > > these configs [4]? In this case I am but wanted to ask and I don't think 
> > > this sets a precedent as not all changes are equal.
> > 
> > I'm OK with this and I think the quality warning sets an appropriate 
> > expectation. As I mentioned in the meeting, my opinion is I think 
> > sufficiently trivial changes are fine on this basis. I also wouldn't try 
> > to set a hard precedent because each thing needs review on whether it's 
> > "trivial", but I support a spirit of accepting simple changes without 
> > requiring full blown 3rd party CI, given the quality warnings we have 
> > for the configs mentioned.
> 
> I think it is important to clarify that for both LXC and Xen testing should be able to happen in the upstream CI
> system. Both are open source projects and the major gotcha to testing Xen in the past (reboots) should be possible
> with Zuulv3. Typically we should fall back on third party CI when there are special hardware requirements or licenses
> that prevent us from running software freely on our existing CI system. For open source tools like LXC and Xen I don't
> believe this is a problem.
yes that is all true. at present we have not had time to sit down and create a job for each.
matt did have a poc job proposed for lxc which was partly working. i might consier creatign a job for each that runs as
a periodic job and or on  a subset of nova patches but at present  i have some other ci jobs
that i want to work on first. lxc/xen work for me is very much in the hobby work catagory but i
did enjoy using nova with libvirt/lxc in the past and would like to see it work again in the future.
it was quite nice for doing nested devstack without the overhead of two levels of vms. although when you
get nested virt working its close from a performance point of view but still uses more memory then lxc.

the lxc job itself in partalar is not much work to enabel the issue is that we cant actully pass tempest with lxc
currently the cloud init fix will help but we also need to modify devstack to create a useable lxc image which is
also relitivly trivial just need to be done.
> 
> > 
> > -melanie
> > 
> > > [1] 
> > > http://eavesdrop.openstack.org/meetings/nova/2019/nova.2019-10-17-14.00.log.html#l-287 
> > > 
> > > [2] https://review.opendev.org/#/c/667976/
> > > [3] https://review.opendev.org/#/c/687827/
> > > [4] 
> > > https://github.com/openstack/nova/blob/1a226aaa9e8c969ddfdfe198c36f7966b1f692f3/nova/virt/libvirt/driver.py#L609 
> 
>