Open Stack

On Fri, Jul 15, 2016, at 03:46 PM, Ben Nemec wrote:
> I think this probably makes sense, but some more thoughts inline.
> 
> On 07/15/2016 03:13 PM, Stephane Miller wrote:
> > To better support diskimage-builder based IPA images going forward, we'd
> > like to move the ironic-agent element into the ironic-python-agent
> > repository. This will involve:
> > 
> > - Improving support for having multiple copies of an element, so that we
> > may deprecate the diskimage-builder repository copy of the element. See
> > this change and related: https://review.openstack.org/#/c/334785
> > - Moving the element into the repository. This change has been proposed
> > as https://review.openstack.org/#/c/335583/
> > - Deprecating the diskimage-builder copy of the element (TBD)
> > - Adding tests to gate IPA changes on DIB builds (TBD)

We now have some machinery to write per-element tests which result in an
image build and the ability to assert properties of that image. AFAIK no
downstreams of DIB have begun using it but this seems like a great
candidate.

> 
> We could potentially add tripleo-ci to the IPA repo, which would take
> care of this.  As an added bonus, it could cover both the introspection
> and deployment use cases for IPA.
> 
> On the other hand, if a separate Ironic job were added to cover this,
> tripleo could stop ever building new IPA images in CI except in the
> promote jobs when we bump our version of IPA.  This would delay our
> finding problems with IPA element changes, but realistically I'm not
> sure how many of those are happening these days anyway.  I'd expect that
> most changes are happening in IPA itself, which we don't currently CI.
> 
> > - Add upload of DIB-built images to tarballs.openstack.org
> > <http://tarballs.openstack.org> (TBD)
> 
> We would also need to resolve https://review.openstack.org/#/c/334042/
> 
> I'm not clear why, but the ironic-agent element was given special
> treatment in disk-image-create (which is evil, but what's done is done)
> and we'd need to figure out why and a solution that wouldn't require
> referencing an out-of-tree element in diskimage-builder.
> 

I agree that this is something we should solve, but I don't think its a
blocker for the element moving out of tree - I think the (nasty) dib
special-casing will still apply as long as the element is named the
same?

I suspect this is a ways off, but an interesting question will be what
distros to base these images off of. AIUI the current published image is
CoreOS based which is something we haven't written an element for (yet).
I don't think there's any issues here, just a lot of options - Do we add
CoreOS support, do you publish multiple images built on various distros
we currently support?

> > 
> > Many IPA deployers currently use DIB based IPA images using the
> > ironic-agent element. However, IPA does not officially support DIB - IPA
> > changes are not tested against DIB, nor are DIB-built images published.
> 
> tripleo-ci actually does publish images, but they aren't well publicized
> at this point, and it only does so when we promote a repo.
> 
> > 
> > This has the following disadvantages:
> > 
> > - The DIB element is not versioned along with IPA, resulting in
> > potential version mismatch and breakage
> > - ironic-agent element changes are not tested with DIB prior to merge
> 
> This isn't true today.  tripleo-ci runs against all diskimage-builder
> changes and uses an IPA ramdisk.  The version mismatch is a legit
> problem with the current setup, although I'm not aware of any actual
> breakages that have happened (which doesn't necessarily mean they
> haven't :-).
> 

I think there's another aspect to this which is that by hosting IPA in
tree we are effectively saying that DIB should co-gate with IPA changes
(how else can IPA test changes to its element?). The problem with this
is that DIB installs a lot of things and there isn't much value in us
co-gating with every thing we install - it also isn't sustainable.
Really, we want IPA to gate on changes to the IPA element and for DIB to
have robust enough testing that it will reliably produce a workable OS
for the IPA install logic to run in. I think that moving the IPA element
in to the IPA tree makes a lot of sense from this standpoint.

As for breakages from not co-gating - all of the dib + ironic breakages
I remember were when we used the old ramdisk element which had a lot
more ironic specific logic in the element. Now that IPA is a thing and
isn't a bunch of bash inside of DIB the surface area for DIB to break
Ironic is actually pretty low (which is awesome).

> > 
> > Understandably, tripleo and other projects may have concerns with regard
> > to this change. I hope to start a discussion here so that those concerns
> > can be addressed. Further in-depth discussion of this issue can be found
> > in the relevant launchpad bug:
> > https://bugs.launchpad.net/ironic-python-agent/+bug/1590935
> > 
> > Thanks,
> > Stephane


Cheers,
Greg