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[kolla][tripleo] Podman/buildah


Whats the plan for Kubernetes integration at this point? I keep seeing more and more talk/work on integrating podman and paunch and such but its a lot of work that doesn't apply when switching to Kubernetes?

Thanks,
Kevin
________________________________
From: Alex Schultz [aschultz at redhat.com]
Sent: Wednesday, June 05, 2019 7:59 AM
To: Sean Mooney
Cc: Mark Goddard; Emilien Macchi; openstack-discuss
Subject: Re: [kolla][tripleo] Podman/buildah



On Wed, Jun 5, 2019 at 8:46 AM Sean Mooney <smooney at redhat.com<mailto:smooney at redhat.com>> wrote:
On Wed, 2019-06-05 at 13:47 +0100, Mark Goddard wrote:
> On Wed, 5 Jun 2019 at 13:28, Emilien Macchi <emilien at redhat.com<mailto:emilien at redhat.com>> wrote:
> >
> > On Wed, Jun 5, 2019 at 5:21 AM Mark Goddard <mark at stackhpc.com<mailto:mark at stackhpc.com>> wrote:
> > [...]
> > >
> > > I understand that Tripleo uses buildah to build images already (please
> > > correct me if I'm wrong). How is this achieved with kolla? Perhaps
> > > using 'kolla-build --template-only' to generate Dockerfiles then
> > > invoking buildah separately? Are you planning to work on adding
> > > buildah support to kolla itself?
> >
> >
> > That's what we did indeed, we use Kolla to generate Dockerfiles, then call Buildah from tripleoclient to build
> > containers.
> > We have not planned (yet) to port that workflow to Kolla, which would involve some refacto in the build code (last
> > time I checked).
> >
> > I wrote a blog post about it a while ago:
> > https://my1.fr/blog/openstack-containerization-with-podman-part-5-image-build/
>
> Thanks for following up. It wouldn't be a trivial change to add
> buildah support in kolla, but it would have saved reimplementing the
> task parallelisation in Tripleo and would benefit others too. Never
> mind.
actully im not sure about that buildah should actully be pretty simple to add support for.
its been a while but we looksed at swaping out the building with a python script a few years ago
https://review.opendev.org/#/c/503882/
and it really did not take that much to enable so simply invoking buildah in a simlar maner should be trivail.


The issue was trying to build the appropriate parallelization logic based on the kolla container build order[0].  We're using the --list-dependencies to get the ordering for the build[1] and then run it through our builder[2].  You wouldn't want to do it serially because it's dramatically slower.  Our buildah builder is only slightly slower than the docker one at this point.

podman support will be harder but again we confied all interaction with docker in kolla-ansibel to be via
https://github.com/openstack/kolla-ansible/blob/master/ansible/library/kolla_docker.py
so we sould jsut need to write a similar module that would work with podman and then select the correct one to use.
the interface is a little large but it shoudld reactively mechanical to implement podman supprot.

The podman support is a bit more complex because there is no daemon associated with it. We wrote systemd/podman support into paunch[3] for us to handle the management of the life cycles of the containers. We'd like to investigate switching our invocation of paunch from cli to an ansible plugin/module which might be beneficial for kolla-ansible as well.

Thanks,
-Alex

[0] https://opendev.org/openstack/tripleo-common/src/branch/master/tripleo_common/image/builder/buildah.py#L156
[1] https://opendev.org/openstack/tripleo-common/src/branch/master/tripleo_common/image/kolla_builder.py#L496
[2] https://opendev.org/openstack/python-tripleoclient/src/branch/master/tripleoclient/v1/container_image.py#L207-L228
[3] https://opendev.org/openstack/paunch

>
> > --
> > Emilien Macchi
>
>


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