[openstack-dev] [TripleO] Forming our plans around Ansible

Steve Baker sbaker at redhat.com
Tue Jul 11 22:53:03 UTC 2017

On Tue, Jul 11, 2017 at 6:51 AM, James Slagle <james.slagle at gmail.com>

> On Mon, Jul 10, 2017 at 11:37 AM, Lars Kellogg-Stedman <lars at redhat.com>
> wrote:
> > On Fri, Jul 7, 2017 at 1:50 PM, James Slagle <james.slagle at gmail.com>
> wrote:
> >>
> >> There are also some ideas forming around pulling the Ansible playbooks
> >>
> >> and vars out of Heat so that they can be rerun (or run initially)
> >> independently from the Heat SoftwareDeployment delivery mechanism:
> >
> >
> > I think the closer we can come to "the operator runs ansible-playbook to
> > configure the overcloud" the better, but not because I think Ansible is
> > inherently a great tool: rather, I think the many layers of indirection
> in
> > our existing model make error reporting and diagnosis much more
> complicated
> > that it needs to be.  Combined with Puppet's "fail as late as possible"
> > model, this means that (a) operators waste time waiting for a deployment
> > that is ultimately going to fail but hasn't yet, and (b) when it does
> fail,
> > they need relatively intimate knowledge of our deployment tools to
> backtrack
> > through logs and find the root cause of the failure.
> >
> > If we can offer a deployment mode that reduces the number of layers
> between
> > the operator and the actions being performed on the hosts I think we
> would
> > win on both fronts: faster failures and reporting errors as close as
> > possible to the actual problem will result in less frustration across the
> > board.
> >
> > I do like Steve's suggestion of a split model where Heat is responsible
> for
> > instantiating OpenStack resources while Ansible is used to perform host
> > configuration tasks.  Despite all the work done on Ansible's OpenStack
> > modules, they feel inflexible and frustrating to work with when compared
> to
> > Heat's state-aware, dependency ordered deployments.  A solution that
> allows
> > Heat to output configuration that can subsequently be consumed by
> Ansible --
> > either running manually or perhaps via Mistral for
> API-driven-deployments --
> > seems like an excellent goal.  Using Heat as a "front-end" to the process
> > means that we get to keep the parameter validation and documentation
> that is
> > missing in Ansible, while still following the Unix philosophy of giving
> you
> > enough rope to hang yourself if you really want it.
> This is excellent input, thanks for providing it.
> I think it lends itself towards suggesting that we may like to persue
> (again) adding native Ironic resources to Heat. If those were written
> in a way that also addressed some of the feedback about TripleO and
> the baremetal deployment side, then we could continue to get the
> advantages from Heat that you mention.
> My personal opinion to date is that Ansible's os_ironic* modules are
> superior in some ways to the Heat->Nova->Ironic model. However, just a
> Heat->Ironic model may work in a way that has the advantages of both.

I too would dearly like to get nova out of the picture. Our placement needs
mean the scheduler is something we need to work around, and it discards
basically all context for the operator when ironic can't deploy for some

Whether we use a mistral workflow[1], a heat resource, or ansible
os_ironic, there will still need to be some python logic to build the
config drive ISO that injects the ssh keys and os-collect-config bootstrap.

Unfortunately ironic iPXE boot from iSCSI[2] doesn't support config-drive
(still?) so the only option to inject ssh keys is the nova ec2-metadata
service (or equivalent). I suspect if we can't make every ironic deployment
method support config-drive then we're stuck with nova.

I don't have a strong preference for a heat resource vs mistral vs ansible
os_ironic, but given there is some python logic required anyway, I would
lean towards a heat resource. If the resource is general enough we could
propose it to heat upstream, otherwise we could carry it in tripleo-common.

Alternatively, we can implement a config-drive builder in tripleo-common
and invoke that from mistral or ansible.

[1] https://review.openstack.org/#/c/313048/1
[2] http://specs.openstack.org/openstack/ironic-specs/
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