Open Stack

*Snip*

> Indeed, this has literally none of the benefits of the ideal Heat 
> deployment enumerated above save one: it may be entirely the wrong tool 
> in every way for the job it's being asked to do, but at least it is 
> still well-integrated with the rest of the infrastructure.

> Now, at the Mitaka summit we discussed the idea of a 'split stack', 
> where we have one stack for the infrastructure and a separate one for 
> the software deployments, so that there is no longer any tight 
> integration between infrastructure and software. Although it makes me a 
> bit sad in some ways, I can certainly appreciate the merits of the idea 
> as well. However, from the argument above we can deduce that if this is 
> the *only* thing we do then we will end up in the very worst of all 
> possible worlds: the wrong tool for the job, poorly integrated. Every 
> single advantage of using Heat to deploy software will have evaporated, 
> leaving only disadvantages.

I think Heat is a very powerful tool having done the container integration
into the tripleo-heat-templates I can see its appeal.  Something I learned
from integration, was that Heat is not the best tool for container deployment,
at least right now.  We were able to leverage the work in Kolla, but what it
came down to was that we're not using containers or Kolla to its max potential.

I did an evaluation recently of tripleo and kolla to see what we would gain
if the two were to combine. Let's look at some items on tripleo's roadmap.
Split stack, as mentioned above, would be gained if tripleo were to adopt
Kolla.  Tripleo holds the undercloud and ironic.  Kolla separates config
and deployment.  Therefore, allowing for the decoupling for each piece of
the stack.  Composable roles, this would be the ability to land services
onto separate hosts on demand.  Kolla also already does this [1]. Finally,
container integration, this is just a given :).

In the near term, if tripleo were to adopt Kolla as its overcloud it would
be provided these features and retire heat to setting up the baremetal nodes
and providing those ips to ansible.  This would be great for kolla too because
it would provide baremetal provisioning.

Ian Main and I are currently working on a POC for this as of last week [2].
It's just a simple heat template :).

I think further down the road we can evaluate using kubernetes [3].
For now though,  kolla-anisble is rock solid and is worth using for the
overcloud.

Thanks!
-Ryan

[1] - https://github.com/openstack/kolla/blob/master/ansible/inventory/multinode
[2] - https://github.com/rthallisey/kolla-heat-templates
[3] - https://review.openstack.org/#/c/255450/