Clint Byrum <cl...@fewbar.com> wrote on 09/25/2014 12:13:53 AM:

> Excerpts from Mike Spreitzer's message of 2014-09-24 20:49:20 -0700:
> > Steven Dake <sd...@redhat.com> wrote on 09/24/2014 11:02:49 PM:
> > > ...
> > ...
> > Does TripleO require container functionality that is not available
> > when using the Docker driver for Nova?
> > 
> > As far as I can tell, the quantitative handling of capacities and
> > demands in Kubernetes is much inferior to what Nova does today.
> > 
> 
> Yes, TripleO needs to manage baremetal and containers from a single
> host. Nova and Neutron do not offer this as a feature unfortunately.

In what sense would Kubernetes "manage baremetal" (at all)?
By "from a single host" do you mean that a client on one host
can manage remote baremetal and containers?

I can see that Kubernetes allows a client on one host to get
containers placed remotely --- but so does the Docker driver for Nova.

> 
> > > As far as use cases go, the main use case is to run a specific 
> > > Docker container on a specific Kubernetes "minion" bare metal host.

Clint, in another branch of this email tree you referred to
"the VMs that host Kubernetes".  How does that square with
Steve's text that seems to imply bare metal minions?

I can see that some people have had much more detailed design
discussions than I have yet found.  Perhaps it would be helpful
to share an organized presentation of the design thoughts in
more detail.

> > 
> > If TripleO already knows it wants to run a specific Docker image
> > on a specific host then TripleO does not need a scheduler.
> > 
> 
> TripleO does not ever specify destination host, because Nova does not
> allow that, nor should it. It does want to isolate failure domains so
> that all three Galera nodes aren't on the same PDU, but we've not really
> gotten to the point where we can do that yet.

So I am still not clear on what Steve is trying to say is the main use 
case.
Kubernetes is even farther from balancing among PDUs than Nova is.
At least Nova has a framework in which this issue can be posed and solved.
I mean a framework that actually can carry the necessary information.
The Kubernetes scheduler interface is extremely impoverished in the
information it passes and it uses GO structs --- which, like C structs,
can not be subclassed.
Nova's filter scheduler includes a fatal bug that bites when balancing and 
you want more than
one element per area, see https://bugs.launchpad.net/nova/+bug/1373478.
However: (a) you might not need more than one element per area and
(b) fixing that bug is a much smaller job than expanding the mind of K8s.

Thanks,
Mike
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