[openstack-dev] [TripleO][Tuskar] Terminology

Tzu-Mainn Chen tzumainn at redhat.com
Sat Dec 14 00:31:05 UTC 2013

Thanks for the reply!  Let me try and address one particular section for now,
since it seems to be the part causing the most confusion:

> >      * SERVICE CLASS - a further categorization within a service role for a
> >      particular deployment.
> > 
> >           * NODE PROFILE - a set of requirements that specify what
> >           attributes a node must have in order to be mapped to
> >                            a service class
> I think I still need some more information about the above two. They
> sound vaguely like Cobbler's system profiles... :)

I admit that this concept was a bit fuzzy for me as well, but after a few IRC
chats, I think I have a better handle on this.  Let me begin with my understanding of what
happens in Heat, using Heat terminology:

A Heat stack template defines RESOURCES.  When a STACK is deployed using that template,
the resource information in the template is used to instantiate an INSTANCE of that
resource on a NODE.  Heat can pass a FLAVOR (flavors?) to nova-scheduler in order to
filter for appropriate nodes.

So: based on that explanation, here's what Tuskar has been calling the above:

RESOURCE == SERVICE CLASS (at the very least, it's a one-to-one correspondence)
???    == ROLE

The ??? is because ROLE is entirely a Tuskar concept, based on what TripleO views
as the fundamental kinds of building blocks for an overcloud: Compute, Controller,
Object Storage, Block Storage.  A ROLE essentially categorizes RESOURCES/SERVICE CLASSES;
for example, the Control ROLE might contain a control-db resource, control-secure resource,
control-api resource, etc.

Heat cares only about the RESOURCE and not the ROLE; if the roles were named Foo1, Foo2, Foo3,
and Barney, Heat would not care.  Also, if the UI miscategorized, say, the control-db resource
under the Block Storage category - Heat would again not care, and the deploy action would work.

>From that perspective, I think the above terminology should either *be* the Heat term, or be
a word that closely corresponds to the intended purpose.  For example, I think DEPLOYMENT reasonably
describes a STACK, but I don't think SERVICE CLASS works for RESOURCE.  I also think ROLE should be
RESOURCE CATEGORY, since that seems to me to be the most straightforward description of its purpose.

People with more experience in Heat, please correct any of my misunderstandings!


> Best,
> -jay
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