Open Stack

On Sun, Oct 27, 2013 at 11:23:20PM -0400, Lakshminaraya Renganarayana wrote:
> A few us at IBM studied Steve Baker's proposal on HOT Software
> Configuration. Overall the proposed constructs and syntax are great -- we
> really like the clean syntax and concise specification of components. We
> would like to propose a few minor extensions that help with better
> expression of dependencies among components and resources, and in-turn
> enable cross-vm coordination. We have captured our thoughts on this on the
> following Wiki page
> 
> https://wiki.openstack.org/wiki/Heat/Blueprints/hot-software-config-ibm-response

Thanks for putting this together.  I'll post inline below with cut/paste
from the wiki followed by my response/question:

> E2: Allow usage of component outputs (similar to resources):
> There are fundamental differences between components and resources...

So... lately I've been thinking this is not actually true, and that
components are really just another type of resource.  If we can implement
the software-config functionality without inventing a new template
abstraction, IMO a lot of the issues described in your wiki page no longer
exist.

Can anyone provide me with a clear argument for what the "fundamental
differences" actually are?

My opinion is we could do the following:
- Implement software config "components" as ordinary resources, using the
  existing interfaces (perhaps with some enhancements to dependency
  declaration)
- Give OS::Nova::Server a components property, which simply takes a list of
  resources which describe the software configuration(s) to be applied

This provides a lot of benefits:
- Uniformity of interfaces (solves many of the interface-mapping issues you
  discuss in the wiki)
- Can use provider resources and environments functionality unmodified
- Conceptually simple, we don't have to confuse everyone with a new
  abstraction sub-type and related terminology
- Resources describing software components will be stateful, as described
  in (E4), only the states would be the existing resource states, e.g
  CREATE, IN_PROGRESS == CONFIGURING, and CREATE, COMPLETE ==
  CONFIG_COMPLETE

Thoughts?

Steve