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On 13 June 2013 23:08, Mark McLoughlin <markmc at redhat.com> wrote:


>
> Or another way of thinking about it is if autoscaling was a standalone
> service provided by the heat project, anyone running that service would
> have to look very carefully at any heat security advisories to check
> whether it applies to the autoscaling service.
>
> But I'm fine with the "let's build it as a standalone service in Heat
> and then see if it makes sense to split it out" approach.

Well, I don't think you want more than one thing driving nova - if you
have autoscaling, and templates/metadata in use, you don't want deploy
changes from the metadata side to be countermanded by scaling
responses - they need to act in concert. So there is definitely
coupling there.

This implies to me that there are three concerns:
 - when to scale and how much [AS]
 - when to deploy and what [templates/metadata]
 - when to ask nova to do something [cluster management]

At the moment heat does all three - and IMO thats fine - but if we
split out AS, we need to either have AS depend on heat, or *also*
split out cluster management, or it will be liable to behave horribly
when deploys trigger load.

FWIW I don't see heat as 'that thing that does templates' - service
orchestration is all about metadata, scaling, cluster introspection.

-Rob [not a heat dev, take with a grain of salt]
-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Cloud Services