Open Stack

On 10/12/13 12:46, Richard Lee wrote:
> Hey all,
>
> We're working on a blueprint
> <https://blueprints.launchpad.net/heat/+spec/preview-stack> that adds
> the ability to preview what a given template+parameters would create in
> terms of resources.  We think this would provide significant value for
> blueprint authors and for other heat users that want to see what
> someone's template would create before actually launching resources (and
> possibly having to pay for them).

+1 for this use case.

BTW AWS supports something similar, which we never bothered to implement 
in the compatibility API. You might want to do some research on that as 
a starting point:

http://docs.aws.amazon.com/AWSCloudFormation/latest/APIReference/API_EstimateTemplateCost.html

However the fact that we have pluggable resource types would make it 
very difficult for us to do cost calculations inside Heat (and, in fact, 
CloudFormation doesn't do that either, it just spits out a URL for their 
separate calculator) - e.g. it's very hard to know which resources will 
create, say, a Nova server unless they are all annotated in some way.

Are you thinking the API will simply return a list of resource types and 
counts? e.g.:

{
    "OS::Nova::Server": 2,
    "OS::Cinder::Volume": 1,
    "OS::Neutron::FloatingIP: 1
}

If so, +1 for that implementation too. Don't forget that you will have 
to recurse through provider templates, which may not contain what they 
say on the tin.

cheers,
Zane.