Open Stack

> From: Steven Hardy <shardy at redhat.com>
> To: openstack-dev at lists.openstack.org
> Date: 07/07/2014 10:39
> Subject: [openstack-dev] [heat] Update behavior for CFN compatible
resources
>
> Hi all,
>
> Recently I've been adding review comments, and having IRC discussions
about
> changes to update behavior for CloudFormation compatible resources.
>
> In several cases, folks have proposed patches which allow non-destructive
> update of properties which are not allowed on AWS (e.g which would result
> in destruction of the resource were you to run the same template on CFN).
>
> Here's an example:
>
> https://review.openstack.org/#/c/98042/
>
> Unfortunately, I've not spotted all of these patches, and some have been
> merged, e.g:
>
> https://review.openstack.org/#/c/80209/
>
> Some folks have been arguing that this minor deviation from the AWS
> documented behavior is OK.  My argument is that is definitely is not,
> because if anyone who cares about heat->CFN portability develops a
template
> on heat, then runs it on CFN a non-destructive update suddenly becomes
> destructive, which is a bad surprise IMO.

+1

>
> I think folks who want the more flexible update behavior should simply
use
> the native resources instead, and that we should focus on aligning the
CFN
> compatible resources as closely as possible with the actual behavior on
> CFN.

+1 on that as well

>
> What are peoples thoughts on this?
>
> My request, unless others strongly disagree, is:
>
> - Contributors, please check the CFN docs before starting a patch
>   modifying update for CFN compatible resources
> - heat-core, please check the docs and don't approve patches which make
>   heat behavior diverge from that documented for CFN.
>
> The AWS docs are pretty clear about update behavior, they can be found
> here:
>
> http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-
> template-resource-type-ref.html
>
> The other problem, if we agree that aligning update behavior is
desirable,
> is what we do regarding deprecation for existing diverged update
behavior?
>
> Steve
>
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