Open Stack

On Mon, Jan 04, 2016 at 03:53:07PM -0500, Jay Dobies wrote:
> I ran into an issue in a review about moving environment resolution from
> client to server [1]. It revolves around clients being able to access older
> versions of servers (that's a pretty simplistic description; see [2] for the
> spec).
> 
> Before the holiday, Steve Hardy and I were talking about the complications
> involved. In my case, there's no good way to differentiate an older server
> from a legitimate error.
> 
> Since the API isn't versioned to the extent that we can leverage that value,
> I was looking into using the template versions call. Something along the
> lines of:
> 
>   supported_versions = hc.template_versions.list()
>   version_nums = [i.to_dict()['version'].split('.')[1] for i in
> supported_versions]
>   mitaka_or_newer = [i for i in version_nums if i >= '2016-04-08']
> 
> Yes, I'm planning on cleaning that up before submitting it :)
> 
> What I'm wondering is if I should make this into some sort of generalized
> utility method in the client, under the assumption that we'll need this sort
> of check in the future for the same backward compatibility requirements.
> 
> So a few questions:
> 
> 1. Does anyone strongly disagree to checking supported template versions as
> a way of determining the specifics of the server API.

Ok, so some valid concerns have been raised over deriving things using the
HOT version (although I do still wonder if the environment itself should be
versioned, just like the templates, then we could rev the environment
verion and say it supports a list, vs changing anything in the API, but
that's probably a separate discussion).

Taking a step back for a moment, the original discussion was around
providing transparent access to the new interface via heatclient, but that
isn't actually a hard requirement - the old interface works fine for many
users, so we could just introduce a new interface (which would eventually
become the default, after all non-EOL heat versions released support the
new API argument):

Currently we do:

heat stack-create foo -f foo.yaml -e a.yaml -e b.yaml

And this implies some client-side resolution of the multiple -e arguments.

-e is short for "--environment-file", but we could introduce a new format,
e.g "-E", short for "--environment-files":

heat stack-create foo -f foo.yaml -E a.yaml -E b.yaml

This option would work the same way as the current interface, but it would
pass the files unmodified for resolution inside heat (by using the new API
format), and as it's opt-in, it's leaving all the current heatclient
interfaces alone without any internal fallback logic?

Steve