[openstack-dev] [Heat] Status of the Support Conditionals in Heat templates

Steven Hardy shardy at redhat.com
Fri Dec 18 11:07:34 UTC 2015

On Wed, Dec 09, 2015 at 01:42:13PM +0300, Sergey Kraynev wrote:
>    Hi Heaters,
>    On the last IRC meeting we had a question about Support Conditionals spec
>    [1].
>    Previous attempt for this staff is here [2].
>    The example of first POC in Heat can be reviewed here [3]
>    As I understand we have not had any complete decision about this work.
>    So I'd like to clarify feelings of community about it. This clarification
>    may be done as answers for two simple questions:
>     - Why do we want to implement it?
>     - Why do NOT we want to implement it?
>    My personal feeling is:
>    - Why do we want to implement it?
>        * A lot of users wants to have similar staff.
>        * It's already presented in AWS, so will be good to have this
>    feature in Heat too.
>     - Why do NOT we want to implement it?
>        * it can be solved with Jinja [4] . However I don't think, that it's
>    really important reason for blocking this work.
>    Please share your idea about two questions above.
>    It should allows us to eventually decide, want we implement it or not.

This has been requested for a long time, and there have been several
previous discussions, which all ended up in debating the implementation,
rather than focussing on the simplest possible way to meet the user

I think this latest attempt provides a simple way to meet the requirement,
improves out CFN compatibility, and is inspired by an interface which has
been proven to work.

So I'm +1 on going ahead with this - the implementation looks pretty simple :)

We've debated Jinja and other solutions before and dismissed them
as either unsafe to run inside the heat service, or potentially too
complex - this proposed solution appears to resolve both those concerns.


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