On 31/03/16 18:10, Zane Bitter wrote:
I'm in favour of some sort of variable-based implementation for a few
reasons. One is that (5) seems to come up fairly regularly in a complex
deployment like TripleO. Another is that Fn::If feels awkward compared
to get_variable.
I actually have to revise this last part after reviewing the patches.
get_variable can't replace Fn::If, because we'd still need to handle
stuff of the form:
some_property: {if: [{get_variable: some_var},
{get_resource: res1},
{get_resource: res2}]
where the alternatives can't come from a variable because they contain
resource references and we have said we'd constrain variables to be static.
In fact the intrinsic functions that could be allowed in the first
argument to the {if: } function would have to constrained in the same
way as the constraint field in the resource, because we should only
validate and obtain dependencies from _one_ of the alternates, so we
need to be able to determine which one statically and not have to wait
until the actual value is resolved. This is possibly the strongest
argument for keeping on the cfn implementation course.
cheers,
Zane.
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