On Friday, November 7, 2014 11:39:53 AM UTC-6, Felix.Frank wrote:
>
> On 11/07/2014 03:40 PM, jcbollinger wrote:
> > If you need to support multiple some::fun_instances, with some but not
> > all sharing any given $sname (i.e. a many to many relationship), then
> > you're going to need to make deeper changes.
>
> Yeah.
>
> FWIW, this is the one use case that worries me most when thinking about
> patterns to eliminate the defined() horror.
>
> define something::specific($group) {
> file { "/things/$group/$name": }
> if !defined( File["/things/$group"] ) {
> file { "/things/$group": ensure => directory }
> }
> }
>
> I.e., a defined type of which some but not all instances depend on a
> shared resource. Constraints could ensure a consistent catalog, but how
> can the dependency be automatically satisfied without defined() or
> ensure_resource()?
>
>
Well, my original idea for Constraints called for them to handle this issue
by synthesizing a resource in the event that there were constraints
declared on a resource that was not itself declared. They were also to set
resource parameter values under certain circumstances. Those are rather
trickier propositions than validating declared resources, though, and I
doubt they could be achieved without support from the Puppet core. Relying
on such a facility would be better than using defined() or
ensure_resource(), though, because the declared constraints collectively
describe the requirements on the resource so that you don't have to guess
about them.
As an alternative, we had a discussion in the dev group a couple of months
back where I advanced the proposition that the distinction between resource
declarations and (old style) resource overrides be removed. This is
similar, but not identical, to the longstanding proposition to have Puppet
merge identical resource declarations. As I understand it, though, a
different direction was chosen.
John
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