On Tuesday, May 20, 2014 2:41:41 AM UTC-5, Bruno Bieth wrote:
>
>
> I'd like to do something like this
>
>
> define mytype() {}
>
> define delete_mytype() {}
>
> mytype { 'a': }
> mytype { 'b': }
> mytype { 'c': }
>
> $existing_mytypes = # something from facter
>
> # but this doesn't work
> $wanted_mytypes = Mytype <||>
>
No, it wouldn't. I don't think collectors are rvalues, but if they were,
they would probably evaluate to (1) an array of resource references, (2) in
some unspecified order. But the contents of a resource collection are
evaluated very late, so as to ensure that all matching resources are
included in it. That's too late for the value to be used to declare other
resources (else the purpose of late evaluation would not be served).
Additionally, facts are traditionally strings. In very recent Facter they
can be arrays and hashes, too, but nowhere in there can you get resource
references. You can get resource names, however.
>
> Mytype<||> -> Delete_mytype<||>
>
> delete_mytype { diff( $existing_mytypes, $wanted_mytypes ) }
>
>
> I believe I could do something along those lines but it creates as many
> files as mytype invocation :
>
>
I don't understand. That is, of course you get one resource per declared
Mytype instance -- that's what you specify by declaring those resources.
Why would you expect something different?
>
> defined mytype() {
> # persist $name in the filesystem
> }
>
> class prepare_mytypes {
> # cleanup files created by previous invocation of mytype
> }
>
> Class['prepare_mytypes'] ->
> Mytype<||> ->
> Class['remove_old_mytypes']
>
> class remove_old_mytypes {
>
> # look for files created by mytype
> # perform the same diff as explained above
> }
>
>
> Any idea?
>
So you are trying to remove unmanaged resources of the specified type?
Puppet has built-in support for that for plugin resource types that meet a
couple of fairly simple criteria. You would even dispense with any need
for facter to be involved if you wrote your type as a (custom) type /
provider pair.
On the other hand, if you must do this with defined types, then you can
probably follow an approach similar to what you are attempting.
The main issue here is with attempting to glean from the catalog under
construction what instances of Mytype have been declared. It is *always*poor
form to base catalog-building decisions on what has already been added
to the catalog, as doing so introduces evaluation-order dependence into
your manifest set. Evaluation order is not specified, so evaluation-order
dependence makes the contents of the constructed catalog incompletely
defined and subject to unexpected change.
Instead of querying the catalog, you should know independently what
resources of your type are intended to be present. An array of their names
would be suitable. These days, the recommendation would probably be to
maintain that data in Hiera. You then use that both to declare the wanted
resources and to determine (based on the data from Facter) what unwanted
resources are present. Puppet doesn't have a built-in diff() function, but
it shouldn't be too hard to write a custom function to do what you need.
For prototyping, you could probably do it with a combination of
inline_template() to perform the heavy lifting with split() to convert the
template output from string to array.
John
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