Puppet users - Apr 2013 - Retrieve scoped resource defaults from class method in custom type

[accidently sent this to puppet-dev, re-posting to puppet-users]

Hello puppet-users,

I am working on a module that provides a custom type. The type when
called will create new resources in the catalog using syntax like:

Puppet::Type.type(:file).new(:title => ''blah'')

This works fine and the resources are added as expected. However, I am
unable to apply any scoped defaults to the generated resources. So
something like:

File {
  mode => 0750
}

would not be applied to the generated resources. I understand that this
is most likely because I am altering the catalog directly.

The only thing I can think of doing would be to retrieve the scoped
attributes first, and then apply them to the generated resource. I have
been trying to do this with code like:

f = Puppet::Type.type(:file)
f.allattrs.each do |attrname|
  attrvalue = f.value(attrname)
  puts "#{attrname} = #{attrvalue}"
end

I know this doesn''t work, but wanted to throw this out there to see if
I
am taking the wrong approach at fetching resource defaults from the
scope in which my custom type is called.

Thanks for any help or insight.

- Ryan

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On Tue, 30 Apr 2013 15:37:11 -0700
Ryan Uber <ru@ryanuber.com> wrote:
> [accidently sent this to puppet-dev, re-posting to puppet-users]
> 
> Hello puppet-users,
> 
> I am working on a module that provides a custom type. The type when
> called will create new resources in the catalog using syntax like:
> 
> Puppet::Type.type(:file).new(:title => ''blah'')
> 
> This works fine and the resources are added as expected. However, I am
> unable to apply any scoped defaults to the generated resources. So
> something like:
> 
> File {
>   mode => 0750
> }
> 
were do you generate the resources? Puppet already has a method
"eval_generate" that every type can implement and which has to return
an array of generated resources (that''s how puppet generates implicit
file resource when you use `recurse`). These resources are
automatically added to the catalog.

So e.g.

    Puppet::Type.newtype(:foo) do
      newparam(:name)
      [...]
      def eval_generate
        resources = []
        resources << Puppet::Type.type(:file).new(:title =>
''blah'')
        resources
      end
    end

I played with it a little bit (wanted to make a proof of concept for
a `dirtree` type that simulates the behaviour of `mkdir -p`) but I hit
problems because autorequirements of generated resources do not seem to
work (e.g. You have File[''/foo''] in your puppet manifest and
your
custom type generates a resource File[''/foo/bar''] there a no
automatic
dependencies so File[''/foo/bar''] may be applied before
File[''/foo''] but
maybe I am wrong about that one.

-Stefan

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Hi Stefan,

My apologies that I did not get back sooner. What you are suggesting
yields the same results I was seeing before. Let me try to explain
better:

Using no modules (just standard puppet types), I can do this:
---
Package {
  notify => Exec["package-changed"]
}

exec { "package-changed":
  command => "/bin/true",
  refreshonly => true;
}

package { "vim-enhanced":
  ensure => installed;
}
---

If the above code happens to install vim-enhanced, then I will see
output like this:
---
Notice: /Stage[main]//Package[vim-enhanced]/ensure: created
Notice: /Stage[main]//Exec[package-changed]: Triggered
''refresh'' from 1
events
Notice: Finished catalog run in 4.75 seconds
---

The ''Package {}'' defaults are applied and the Exec gets
notified.

Now, I write a simple module with a type like this:
---
Puppet::Type.newtype(:foo) do
  newparam(:title) do
    isnamevar
  end
  def eval_generate
    resources = []
    resources << Puppet::Type.type(:package).new(:title => self.title)
    resources
  end
end
---

All it does is add a new package resource via eval_generate. I execute
it using a manifest that looks like this:
---
Package {
  notify => Exec["package-changed"]
}

exec { "package-changed":
  command => "/bin/true",
  refreshonly => true;
}

foo { "vim-enhanced": }
---

It yields the following:
---
Notice: /Package[vim-enhanced]/ensure: created
Notice: Finished catalog run in 5.10 seconds
---

The Exec from the resource defaults in my current scope is not notified.
If they were, the Exec resource should have run, just like in the first
example.

I am looking for a way to generate resources from a type, and have the
resource defaults from the scope they are defined applied to them.

Any other thoughts or suggestions are most appreciated, as always.

Thanks!
- Ryan
> From: "Stefan Schulte" <stefan.schulte@taunusstein.net>
> To: puppet-users@googlegroups.com
> Sent: Wednesday, May 1, 2013 4:54:38 AM
> Subject: Re: [Puppet Users] Retrieve scoped resource defaults from class
> method in custom type
> 
> On Tue, 30 Apr 2013 15:37:11 -0700
> Ryan Uber <ru@ryanuber.com> wrote:
> 
> > [accidently sent this to puppet-dev, re-posting to puppet-users]
> > 
> > Hello puppet-users,
> > 
> > I am working on a module that provides a custom type. The type when
> > called will create new resources in the catalog using syntax like:
> > 
> > Puppet::Type.type(:file).new(:title => ''blah'')
> > 
> > This works fine and the resources are added as expected. However, I am
> > unable to apply any scoped defaults to the generated resources. So
> > something like:
> > 
> > File {
> >   mode => 0750
> > }
> > 
> 
> were do you generate the resources? Puppet already has a method
> "eval_generate" that every type can implement and which has to
return
> an array of generated resources (that''s how puppet generates
implicit
> file resource when you use `recurse`). These resources are
> automatically added to the catalog.
> 
> So e.g.
> 
>     Puppet::Type.newtype(:foo) do
>       newparam(:name)
>       [...]
>       def eval_generate
>         resources = []
>         resources << Puppet::Type.type(:file).new(:title =>
''blah'')
>         resources
>       end
>     end
> 
> I played with it a little bit (wanted to make a proof of concept for
> a `dirtree` type that simulates the behaviour of `mkdir -p`) but I hit
> problems because autorequirements of generated resources do not seem to
> work (e.g. You have File[''/foo''] in your puppet manifest
and your
> custom type generates a resource File[''/foo/bar''] there a
no automatic
> dependencies so File[''/foo/bar''] may be applied before
File[''/foo''] but
> maybe I am wrong about that one.
> 
> -Stefan
> 
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> 
> 
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On Sunday, May 5, 2013 2:23:25 PM UTC-5, Ryan R. Uber
wrote:
>
> Hi Stefan, 
>
> My apologies that I did not get back sooner. What you are suggesting 
> yields the same results I was seeing before. Let me try to explain 
> better: 
>
>
I think Stefan understood the question.  He advised you on the appropriate 
interface for a resource type to use for adding generated resources to the 
catalog, but he was clearly uncertain about whether using that approach 
(which you should do regardless) would be sufficient to resolve your issue.

I think the final answer is probably that the Puppet API does not provide a 
mechanism for what you''re asking.  It''s certainly good that
Puppet doesn''t
automatically exhibit the behavior you describe, but I don''t think it 
provides even an optional way to obtain the defaults.  If it did, however, 
then probably it would be associated with a scope object, since resource 
defaults are (dynamic) scope-dependent.

Can you implement your resource type as a defined type?  That would give 
you resource defaults automatically.


John

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