Puppet users - Apr 2013 - Help me with overriding define resource

We are trying to override a resource that was created with
''define'' but we are receiving the following error: Only
subclasses can override parameters at /etc/puppet/manifests/...

Here is a specific example:  https://gist.github.com/anonymous/5428129

Is this even possible? If not, how would you work around this?

Thanks




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On Saturday, April 20, 2013 8:45:24 PM UTC-5, Smashed
wrote:
>
> We are trying to override a resource that was created with
''define'' but we
> are receiving the following error: Only subclasses can override parameters 
> at /etc/puppet/manifests/... 
>
> Here is a specific example:  https://gist.github.com/anonymous/5428129 
>
> Is this even possible? If not, how would you work around this? 
>
>
The parameters of resources of defined types can be overridden just the 
same as parameters of native types.  I don''t see anything in your gist
that
explains the error you describe.  It is incomplete, however, in that 
nothing in it declares the referenced resources
Package[''nrpe''] and
Service[''nrpe''], and nothing declares class
''foo'', which presumably is
supposed to be where the error occurs.

If you provide a complete example that genuinely reproduces the error then 
we can be more helpful.  If you provide the full error message that goes 
with the example you provide then we can be more helpful.


John

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It looks like when you use composition you can''t redefine a class:
https://gist.github.com/anonymous/5445418 IE.. you can''t redefine a
resource that was included.

I feel like the composition method listed above should work as definition is
still part of the same node. Seems a bit hacky to create a class just to
subclass something you want to override. Thoughts?


On Apr 22, 2013, at 8:04 AM, jcbollinger <John.Bollinger@stJude.org>
wrote:
> 
> 
> On Saturday, April 20, 2013 8:45:24 PM UTC-5, Smashed wrote:
> We are trying to override a resource that was created with
''define'' but we are receiving the following error: Only
subclasses can override parameters at /etc/puppet/manifests/...
> 
> Here is a specific example:  https://gist.github.com/anonymous/5428129 
> 
> Is this even possible? If not, how would you work around this? 
> 
> 
> The parameters of resources of defined types can be overridden just the
same as parameters of native types.  I don''t see anything in your gist
that explains the error you describe.  It is incomplete, however, in that
nothing in it declares the referenced resources
Package[''nrpe''] and Service[''nrpe''], and
nothing declares class ''foo'', which presumably is supposed to
be where the error occurs.
> 
> If you provide a complete example that genuinely reproduces the error then
we can be more helpful.  If you provide the full error message that goes with
the example you provide then we can be more helpful.
> 
> 
> John
> 
> 
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>  
>  
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On Tuesday, April 23, 2013 12:02:49 PM UTC-5, Smashed
wrote:
>
> It looks like when you use composition you can''t redefine a class:
> https://gist.github.com/anonymous/5445418 IE.. you can''t redefine
a
> resource that was included.
>

That is correct.  It is also a different case from the one in your earlier 
gist.

 
>
> I feel like the composition method listed above should work as definition 
> is still part of the same node. Seems a bit hacky to create a class just to
> subclass something you want to override. Thoughts?
>
>
Overriding resource parameters is the primary purpose of class inheritance 
in Puppet.  It''s not hacky to use a tool for its intended purpose. 
What''s
hacky is subclassing without overriding any resource parameters.

A class represents some coherent unit of configuration space (or ought to 
do), so why would it be sensible to allow random declarations in any 
unrelated place to override the declarations a given class makes?  Using a 
subclass to declare overrides involves at least a pro forma acknowledgement 
that the purpose and use of the overridden declaration is understood at the 
point where it is override is declared.  Composition does not have the same 
effect.

In particular, being part of the same node is no distinguishing 
characteristic at all.  For any given catalog compilation *all*declarations that
are evaluated apply to the same node.


John

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John, you''re such a tease ;-)

While I mostly agree with the points you''re making (as so often), I
feel
that this thread is incomplete without giving an example of the
syntactically correct implementation of the original idea.

Note that this approach has a number of issues and should usually be
avoided. Use at your own peril.

class composition {
  include base_class

  // wrong:
  //Definition[''TestCase''] {
  // right:
  Definition<| title == ''TestCase'' |> {
    var => ''/tmp/bar'',
  }
}

On 04/24/2013 03:56 PM, jcbollinger wrote:
> A class represents some coherent unit of configuration space (or ought
> to do), so why would it be sensible to allow random declarations in any
> unrelated place to override the declarations a given class makes?  Using
> a subclass to declare overrides involves at least a pro forma
> acknowledgement that the purpose and use of the overridden declaration
> is understood at the point where it is override is declared. 
> Composition does not have the same effect.
HTH,
Felix

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