Puppet users - Nov 2011 - Variables inside node definition

Hi All,

How would I go about achieving the following?

node basenode {
     include motd
}

node www inherits basenode {
    $purpose = "web server"
}

In the "motd" module, I have a template that formats a standard
/etc/motd
file and I want to make use of the $purpose variable. When I access
scope.lookupvar(''::purpose''), I get undefined.

Thanks,
Gonzalo

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On Nov 17, 3:16 pm, Gonzalo Servat <gser...@gmail.com>
wrote:
> Hi All,
>
> How would I go about achieving the following?
>
> node basenode {
>      include motd
>
> }
>
> node www inherits basenode {
>     $purpose = "web server"
>
> }
>
> In the "motd" module, I have a template that formats a standard
/etc/motd
> file and I want to make use of the $purpose variable. When I access
> scope.lookupvar(''::purpose''), I get undefined.

I''m sure you do.  Class[''motd''] is evaluated in the
scope of node
''basenode'', which does not define a variable of that name. 
Moreover,
node variables are not in top scope and do not have qualified names,
so your particular use of scope.lookupvar() would not work anyway.

You have a great use case here for external data: instead of using a
node variable to communicate the machine''s purpose, you could instead
have class motd look it up via extlookup() or hiera.

Alternatively, if you were using an ENC then it would be easy to set
$purpose as a global variable, in which case your current template
would be right.

There are also approaches involving class inheritance in addition to
node inheritance.

If you''re considering node basenode abstract, meaning that every
client must match a subnode rather than basenode itself, then you
could parameterize class motd and have each subnode pass the purpose
variable that way (basenode would no longer declare motd).  I''m not
fond of class parameterization, but it could work.


John

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On Sat, Nov 19, 2011 at 12:58 AM, jcbollinger
<John.Bollinger@stjude.org>wrote:
> [..snip..]
>
>
You have a great use case here for external data: instead of using
a
> node variable to communicate the machine''s purpose, you could
instead
> have class motd look it up via extlookup() or hiera.
>
Thanks for replying John. I hadn''t looked into extlookup() until you
mentioned this. It''s just what I need! I also have a custom facter
variable
that defines which data centre the server is in, which fits in nicely with
extlookup() to look into a dc-specific CSV file.

I''m not using ENC as I do call a few defines from node definitions, and
I
don''t think there is a way of calling defines from a YAML node
definition?

Thanks again for the pointer!

- Gonzalo

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On Nov 18, 6:20 pm, Gonzalo Servat <gser...@gmail.com>
wrote:
> On Sat, Nov 19, 2011 at 12:58 AM, jcbollinger
<John.Bollin...@stjude.org>wrote:
>
> > [..snip..]
>
> You have a great use case here for external data: instead of using a
>
> > node variable to communicate the machine''s purpose, you could
instead
> > have class motd look it up via extlookup() or hiera.
>
> Thanks for replying John. I hadn''t looked into extlookup() until
you
> mentioned this. It''s just what I need! I also have a custom facter
variable
> that defines which data centre the server is in, which fits in nicely with
> extlookup() to look into a dc-specific CSV file.

Great, I''m glad to hear it.

> I''m not using ENC as I do call a few defines from node
definitions, and I
> don''t think there is a way of calling defines from a YAML node
definition?

You are correct.  External node classifiers cannot declare individual
resources, including defined type instances.  You would have to wrap
yours in classes to use an ENC.  I''m sure it would be possible, but it
might be more work than you want to undertake right now.


John

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