Puppet users - Jan 2009 - Making a variable visible in parent class (scoping)

So I need a variable in a child class to be visible to the parent
class and I''m wondering how I can do that?  The docs say "You will
almost always find that you can avoid resetting variable values using
the built in conditionals:" but I guess this is one of those cases
where it just isn''t possible:

node default {}

node testserver inherits default {
  include testclasses                     <- (this is where I need
$var to be visible)
}

node test1.example.com inherits testserver {
  $var = "host server name"
}

As far as I can tell, there''s no way to include another node,
otherwise I could have "test1.example.com" include
"testserver"
instead of inheriting.  I can''t set a variable in the parent class
from the child class because variables in puppet can only be set
once.  And, the way it is right now, exactly as it is above, $var
evaluates to nil because the $var declaration is out of the scope of
the parent class.

I don''t want to include "testclasses" in
"test1.example.com" because
then I''m going to have to include it for every individual
"testserver"
node defeating the whole purpose of inheritance, cluttering up the
config files and making it easier to make mistakes.  So far, this is
the only way I''ve been able to get it to work but it''s a
kludge and
I''d prefer to avoid it.

I tried something like this as well:

node default {}

node testserver inherits default {
  $var = ["text1", "text2"]
}

node test1.example.com inherits testserver {
  $var += ["text3"]
}

but the parameter of the puppet type I''m trying to set with $var
(nagios_host: hostgroups) doesn''t accept arrays.  So if a child class
can append to an array in a parent class, is there a way to get the
string version of an array with all the elements concatenated together
with a "," in between each element?  Either that or is there a way I
can get the "hostgroups" parameter in the "nagios_host" type
to accept
arrays?

I feel like I''ve got to be missing something here.  Thanks.

Scott
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On Jan 17, 2009, at 12:31 AM, Scott wrote:
>
> So I need a variable in a child class to be visible to the parent
> class and I''m wondering how I can do that?  The docs say "You
will
> almost always find that you can avoid resetting variable values using
> the built in conditionals:" but I guess this is one of those cases
> where it just isn''t possible:
>
> node default {}
>
> node testserver inherits default {
>  include testclasses                     <- (this is where I need
> $var to be visible)
> }
>
> node test1.example.com inherits testserver {
>  $var = "host server name"
> }
>
> As far as I can tell, there''s no way to include another node,
> otherwise I could have "test1.example.com" include
"testserver"
> instead of inheriting.  I can''t set a variable in the parent class
> from the child class because variables in puppet can only be set
> once.  And, the way it is right now, exactly as it is above, $var
> evaluates to nil because the $var declaration is out of the scope of
> the parent class.
>
> I don''t want to include "testclasses" in
"test1.example.com" because
> then I''m going to have to include it for every individual
"testserver"
> node defeating the whole purpose of inheritance, cluttering up the
> config files and making it easier to make mistakes.  So far, this is
> the only way I''ve been able to get it to work but it''s a
kludge and
> I''d prefer to avoid it.
>
> I tried something like this as well:
>
> node default {}
>
> node testserver inherits default {
>  $var = ["text1", "text2"]
> }
>
> node test1.example.com inherits testserver {
>  $var += ["text3"]
> }
>
> but the parameter of the puppet type I''m trying to set with $var
> (nagios_host: hostgroups) doesn''t accept arrays.  So if a child
class
> can append to an array in a parent class, is there a way to get the
> string version of an array with all the elements concatenated together
> with a "," in between each element?  Either that or is there a
way I
> can get the "hostgroups" parameter in the "nagios_host"
type to accept
> arrays?
>
> I feel like I''ve got to be missing something here.  Thanks.
The only real way to do this is to use an external nodes tool.  I''ve  
attached a simple script that serves node infromation out of YAML  
files; it isn''t awesome but it''ll do what you want, anyway.

-- 
All power corrupts, but we need the electricity.
     -- Unknown
---------------------------------------------------------------------
Luke Kanies | http://reductivelabs.com | http://madstop.com

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Luke, thanks for the reply.  So just to clarify, you can''t even have a
child class append to an array declared in the parent class and have
it visible in the parent class?

Scott

On Jan 19, 9:44 pm, Luke Kanies <l...@madstop.com>
wrote:
> On Jan 17, 2009, at 12:31 AM, Scott wrote:
>
>
>
>
>
> > So I need a variable in a child class to be visible to the parent
> > class and I''m wondering how I can do that?  The docs say
"You will
> > almost always find that you can avoid resetting variable values using
> > the built in conditionals:" but I guess this is one of those
cases
> > where it just isn''t possible:
>
> > node default {}
>
> > node testserver inherits default {
> >  include testclasses                     <- (this is where I need
> > $var to be visible)
> > }
>
> > node test1.example.com inherits testserver {
> >  $var = "host server name"
> > }
>
> > As far as I can tell, there''s no way to include another node,
> > otherwise I could have "test1.example.com" include
"testserver"
> > instead of inheriting.  I can''t set a variable in the parent
class
> > from the child class because variables in puppet can only be set
> > once.  And, the way it is right now, exactly as it is above, $var
> > evaluates to nil because the $var declaration is out of the scope of
> > the parent class.
>
> > I don''t want to include "testclasses" in
"test1.example.com" because
> > then I''m going to have to include it for every individual
"testserver"
> > node defeating the whole purpose of inheritance, cluttering up the
> > config files and making it easier to make mistakes.  So far, this is
> > the only way I''ve been able to get it to work but
it''s a kludge and
> > I''d prefer to avoid it.
>
> > I tried something like this as well:
>
> > node default {}
>
> > node testserver inherits default {
> >  $var = ["text1", "text2"]
> > }
>
> > node test1.example.com inherits testserver {
> >  $var += ["text3"]
> > }
>
> > but the parameter of the puppet type I''m trying to set with
$var
> > (nagios_host: hostgroups) doesn''t accept arrays.  So if a
child class
> > can append to an array in a parent class, is there a way to get the
> > string version of an array with all the elements concatenated together
> > with a "," in between each element?  Either that or is there
a way I
> > can get the "hostgroups" parameter in the
"nagios_host" type to accept
> > arrays?
>
> > I feel like I''ve got to be missing something here.  Thanks.
>
> The only real way to do this is to use an external nodes tool.
 I''ve  
> attached a simple script that serves node infromation out of YAML  
> files; it isn''t awesome but it''ll do what you want,
anyway.
>
> --
> All power corrupts, but we need the electricity.
>      -- Unknown
> ---------------------------------------------------------------------
> Luke Kanies |http://reductivelabs.com|http://madstop.com
>
>  external_nodes.rb
> 1KViewDownload
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On Jan 21, 2009, at 11:21 PM, Scott wrote:
> Luke, thanks for the reply.  So just to clarify, you can''t even
have a
> child class append to an array declared in the parent class and have
> it visible in the parent class?

It''s a question of ordering - by the time the child class has an  
opportunity to extend an array, that array has already been used by an  
included class.

So sure, you can extend the array, it just won''t do any good. :/

-- 
A government big enough to give you everything you want is big enough
to take from you everything you have. --Gerald R. Ford
---------------------------------------------------------------------
Luke Kanies | http://reductivelabs.com | http://madstop.com


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