Puppet users - Mar 2013 - Correct means to tell if a class is instantiated/defined

All,

I am using puppet 3.1.1 and I need to know if a class has been defined.  I 
have tried defined() and tagged(), but neither seem to work.  They either 
return true when the class was not include for that node or false when it 
is included.

Here is the use case:

My admin users are defined (virtual) in a class and I need to add them to 
groups for different nodes.  As groups cant be have their members managed, 
but rather user have their membership managed.  For example the mysql group 
for database servers and httpd for web servers.  


  #in the service class there is a
tag(''''mysql-serve'')
  if tagged(''mysql-server'') {
     $groups = [ ''wheel'', $mysql::params::group ] 
   } else {
     $groups = [''wheel'' ]
   }
  
  #My understand is NOT to use Class[''mysql::service'']
  if defined(''mysql::service'') {
     $groups = [ ''wheel'', $mysql::params::group ] 
   } else {
     $groups = [''wheel'' ]
   }



Thanks!


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Hi,

On 03/20/2013 01:37 PM, Kubes wrote:
> I am using puppet 3.1.1 and I need to know if a class has been defined.
>  I have tried defined() and tagged(), but neither seem to work.  They
> either return true when the class was not include for that node or false
please don''t. You''re making yourself parse order dependent and
that
*will* bite you at some point down the road. Do not even try.

You may get away with declaring a subclass instead, and have class
mysql::service include that subclass in order to achieve the necessary
modification.

Otherwise, your best choice is probably external data, as in hiera.

That being said:
> when it is included.  #My understand is NOT to use
Class[''mysql::service'']
How have you come to understand this? I would have thought that Class[]
is fine.

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Thanks for the response.

On Wednesday, March 20, 2013 8:43:00 AM UTC-4, Felix.Frank
wrote:
>
> Hi, 
>
> On 03/20/2013 01:37 PM, Kubes wrote: 
> > I am using puppet 3.1.1 and I need to know if a class has been
defined.
> >  I have tried defined() and tagged(), but neither seem to work.  They 
> > either return true when the class was not include for that node or
false
>
> please don''t. You''re making yourself parse order
dependent and that
> *will* bite you at some point down the road. Do not even try. 
>
>
You may get away with declaring a subclass instead, and have class
> mysql::service include that subclass in order to achieve the necessary 
> modification. 
>
> I was checking for a subclass "mysql::service"
 
> Otherwise, your best choice is probably external data, as in hiera. 
>
Thanks, but I dont understand how heira solve the issues, can you please 
elaborator a bit for me?  I an using heira for storing my user info, but I 
dont know how to use it to handle if a node is a db server, etc?
 
>
> That being said: 
>
> > when it is included.  #My understand is NOT to use 
> Class[''mysql::service''] 
>
> How have you come to understand this? I would have thought that Class[] 
> is fine. 
>
Via post on this group and the documentation.   Using Resource[] is only 
needed for resource refferences, as I understand it.
http://docs.puppetlabs.com/references/latest/function.html#defined
 

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Hi again,

On 03/20/2013 01:56 PM, Kubes wrote:
>     You may get away with declaring a subclass instead, and have class
>     mysql::service include that subclass in order to achieve the necessary
>     modification.
> 
> I was checking for a subclass "mysql::service"
Not really. The class is named mysql::service, but I sincerely hope it
is not inheriting anything.

Point in fact - if you are not yet very keen on inheritance and how it
works, I advise to steer clear for the moment.
>     Otherwise, your best choice is probably external data, as in hiera.
> 
> Thanks, but I dont understand how heira solve the issues, can you please
> elaborator a bit for me?  I an using heira for storing my user info, but
> I dont know how to use it to handle if a node is a db server, etc?
You have it working already? Excellent!

The idea is simple: Introduce a hiera value that, for each node, tells
it whether it is a mysql server or not.

Each last of your nodes can then e.g.

if hiera("mysql-server") == "true" { include mysql }

It is now trivial to use the same hiera value in other places.
>     How have you come to understand this? I would have thought that Class[]
>     is fine.
> 
> 
> Via post on this group and the documentation.   Using Resource[] is only
> needed for resource refferences, as I understand it.
> http://docs.puppetlabs.com/references/latest/function.html#defined
Ah, misunderstanding.

defined() will tell you whether the class *exists*, not if this node has
included the class. (At least that''s what I make of the documentation).

HTH,
Felix

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