Puppet users - Jun 2010 - To External Nodes, or not to External Nodes

I had started converting my node manifests to external nodes (in yaml
format), to make them machine readable/writable, so that we could
write scripts to parse them. However, I really can''t get it right in
my head that by doing that I am forced to pass parameters to classes
by setting a series of variables in the node. It just doesn''t seem
right to me. It''s a lot less readable than using a definition which at
least indicates some sort of intent on what the variables are for and
how they are used.

Am I the only person in the universe who thinks this?

The only alternative I can see is the extlookup() function, which at
least lets me use definitions in my node manifests, and therefore
keeps the intent and is more readable, while at the same time storing
machine parseable data in an external file.

Do I have any other options?

Doug.

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> Do I have any other options?
waiting for 2.6 which will have class parameters.

cheers pete
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On 25.06.2010 19:42, Douglas Garstang wrote:
> I had started converting my node manifests to external nodes (in yaml
> format), to make them machine readable/writable, so that we could
> write scripts to parse them. However, I really can''t get it right
in
> my head that by doing that I am forced to pass parameters to classes
> by setting a series of variables in the node. It just doesn''t seem
> right to me. It''s a lot less readable than using a definition
which at
> least indicates some sort of intent on what the variables are for and
> how they are used.
>    
External nodes are powerful because they allow a script to generate some 
standard variables, and to break some inheritance rules which are 
present in the nodes.pp. So if you are just creating yaml files for 
nodes it''s probably not a good idea. Where is good will probably be the
next question. Well a lot of places. If you want to store your info in 
AD along with the windows machines this is a good way. Or if you want a 
web interface.

The clear advantage over nodes.pp would be in a case where you would 
want to override the value of a variable in a derived class. In the 
nodes.pp if the variable is used in an include in the base node even if 
you override it you won''t gain anything. On the other hand, here, 
because you generate the yaml dynamically you can set the variables 
before the includes, and also have some inheritance defined and 
understood only by the script (ie puppet will only get the final result).

It would be wise to try this with foreman or puppet dashboard.


I''m not sure if I''ve hit your question right. If I''ve
misunderstood it
sorry my bad. :"> :)


Silviu
> Am I the only person in the universe who thinks this?
>
> The only alternative I can see is the extlookup() function, which at
> least lets me use definitions in my node manifests, and therefore
> keeps the intent and is more readable, while at the same time storing
> machine parseable data in an external file.
>
> Do I have any other options?
>
> Doug.
>
>    
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On Fri, Jun 25, 2010 at 1:04 PM, Silviu Paragina <silviu@paragina.ro>
wrote:
> On 25.06.2010 19:42, Douglas Garstang wrote:
>>
>> I had started converting my node manifests to external nodes (in yaml
>> format), to make them machine readable/writable, so that we could
>> write scripts to parse them. However, I really can''t get it
right in
>> my head that by doing that I am forced to pass parameters to classes
>> by setting a series of variables in the node. It just doesn''t
seem
>> right to me. It''s a lot less readable than using a definition
which at
>> least indicates some sort of intent on what the variables are for and
>> how they are used.
>>
>
> External nodes are powerful because they allow a script to generate some
> standard variables, and to break some inheritance rules which are present
in
> the nodes.pp. So if you are just creating yaml files for nodes
it''s probably
> not a good idea. Where is good will probably be the next question. Well a
> lot of places. If you want to store your info in AD along with the windows
> machines this is a good way. Or if you want a web interface.
Yes, but you lose the ability to use definitions, which is a HUGE
problem. As I said earlier, if you can''t use definitions in your node
manifests, then you have  to put the definitions into modules, set
variables in the nodes, and then include those modules. This makes the
configuration far less readable. The only reason I was looking at
external nodes was because we wanted to store all the data passed from
the nodes to the modules in a machine readable format.
>
> The clear advantage over nodes.pp would be in a case where you would want
to
> override the value of a variable in a derived class. In the nodes.pp if the
> variable is used in an include in the base node even if you override it you
> won''t gain anything. On the other hand, here, because you generate
the yaml
> dynamically you can set the variables before the includes, and also have
> some inheritance defined and understood only by the script (ie puppet will
> only get the final result).
Not sure I follow, but this:

classes:
   - moduleA
parameters:
  - key1: var1
  - key2: var2
  - key3: var3

class moduleA {
  <do something with key1>
}

is a LOT less readable than:

node A {
  definition1 { name: key1 => var1 }
}

define definition1 {
  <do something with key1>
}

Doug

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