Puppet users - Apr 2013 - Hiera Automatic Parameter Lookup Question

This may be a dumb question, but here goes


So I''m running on Puppet 3.1.1 on RHEL5, and i''ve been using
Hiera since 2.5/2.6 ish and it''s been great!!  I was reading up on
Automatic Parameter Lookups and would love to use it for my modules.  But I
can''t seem to ever get Hiera/Puppet to load the value i''ve set
in my yaml files. I feel like I must be missing something.


I''ve worked my way through the docs, and am just not sure what
I''m missing. I decided to use the 2.7 example, just to see what it did
and noticed that this

  $puppetservertest = hiera(''puppet::puppetservertest'',
''test''),
 

Doesn''t work, 

but this 

  $puppetservertest = hiera(''puppetservertest'',
''test''),

Does! 

I''m working on my puppet module, so I was expecting the lookup to grab
the variable from my puppet.yaml file (which it does in the second example)

My test puppet.yaml file is pretty simple, it looks like this


# Parameters for Puppet Class
---
puppetservertest:        - ''puppet.example.com''


If anyone can shed some light on this it would be awesome!

Thanks

-a

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When you use the hiera() function, you ate by definition not doing automatic
param lookup. :-) whatever you put in for the first argument is the key that
will be looked up via hiera verbatim. If you leave the class parameter without a
default and instantiate it without a value, puppet will prefix the name of the
class to the param name with double colons and use that as the lookup key in
hiera.

--
Brian Lalor
blalor@bravo5.org

On Apr 18, 2013, at 4:15 PM, Alaric <paxindustria@gmail.com> wrote:
> This may be a dumb question, but here goes
> 
> 
> So I''m running on Puppet 3.1.1 on RHEL5, and i''ve been
using Hiera since 2.5/2.6 ish and it''s been great!!  I was reading up
on Automatic Parameter Lookups and would love to use it for my modules.  But I
can''t seem to ever get Hiera/Puppet to load the value i''ve set
in my yaml files. I feel like I must be missing something.
> 
> 
> I''ve worked my way through the docs, and am just not sure what
I''m missing. I decided to use the 2.7 example, just to see what it did
and noticed that this
> 
>  $puppetservertest = hiera(''puppet::puppetservertest'',
''test''),
> 
> 
> Doesn''t work, 
> 
> but this 
> 
>  $puppetservertest = hiera(''puppetservertest'',
''test''),
> 
> Does! 
> 
> I''m working on my puppet module, so I was expecting the lookup to
grab the variable from my puppet.yaml file (which it does in the second example)
> 
> My test puppet.yaml file is pretty simple, it looks like this
> 
> 
> # Parameters for Puppet Class
> ---
> puppetservertest:        - ''puppet.example.com''
> 
> 
> If anyone can shed some light on this it would be awesome!
> 
> Thanks
> 
> -a
> 
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> 
> 
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On Thursday, April 18, 2013 3:42:32 PM UTC-5, blalor
wrote:
>
> When you use the hiera() function, you ate by definition not doing 
> automatic param lookup. :-) whatever you put in for the first argument is 
> the key that will be looked up via hiera verbatim. If you leave the class 
> parameter without a default and instantiate it without a value, puppet will
> prefix the name of the class to the param name with double colons and use 
> that as the lookup key in hiera. 
>
>
So, yes, the main issue here is that the keys in your hiera data files must 
match the ones by which Puppet attempts to look up the data.  The keys are 
opaque to hiera, and the context of each lookup nearly so.  If you want to 
lookup key ''puppet::puppetservertest'' then that key must
appear in the data
-- it is a different key from ''puppetservertest'', regardless
of where the
hiera() call appears.

Moreover, I wanted to point out that, contrary to Brian''s implication, 
automated class parameter binding is independent of whether parameters have 
explicit default values.  If you do not bind a parameter''s value via a 
class''s declaration (and you shouldn''t) then Puppet attempts
to look up a
value for it via hiera, regardless of whether an explicit default value is 
declared by the class.  Only if the hiera lookup fails is an explicit 
default used.


John

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On Apr 19, 2013, at 9:34 AM, jcbollinger <John.Bollinger@stJude.org>
wrote:
> Moreover, I wanted to point out that, contrary to Brian''s
implication, automated class parameter binding is independent of whether
parameters have explicit default values.  If you do not bind a
parameter''s value via a class''s declaration (and you
shouldn''t) then Puppet attempts to look up a value for it via hiera,
regardless of whether an explicit default value is declared by the class.  Only
if the hiera lookup fails is an explicit default used.

That''s kind of cool.  

class foo (
    $bar => hiera(''baz'', ''bap''),
) { }

So $bar will be set to "bap" only if foo::bar and baz are not found in
Hiera, in that order?

--
Brian Lalor
blalor@bravo5.org


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On Friday, April 19, 2013 8:49:14 AM UTC-5, blalor
wrote:
>
> On Apr 19, 2013, at 9:34 AM, jcbollinger
<John.Bo...@stJude.org<javascript:>>
> wrote:
>
> Moreover, I wanted to point out that, contrary to Brian''s
implication,
> automated class parameter binding is independent of whether parameters have
> explicit default values.  If you do not bind a parameter''s value
via a
> class''s declaration (and you shouldn''t) then Puppet
attempts to look up a
> value for it via hiera, regardless of whether an explicit default value is 
> declared by the class.  Only if the hiera lookup fails is an explicit 
> default used.
>
>
> That''s kind of cool.  
>
> class foo (
>     $bar => hiera(''baz'', ''bap''),
> ) { }
>
> So $bar will be set to "bap" only if foo::bar and baz are not
found in
> Hiera, in that order? 
>
>
I had to study that for a minute to see what you meant, but yes, that is 
correct for Puppet 3.  Puppet 2 will differ.  Puppet 3 may perform both 
lookups even when foo::bar is found, however, even though in that case it 
doesn''t use the result of the ''baz'' lookup.  That
could be significant
under some circumstances, such as when using an Hiera back-end that is 
expensive to call.


John

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