[chef] Re: Understanding node attributes set from 'role' cookbooks

[Noah Kantrowitz < >]

On Mar 14, 2014, at 5:44 AM, Lewis Thompson 
<
 >
 wrote:

> Hello,
> 
> I'm in the process of converting my roles into role cookbooks.  A
> minority of these roles set attributes and these are causing me
> problems.
> 
> Assuming my cookbook a has the following in an attributes file:
> 
>  default['a']['b'] = true
> 
> I can override this in a cookbook recipe as expected:
> 
>  node.default['a']['b'] = false
> 
> However, as soon as attributes files start performing logic based on
> attributes things break down as demonstrated in the following example
> cookbook (roleattributes):
> 
> attributes file:
> 
>  default['roleattributes']['test'] = true
>  if node['roleattributes']['test'] == true
>    default['roleattributes']['testistrue'] = true
>  else
>    default['roleattributes']['testistrue'] = false
>  end
> 
> default recipe:
> 
>  node.normal['roleattributes']['test'] = false
>  require 'pp'
>  pp node.debug_value(:roleattributes, :test)
>  pp node.debug_value(:roleattributes, :testistrue)
> 
> The output from the pp command during a Chef run is (with all
> not_present stripped for clarity):
> 
>  # pp node.debug_value(:roleattributes, :test)
>   ["default", true],
>   ["normal", false],
>  # pp node.debug_value(:roleattributes, :testistrue)
>   ["default", true],
> 
> As can be seen node['roleattributes']['test'] is correctly false while
> node['roleattributes']['testistrue'] is true.  By comparison when I
> define roleattributes.test=false in my role normal attributes I get a
> different result:
> 
>  # pp node.debug_value(:roleattributes, :test)
>   ["default", true],
>   ["normal", false],
>  # pp node.debug_value(:roleattributes, :testistrue)
>   ["default", false],
> 
> Is there any way around this somewhat unexpected (to me) behaviour?
> At the moment it is holding up a full migration towards role cookbooks
> (to allow versioning, etc.)

Move that logic into recipe or resource code so it can be lazily evaluated. 
The problem is that attribute files are run once at the start a run so having 
any logic based on values that might change later (either due to overrides or 
anything else) doesn't change the outcome of that execution (since it already 
happened).

--Noah

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