Re: attribute value availability + the implicit dependency graph and chef-deploy patch

[Ian Kallen <spidaman.list@gmail.com>]

Adam Jacob wrote:
> http://wiki.opscode.com/display/chef/Anatomy+of+a+Chef+Run
>
> Libraries are loaded first, then Attributes, then Definitions,
> followed by Recipes.
>
> (This is because you may have an Attribute that is set in one
> cookbook, but utilized in another.
Great, thanks Adam. Let me make sure I'm following the semantics. Given 
N cookbooks, the order in which each of the respective attributes loaded 
is non-deterministic. Ergo a recipe can depend on values being set for 
attributes in *any* cookbook but having values from one cookbook's 
attributes depend on values set in another's is essentially a dice roll. 
Therefore in this case (assume elsewhere we've required another 
cookbook's recipe where that cookbook's attributes file sets "apache" 
but it doesn't matter, cookbook attribute processing isn't ordered in 
anyway)

passenger[:apache_load_path] = 
"#{apache[:dir]}/mods-available/passenger.load" if attribute?("apache")

whether node[:passenger][:apache_load_path] ever gets set is a matter of 
luck; the "apache" attribute may or may not be set when this is being 
processed. However, if the cookbook needs information from another, it 
must access it in the recipe to rely on it being set. Is that right?

--
Ian Kallen
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