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

[Adam Jacob <adam@opscode.com>]

On Thu, Apr 23, 2009 at 12:46 PM, Ian Kallen <spidaman.list@gmail.com> wrote:
> 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?

Yep.  That is why the solution may very well be include_attribute,
with similar semantics to recipes.  It lets us out of that trap.

Adam

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Opscode, Inc.
Adam Jacob, CTO
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