[chef] Re: stopping recipe execution early

[Chris Roberts < >]

Hi,

Awhile back I did some work around tools to allow overriding a node's  
current runlist. While explicit overrides of the run list are now in Chef  
proper, implicit overrides are not and were extracted out into a library:  
runlist_modifiers[1][2].

This library allows for two features, explicitly setting what recipes are  
allowed to run as well as restricting what recipes are allowed to  
run. One feature within this implementation to allow expected behavior when  
dealing with a restricted recipe is ensuring that other recipes with a  
dependency on a restricted recipe are not run. The reason for this  
being that when a recipe does an include_recipe, it has an expectation that  
resources will be made available from that inclusion, thus if recipe is not  
allowed to run then recipes with a dependency on the restricted recipe 
should be implicitly restricted from the run list as well.

All of this leads to a very simple "tool" the runlist_modifiers cookbook 
provides. If you add the runlist_modifiers as a dependency on your cookbook,  
you can then do something like this in your recipe:

unless(some_condition_to_run_recipe)
 raise Chef::Exceptions::RestrictedRecipe(self.recipe_name)
end
...

This will not only restrict the recipe from being loaded, but it will unroll  
any previously loaded recipes that are dependent on this given recipe.

With your description of your use case, this may not be directly applicable.  
Since you state you want to stop a recipe's execution early, it implies that  
there may be resources being defined prior to the stop point that you will  
want defined regardless. Splitting those bits out into separate recipes would  
likely make the runlist_modifiers more applicable. Hope this is at least  
some what helpful for another approach that can be taken to accomplish what  
you're looking for.

- Chris

[1] http://community.opscode.com/cookbooks/runlist_modifiers
[2] https://github.com/hw-cookbooks/runlist_modifiers

Pitucha, Stanislaw Izaak writes:

> Hi all,
> Is there some official (or at least working) way to stop execution of a
> recipe early? (without affecting the rest of the run list)
> For example if I have the whole recipe depending on a single switch, I could
> just put it inside of:
>
> if node[:switch]
>   ....
> end
>
> but that would be spanning a couple of screens of code - not the cleanest
> solution. Is there a good way to stop execution without throwing an
> exception, so that I can do:
>
> some_stop_function unless node[:switch]
>
> Regards,
> Stanisław Pitucha
> Cloud Services
> Hewlett Packard