[chef] Re: Design about Running recipes Incrementally and Cleanup after Recipe removal

[Brad Knowles < >]

On Mar 19, 2012, at 4:04 PM, Hui Hu wrote:

> 1)  Running recipes Incrementally
> Assume a node has a run_list : [A,B,C] , now I want to add a new recipe D 
> into its run_list, then run chef-client. So chef-client will re-run 
> A,B,C,D.  However, re-run A,B,C is unneccessary, and sometimes I don't want 
> A,B,C to be re-ran which will cause service provided in A,B,C to be restart.

If you write your recipes correctly, when A,B, & C run for the second time, 
they will be able to determine that nothing needs to change, and therefore 
they won't restart any services.  This is what it means to be "idempotent".  
The Opscode folks are responsible for making their code idempotent inside of 
chef-client, and it's up to *YOU* to make sure that your recipes are also 
idempotent.

Otherwise, you made the bed of thorns, and now you get to lay in it.

> 2)  Cleanup after Recipe removal 
> This problem is described here : 
> http://help.opscode.com/discussions/questions/271-cleanup-after-recipe-removal
>  .
> 
> It says when a recipe is removed from the old run_list,  can chef-client 
> detects the change, and remove the packages/files/init.d services installed 
> by that recipe ?   Maybe adding a rollback() method in every recipe to do 
> this kind of removal and let chef-client call rollback() automactically ?

Again, that's up to you.  You write your cookbooks and recipes in such a way 
that they can appropriately de-install themselves, and that will happen.

Otherwise, well, you get out of the system what you put into it.

-- 
Brad Knowles 
<
 >
SAGE Level IV, Chef Level 0.0.1