[chef] Re: Re: Wrapper Cookbooks and Computed Attributes

[Justin Lőcsei < >]

Thank you for your responses, Ranjib and Torben.  

I'm using Chef 11, and am still a little new to using Chef server, as my previous experience was just using Chef solo for a few small-scale projects.  I'm also using Berkshelf to manage cookbooks, and will likely be adding knife-spork to the workflow as well; I'm still trying to figure out which tools will work best.  I have read up on the different levels of attribute precedence in Chef 11, and am using them in most of my code to do what I want.  However, even with the well-defined system of attribute precedence, it doesn't seem like there's a way to override an attribute in an attribute file that's already been loaded and have it be used to compute other attribute in that already-loaded file, as confirmed by the ticket that Torben linked to.

Speaking of Torben, thank you for the links and possible solutions.  It's good to know that the non-DRY version is possible, if not exactly optimal, so that might be a fallback if nothing else works.  However, the ruby_block (thanks for the clarification Ranjib) used to re-evaluate an arbitrary cookbook's attributes seems like it might be the way to go, as I've just tried that out with my wrapper cookbooks and it does exactly what I want.  

Thanks for the clarification about using `node.set` as well.  I was using `override` in the attribute file mainly because I had seen examples of people using `override` as part of the wrapper-cookbook pattern, but the docs do seem to indicate that `set` / `normal` have a higher precedence than `default`, and should be enough to bend the wrapped cookbook to a wrapper's will.

Thanks again for your help!

On Thu, Aug 15, 2013 at 1:26 AM, Torben Knerr < " target="_blank"> > wrote:

For example, say I have a cookbook called "example".  In its
attributes/default.rb file, it has these two lines:

default['example']['version'] = '1.0'
default['example']

['module'] = "example-#{example['version']}"

By default, the value of node['example']['module'] should be properly set to
"example-1.0".  If I set the version to "1.1" using a role, I can access
node['example']['module'] in a recipe, and its value should be "example-1.1",
which is great.  However, if I set up a wrapper cookbook named
"mycompany-example" and have its attributes/default.rb file contain the line
"

override['example']['version'] = '1.1'", accessing node['example']['module']
in a recipe will give me a value of "example-1.0", even though accessing
node['example']['version'] would correctly be '1.1'.  The ideal outcome would
be to have the module value be "example-1.1", and I'm lost as to how to make
that happen.

You are running into this:

http://tickets.opscode.com/browse/CHEF-4234

TL;DR

In your wrapper cookbook either repeat the computed node attribute...

```

node.set

['example']['version'] = '1.1'

# not DRY but works

node.set['example']

['module'] = "example-#{example['version']}"

```

...or use this to re-evaluate the original attributes file in your wrapper cookbook (see http://docs.opscode.com/chef/essentials_cookbook_recipes.html#reload-attributes):

```

node.set

['example']['version'] = '1.1'

# now re-evaluate the default attributes file from the example cookbook

node.from_file(run_context.resolve_attribute("example", "default.rb"))

```

Also notice that `set` is enough -- you don't need to `override`. Not sure if that was intended in your example... 

Cheers, 

Torben

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