CODEWITHSUNDEEP
chef-infra
wojciechz
wojciechz

Reputation: 1186

Use default attribute value unless overriden in node attributes

What would be most polite way to have a default value for an attribute in chef that is used in template?

so in default/attributes.rb I have a default value:

default['my_attribute'] = 'some_default_value'

I'd like to override it on some chosen nodes with node attributes:

node['my_attribute'] = 'some_defined_value'

And in my templates I'd like to just use:

@my_attribute

which would take value from default['my_attribute'] or node['my_attribute'] (if defined)

What would be the most polite and Chef'ish way to do that?

Upvotes: 0

Views: 1627

Answers (1)

sethvargo
sethvargo

Reputation: 26997

Ohai!

First, I would recommend you have a look at the attribute-precedence model for reference.

You are correct, in your attribute file, define something like this (note, it's common practice to namespace attributes after the cookbook): 

default['cookbook']['attribute'] = 'original_value'

And then in a recipe, you can mutate the node object by calling node.set:

node.set['cookbook']['attribute'] = 'new_value'

This will save the current node state and persist back to the server (if using a Chef Server).

Then, in your template resource, just pass the value in directly:

template '/tmp/foo.txt' do
  variables(
    :my_attribute => node['cookbook']['attribute']
  )
end

Upvotes: 2

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