Chef: How do I override default attributes in roles?

问题

I'm using the opscode nginx cookbook for configuring the nginx server on my nodes. The nginx cookbook has some default attributes I'd like to override in my role ("web_server").

These are the attributes I'd like to override:

default['nginx']['version'] = "1.2.2" # in cookbooks/nginx/attributes/default.rb
default['nginx']['source']['prefix'] = "/opt/nginx-#{node['nginx']['version']}" # in cookbooks/nginx/attributes/source.rb

In my roles/web_server.rb file I have something like this:

name "web_server"
description "Setup a web server"
run_list "role[base]", "recipe[nginx]"
override_attributes 'nginx' => {
  'install_method' => "source",
  'version' => "1.2.3",
  'source' => { "prefix" => "/opt/nginx", "checksum" => nil }
}

However, when running the chef-client the nginx recipe ignores my overrides and uses the default ones.

What am I doing wrong here?

Thanks!

回答1:

According to the Chef Attribute Preference document, this should work:

name "web_server"
description "Setup a web server"
run_list "role[base]", "recipe[nginx]"
default_attributes 'nginx' => {
  'install_method' => "source",
  'version' => "1.2.3",
  'source' => { "prefix" => "/opt/nginx", "checksum" => nil }
}

You shouldn’t use override_attributes in roles. Once you start using overrides instead of defaults, you’ll quickly end up finding you’ve used the strongest possible override and have no further way to override it. Use default_overrides instead.

The precedence rules around attributes, using only the default level are actually pretty same:

If there is one, the attribute from the role is used, e.g., require_two_factor_auth is forced to true with default_overrides in role[single_sign_on], even in QA
If there is one, the attribute from the environment is used, e.g., require_two_factor_auth is forced to true in production
If there is one, the attribute from the recipe is used, e.g., require_two_factor_auth is set to true in auth::two_factor
Finally, the sane default attribute from the default attribute file is used, e.g., require_two_factor_auth = false

However, it’s extremely unusual for the same attribute to be set in all four of those places, though. If the correct value of the attribute really depends on the recipe and the role and and the environment, then usually the resulting value combines features of all three, and a different attribute is set at each level and combined in the recipe.

If this isn’t working, two possibilities are:

Edited role not uploaded to server
Overriding run list with chef-client -o "recipe[nginx]" instead of chef-client -o role[web_server] or plain chef-client

If that’s not the case, please provide more detail. I use this all the time and it’s always worked, and I’d be concerned if there were edge cases where this does not behave as documented.

回答2:

The attribute precedence chart [1] shows that these four options rank above your role:

12. An override attribute located in an environment
13. A force_override attribute located in a cookbook attribute file
14. A force_override attribute located in a recipe
15. An automatic attribute identified by Ohai at the start of the chef-client run

If these don't appear to be the cause, then perhaps changing your formatting might help. I would write it like:

override_attributes(
  nginx: {
    install_method: 'source',
    version: '1.2.3',
    source: {
      prefix: '/opt/nginx',
      checksum: [ ],
    },
  }
)

[1] https://docs.chef.io/attributes.html#attribute-precedence

回答3:

The only problem I could guess is that these attributes must have been over-ridden by force_overridden attribute. Also ensure that the attributes you have over-ridden are available for the runlist(since I'm skeptical about the way you have arranged your role file)

回答4:

Did you check the attribute precedence order here? https://docs.chef.io/attributes.html#attribute-precedence

Make sure there are no attributes overridden on a node directly in your recipe.

回答5:

You can also use override attributes in role editor (in web or knife role edit)

{
  "name": "web_server",
  "description": "nginx version",
  "json_class": "Chef::Role",
  "default_attributes": {

  },
  "override_attributes": {
    "nginx": {
      "version": "1.2.2"
    }
  },
  "chef_type": "role",
  "run_list": [
  "recipe[]",
  "recipe[]"
  ],
  "env_run_lists": {

  }
}

回答6:

Have you tried with parentheses? I tried your example with parentheses and got the default attributes overridden.

# your roles/web_server.rb file

override_attributes(
  'nginx' => {
    'install_method' => "source",
    'version' => "1.2.3",
    'source' => { "prefix" => "/opt/nginx", "checksum" => nil }
  }
)

来源：https://stackoverflow.com/questions/12144592/chef-how-do-i-override-default-attributes-in-roles

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