A collection of helper methods to use in Opscode Chef recipes
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README.md

Chef Helpers

This gem includes miscellaneous add-on helper methods for Opscode Chef.

Installation

To use helper methods in your Chef recipes, use following code in your recipe:

chef_gem 'chef-helpers'
require 'chef-helpers'

To use the helpers locally in knife exec scripts or Knife plugins, just add the chef-helpers gem to your dependencies and require 'chef-helpers'.

Usage

Detailed documentation of the helper methods can be seen at http://rdoc.info/github/3ofcoins/chef-helpers/

Finding existing templates and cookbook files

The recipe DSL is extended with ChefHelpers::HasSource module that provides methods for checking which templates and cookbook files exist on the Chef server. Detailed docs are available at http://rdoc.info/github/3ofcoins/chef-helpers/ChefHelpers/HasSource

Chef::Node#allies

The node.allies method returns an array of node's allies. These are: all nodes in the same environment (if the environment is not _default), plus nodes specified by allies attribute. The allies attribute - if set - should be an array of node names or node search queries; the named nodes and search results will be added to node's allies.

This is mostly useful when defining firewall or other access rules, to easily limit access to insides of a cluster plus a handful of friendly machines.

Chef::Node#ip_for

The node.ip_for(other_node) method decides, which IP address should the node use to contact the other node, and returns this IP as a string. It is particularly useful when your setup spans across cloud availability zones or different providers. At the moment only EC2 and nodes with public ipaddress are supported; suggestions are welcome.

If both nodes are on EC2 and in the same region, then other node's ec2.local_ipv4 attribute is used. Otherwise, if other node is a cloud instance, its cloud_public.ipv4 attribute is used. Otherwise, other node's ipaddress is used.

JSONPath access to attributes

The Chef::Node class is monkey-patched to allow easy deep access to the attributes using the JSONPath syntax:

chef > require 'chef-helpers'
 => true 
chef > node['$..name']
 => ["portinari-2.local", "Java(TM) SE Runtime Environment", "Java HotSpot(TM) 64-Bit Server VM", "Darwin"] 
chef > node['$.kernel.name']
 => ["Darwin"] 

Regular access to attributes is preserved; JSONPath is used only when the attribute name starts with $ character, or if a JSONPath instance is used for indexing.

The jsonpath gem is used for the implementation. While the original gem allows modification, it's not straightforward to achieve with Chef's attributes, so only reading attributes with JSONPath is supported.

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request