A common use-case for applications is to have Chef configure your systems and use Capistrano to deploy the applications that run on them.
Capistrano Chef is a Capistrano 3 extension that makes Chef and Capistrano 3 get along like best buds.
Note: this latest version of this gem will not work for Capistrano versions prior to 3. Please use version 0.1.0 or earlier if you want to use Capistrano Chef with Capistrano 2.
The Capistrano configuration has a facility to specify the roles for your application and which servers are members of those roles. Chef has its own roles. If you're using both Chef and Capistrano, you don't want to have to tell them both about which servers you'll be deploying to, especially if they change often.
capistrano-chef provides some helpers to query your Chef server from Capistrano to define these roles.
A normal deploy.rb in an app using capistrano defines a roles like this:
role :web, '10.0.0.2', '10.0.0.3'
role :db, '10.0.0.2', :primary => true
Using capistrano-chef, you can do this:
require 'capistrano/chef'
chef_role :web 'roles:web'
chef_role :db, 'roles:database_master', :primary => true,
:attribute => :private_ip,
:limit => 1
Use a Hash to get a specific network interface: (the Hash must be in the form of { 'interface-name' => 'network-family-name' })
chef_role :web, 'roles:web', :attribute => { :eth1 => :inet }
For a more deep and complex attribute search, use a Proc object:
(Example, to get 'eth1.inet.ipaddress': http://wiki.opscode.com/display/chef/Search#Search-SearchonlyreturnsIPAddressoftheNode%2Cnotofaspecificinterface)
chef_role :web, 'roles:web', :attribute => Proc.new do |n|
n["network"]["interfaces"]["eth1"]["addresses"].select{|address, data| data["family"] == "inet" }.keys.first
end
This defines the same roles using Chef's search feature. Nodes are searched using the given query. The node's ipaddress attribute is used by default, but other attributes can be specified in the options as shown in the examples above. The rest of the options are the same as those used by Capistrano.
You can also define multiple roles at the same time if the host list is identical. Instead of running multiple searches to the Chef server, you can pass an Array to chef_role:
chef_role [:web, :app], 'roles:web'
A Chef server is expected to be available and Knife is used to configure the extension, looking for knife.rb the keys needed in .chef in the current directory or one its parent directories.
If you're using Opscode Hosted Chef these files will be provided for you. If not, the configuration can be generated with knife configure -i. See the Chef Documentation for more details.
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