Chef::Rewind

This adds a simple function to the Chef library scope to rewind an existing resource. If the given resource does not exist, a Chef::Exceptions::ResourceNotFound exception will be raised.

This function is designed to assist the library cookbook pattern.

Effectively, the rewind resource allows you to monkeypatch a cookbook that you would rather not modify directly. It will modify some properties of a resource, during the complile phase, before chef-client actually starts the run phase.

Installation

Add this line to your application's Gemfile:

gem 'chef-rewind'

And then execute:

$ bundle

Or install it yourself as:

$ gem install chef-rewind

Usage

# file postgresql/recipes/server.rb
user "postgres" do
  uid  26
  home '/home/postgres'
  supports  :manage_home => true
end

# file my-postgresql/recipes/server.rb
chef_gem "chef-rewind"
require 'chef/rewind'

include_recipe "postgresql::server"

rewind "user[postgres]" do
  home '/var/lib/pgsql/9.2'
end

The user "postgres" will act once with the home directory '/var/lib/pgsql/9.2 and the cookbook_name attribute is now "my-postgresql" instead of "postgresql". This last part is particularly important for templates and cookbook files.

Gotchas Important

The rewind method does not automatically change the cookbook_name attribute for a resource to the current cookbook. Doing so could cause some unexpected behavior, particularly for less expert chef users.

Example 

# file postgresql/recipes/server.rb
template "/var/pgsql/data/postgresql.conf" do
  source  "postgresql.conf.erb"
  owner "postgres"
end

# file my-postgresql/recipes/server.rb
chef_gem "chef-rewind"
require 'chef/rewind'

include_recipe "postgresql::server"
# my-postgresql.conf.erb located inside my-postgresql/templates/default/my-postgresql.conf.erb
rewind :template => "/var/pgsql/data/postgresql.conf" do
  source "my-postgresql.conf.erb"
  cookbook_name "my-postgresql"
end

If you do not specify cookbook_name the rewind function will likely return an error since Chef will look in the postgresql cookbook for the source file and not in the my-postgresql cookbook.

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