gistfile1.rb

  def get_node(instance)
    query_node = Chef::Search::Query.new
    query = "name:#{instance}"
    if block_given?
      query_node.search('node', query) do |node|
        yield node
      end
    else
      query_node.search('node', query).first.first
    end
  end

  def set_role!(node_item, new_role)
    node_item.run_list("role[#{new_role}]")
    node_item.save
  end

  def switch_role!(instance, role)
    run_list = ""
    fqdn = nil
    while "role[#{role}]" != run_list
      get_node(instance) do |node|
        set_role!(node, role)
      end
      get_node(instance) do |node|
        ui.msg "New run_list: #{node.run_list}"
        run_list = node.run_list.to_s
        fqdn = node.fqdn
      end
    end
    return fqdn, role
  end