crowbar: Generate an event when a cluster config is changed

For now, we're only interested in changes in the public/admin name of
haproxy. This event will be consumed by OpenStack barclamp so they know
that the endpoint is changing.

We may add other relevant attributes to the event later on if required.

crowbar_framework/app/models/pacemaker_service.rb

@@ -15,6 +15,8 @@
 # limitations under the License.
 #
 
+require "set"
+
 class PacemakerService < ServiceObject
   def initialize(thelogger)
     super(thelogger)
@@ -439,6 +441,30 @@ def apply_role_post_chef_call(old_role, role, all_nodes)
 
     apply_cluster_roles_to_new_nodes_post_chef_call(role)
 
+    # let's not consider the first time the proposal is applied as worth
+    # sending an event
+    if !old_role.nil? && !role.nil?
+      old_attributes = old_role.default_attributes["pacemaker"]
+      new_attributes = role.default_attributes["pacemaker"]
+
+      changed_attributes = Set.new
+
+      if old_attributes["haproxy"]["public_name"] != new_attributes["haproxy"]["public_name"]
+        changed_attributes.add("haproxy.public_name")
+      end
+      if old_attributes["haproxy"]["admin_name"] != new_attributes["haproxy"]["admin_name"]
+        changed_attributes.add("haproxy.admin_name")
+      end
+
+      unless changed_attributes.empty?
+        details = {
+          cluster: "#{PacemakerServiceObject.cluster_key}:#{role.inst}",
+          attributes: changed_attributes
+        }
+        Crowbar::EventDispatcher.trigger_hooks("cluster_changed", details)
+      end
+    end
+
     @logger.debug("Pacemaker apply_role_post_chef_call: leaving")
   end