Document how to disable Telemetry and Notifications

In this patch, we document how to disable Telemetry servics and
OpenStack notifications as well.
It also explains how NotificationDriver parameter works.

Change-Id: I049e937fcdeed30f1f8159d118cb302fc23e92d4

doc/source/install/advanced_deployment/disable_telemetry.rst

@@ -0,0 +1,28 @@
+Disable Telemetry
+=================
+
+This guide assumes that your undercloud is already installed and ready to
+deploy an overcloud without Telemetry services.
+
+Deploy your overcloud without Telemetry services
+------------------------------------------------
+
+If you don't need or don't want Telemetry services (Ceilometer, Gnocchi,
+Panko and Aodh), you can disable the services by adding this environment
+file when deploying the overcloud::
+
+    openstack overcloud deploy --templates \
+    -e /usr/share/openstack-tripleo-heat-templates/environments/disable-telemetry.yaml
+
+Disabling Notifications
+~~~~~~~~~~~~~~~~~~~~~~~
+
+When Telemetry is disabled, OpenStack Notifications will be disabled as well, and
+the driver will be set to 'noop' for all OpenStack services.
+If you would like to restore notifications, you would need to set NotificationDriver to
+'messagingv2' in your environment.
+
+.. Warning::
+
+   NotificationDriver parameter can only support 'noop' and 'messagingv2' for now.
+   Also note that 'messaging' driver is obsolete and isn't supported by TripleO.

doc/source/install/advanced_deployment/features.rst

@@ -19,3 +19,4 @@ Documentation on how to enable and configure various features available in
    deployed_server
    security_hardening
    api_policies
+   disable_telemetry