Document notification_driver possible values

Add list of drivers to help and FAQ.

Closes-Bug: #1440480
Change-Id: Ia0ea4693f88aa7550e55e7fb63111065ad9b6c3b

doc/source/FAQ.rst

@@ -29,3 +29,13 @@ automatically for each of these topics. To change the queue names,
 change the notification topic using the ``notification_topics``
 configuration option. The option accepts a list of values, so it is
 possible to publish to multiple topics.
+
+What are the other choices of notification drivers available?
+=============================================================
+
+- messaging    Send notifications using the 1.0 message format.
+- messagingv2  Send notifications using the 2.0 message format (with a message envelope).
+- routing      Configurable routing notifier (by priority or event_type).
+- log          Publish notifications via Python logging infrastructure.
+- test         Store notifications in memory for test verification.
+- noop         Disable sending notifications entirely.

oslo_messaging/notify/notifier.py

@@ -29,7 +29,9 @@ from oslo_messaging import serializer as msg_serializer
 _notifier_opts = [
     cfg.MultiStrOpt('notification_driver',
                     default=[],
-                    help='Driver or drivers to handle sending notifications.'),
+                    help='The Drivers(s) to handle sending notifications. '
+                         'Possible values are messaging, messagingv2, routing,'
+                         'log, test, noop'),
     cfg.ListOpt('notification_topics',
                 default=['notifications', ],
                 deprecated_name='topics',