add getting aodh alarms from notifications

Implements: blueprint aodh-message-bus-notifications
Signed-off-by: dongwenjuan <dong.wenjuan@zte.com.cn>
Change-Id: I2b0ab5023b7182a15fa831fc43d17466fd5149ee

specs/ocata/aodh-message-bus-notifications.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+==============================================
+Get Aodh Alarms From Message Bus Notifications
+==============================================
+
+Get Aodh alarms immediately via notification from the message bus.
+
+Problem description
+===================
+
+Currently Aodh datasource queries Aodh alarms periodically. It is not in time
+and it is also not efficient, since most query will get no change when the
+interval of alarm evaluation in Aodh is larger than the interval of pulling
+Aodh alarm in Vitrage.
+
+Proposed change
+===============
+
+Aodh `update_method` in vitrage config file will be configured with:
+/etc/vitrage/vitrage.conf
+```
+    [aodh]
+    update_method = push
+
+Add a new notification topic in Aodh config file:
+/etc/aodh/aodh.conf
+```
+    [oslo_messaging_notifications]
+    topics = vitrage_notifications
+
+Vitrage listener will get the alarm events from the message bus. Aodh driver
+will filter the needed event types, enrich the events and then send them to
+the queue for the Aodh transformer to create, update or delete the entity 
+vertex.
+
+Alternatives
+------------
+
+None
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+None
+
+Security impact
+---------------
+
+None
+
+Pipeline impact
+---------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance/Scalability Impacts
+-------------------------------
+
+performance improvement of getting Aodh alarms
+
+
+Other deployer impact
+---------------------
+
+** Config `update_method` as 'push' in `Aodh` section in vitrage config file.
+** Add the `vitrage_notifications` topic in `oslo_messaging_notifications`
+   section in Aodh config file.
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  dongwenjuan <dong.wenjuan@zte.com.cn>
+
+Work Items
+----------
+
+None
+
+Future lifecycle
+================
+
+None
+
+Dependencies
+============
+
+None
+
+Testing
+=======
+
+Unit tests and tempest tests.
+
+Documentation Impact
+====================
+
+Documentation will be modified to describe how to configure the notification
+topics in Aodh when using devstack to deploy OpenStack env.
+
+References
+==========
+
+None