Migrate to use Aodhclient for alarm resources

Blueprint migrate-to-use-aodh-for-alarms

Change-Id: I34b9ddb6cf03a8252276152f47802559fd9e031b

specs/newton/migrate-to-use-aodh.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
+
+
+===================
+Migrate to use Aodh
+===================
+
+Include the URL of your launchpad blueprint:
+
+https://blueprints.launchpad.net/heat/+spec/migrate-to-use-aodh-for-alarms
+
+This blueprint will migrate to use Aodh service directly for alarm resources.
+
+
+Problem description
+===================
+
+Ceilometer has moved all the alarming code and subsystem to the Aodh project:
+https://review.openstack.org/#/c/196552
+https://review.openstack.org/#/c/197161
+
+Although now we can use ceilometer-client to redirect to Aodh endpoint when
+creating alarm resources:
+https://review.openstack.org/#/c/202938
+
+But there are some reasons I believe we should to migrate to use
+Aodh service directly:
+
+1. Ceilometer team plans to deprecate/remove the function of redirecting,
+   maybe in two releases
+
+2. Aodh is the independent alarming service
+
+
+Proposed change
+===============
+
+1. This spec proposes to use Aodh service for alarm resources.
+For mostly alarm resources (except OS::Ceilometer::CombinationAlarm)
+can compatible with the current implementation.
+
+2. The problem is that we can't manage the OS::Ceilometer::CombinationAlarm
+by Aodh client, because Aodh client does not support. The combination alarm
+is deprecated and disabled by default in Aodh, and the new composite rule
+alarm is recommended to use. So this spec proposes to deprecate
+OS::Ceilometer::CombinationAlarm and to add the new composite rule
+alarm resource plug-in named 'OS::Aodh::CompositeAlarm'
+
+
+Alternatives
+------------
+
+None.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  huangtianhua@huawei.com
+  liusheng@huawei.com
+
+
+Milestones
+----------
+
+  newton-2
+
+Work Items
+----------
+
+1. Add Aodh client plugin.
+
+2. Migrate to use Aodh service to manage the alarm resources's lifecycle,
+   including threshold alarm , composite alarm, gnocchi_resources_threshold
+   alarm, gnocchi_aggregation_by_metrics_threshold alarm and
+   gnocchi_aggregation_by_resources_threshold alarm.
+
+3. Set resource_registry to map Ceilometer alarms to Aodh alarms, to make
+   sure older templates with Ceilometer alarms still work.
+
+4. Add corresponding tests.
+
+5. Modify all related docs with word 'Ceilometer'.
+
+
+Dependencies
+============
+
+None