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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
+
+==========================================
+Backup capability
+==========================================
+
+https://blueprints.launchpad.net/cinder/+spec/discovering-system-capabilities
+
+The spec [1] made a decision that a new API will be created for users or other
+projects to discover system capabilities of Cinder. This spec is a follow-up,
+and defines the new interface.
+
+Problem description
+===================
+Currently Horizon knows whether backup services are enabled through a config
+setting “enable_backup" which needs to set manually. This is not only
+cumbersome but also prone to operator error.
+
+Use Cases
+=========
+
+Horizon can do some queries to know whether backup services are enabled without
+manually setting config file.
+
+Proposed change
+===============
+
+A new API will be added to query system capabilities. At first, the result only
+contains whether backup services are enabled.
+
+Alternatives
+------------
+
+Please see [1].
+
+Data model impact
+-----------------
+
+None.
+
+REST API impact
+---------------
+
+Add a new API to query system capabilities. At first only backup is included.
+
+.. code:: javascript
+
+    GET /capabilities
+
+    {
+        "service": {
+            "volume-backups": {
+                "available": true
+            }
+        }
+    }
+
+Security impact
+---------------
+
+None.
+
+Notifications impact
+--------------------
+
+None.
+
+Other end user impact
+---------------------
+
+User can use the interface to query backup capability.
+
+Performance Impact
+------------------
+
+New API and should not impact existed APIs.
+
+Other deployer impact
+---------------------
+
+Operator no longer has to manually set “enable_backup” in Horizon config
+settings file. Back-compat story for this Horizon config change is out of
+scope for this spec.
+
+
+Developer impact
+----------------
+
+Other capabilities can be added later if needed.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  lixiaoy1
+
+Work Items
+----------
+
+* Add API to query system capabilities, currently only backup.
+* Add test cases.
+* Update API docs.
+
+Dependencies
+============
+
+None.
+
+Testing
+=======
+
+Unit, functional and tempest test cases will be added to validate this new
+API.
+
+Documentation Impact
+====================
+
+* New API and client call in Cinder needs to be documented.
+
+References
+==========
+
+..[1] https://specs.openstack.org/openstack/cinder-specs/specs/newton/discovering-system-capabilities.html