Deleting volume metadata keys with a single request

Deleting multiple volume metadata keys with a single request
to improve performance.

Related blueprint: delete-multiple-metadata-keys

Change-Id: Iddff8ff3ee4d8690f6ec9d3f45181f1f6e7c1ff1

specs/newton/delete-multiple-metadata-keys.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
+
+
+====================================
+Delete multiple volume metadata keys
+====================================
+
+https://blueprints.launchpad.net/cinder/+spec/delete-multiple-metadata-keys
+
+Problem description
+====================
+The current implementation of Cinder API functionality supports deleting of
+multiple volume metadata as multiple requests for deleting only one metadata
+key with a request. The more keys are necessary to remove, the more API
+requests and DB queries are needed. It would be more efficient to delete
+multiple metadata keys with a single request at a time.
+
+Use Cases
+=========
+
+Deleting multiple volume metadata keys with a single request.
+
+Proposed change
+================
+To delete multiple metadata items without affecting the remaining ones,
+just update the metadata items with the updated complete list of ones
+(without items to delete) in the body of the request. On success, the
+server responds with a 200 status code.
+
+.. note:: A PUT request should use etags to avoid the lost update problem.
+
+Alternatives
+------------
+Have a request that deletes all keys rather than a specified list as an
+option.
+
+Data model impact
+-----------------
+None
+
+REST API impact
+---------------
+The existing API for update metadata will be used in this case. The API
+call will fail in the case some of the items that are specified to delete
+does not exist. The API call will send the set of keys that are supposed
+to be updated and ignore missing keys.
+
+Security impact
+---------------
+None
+
+Notifications impact
+--------------------
+One delete notification will be emitted per metadata item deleted as today.
+
+Other end user impact
+---------------------
+A user will have new API.
+
+Performance Impact
+------------------
+The deleting of a volume metadata keys with a single request allows to
+improve performance by reducing DB calls. It's very important in case with
+many keys. Better performance due to fewer request round trips.
+
+Other deployer impact
+---------------------
+None
+
+Developer impact
+----------------
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+Primary assignee:
+Yuriy Nesenenko(ynesenenko@mirantis.com)
+
+Work Items
+----------
+* Extend python-cinderclient to support new API.
+* Add unit and tempest tests.
+
+Dependencies
+============
+
+Depends on Cinder API microversion.
+Depends on API WG patch https://review.openstack.org/281511/
+Depends on API WG patch https://review.openstack.org/301846/
+
+Testing
+=======
+
+Unit and functional tests are needed to ensure response is working correctly.
+
+Documentation Impact
+====================
+
+Documents concerning the API will need to reflect these changes.
+
+References
+==========
+
+None