Merge "Support get volume metadata summary"

specs/pike/support-get-volume-metadata-summary.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
+
+===================================
+Support get volume metadata summary
+===================================
+
+https://blueprints.launchpad.net/cinder/+spec/metadata-for-volume-summary
+
+
+Support get volumes' metadata through volume summary API.
+
+Problem description
+===================
+
+Currently, Cinder supports filter volumes with metadata. But in some case,
+users don't know what metadata all the volumes contain or what metadata is
+valid to filter volumes. Then users need to show the volumes one by one to get
+the correct metadata, this is really a heavy and unfriendly way. Imaging that
+if there are hundreds of volumes, admin users will take a very long time to
+query all metadata.
+
+Use Cases
+=========
+
+1. For users, they can get all the metadata easily just through one API
+request.
+2. For dashboard, such as Horizon, it can use this metadata information to show
+end users a dropdown list.
+
+Proposed change
+===============
+
+1. DB layer change:
+    All the volumes' metadata can be got by the sql query.
+
+2. API layer change:
+    Add a new micro version. Add "metadata" to volume-summary API response
+    body. The body will be like::
+
+    "metadata": {"key1": ["value1"],"key2": ["value2", "value3"]}
+
+Alternatives
+------------
+
+Leave as it is. Let the operators get volumes metadata by themselves through
+some peripheral ways. Such as, create a script to call volume-list-detail API
+and then analyse the result one by one.
+
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+A new microversion will be created.
+
+Cinder-client impact
+--------------------
+
+Now both OpenStackClient and CinderClient don't support volume-summary
+command. We can add them as well.
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+There is a little performance influence about volume-summary API since a new
+sql query action will be added.
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  wangxiyuan(wangxiyuan@huawei.com)
+
+Work Items
+----------
+
+* Add a new microversion.
+* Add volumes'metadata to the volume-summary API's response body.
+* Add client side support.
+
+Dependencies
+============
+
+None
+
+Testing
+=======
+
+* Add unit tests.
+
+Documentation Impact
+====================
+
+Update API documentation.
+
+References
+==========
+
+None