Spec: Add a "delete" method to the v2 storage interface

See "specs/train/add_delete_method_v2_storage.rst" for details.

Change-Id: I9b2531225895a4f8769112078f4fc4e443a31696
Story: 2005395
Task: 30791

specs/template.rst

@@ -173,7 +173,7 @@ security best practices.  For further information, feel free to reach out
 to the OpenStack Security Group at openstack-security@lists.openstack.org.
 
 Notifications Impact
-----------------------------
+--------------------
 
 Please specify any changes to notifications or auditing. Be that an extra
 notification, changes to an existing notification, or removing a notification.

specs/train/add_delete_method_v2_storage.rst

@@ -0,0 +1,119 @@
+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=================================================
+Add a "delete" method to the v2 storage interface
+=================================================
+
+https://storyboard.openstack.org/#!/story/2005395
+
+Problem Description
+===================
+
+.. note:: This spec is the detailed implementation of one part of a larger
+          spec. If you haven't read it yet, please see
+          https://specs.openstack.org/openstack/cloudkitty-specs/specs/train/reset_scope_state.html
+
+Currently, there is no way to delete data from a v2 storage backend *via*
+cloudkitty. However, this is required in order to reset the state of a
+scope (see note above).
+
+Proposed Change
+===============
+
+A ``delete`` method will be added to the v2 storage interface and implemented
+in the v2 storage drivers. It will take three parameters:
+
+* ``begin`` (datetime object, optional): The start of the period for which data
+  should be deleted.
+
+* ``end`` (datetime object, optional): The end of the period for which data
+  should be deleted.
+
+* ``filters`` (dict, optional): A dict of optional filters allowing to select
+  data marked for deletion.
+
+Alternatives
+------------
+
+None.
+
+Data model impact
+-----------------
+
+No changes will be made to the data model. However, it will be possible to
+delete data from the storage backend through cloudkitty now.
+
+REST API impact
+---------------
+
+None. Described in another spec.
+
+Security impact
+---------------
+
+None. API security impact is described in other specs.
+
+Notifications Impact
+--------------------
+
+None. Described in another spec.
+
+Other end user impact
+---------------------
+
+None.
+
+Performance Impact
+------------------
+
+Data deletion may slow down and put some load on the storage backend.
+
+Other deployer impact
+---------------------
+
+None.
+
+Developer impact
+----------------
+
+Changes related to scope state reset will need to be rebased on this change.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  peschk_l
+
+Work Items
+----------
+
+Add the ``delete`` method to the v2 storage interface and implement it in the
+InfluxDB storage driver.
+
+Dependencies
+============
+
+Spec: allowing to get/reset the state of a scope. https://specs.openstack.org/openstack/cloudkitty-specs/specs/train/reset_scope_state.html
+
+Testing
+=======
+
+In addition to unit tests, Tempest scenarios testing the whole scope state
+reset action will be added.
+
+Documentation Impact
+====================
+
+The ``delete`` method will be added to the autogenerated documentation.
+
+References
+==========
+
+Spec: allowing to get/reset the state of a scope. https://specs.openstack.org/openstack/cloudkitty-specs/specs/train/reset_scope_state.html