Enable custom resource classes in quotas spec

specs/quota-custom-resource-class.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
+
+===============================
+Quota per custom resource class
+===============================
+
+https://blueprints.launchpad.net/nova/+spec/tbd
+
+With this blueprint we introduce a way to define and use quotas per custom
+resources classes, so that operator can limit how DC resources are utilized.
+
+Problem description
+===================
+
+Currently, quotas in Nova are restricted only for selected resources like CPU
+cores, ram, floating IPs, and for non-resource things: number of instances,
+metadata items, key pairs, server groups and so on. Introducing `custom
+resource classes`_ within placement service, allows operator to create
+resources, which are unknown to the quota mechanism.
+
+Use Cases
+---------
+
+As an operator I’d like to define quota for custom resource classes, so that
+amount of such resources can be limited per project and/or per user.
+
+Proposed change
+===============
+
+We propose to add ability for dynamically adding custom resource classes to
+resources which ``QuotaEngine`` can handle, and track the usage like all the
+other resources.
+
+Alternatives
+------------
+
+As an alternative, we could leverage Quota Classes to be used instead of
+affecting QuotaEngine, although it will require slightly more effort in
+implementation, since there is no tracking of resources within that model, and,
+what's more important, quota classes are used for setting/changing defaults
+which comes from configuration.
+
+We could also make a custom scheduler filter, which would count the resources
+usage and limits for anything operator needs, however this will have
+performance impact, since originally limits are checked during API call, and
+scheduler filters are executed on scheduling phase.
+
+Data model impact
+-----------------
+
+New attribute ``uuid`` will be added to the ``Quotas`` object.
+
+REST API impact
+---------------
+
+New API methods will be introduced to list/add/delete/modify to the
+``os-quota-sets`` for a project and optionally user.
+
+Optionally, ``GET /os-quota-sets/{tenant_id}`` will provide a list of custom
+resources in under ``quota_set["custom_resources"]`` key in JSON response.
+
+* Getting the list of defined custom resources in limits:
+
+  .. code::
+
+     GET /os-quota-sets/{tenant_id}/custom_resource
+
+     200 OK
+     Content-Type: application/json
+
+     {
+         "custom_resources": [
+             {
+                 "name": "name of custom resource class",
+                 "UUID": "uuid of custom resource class from resource provider",
+                 "limit": 0
+             },
+              ...
+         ]
+     }
+
+* Getting a definition of the particular custom resources in limits:
+
+  .. code::
+
+     GET /os-quota-sets/{tenant_id}/custom_resource/{resource_uuid}
+
+     200 OK
+     Content-Type: application/json
+
+     {
+         "name": "name of custom resource class",
+         "UUID": "uuid of custom resource class from resource provider",
+         "limit": 0
+     }
+
+* Adding custom resource to quotas:
+
+  .. code::
+
+     POST /os-quota-sets/{tenant_id}/custom_resource
+
+  with a payload:
+
+  .. code::
+
+     Content-Type: application/json
+
+     {
+         "name": "name of custom resource class",
+         "UUID": "uuid of custom resource class from resource provider",
+         "limit": 0
+     }
+
+  Response body is empty. Response code will be ``201 Created`` on success, or
+  ``409 Conflict`` if there is resource with such UUID already created.
+
+  * ``200 OK`` on success.
+  * ``400 Bad Request`` for bad or invalid syntax.
+  * ``409 Conflict`` if there is resource with such UUID already created.
+
+* Updating limit value for the custom resource:
+
+  .. code::
+
+     PUT /os-quota-sets/{tenant_id}/custom_resource/{resource_uuid}
+
+  with a payload:
+
+  .. code::
+
+     Content-Type: application/json
+
+     {
+         "limit": 10
+     }
+
+  Response body is empty. Response code will be:
+
+  * ``200 OK`` on success.
+  * ``400 Bad Request`` for bad or invalid syntax.
+  * ``404 Not Found`` on undefined custom resource.
+
+* Removing the custom resource from limits:
+
+  .. code::
+
+     DELETE /os-quota-sets/{tenant_id}/custom_resource/{resource_uuid}
+
+  Request body is empty. Response body is empty. Response code will be:
+
+  * ``200 OK`` on success.
+  * ``404 Not Found`` on undefined custom resource.
+
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+Nova-client and/or openstack client should be updated to be able to provide
+custom resource class as an argument for ``quota*`` subcommands.
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+Upgrade impact
+--------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  <launchpad-id or None>
+
+Other contributors:
+  <launchpad-id or None>
+
+Work Items
+----------
+
+* DB changes
+* Hook to register custom resource class in ``QuotaEngine._resources`` dict
+* API implementation
+
+Dependencies
+============
+
+None
+
+Testing
+=======
+
+Unit test have to be provided.
+
+Documentation Impact
+====================
+
+Documentation of additional API calls have to be updated.
+
+References
+==========
+
+None
+
+History
+=======
+
+.. list-table:: Revisions
+   :header-rows: 1
+
+   * - Release Name
+     - Description
+   * - Rocky
+     - Introduced
+
+.. _custom resource classes: https://specs.openstack.org/openstack/nova-specs/specs/ocata/implemented/custom-resource-classes.html