Restrict CONF.quota.driver to DB and noop quota drivers

The quota driver config option was deprecated in Newton via
change 430638888c. That was a
bit wrong in that the config option shouldn't have been
deprecated since we still use it, but we wanted to deprecate
the ability to load custom quota driver classes, which is done
in this change.

To be clear, this doesn't remove the option nor the ability
to configure the quota driver, it only removes the ability
to class-load out of tree quota drivers.

Change-Id: I021a2bcb923739409b393cbb2684ffdf20180f73

nova/conf/quota.py

@@ -287,24 +287,21 @@ to help keep quota usage up-to-date and reduce the impact of out of sync usage
 issues. Note that quotas are not updated on a periodic task, they will update
 on a new reservation if max_age has passed since the last reservation.
 """),
-# TODO(pumaranikar): Add a new config to select between the db_driver and
-# the no_op driver using stevedore.
     cfg.StrOpt('driver',
-        default='nova.quota.DbQuotaDriver',
-        deprecated_for_removal=True,
-        deprecated_since='14.0.0',
-        deprecated_group='DEFAULT',
-        deprecated_name='quota_driver',
-        help="""
-The quota enforcer driver.
-
+               default='nova.quota.DbQuotaDriver',
+               choices=('nova.quota.DbQuotaDriver',
+                        'nova.quota.NoopQuotaDriver'),
+               help="""
 Provides abstraction for quota checks. Users can configure a specific
 driver to use for quota checks.
 
 Possible values:
 
-* nova.quota.DbQuotaDriver (default) or any string representing fully
-  qualified class name.
+* nova.quota.DbQuotaDriver: Stores quota limit information
+  in the database and relies on the quota_* configuration options for default
+  quota limit values. Counts quota usage on-demand.
+* nova.quota.NoopQuotaDriver: Ignores quota and treats all resources as
+  unlimited.
 """),
     cfg.BoolOpt('recheck_quota',
         default=True,

nova/quota.py

@@ -20,7 +20,6 @@ import copy
 
 from oslo_log import log as logging
 from oslo_utils import importutils
-import six
 
 import nova.conf
 from nova import context as nova_context
@@ -995,21 +994,18 @@ class CountableResource(AbsoluteResource):
 class QuotaEngine(object):
     """Represent the set of recognized quotas."""
 
-    def __init__(self, quota_driver_class=None):
+    def __init__(self, quota_driver=None):
         """Initialize a Quota object."""
         self._resources = {}
-        self._driver_cls = quota_driver_class
-        self.__driver = None
+        # NOTE(mriedem): quota_driver is ever only supplied in tests with a
+        # fake driver.
+        self.__driver = quota_driver
 
     @property
     def _driver(self):
         if self.__driver:
             return self.__driver
-        if not self._driver_cls:
-            self._driver_cls = CONF.quota.driver
-        if isinstance(self._driver_cls, six.string_types):
-            self._driver_cls = importutils.import_object(self._driver_cls)
-        self.__driver = self._driver_cls
+        self.__driver = importutils.import_object(CONF.quota.driver)
         return self.__driver
 
     def register_resource(self, resource):

nova/tests/unit/compute/test_compute_cells.py

@@ -66,7 +66,7 @@ def stub_call_to_cells(context, instance, method, *args, **kwargs):
     # Use NoopQuotaDriver in child cells.
     saved_quotas = quota.QUOTAS
     quota.QUOTAS = quota.QuotaEngine(
-            quota_driver_class=quota.NoopQuotaDriver())
+            quota_driver=quota.NoopQuotaDriver())
     compute_api.QUOTAS = quota.QUOTAS
     try:
         return fn(context, instance, *args, **kwargs)
@@ -88,7 +88,7 @@ def stub_cast_to_cells(context, instance, method, *args, **kwargs):
     # Use NoopQuotaDriver in child cells.
     saved_quotas = quota.QUOTAS
     quota.QUOTAS = quota.QuotaEngine(
-            quota_driver_class=quota.NoopQuotaDriver())
+            quota_driver=quota.NoopQuotaDriver())
     compute_api.QUOTAS = quota.QUOTAS
     try:
         fn(context, instance, *args, **kwargs)

nova/tests/unit/test_quota.py

@@ -489,15 +489,8 @@ class QuotaEngineTestCase(test.TestCase):
         self.assertEqual(quota_obj._resources, {})
         self.assertIsInstance(quota_obj._driver, quota.DbQuotaDriver)
 
-    def test_init_override_string(self):
-        quota_obj = quota.QuotaEngine(
-            quota_driver_class='nova.tests.unit.test_quota.FakeDriver')
-
-        self.assertEqual(quota_obj._resources, {})
-        self.assertIsInstance(quota_obj._driver, FakeDriver)
-
     def test_init_override_obj(self):
-        quota_obj = quota.QuotaEngine(quota_driver_class=FakeDriver)
+        quota_obj = quota.QuotaEngine(quota_driver=FakeDriver)
 
         self.assertEqual(quota_obj._resources, {})
         self.assertEqual(quota_obj._driver, FakeDriver)
@@ -528,7 +521,7 @@ class QuotaEngineTestCase(test.TestCase):
         context = FakeContext('test_project', 'test_class')
         driver = FakeDriver(by_user=dict(
                 fake_user=dict(test_resource=42)))
-        quota_obj = quota.QuotaEngine(quota_driver_class=driver)
+        quota_obj = quota.QuotaEngine(quota_driver=driver)
         result = quota_obj.get_by_project_and_user(context, 'test_project',
                                        'fake_user', 'test_resource')
 
@@ -542,7 +535,7 @@ class QuotaEngineTestCase(test.TestCase):
         context = FakeContext('test_project', 'test_class')
         driver = FakeDriver(by_project=dict(
                 test_project=dict(test_resource=42)))
-        quota_obj = quota.QuotaEngine(quota_driver_class=driver)
+        quota_obj = quota.QuotaEngine(quota_driver=driver)
         result = quota_obj.get_by_project(context, 'test_project',
                                           'test_resource')
 
@@ -555,7 +548,7 @@ class QuotaEngineTestCase(test.TestCase):
         context = FakeContext('test_project', 'test_class')
         driver = FakeDriver(by_class=dict(
                 test_class=dict(test_resource=42)))
-        quota_obj = quota.QuotaEngine(quota_driver_class=driver)
+        quota_obj = quota.QuotaEngine(quota_driver=driver)
         result = quota_obj.get_by_class(context, 'test_class', 'test_resource')
 
         self.assertEqual(driver.called, [
@@ -564,7 +557,7 @@ class QuotaEngineTestCase(test.TestCase):
         self.assertEqual(result, 42)
 
     def _make_quota_obj(self, driver):
-        quota_obj = quota.QuotaEngine(quota_driver_class=driver)
+        quota_obj = quota.QuotaEngine(quota_driver=driver)
         resources = [
             quota.AbsoluteResource('test_resource4'),
             quota.AbsoluteResource('test_resource3'),

releasenotes/notes/rocky-quota-driver-config-6459e19ef2b43aa2.yaml

@@ -0,0 +1,11 @@
+---
+upgrade:
+  - |
+    The ``[quota]/driver`` configuration option is no longer deprecated
+    but now only allows one of two possible values:
+
+    * ``nova.quota.DbQuotaDriver``
+    * ``nova.quota.NoopQuotaDriver``
+
+    This means it is no longer possible to class-load custom out-of-tree
+    quota drivers.