conf: Remove 'db_driver' config opt

This option has been deprecated for a long time and any kinks, where
they existed, should have long since been worked out. Time to kill it.

Change-Id: Ifa686b5ce5e8063a8e5f2f22c89124c1d4083b80

nova/conf/database.py

@@ -21,17 +21,6 @@ from nova.conf import paths
 _DEFAULT_SQL_CONNECTION = 'sqlite:///' + paths.state_path_def('nova.sqlite')
 
 
-# NOTE(sdague): we know of at least 1 instance of out of tree usage
-# for this config in RAX. They used this because of performance issues
-# with some queries. We think the right path forward is fixing the
-# SQLA queries to be more performant for everyone.
-db_driver_opt = cfg.StrOpt('db_driver',
-    default='nova.db',
-    deprecated_for_removal=True,
-    deprecated_since='13.0.0',
-    help='The driver to use for database access')
-
-
 # NOTE(markus_z): We cannot simply do:
 # conf.register_opts(oslo_db_options.database_opts, 'api_database')
 # If we reuse a db config option for two different groups ("api_database"
@@ -115,7 +104,6 @@ def enrich_help_text(alt_db_opts):
 
 def register_opts(conf):
     oslo_db_options.set_defaults(conf, connection=_DEFAULT_SQL_CONNECTION)
-    conf.register_opt(db_driver_opt)
     conf.register_opts(api_db_opts, group=api_db_group)
 
 
@@ -128,6 +116,6 @@ def list_opts():
     # in the "sample.conf" file, I omit the listing of the "oslo_db_options"
     # here.
     enrich_help_text(api_db_opts)
-    return {'DEFAULT': [db_driver_opt],
-            api_db_group: api_db_opts,
-            }
+    return {
+        api_db_group: api_db_opts
+    }

nova/db/base.py

@@ -14,21 +14,14 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-"""Base class for classes that need modular database access."""
+"""Base class for classes that need database access."""
 
-from oslo_utils import importutils
-
-import nova.conf
-
-
-CONF = nova.conf.CONF
+import nova.db
 
 
 class Base(object):
     """DB driver is injected in the init method."""
 
-    def __init__(self, db_driver=None):
+    def __init__(self):
         super(Base, self).__init__()
-        if not db_driver:
-            db_driver = CONF.db_driver
-        self.db = importutils.import_module(db_driver)
+        self.db = nova.db

nova/manager.py

@@ -91,7 +91,7 @@ class ManagerMeta(profiler.get_traced_meta(), type(PeriodicTasks)):
 class Manager(base.Base, PeriodicTasks):
     __trace_args__ = {"name": "rpc"}
 
-    def __init__(self, host=None, db_driver=None, service_name='undefined'):
+    def __init__(self, host=None, service_name='undefined'):
         if not host:
             host = CONF.host
         self.host = host
@@ -99,7 +99,7 @@ class Manager(base.Base, PeriodicTasks):
         self.service_name = service_name
         self.notifier = rpc.get_notifier(self.service_name, self.host)
         self.additional_endpoints = []
-        super(Manager, self).__init__(db_driver)
+        super(Manager, self).__init__()
 
     def periodic_tasks(self, context, raise_on_error=False):
         """Tasks to be run at a periodic interval."""

releasenotes/notes/remove-db_driver-config-opt-50110843b3221fc4.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - |
+    The ``db_driver`` configuration option was deprecated in a previous release
+    and has now been removed. This option allowed you to replace the SQLAlchemy
+    database layer with one of your own. The approach was deprecated and
+    unsupported, and it is now time to remove it completely.