Update metering agent to use stevedore alias for driver

Currently the metering agent is using the old import method,
use stevedore instead.

DocImpact

Two places in the networking guide should change to
'driver = iptables' from current format.

Partial-Bug: #1504536
Change-Id: I1e6d196a3ada8fbfc2b70d6a983984d8db09bbd0

neutron/services/metering/agents/metering_agent.py

@@ -21,9 +21,9 @@ import oslo_messaging
 from oslo_service import loopingcall
 from oslo_service import periodic_task
 from oslo_service import service
-from oslo_utils import importutils
 from oslo_utils import timeutils
 
+from neutron.services.metering.drivers import utils as driverutils
 from neutron._i18n import _, _LE, _LI, _LW
 from neutron.agent.common import config
 from neutron.agent import rpc as agent_rpc
@@ -86,8 +86,8 @@ class MeteringAgent(MeteringPluginRpc, manager.Manager):
         LOG.info(_LI("Loading Metering driver %s"), self.conf.driver)
         if not self.conf.driver:
             raise SystemExit(_('A metering driver must be specified'))
-        self.metering_driver = importutils.import_object(
-            self.conf.driver, self, self.conf)
+        self.metering_driver = driverutils.load_metering_driver(self,
+                                                                self.conf)
 
     def _metering_notification(self):
         for label_id, info in self.metering_infos.items():

neutron/services/metering/drivers/utils.py

@@ -0,0 +1,42 @@
+# Copyright 2017 Red Hat, Inc.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from oslo_log import log as logging
+
+from neutron._i18n import _LE
+from neutron.common import utils as utils
+
+
+LOG = logging.getLogger(__name__)
+
+METERING_NAMESPACE = 'neutron.services.metering_drivers'
+
+
+def load_metering_driver(plugin, conf):
+    """Load metering driver
+
+    :param plugin: the metering plugin
+    :param conf: driver configuration object
+    :raises SystemExit of 1 if driver cannot be loaded
+    """
+
+    try:
+        loaded_class = utils.load_class_by_alias_or_classname(
+                METERING_NAMESPACE, conf.driver)
+        return loaded_class(plugin, conf)
+    except ImportError:
+        LOG.error(_LE("Error loading metering driver '%s'"),
+                  conf.driver)
+        raise SystemExit(1)

neutron/tests/unit/services/metering/agents/test_metering_agent.py

@@ -54,7 +54,7 @@ class TestMeteringOperations(base.BaseTestCase):
 
         self.noop_driver = ('neutron.services.metering.drivers.noop.'
                             'noop_driver.NoopMeteringDriver')
-        cfg.CONF.set_override('driver', self.noop_driver)
+        cfg.CONF.set_override('driver', 'noop')
         cfg.CONF.set_override('measure_interval', 0)
         cfg.CONF.set_override('report_interval', 0)
 
@@ -230,9 +230,7 @@ class TestMeteringDriver(base.BaseTestCase):
         super(TestMeteringDriver, self).setUp()
         metering_agent_config.register_metering_agent_opts()
 
-        self.noop_driver = ('neutron.services.metering.drivers.noop.'
-                            'noop_driver.NoopMeteringDriver')
-        cfg.CONF.set_override('driver', self.noop_driver)
+        cfg.CONF.set_override('driver', 'noop')
 
         self.agent = metering_agent.MeteringAgent('my agent', cfg.CONF)
         self.driver = mock.Mock()
@@ -244,7 +242,7 @@ class TestMeteringDriver(base.BaseTestCase):
         with mock.patch.object(metering_agent, 'LOG') as log:
             self.agent.add_metering_label(None, ROUTERS)
             log.exception.assert_called_with(mock.ANY,
-                                             {'driver': self.noop_driver,
+                                             {'driver': 'noop',
                                               'func': 'add_metering_label'})
 
     def test_add_metering_label_runtime_error(self):
@@ -253,7 +251,7 @@ class TestMeteringDriver(base.BaseTestCase):
         with mock.patch.object(metering_agent, 'LOG') as log:
             self.agent.add_metering_label(None, ROUTERS)
             log.exception.assert_called_with(mock.ANY,
-                                             {'driver': self.noop_driver,
+                                             {'driver': 'noop',
                                               'func':
                                               'add_metering_label'})
 

releasenotes/notes/metering-driver-stevedore-alias-2c4fdb0556205a3a.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - The metering agent driver can now be specified with a stevedore
+    alias in the ``metering_agent.ini`` file. For example,
+    ``driver = iptables`` instead of
+    ``driver = neutron.services.metering.iptables.iptables_driver:IptablesMeteringDriver``.

setup.cfg

@@ -151,6 +151,9 @@ neutron.agent.firewall_drivers =
     iptables = neutron.agent.linux.iptables_firewall:IptablesFirewallDriver
     iptables_hybrid = neutron.agent.linux.iptables_firewall:OVSHybridIptablesFirewallDriver
     openvswitch = neutron.agent.linux.openvswitch_firewall:OVSFirewallDriver
+neutron.services.metering_drivers =
+    noop = neutron.services.metering.drivers.noop.noop_driver:NoopMeteringDriver
+    iptables = neutron.services.metering.iptables.iptables_driver:IptablesMeteringDriver
 tempest.test_plugins =
     neutron_tests = neutron.tests.tempest.plugin:NeutronTempestPlugin