Remove support for single backend config

It was not recommended for some releases, deprecated in Newton, so let's
remove it in Ocata.

Change-Id: If7e76ad904179a89ca98eb81ebe40e0243245672
Related-Bug: 1630975

cinder/cmd/volume.py

@@ -46,7 +46,7 @@ i18n.enable_lazy()
 # Need to register global_opts
 from cinder.common import config  # noqa
 from cinder.db import api as session
-from cinder.i18n import _, _LW
+from cinder.i18n import _, _LE
 from cinder import service
 from cinder import utils
 from cinder import version
@@ -109,15 +109,9 @@ def main():
                 launcher.launch_service(server)
                 service_started = True
     else:
-        LOG.warning(_LW('Configuration for cinder-volume does not specify '
-                        '"enabled_backends", using DEFAULT as backend. '
-                        'Support for DEFAULT section to configure drivers '
-                        'will be removed in the next release.'))
-        server = service.Service.create(binary='cinder-volume',
-                                        coordination=True,
-                                        cluster=CONF.cluster)
-        launcher.launch_service(server)
-        service_started = True
+        LOG.error(_LE('Configuration for cinder-volume does not specify '
+                      '"enabled_backends". Using DEFAULT section to configure '
+                      'drivers is not supported since Ocata.'))
 
     if not service_started:
         msg = _('No volume service(s) started successfully, terminating.')

cinder/tests/unit/test_cmd.py

@@ -156,21 +156,8 @@ class TestCinderVolumeCmd(test.TestCase):
     def test_main(self, log_setup, monkey_patch, service_create,
                   get_launcher):
         CONF.set_override('enabled_backends', None)
-        launcher = get_launcher.return_value
-        server = service_create.return_value
-
-        cinder_volume.main()
-
-        self.assertEqual('cinder', CONF.project)
-        self.assertEqual(CONF.version, version.version_string())
-        log_setup.assert_called_once_with(CONF, "cinder")
-        monkey_patch.assert_called_once_with()
-        get_launcher.assert_called_once_with()
-        service_create.assert_called_once_with(binary='cinder-volume',
-                                               coordination=True,
-                                               cluster=None)
-        launcher.launch_service.assert_called_once_with(server)
-        launcher.wait.assert_called_once_with()
+        self.assertRaises(SystemExit, cinder_volume.main)
+        self.assertFalse(service_create.called)
 
     @mock.patch('cinder.service.get_launcher')
     @mock.patch('cinder.service.Service.create')

releasenotes/notes/remove-single-backend-7bf02e525bbbdd3a.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - Configurations that are setting backend config in ``[DEFAULT]``
+    section are now not supported. You should use ``enabled_backends``
+    option to set up backends.