Remove deprecated ability to load scheduler_host_manager from path

The ability to load the scheduler_host_manager from a random
classpath was deprecated in Mitaka. This removes that ability
so that only the entrypoints in Nova's setup.cfg can be used
to load the scheduler host manager.

The scheduler_host_manager config option is updated to only
allow the choices that are currently in the setup.cfg.

And a release note is added for the upgrade impact of dropping
the deprecated classpath loading ability.

Change-Id: I886c74afac02d100d472b78522e8295748276e4d
Related-Bug: #1403020

nova/conf/scheduler.py

@@ -245,6 +245,7 @@ configuration.
 
 sched_driver_host_mgr_opt = cfg.StrOpt("scheduler_host_manager",
         default="host_manager",
+        choices=("host_manager", "ironic_host_manager"),
         help="""
 The scheduler host manager to use, which manages the in-memory picture of the
 hosts that the scheduler uses.
@@ -255,10 +256,6 @@ namespace 'nova.scheduler.host_manager' of file 'setup.cfg'. For example,
 option as of the Mitaka release is 'ironic_host_manager', which should be used
 if you're using Ironic to provision bare-metal instances.
 
-This option also supports a full class path style, for example
-"nova.scheduler.host_manager.HostManager", but note this support is deprecated
-and will be dropped in the N release.
-
 * Services that use this:
 
     ``nova-scheduler``

nova/scheduler/driver.py

@@ -22,12 +22,10 @@ Scheduler base class that all Schedulers should inherit from
 import abc
 
 from oslo_log import log as logging
-from oslo_utils import importutils
 import six
 from stevedore import driver
 
 import nova.conf
-from nova.i18n import _, _LW
 from nova import objects
 from nova import servicegroup
 
@@ -41,29 +39,10 @@ class Scheduler(object):
     """The base class that all Scheduler classes should inherit from."""
 
     def __init__(self):
-        try:
-            self.host_manager = driver.DriverManager(
-                    "nova.scheduler.host_manager",
-                    CONF.scheduler_host_manager,
-                    invoke_on_load=True).driver
-        # TODO(Yingxin): Change to catch stevedore.exceptions.NoMatches
-        # after stevedore v1.9.0
-        except RuntimeError:
-            # NOTE(Yingxin): Loading full class path is deprecated and
-            # should be removed in the N release.
-            try:
-                self.host_manager = importutils.import_object(
-                    CONF.scheduler_host_manager)
-                LOG.warning(_LW("DEPRECATED: scheduler_host_manager uses "
-                                "classloader to load %(path)s. This legacy "
-                                "loading style will be removed in the "
-                                "N release."),
-                            {'path': CONF.scheduler_host_manager})
-            except (ImportError, ValueError):
-                raise RuntimeError(
-                        _("Cannot load host manager from configuration "
-                          "scheduler_host_manager = %(conf)s."),
-                        {'conf': CONF.scheduler_host_manager})
+        self.host_manager = driver.DriverManager(
+                "nova.scheduler.host_manager",
+                CONF.scheduler_host_manager,
+                invoke_on_load=True).driver
         self.servicegroup_api = servicegroup.API()
 
     def run_periodic_tasks(self, context):

nova/tests/unit/scheduler/test_scheduler.py

@@ -23,7 +23,6 @@ from nova import context
 from nova import objects
 from nova.scheduler import caching_scheduler
 from nova.scheduler import chance
-from nova.scheduler import driver
 from nova.scheduler import filter_scheduler
 from nova.scheduler import host_manager
 from nova.scheduler import ironic_host_manager
@@ -208,23 +207,6 @@ class SchedulerInitTestCase(test.NoDBTestCase):
         self.flags(scheduler_host_manager='nonexist_host_manager')
         self.assertRaises(RuntimeError, self.driver_cls)
 
-    # NOTE(Yingxin): Loading full class path is deprecated and should be
-    # removed in the N release.
-    @mock.patch.object(driver.LOG, 'warning')
-    @mock.patch.object(host_manager.HostManager, '_init_instance_info')
-    @mock.patch.object(host_manager.HostManager, '_init_aggregates')
-    def test_init_using_classpath_to_hostmanager(self,
-                                                 mock_init_agg,
-                                                 mock_init_inst,
-                                                 mock_warning):
-        self.flags(
-            scheduler_host_manager=
-            'nova.scheduler.ironic_host_manager.IronicHostManager')
-        manager = self.driver_cls().host_manager
-        self.assertIsInstance(manager, ironic_host_manager.IronicHostManager)
-        warn_args, kwargs = mock_warning.call_args
-        self.assertIn("DEPRECATED", warn_args[0])
-
 
 class SchedulerTestCase(test.NoDBTestCase):
     """Test case for base scheduler driver class."""

releasenotes/notes/rm-sched-host-mgr-class-load-2a86749a38f0688d.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - The ability to load a custom scheduler host manager via the
+    ``scheduler_host_manager`` configuration option was deprecated
+    in the 13.0.0 Mitaka release and is now removed in the 14.0.0 Newton
+    release.