Merge "Use stevedore for scheduler host manager"

nova/conf/scheduler.py

@@ -245,12 +245,20 @@ configuration.
 """)
 
 sched_driver_host_mgr_opt = cfg.StrOpt("scheduler_host_manager",
-        default="nova.scheduler.host_manager.HostManager",
+        default="host_manager",
         help="""
-The scheduler host manager class to use. Aside from the default, the only other
-option as of the Mitaka release is
-'nova.scheduler.ironic_host_manager.IronicHostManager', which should be used if
-you're using Ironic to provision bare-metal instances.
+The scheduler host manager to use, which manages the in-memory picture of the
+hosts that the scheduler uses.
+
+The option value should be chosen from one of the entrypoints under the
+namespace 'nova.scheduler.host_manager' of file 'setup.cfg'. For example,
+'host_manager' is the default setting. Aside from the default, the only other
+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/driver.py

@@ -21,23 +21,49 @@ 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
 
 CONF = nova.conf.CONF
 
+LOG = logging.getLogger(__name__)
+
 
 @six.add_metaclass(abc.ABCMeta)
 class Scheduler(object):
     """The base class that all Scheduler classes should inherit from."""
 
     def __init__(self):
-        self.host_manager = importutils.import_object(
-                CONF.scheduler_host_manager)
+        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.servicegroup_api = servicegroup.API()
 
     def run_periodic_tasks(self, context):

nova/tests/unit/scheduler/test_scheduler.py

@@ -21,7 +21,9 @@ import mock
 
 from nova import context
 from nova import objects
+from nova.scheduler import driver
 from nova.scheduler import host_manager
+from nova.scheduler import ironic_host_manager
 from nova.scheduler import manager
 from nova import servicegroup
 from nova import test
@@ -117,6 +119,54 @@ class SchedulerManagerTestCase(test.NoDBTestCase):
                                               mock.sentinel.instance_uuids)
 
 
+class SchedulerInitTestCase(test.NoDBTestCase):
+    """Test case for base scheduler driver initiation."""
+
+    driver_cls = fakes.FakeScheduler
+
+    @mock.patch.object(host_manager.HostManager, '_init_instance_info')
+    @mock.patch.object(host_manager.HostManager, '_init_aggregates')
+    def test_init_using_default_hostmanager(self,
+                                            mock_init_agg,
+                                            mock_init_inst):
+        manager = self.driver_cls().host_manager
+        self.assertIsInstance(manager, host_manager.HostManager)
+
+    @mock.patch.object(host_manager.HostManager, '_init_instance_info')
+    @mock.patch.object(host_manager.HostManager, '_init_aggregates')
+    def test_init_using_ironic_hostmanager(self,
+                                           mock_init_agg,
+                                           mock_init_inst):
+        self.flags(scheduler_host_manager='ironic_host_manager')
+        manager = self.driver_cls().host_manager
+        self.assertIsInstance(manager, ironic_host_manager.IronicHostManager)
+
+    @mock.patch.object(host_manager.HostManager, '_init_instance_info')
+    @mock.patch.object(host_manager.HostManager, '_init_aggregates')
+    def test_init_nonexist_hostmanager(self,
+                                       mock_init_agg,
+                                       mock_init_inst):
+        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/config_scheduler_host_manager_driver-a543a74ea70f5e90.yaml

@@ -0,0 +1,9 @@
+---
+upgrade:
+  - |
+    The option ``scheduler_host_manager`` is now changed to use entrypoint
+    instead of full class path. Set one of the entrypoints under the namespace
+    'nova.scheduler.host_manager' in 'setup.cfg'. Its default value is
+    'host_manager'. The full class path style is still supported in current
+    release. But it is not recommended because class path can be changed and
+    this support will be dropped in the next major release.

setup.cfg

@@ -187,6 +187,10 @@ nova.ipv6_backend =
     rfc2462 = nova.ipv6.rfc2462
     account_identifier = nova.ipv6.account_identifier
 
+nova.scheduler.host_manager =
+    host_manager = nova.scheduler.host_manager:HostManager
+    ironic_host_manager = nova.scheduler.ironic_host_manager:IronicHostManager
+
 [build_sphinx]
 all_files = 1
 build-dir = doc/build