Remove LazyLoad of Scheduler Clients

Things have changed here on Walton's Mountain since LazyLoad was
introduced [1]. It seems to have been created to avoid a circular
import, but as this patch should attest, that's no longer an issue.

Why change this now, besides removing weird and complicated code?
Because a subsequent patch needs to access a *property* of the report
client from the compute manager. As written, LazyLoad only lets you get
at *methods* (as functools.partial). There are other ways to solve that
while preserving the deferred import, but if this works, it's the better
solution.

[1] Ie5732baf9709cd0cb951eae4638910372c79e5f1

Change-Id: I1f97d00fb7633f173370ed6787c9a71ecd8106d5

nova/scheduler/client/__init__.py

@@ -13,38 +13,17 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import functools
-
-from oslo_utils import importutils
-
+from nova.scheduler.client import query
+from nova.scheduler.client import report
 from nova.scheduler import utils
 
 
-class LazyLoader(object):
-
-    def __init__(self, klass, *args, **kwargs):
-        self.klass = klass
-        self.args = args
-        self.kwargs = kwargs
-        self.instance = None
-
-    def __getattr__(self, name):
-        return functools.partial(self.__run_method, name)
-
-    def __run_method(self, __name, *args, **kwargs):
-        if self.instance is None:
-            self.instance = self.klass(*self.args, **self.kwargs)
-        return getattr(self.instance, __name)(*args, **kwargs)
-
-
 class SchedulerClient(object):
     """Client library for placing calls to the scheduler."""
 
     def __init__(self):
-        self.queryclient = LazyLoader(importutils.import_class(
-            'nova.scheduler.client.query.SchedulerQueryClient'))
-        self.reportclient = LazyLoader(importutils.import_class(
-            'nova.scheduler.client.report.SchedulerReportClient'))
+        self.queryclient = query.SchedulerQueryClient()
+        self.reportclient = report.SchedulerReportClient()
 
     @utils.retry_select_destinations
     def select_destinations(self, context, spec_obj, instance_uuids,

nova/tests/unit/conductor/tasks/test_live_migrate.py

@@ -629,12 +629,12 @@ class LiveMigrationTaskTestCase(test.NoDBTestCase):
 
     @mock.patch.object(objects.ComputeNode, 'get_by_host_and_nodename',
                        side_effect=exception.ComputeHostNotFound(host='host'))
-    def test_remove_host_allocations_compute_host_not_found(self, get_cn):
+    @mock.patch('nova.scheduler.client.report.SchedulerReportClient.'
+                'remove_provider_tree_from_instance_allocation')
+    def test_remove_host_allocations_compute_host_not_found(
+            self, remove_provider, get_cn):
         """Tests that failing to find a ComputeNode will not blow up
         the _remove_host_allocations method.
         """
-        with mock.patch.object(
-                self.task.scheduler_client.reportclient,
-                'remove_provider_from_instance_allocation') as remove_provider:
-            self.task._remove_host_allocations('host', 'node')
+        self.task._remove_host_allocations('host', 'node')
         remove_provider.assert_not_called()

nova/tests/unit/scheduler/test_client.py

@@ -40,12 +40,10 @@ class SchedulerClientTestCase(test.NoDBTestCase):
     def test_select_destinations(self, mock_select_destinations):
         fake_spec = objects.RequestSpec()
         fake_spec.instance_uuid = uuids.instance
-        self.assertIsNone(self.client.queryclient.instance)
 
         self.client.select_destinations('ctxt', fake_spec,
                 [fake_spec.instance_uuid])
 
-        self.assertIsNotNone(self.client.queryclient.instance)
         mock_select_destinations.assert_called_once_with('ctxt', fake_spec,
                 [fake_spec.instance_uuid], False, False)
 
@@ -97,11 +95,8 @@ class SchedulerClientTestCase(test.NoDBTestCase):
     @mock.patch.object(scheduler_report_client.SchedulerReportClient,
                        'update_compute_node')
     def test_update_compute_node(self, mock_update_compute_node):
-        self.assertIsNone(self.client.reportclient.instance)
-
         self.client.update_compute_node(mock.sentinel.ctx, mock.sentinel.cn)
 
-        self.assertIsNotNone(self.client.reportclient.instance)
         mock_update_compute_node.assert_called_once_with(
             mock.sentinel.ctx, mock.sentinel.cn)