From 036fb56ab3779ebb37804487aecbfaa69e764b3b Mon Sep 17 00:00:00 2001
From: Kevin_Zheng <zhengzhenyu@huawei.com>
Date: Tue, 22 May 2018 20:00:16 +0800
Subject: [PATCH] Only run placement request filters when Placement will be
 called

Any enabled placement request filters are processed during scheduling
here:

https://github.com/openstack/nova/blob/d78055/nova/scheduler/manager.py#L127

But then if we're doing a rebuild, or the driver.USES_ALLOCATION_CANDIDATES
is False, we don't call placement:

https://github.com/openstack/nova/blob/d78055/nova/scheduler/manager.py#L132

https://github.com/openstack/nova/blob/d78055/nova/scheduler/manager.py#L135

So we're unnecessarily processing the request spec filters (like
querying the aggregates table) in those conditions.

Change-Id: I8ed019c2208c28bb733aac961e855ce77f332a1e
Closes-bug: #1772523
---
 nova/scheduler/manager.py                   | 14 ++++++++------
 nova/tests/unit/scheduler/test_scheduler.py |  5 ++++-
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/nova/scheduler/manager.py b/nova/scheduler/manager.py
index 6d2e902a37af..5c85642ac3a5 100644
--- a/nova/scheduler/manager.py
+++ b/nova/scheduler/manager.py
@@ -123,16 +123,18 @@ class SchedulerManager(manager.Manager):
                                                            request_spec,
                                                            filter_properties)
 
-        try:
-            request_filter.process_reqspec(ctxt, spec_obj)
-        except exception.RequestFilterFailed as e:
-            raise exception.NoValidHost(reason=e.message)
-
-        resources = utils.resources_from_request_spec(spec_obj)
         is_rebuild = utils.request_is_rebuild(spec_obj)
         alloc_reqs_by_rp_uuid, provider_summaries, allocation_request_version \
             = None, None, None
         if self.driver.USES_ALLOCATION_CANDIDATES and not is_rebuild:
+            # Only process the Placement request spec filters when Placement
+            # is used.
+            try:
+                request_filter.process_reqspec(ctxt, spec_obj)
+            except exception.RequestFilterFailed as e:
+                raise exception.NoValidHost(reason=e.message)
+
+            resources = utils.resources_from_request_spec(spec_obj)
             res = self.placement_client.get_allocation_candidates(ctxt,
                                                                   resources)
             if res is None:
diff --git a/nova/tests/unit/scheduler/test_scheduler.py b/nova/tests/unit/scheduler/test_scheduler.py
index da152c102a86..f9ad1045ff50 100644
--- a/nova/tests/unit/scheduler/test_scheduler.py
+++ b/nova/tests/unit/scheduler/test_scheduler.py
@@ -227,10 +227,12 @@ class SchedulerManagerTestCase(test.NoDBTestCase):
         place_res = ([], {}, None)
         self._test_select_destination(place_res)
 
+    @mock.patch('nova.scheduler.request_filter.process_reqspec')
     @mock.patch('nova.scheduler.utils.resources_from_request_spec')
     @mock.patch('nova.scheduler.client.report.SchedulerReportClient.'
                 'get_allocation_candidates')
-    def test_select_destination_is_rebuild(self, mock_get_ac, mock_rfrs):
+    def test_select_destination_is_rebuild(self, mock_get_ac, mock_rfrs,
+                                           mock_process):
         fake_spec = objects.RequestSpec(
             scheduler_hints={'_nova_check_type': ['rebuild']})
         fake_spec.instance_uuid = uuids.instance
@@ -242,6 +244,7 @@ class SchedulerManagerTestCase(test.NoDBTestCase):
                 self.context, fake_spec,
                 [fake_spec.instance_uuid], None, None, None, False)
             mock_get_ac.assert_not_called()
+            mock_process.assert_not_called()
 
     @mock.patch('nova.scheduler.utils.resources_from_request_spec')
     @mock.patch('nova.scheduler.client.report.SchedulerReportClient.'