From ffbf5918c650e8499de206b73f050d5e8580b04e Mon Sep 17 00:00:00 2001
From: Hongbin Lu <hongbin.lu@huawei.com>
Date: Tue, 20 Feb 2018 22:05:42 +0000
Subject: [PATCH] Skip placement on rebuild in same host

If the instance is rebuilt with a different image in the same
host, we don't need to call placement because there is no change
in resource consumption.

Conflicts:
        nova/scheduler/manager.py
        nova/tests/fixtures.py
        nova/tests/unit/scheduler/test_scheduler.py

NOTE(lyarwood): Pike Conflicts due to the following changes not being
present until Queens Iae904afb6cb4fcea8bb27741d774ffbe986a5fb4,
I03b95a2106624c2ea24835814ca38e954ec7a997 and
Iacb9808ef7188e3419abfac9e8c5fb5a46c71c05.

Change-Id: Ie252271ecfd38a0a1c61c26e323cc03869889f0a
Closes-Bug: #1750623
(cherry-pick from c3a894b6af32ff8ddba728328bc7d4e1339b2964)
(cherry picked from commit 04ea910ad13b412f410ccf520074cacee6bbe13e)
---
 nova/scheduler/manager.py                   |  3 ++-
 nova/tests/fixtures.py                      |  4 ++++
 nova/tests/functional/test_servers.py       | 12 ++++++++++++
 nova/tests/unit/scheduler/test_scheduler.py | 16 ++++++++++++++++
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/nova/scheduler/manager.py b/nova/scheduler/manager.py
index 0db7ddbcfe72..55d6d6ecff4e 100644
--- a/nova/scheduler/manager.py
+++ b/nova/scheduler/manager.py
@@ -119,8 +119,9 @@ class SchedulerManager(manager.Manager):
                                                            request_spec,
                                                            filter_properties)
         resources = utils.resources_from_request_spec(spec_obj)
+        is_rebuild = utils.request_is_rebuild(spec_obj)
         alloc_reqs_by_rp_uuid, provider_summaries = None, None
-        if self.driver.USES_ALLOCATION_CANDIDATES:
+        if self.driver.USES_ALLOCATION_CANDIDATES and not is_rebuild:
             res = self.placement_client.get_allocation_candidates(resources)
             if res is None:
                 # We have to handle the case that we failed to connect to the
diff --git a/nova/tests/fixtures.py b/nova/tests/fixtures.py
index 5d1626fd5d74..c6da93732d58 100644
--- a/nova/tests/fixtures.py
+++ b/nova/tests/fixtures.py
@@ -1446,6 +1446,10 @@ class PlacementApiClient(object):
     def get(self, url):
         return client.APIResponse(self.fixture._fake_get(None, url))
 
+    def put(self, url, body, **kwargs):
+        return client.APIResponse(
+            self.fixture._fake_put(None, url, body, **kwargs))
+
 
 class PlacementFixture(fixtures.Fixture):
     """A fixture to placement operations.
diff --git a/nova/tests/functional/test_servers.py b/nova/tests/functional/test_servers.py
index 7b09df7d1941..f149c4c6477b 100644
--- a/nova/tests/functional/test_servers.py
+++ b/nova/tests/functional/test_servers.py
@@ -1186,6 +1186,15 @@ class ServerRebuildTestCase(integrated_helpers._IntegratedTestBase,
             return self.placement_api.get(
                 '/allocations/%s' % server_uuid).body['allocations']
 
+        def _set_provider_inventory(rp_uuid, resource_class, inventory):
+            # Get the resource provider generation for the inventory update.
+            rp = self.placement_api.get(
+                '/resource_providers/%s' % rp_uuid).body
+            inventory['resource_provider_generation'] = rp['generation']
+            return self.placement_api.put(
+                '/resource_providers/%s/inventories/%s' %
+                (rp_uuid, resource_class), inventory).body
+
         def assertFlavorMatchesAllocation(flavor, allocation):
             self.assertEqual(flavor['vcpus'], allocation['VCPU'])
             self.assertEqual(flavor['ram'], allocation['MEMORY_MB'])
@@ -1213,6 +1222,9 @@ class ServerRebuildTestCase(integrated_helpers._IntegratedTestBase,
 
         flavor = self.api.api_get('/flavors/1').body['flavor']
 
+        # make the compute node full and ensure rebuild still succeed
+        _set_provider_inventory(rp_uuid, "VCPU", {"total": 1})
+
         # There should be usage for the server on the compute node now.
         rp_usages = _get_provider_usages(rp_uuid)
         assertFlavorMatchesAllocation(flavor, rp_usages)
diff --git a/nova/tests/unit/scheduler/test_scheduler.py b/nova/tests/unit/scheduler/test_scheduler.py
index d61cf56d6686..fe545160d6fc 100644
--- a/nova/tests/unit/scheduler/test_scheduler.py
+++ b/nova/tests/unit/scheduler/test_scheduler.py
@@ -168,6 +168,22 @@ class SchedulerManagerTestCase(test.NoDBTestCase):
         place_res = ([], {})
         self._test_select_destination(place_res)
 
+    @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):
+        fake_spec = objects.RequestSpec(
+            scheduler_hints={'_nova_check_type': ['rebuild']})
+        fake_spec.instance_uuid = uuids.instance
+        with mock.patch.object(self.manager.driver, 'select_destinations'
+                ) as select_destinations:
+            self.manager.select_destinations(self.context, spec_obj=fake_spec,
+                    instance_uuids=[fake_spec.instance_uuid])
+            select_destinations.assert_called_once_with(
+                self.context, fake_spec,
+                [fake_spec.instance_uuid], None, None)
+            mock_get_ac.assert_not_called()
+
     @mock.patch('nova.scheduler.utils.resources_from_request_spec')
     @mock.patch('nova.scheduler.client.report.SchedulerReportClient.'
                 'get_allocation_candidates')