From 62464883e1c2ba98e1fddb1284171ca5bef4d8e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ji=C5=99=C3=AD=20Suchomel?= <jiri.suchomel@suse.com>
Date: Tue, 21 Aug 2018 09:10:07 +0200
Subject: [PATCH] Filter out instances without a host when populating AZ

It could happen that instance does not have a host set, e.g.
when its creation failed before it was scheduled.
During online_migration, populate_missing_availability_zones tries to
add missing AZs to all instances. However for instances without a host
there's no reasonable value for AZ (we can't use a logic that bases
the value on a host) so let's skip this kind of instances completely.

Change-Id: Ic6060beaa08af5ea70e5e54fffb94eea58aa7bbf
Closes-Bug: #1788115
(cherry picked from commit 690f91b5c7f7e84a4e6d351b27c05818d947cce1)
(cherry picked from commit ad14e428f82f02d71e0b33ec6d20e7810a978e3b)
(cherry picked from commit 059c2d4a8a9967403755c40beda667c9463848a8)
---
 nova/objects/instance.py                  |  3 +++
 nova/tests/functional/db/test_instance.py | 11 +++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/nova/objects/instance.py b/nova/objects/instance.py
index 1810c12a94d7..da6df09ad1bd 100644
--- a/nova/objects/instance.py
+++ b/nova/objects/instance.py
@@ -1222,7 +1222,10 @@ def _make_instance_list(context, inst_list, db_inst_list, expected_attrs):
 
 @db_api.pick_context_manager_writer
 def populate_missing_availability_zones(context, count):
+    # instances without host have no reasonable AZ to set
+    not_empty_host = models.Instance.host != None  # noqa E711
     instances = (context.session.query(models.Instance).
+        filter(not_empty_host).
         filter_by(availability_zone=None).limit(count).all())
     count_all = len(instances)
     count_hit = 0
diff --git a/nova/tests/functional/db/test_instance.py b/nova/tests/functional/db/test_instance.py
index 38b530134ac8..4394f557b4fb 100644
--- a/nova/tests/functional/db/test_instance.py
+++ b/nova/tests/functional/db/test_instance.py
@@ -50,17 +50,20 @@ class InstanceObjectTestCase(test.TestCase):
         uuid1 = inst1.uuid
         inst2 = self._create_instance(availability_zone="fake",
                                       host="fake-host2")
+        # ... and one without a host (simulating failed spawn)
+        self._create_instance(host=None)
+
         self.assertIsNone(inst1.availability_zone)
         self.assertEqual("fake", inst2.availability_zone)
         count_all, count_hit = (objects.instance.
             populate_missing_availability_zones(self.context, 10))
-        # we get only the instance whose avz was None.
+        # we get only the instance whose avz was None and where host is set
         self.assertEqual(1, count_all)
         self.assertEqual(1, count_hit)
+        # since instance has no avz, avz is set by get_host_availability_zone
+        # to CONF.default_availability_zone i.e 'nova' which is the default
+        # zone for compute services.
         inst1 = objects.Instance.get_by_uuid(self.context, uuid1)
-        # since instance.host was None, avz is set to
-        # CONF.default_availability_zone i.e 'nova' which is the default zone
-        # for compute services.
         self.assertEqual('nova', inst1.availability_zone)
 
         # create an instance with avz as None on a host that has avz.