Merge "Invalidate AZ cache when the instance AZ information is different"

nova/availability_zones.py

@@ -178,6 +178,20 @@ def get_instance_availability_zone(context, instance):
     cache_key = _make_cache_key(host)
     cache = _get_cache()
     az = cache.get(cache_key)
+    az_inst = instance.get('availability_zone')
+    if az_inst is not None and az != az_inst:
+        # NOTE(sbauza): Cache is wrong, we need to invalidate it by fetching
+        # again the right AZ related to the aggregate the host belongs to.
+        # As the API is also calling this method for setting the instance
+        # AZ field, we don't need to update the instance.az field.
+        # This case can happen because the cache is populated before the
+        # instance has been assigned to the host so that it would keep the
+        # former reference which was incorrect. Instead of just taking the
+        # instance AZ information for refilling the cache, we prefer to
+        # invalidate the cache and fetch it again because there could be some
+        # corner cases where this method could be called before the instance
+        # has been assigned to the host also.
+        az = None
     if not az:
         elevated = context.elevated()
         az = get_host_availability_zone(elevated, host)

nova/tests/unit/test_availability_zones.py

@@ -17,6 +17,7 @@
 Tests for availability zones
 """
 
+import mock
 from oslo_config import cfg
 import six
 
@@ -239,7 +240,8 @@ class AvailabilityZoneTestCases(test.TestCase):
 
     def test_get_instance_availability_zone_default_value(self):
         """Test get right availability zone by given an instance."""
-        fake_inst = objects.Instance(host=self.host)
+        fake_inst = objects.Instance(host=self.host,
+                                     availability_zone=None)
 
         self.assertEqual(self.default_az,
                 az.get_instance_availability_zone(self.context, fake_inst))
@@ -250,11 +252,25 @@ class AvailabilityZoneTestCases(test.TestCase):
         service = self._create_service_with_topic('compute', host)
         self._add_to_aggregate(service, self.agg)
 
-        fake_inst = objects.Instance(host=host)
+        fake_inst = objects.Instance(host=host,
+                                     availability_zone=self.availability_zone)
 
         self.assertEqual(self.availability_zone,
                 az.get_instance_availability_zone(self.context, fake_inst))
 
+    @mock.patch.object(az._get_cache(), 'get')
+    def test_get_instance_availability_zone_cache_differs(self, cache_get):
+        host = 'host170'
+        service = self._create_service_with_topic('compute', host)
+        self._add_to_aggregate(service, self.agg)
+        cache_get.return_value = self.default_az
+
+        fake_inst = objects.Instance(host=host,
+                                     availability_zone=self.availability_zone)
+        self.assertEqual(
+            self.availability_zone,
+            az.get_instance_availability_zone(self.context, fake_inst))
+
     def test_get_instance_availability_zone_no_host(self):
         """Test get availability zone from instance if host not set."""
         fake_inst = objects.Instance(host=None, availability_zone='inst-az')

nova/tests/unit/test_metadata.py

@@ -83,7 +83,8 @@ def fake_inst_obj(context):
         metadata={},
         default_ephemeral_device=None,
         default_swap_device=None,
-        system_metadata={})
+        system_metadata={},
+        availability_zone=None)
     nwinfo = network_model.NetworkInfo([])
     inst.info_cache = objects.InstanceInfoCache(context=context,
                                                 instance_uuid=inst.uuid,