Extract getting instance's AZ into a helper module.

An instance's availability zone logic may used by many modules,
so move it from extend API into helper module `nova.availability_zones`.
Also add some tests for the new method.

part of bp: different-availability-zone-filter

Change-Id: I5916a0b09d5dddec338e8e36503953720dfd6bcd

1 files changed, 21 insertions, 0 deletions

diff --git a/nova/tests/test_availability_zones.py b/nova/tests/test_availability_zones.py
index 4bc6db58b..eefa1daf8 100644
--- a/nova/tests/test_availability_zones.py
+++ b/nova/tests/test_availability_zones.py
@@ -25,6 +25,7 @@ from nova import availability_zones as az
 from nova import context
 from nova import db
 from nova import test
+from nova.tests.api.openstack import fakes
 
 CONF = cfg.CONF
 CONF.import_opt('internal_service_availability_zone',
@@ -155,3 +156,23 @@ class AvailabilityZoneTestCases(test.TestCase):
 
         self.assertEquals(zones, ['nova-test', 'nova-test2'])
         self.assertEquals(not_zones, ['nova-test3', 'nova'])
+
+    def test_get_instance_availability_zone_default_value(self):
+        """Test get right availability zone by given an instance."""
+        fake_inst_id = 162
+        fake_inst = fakes.stub_instance(fake_inst_id, host=self.host)
+
+        self.assertEqual(self.default_az,
+                az.get_instance_availability_zone(self.context, fake_inst))
+
+    def test_get_instance_availability_zone_from_aggregate(self):
+        """Test get availability zone from aggregate by given an instance."""
+        host = 'host170'
+        service = self._create_service_with_topic('compute', host)
+        self._add_to_aggregate(service, self.agg)
+
+        fake_inst_id = 174
+        fake_inst = fakes.stub_instance(fake_inst_id, host=host)
+
+        self.assertEqual(self.availability_zone,
+                az.get_instance_availability_zone(self.context, fake_inst))