azure: avoid re-running cloud-init when instance-id is byte-swapped (#84)

Azure stores the instance ID with an incorrect byte ordering for the
first three hyphen delimited parts. This results in invalid
is_new_instance checks forcing Azure datasource to recrawl the metadata
service.

When persisting instance-id from the metadata service, swap the
instance-id string byte order such that it is consistent with
that returned by dmi information. Check whether the instance-id
string is a byte-swapped match when determining correctly whether 
the Azure platform instance-id has actually changed. 

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/unittests/test_datasource/test_azure_helper.py b/tests/unittests/test_datasource/test_azure_helper.py
index bd17f636..007df09f 100644
--- a/tests/unittests/test_datasource/test_azure_helper.py
+++ b/tests/unittests/test_datasource/test_azure_helper.py
@@ -170,6 +170,25 @@ class TestGoalStateParsing(CiTestCase):
         goal_state = self._get_goal_state(instance_id=instance_id)
         self.assertEqual(instance_id, goal_state.instance_id)
 
+    def test_instance_id_byte_swap(self):
+        """Return true when previous_iid is byteswapped current_iid"""
+        previous_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        current_iid = "544CDFD0-CB4E-4B4A-9954-5BDF3ED5C3B8"
+        self.assertTrue(
+            azure_helper.is_byte_swapped(previous_iid, current_iid))
+
+    def test_instance_id_no_byte_swap_same_instance_id(self):
+        previous_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        current_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        self.assertFalse(
+            azure_helper.is_byte_swapped(previous_iid, current_iid))
+
+    def test_instance_id_no_byte_swap_diff_instance_id(self):
+        previous_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        current_iid = "G0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        self.assertFalse(
+            azure_helper.is_byte_swapped(previous_iid, current_iid))
+
     def test_certificates_xml_parsed_and_fetched_correctly(self):
         http_client = mock.MagicMock()
         certificates_url = 'TestCertificatesUrl'