api: handle case where metadata is None

This fixes bug #1158808

Change-Id: Ib63f42417262544b12f3cdf267d3c2f2eb47746a
Signed-off-by: Julien Danjou <julien@danjou.info>

ceilometer/api/controllers/v2.py

@@ -194,9 +194,11 @@ def _flatten_metadata(metadata):
     """Return flattened resource metadata without nested structures
     and with all values converted to unicode strings.
     """
-    return dict((k, unicode(v))
+    if metadata:
-                for k, v in metadata.iteritems()
+        return dict((k, unicode(v))
-                if type(v) not in set([list, dict, set]))
+                    for k, v in metadata.iteritems()
+                    if type(v) not in set([list, dict, set]))
+    return {}
 
 
 class Sample(wtypes.Base):

tests/api/v2/test_list_resources.py

@@ -39,6 +39,27 @@ class TestListResources(FunctionalTest):
         data = self.get_json('/resources')
         self.assertEquals([], data)
 
+    def test_instance_no_metadata(self):
+        counter1 = counter.Counter(
+            'instance',
+            'cumulative',
+            '',
+            1,
+            'user-id',
+            'project-id',
+            'resource-id',
+            timestamp=datetime.datetime(2012, 7, 2, 10, 40),
+            resource_metadata=None
+        )
+        msg = meter.meter_message_from_counter(counter1,
+                                               cfg.CONF.metering_secret,
+                                               'test',
+                                               )
+        self.conn.record_metering_data(msg)
+
+        data = self.get_json('/resources')
+        self.assertEquals(1, len(data))
+
     def test_instances(self):
         counter1 = counter.Counter(
             'instance',