Add accounting for orphans to resource tracker.

Add accounting for orphaned instances to resource tracker.  Orphans
are instances that, for whatever reason, exist on the hypervisor
but are not accounted for in the Nova DB.

Such instances would cause resource tracker to under-report usage
numbers and result in out of memory errors during build.

Change-Id: Icc970e34e01ff8c7dfb000889e5ea6e2d0421c77

nova/tests/test_xenapi.py

@@ -1016,6 +1016,33 @@ class XenAPIVMTestCase(stubs.XenAPITestBase):
             pass
         self.assertTrue(was['called'])
 
+    def test_per_instance_usage_running(self):
+        instance = self._create_instance(spawn=True)
+        instance_type = instance_types.get_instance_type(3)
+
+        expected = {instance['uuid']: {'memory_mb': instance_type['memory_mb'],
+                                       'uuid': instance['uuid']}}
+        actual = self.conn.get_per_instance_usage()
+        self.assertEqual(expected, actual)
+
+        # Paused instances still consume resources:
+        self.conn.pause(instance)
+        actual = self.conn.get_per_instance_usage()
+        self.assertEqual(expected, actual)
+
+    def test_per_instance_usage_suspended(self):
+        # Suspended instances do not consume memory:
+        instance = self._create_instance(spawn=True)
+        self.conn.suspend(instance)
+        actual = self.conn.get_per_instance_usage()
+        self.assertEqual({}, actual)
+
+    def test_per_instance_usage_halted(self):
+        instance = self._create_instance(spawn=True)
+        self.conn.power_off(instance)
+        actual = self.conn.get_per_instance_usage()
+        self.assertEqual({}, actual)
+
     def _create_instance(self, instance_id=1, spawn=True):
         """Creates and spawns a test instance."""
         instance_values = {