Always update nested stacks

There's no reason to not issue an update to a nested stack, so don't bother
trying to decide if its inputs have changed (and especially don't replace
it because it's in a failed state). Overriding _needs_update() also allows
us to remove what was effectively an isinstance check from the previous
handling of failed states.

Change-Id: Ia48ebfcb6c1b3a904f01a83f8f34d8c7a13bb2be
Related-Bug: #1383618

heat/engine/resource.py

@@ -660,9 +660,6 @@ class Resource(object):
     def _needs_update(self, after, before, after_props, before_props,
                       prev_resource):
         if self.status == self.FAILED:
-            if hasattr(self, 'nested'):
-                return True
-            else:
             raise UpdateReplace(self)
 
         if prev_resource is not None:

heat/engine/resources/remote_stack.py

@@ -188,6 +188,12 @@ class RemoteStack(resource.Resource):
                                   % self.name)
         self.heat().stacks.suspend(stack_id=self.resource_id)
 
+    def _needs_update(self, after, before, after_props, before_props,
+                      prev_resource):
+        # Always issue an update to the remote stack and let the individual
+        # resources in it decide if they need updating.
+        return True
+
     def handle_update(self, json_snippet, tmpl_diff, prop_diff):
         if self.resource_id and prop_diff:
             snippet = json_snippet.get('Properties', {})

heat/engine/stack_resource.py

@@ -69,6 +69,12 @@ class StackResource(resource.Resource):
                                                     self.attributes_schema,
                                                     self._resolve_attribute)
 
+    def _needs_update(self, after, before, after_props, before_props,
+                      prev_resource):
+        # Always issue an update to the nested stack and let the individual
+        # resources in it decide if they need updating.
+        return True
+
     def nested(self, force_reload=False, show_deleted=False):
         '''
         Return a Stack object representing the nested (child) stack.

heat/tests/test_autoscaling_update_policy.py

@@ -670,7 +670,7 @@ class AutoScalingGroupTest(common.HeatTestCase):
                                       num_updates_expected_on_updt=9,
                                       num_creates_expected_on_updt=1,
                                       num_deletes_expected_on_updt=1,
-                                      num_reloads_expected_on_updt=12,
+                                      num_reloads_expected_on_updt=13,
                                       update_replace=True,
                                       update_image_id=update_image)
 

heat/tests/test_provider_template.py

@@ -973,7 +973,7 @@ Outputs:
     Value: {'Fn::GetAtt': [NestedResource, value]}
 '''
 
-    EXPECTED = (REPLACE, UPDATE, NOCHANGE) = ('replace', 'update', 'nochange')
+    EXPECTED = (UPDATE, NOCHANGE) = ('update', 'nochange')
     scenarios = [
         ('no_changes', dict(template=main_template,
                             provider=initial_tmpl,
@@ -986,10 +986,10 @@ Outputs:
                                  expect=UPDATE)),
         ('provider_props_change', dict(template=main_template,
                                        provider=prop_change_tmpl,
-                                       expect=REPLACE)),
+                                       expect=NOCHANGE)),
         ('provider_attr_change', dict(template=main_template,
                                       provider=attr_change_tmpl,
-                                      expect=REPLACE)),
+                                      expect=NOCHANGE)),
     ]
 
     def setUp(self):
@@ -1015,19 +1015,12 @@ Outputs:
         updated_stack = parser.Stack(self.ctx, stack.name, tmpl)
         stack.update(updated_stack)
         self.assertEqual(('UPDATE', 'COMPLETE'), stack.state)
-        if self.expect == self.REPLACE:
-            self.assertNotEqual(initial_id,
-                                stack.output('identifier'))
-            self.assertNotEqual(initial_val,
-                                stack.output('value'))
-        elif self.expect == self.NOCHANGE:
         self.assertEqual(initial_id,
                          stack.output('identifier'))
+        if self.expect == self.NOCHANGE:
             self.assertEqual(initial_val,
                              stack.output('value'))
         else:
-            self.assertEqual(initial_id,
-                             stack.output('identifier'))
             self.assertNotEqual(initial_val,
                                 stack.output('value'))
         self.m.VerifyAll()

heat/tests/test_resource_group.py

@@ -440,8 +440,8 @@ class ResourceGroupTest(common.HeatTestCase):
         new_snip = copy.deepcopy(resg.t)
         scheduler.TaskRunner(resg.update, new_snip)()
         self.stack = resg.nested()
-        self.assertEqual((resg.CREATE, resg.COMPLETE), resg.state)
-        self.assertEqual((resg.CREATE, resg.COMPLETE), resg.nested().state)
+        self.assertEqual((resg.UPDATE, resg.COMPLETE), resg.state)
+        self.assertEqual((resg.UPDATE, resg.COMPLETE), resg.nested().state)
         self.assertEqual(2, len(resg.nested()))
         resource_names = [r.name for r in resg.nested().iter_resources()]
         self.assertEqual(['0', '1'], sorted(resource_names))