Fix update on failed stack

In the case of a dependant resource failing, a nested stack will not get
created, so we need to at least create an empty nested stack to allow
the update to work.

Change-Id: I2e83546801bce0da566ec8ef1322e30d695ff02a
Closes-bug: 1411103

heat/engine/stack_resource.py

@@ -21,6 +21,7 @@ from heat.common import exception
 from heat.common.i18n import _
 from heat.common.i18n import _LI
 from heat.common.i18n import _LW
+from heat.common import template_format
 from heat.engine import attributes
 from heat.engine import environment
 from heat.engine import resource
@@ -255,12 +256,21 @@ class StackResource(resource.Resource):
     def update_with_template(self, child_template, user_params=None,
                              timeout_mins=None):
         """Update the nested stack with the new template."""
+        if self.id is None:
+            self._store()
+        name = self.physical_resource_name()
+
         nested_stack = self.nested()
         if nested_stack is None:
-            raise exception.Error(_('Cannot update %s, stack not created')
-                                  % self.name)
+            # if the create failed for some reason and the nested
+            # stack was not created, we need to create an empty stack
+            # here so that the update will work.
+            empty_temp = template_format.parse(
+                "heat_template_version: '2013-05-23'")
+            stack_creator = self.create_with_template(empty_temp, {})
+            stack_creator.run_to_completion()
+            nested_stack = self.nested()
 
-        name = self.physical_resource_name()
         stack = self._parse_nested_stack(name, child_template, user_params,
                                          timeout_mins)
         stack.validate()

heat_integrationtests/functional/test_template_resource.py

@@ -337,6 +337,54 @@ Outputs:
                                 self._stack_output(stack, 'value'))
 
 
+class TemplateResourceUpdateFailedTest(test.HeatIntegrationTest):
+    """Prove that we can do updates on a nested stack to fix a stack."""
+    main_template = '''
+HeatTemplateFormatVersion: '2012-12-12'
+Resources:
+  keypair:
+    Type: OS::Nova::KeyPair
+    Properties:
+      name: replace-this
+      save_private_key: false
+  server:
+    Type: server_fail.yaml
+    DependsOn: keypair
+'''
+    nested_templ = '''
+HeatTemplateFormatVersion: '2012-12-12'
+Resources:
+  RealRandom:
+    Type: OS::Heat::RandomString
+'''
+
+    def setUp(self):
+        super(TemplateResourceUpdateFailedTest, self).setUp()
+        self.client = self.orchestration_client
+        if self.conf.keypair_name:
+            self.keypair_name = self.conf.keypair_name
+        else:
+            self.keypair = self.create_keypair()
+            self.keypair_name = self.keypair.id
+
+    def test_update_on_failed_create(self):
+        # create a stack with "server" dependant on "keypair", but
+        # keypair fails, so "server" is not created properly.
+        # We then fix the template and it should succeed.
+        broken_templ = self.main_template.replace('replace-this',
+                                                  self.keypair_name)
+        stack_identifier = self.stack_create(
+            template=broken_templ,
+            files={'server_fail.yaml': self.nested_templ},
+            expected_status='CREATE_FAILED')
+
+        fixed_templ = self.main_template.replace('replace-this',
+                                                 test.rand_name())
+        self.update_stack(stack_identifier,
+                          fixed_templ,
+                          files={'server_fail.yaml': self.nested_templ})
+
+
 class TemplateResourceAdoptTest(test.HeatIntegrationTest):
     """Prove that we can do template resource adopt/abandon."""