Implement CFN CancelUpdateStack action

Change-Id: I7a4d9de34448f6f3ad964e36347a80a2f2140251
Implements: blueprint cancel-update-stack

etc/heat/policy.json

@@ -8,6 +8,7 @@
     "cloudformation:DescribeStacks": "rule:deny_stack_user",
     "cloudformation:DeleteStack": "rule:deny_stack_user",
     "cloudformation:UpdateStack": "rule:deny_stack_user",
+    "cloudformation:CancelUpdateStack": "rule:deny_stack_user",
     "cloudformation:DescribeStackEvents": "rule:deny_stack_user",
     "cloudformation:ValidateTemplate": "rule:deny_stack_user",
     "cloudformation:GetTemplate": "rule:deny_stack_user",

heat/api/cfn/v1/__init__.py

@@ -31,6 +31,7 @@ class API(wsgi.Router):
         'describe': 'DescribeStacks',
         'delete': 'DeleteStack',
         'update': 'UpdateStack',
+        'cancel_update': 'CancelUpdateStack',
         'events_list': 'DescribeStackEvents',
         'validate_template': 'ValidateTemplate',
         'get_template': 'GetTemplate',

heat/api/cfn/v1/stacks.py

@@ -365,6 +365,20 @@ class StackController(object):
 
         return api_utils.format_response(action, response)
 
+    def cancel_update(self, req):
+        action = 'CancelUpdateStack'
+        self._enforce(req, action)
+        con = req.context
+        stack_name = req.params['StackName']
+        stack_identity = self._get_identity(con, stack_name)
+        try:
+            self.rpc_client.stack_cancel_update(
+                con, stack_identity=stack_identity)
+        except Exception as ex:
+            return exception.map_remote_error(ex)
+
+        return api_utils.format_response(action, {})
+
     def get_template(self, req):
         """
         Implements the GetTemplate API action.

heat/tests/test_api_cfn_v1.py

@@ -941,6 +941,40 @@ class CfnStackControllerTest(HeatTestCase):
 
         self.assertEqual(expected, response)
 
+    def test_cancel_update(self):
+        # Format a dummy request
+        stack_name = "wordpress"
+        params = {'Action': 'CancelUpdateStack', 'StackName': stack_name}
+        dummy_req = self._dummy_GET_request(params)
+        self._stub_enforce(dummy_req, 'CancelUpdateStack')
+
+        # Stub out the RPC call to the engine with a pre-canned response
+        identity = dict(identifier.HeatIdentifier('t', stack_name, '1'))
+
+        self.m.StubOutWithMock(rpc_client.EngineClient, 'call')
+        rpc_client.EngineClient.call(
+            dummy_req.context,
+            ('identify_stack', {'stack_name': stack_name})
+        ).AndReturn(identity)
+
+        rpc_client.EngineClient.call(
+            dummy_req.context,
+            ('stack_cancel_update',
+             {'stack_identity': identity})
+        ).AndReturn(identity)
+
+        self.m.ReplayAll()
+
+        response = self.controller.cancel_update(dummy_req)
+
+        expected = {
+            'CancelUpdateStackResponse': {
+                'CancelUpdateStackResult': {}
+            }
+        }
+
+        self.assertEqual(response, expected)
+
     def test_update_bad_name(self):
         stack_name = "wibble"
         json_template = json.dumps(self.template)