Handle missing plugin in is_service_available

When a client is not installed, Heat should behave as if the service was
unavailable. We recently started exposing exceptions when checking for
service availability, which displayed that it fails if the client plugin
returs None. Let's test and handle that case.

Change-Id: I71d5fd5be2efd7734d8569e4d26ab1b512453343
Closes-Bug: #1543759

heat/common/exception.py

@@ -240,6 +240,10 @@ class ResourceNotAvailable(HeatException):
     msg_fmt = _("The Resource (%(resource_name)s) is not available.")
 
 
+class ClientNotAvailable(HeatException):
+    msg_fmt = _("The client (%(client_name)s) is not available.")
+
+
 class WatchRuleNotFound(EntityNotFound):
     """Keep this for AWS compatiblility."""
     msg_fmt = _("The Watch Rule (%(watch_name)s) could not be found.")

heat/engine/environment.py

@@ -526,7 +526,10 @@ class ResourceRegistry(object):
             if cnxt is None:
                 return True
 
-            return cls.get_class().is_service_available(cnxt)
+            try:
+                return cls.get_class().is_service_available(cnxt)
+            except Exception:
+                return False
 
         def not_hidden_matches(cls):
             return cls.get_class().support_status.status != support.HIDDEN

heat/engine/resource.py

@@ -571,6 +571,10 @@ class Resource(object):
         client_plugin = clients.Clients(context).client_plugin(
             cls.default_client_name)
 
+        if not client_plugin:
+            raise exception.ClientNotAvailable(
+                client_name=cls.default_client_name)
+
         service_types = client_plugin.service_types
         if not service_types:
             return True

heat/tests/test_environment.py

@@ -28,6 +28,7 @@ from heat.engine.resources.openstack.nova import server
 from heat.engine import support
 from heat.tests import common
 from heat.tests import generic_resource
+from heat.tests import utils
 
 
 cfg.CONF.import_opt('environment_dir', 'heat.common.config')
@@ -826,6 +827,15 @@ class ResourceRegistryTest(common.HeatTestCase):
         self.assertIn('ResourceTypeUnSupportedLiberty', types)
         self.assertIn('GenericResourceType', types)
 
+    def test_list_type_with_is_available_exception(self):
+        registry = resources.global_env().registry
+        self.patchobject(
+            generic_resource.GenericResource,
+            'is_service_available',
+            side_effect=exception.ClientNotAvailable(client_name='generic'))
+        types = registry.get_types(utils.dummy_context())
+        self.assertNotIn('GenericResourceType', types)
+
     def test_list_type_with_invalid_type_name(self):
         registry = resources.global_env().registry
         types = registry.get_types(type_name="r'[^\+]'")

heat/tests/test_resource.py

@@ -3115,6 +3115,24 @@ class ResourceAvailabilityTest(common.HeatTestCase):
             service_name=(generic_rsrc.ResourceWithDefaultClientName
                           .default_client_name))
 
+    @mock.patch.object(clients.OpenStackClients, 'client_plugin')
+    def test_service_not_installed_required_extension(
+            self,
+            mock_client_plugin_method):
+        """Test availability of resource when the client is not installed.
+
+        When the client is not installed, we can't create the resource properly
+        so raise a proper exception for information.
+        """
+        mock_client_plugin_method.return_value = None
+
+        self.assertRaises(
+            exception.ClientNotAvailable,
+            generic_rsrc.ResourceWithDefaultClientNameExt.is_service_available,
+            context=mock.Mock())
+        mock_client_plugin_method.assert_called_once_with(
+            generic_rsrc.ResourceWithDefaultClientName.default_client_name)
+
     def test_service_not_available_returns_false(self):
         """Test when the service is not in service catalog.