Move resource_templates to heat.scaling

This introduces a new package for autoscaling code which is
intended for use outside of the Heat engine, and moves the
resource_templates function into a new module, heat.scaling.template.
The function hasn't been changed at all.

Change-Id: I78c420e7a188f2d14780a03b3ea220b9a5fbe86c
Implements: partial blueprint as-lib

heat/engine/resources/autoscaling.py

@@ -22,7 +22,6 @@ from heat.engine import environment
 from heat.engine import resource
 from heat.engine import signal_responder
 
-from heat.common import short_id
 from heat.common import exception
 from heat.common import timeutils as iso8601utils
 from heat.openstack.common import excutils
@@ -34,6 +33,7 @@ from heat.engine.notification import autoscaling as notification
 from heat.engine import properties
 from heat.engine import scheduler
 from heat.engine import stack_resource
+from heat.scaling import template
 
 logger = logging.getLogger(__name__)
 
@@ -281,40 +281,15 @@ class InstanceGroup(stack_resource.StackResource):
         """
         Create a template to represent autoscaled instances.
 
-        Also see _resource_templates.
+        Also see heat.scaling.template.resource_templates.
         """
         instance_definition = self._get_instance_definition()
         old_resources = [(instance.name, instance.t)
                          for instance in self.get_instances()]
-        templates = self._resource_templates(
+        templates = template.resource_templates(
             old_resources, instance_definition, num_instances, num_replace)
         return {"Resources": dict(templates)}
 
-    @staticmethod
-    def _resource_templates(old_resources, resource_definition,
-                            num_resources, num_replace):
-        """
-        Create the template for the nested stack of existing and new instances
-
-        For rolling update, if launch configuration is different, the
-        instance definition should come from the existing instance instead
-        of using the new launch configuration.
-        """
-        old_resources = old_resources[-num_resources:]
-        num_create = num_resources - len(old_resources)
-        num_replace -= num_create
-
-        for i in range(num_resources):
-            if i < len(old_resources):
-                old_name, old_template = old_resources[i]
-                if old_template != resource_definition and num_replace > 0:
-                    num_replace -= 1
-                    yield old_name, resource_definition
-                else:
-                    yield old_name, old_template
-            else:
-                yield short_id.generate_id(), resource_definition
-
     def _replace(self, min_in_service, batch_size, pause_time):
         """
         Replace the instances in the group using updated launch configuration

heat/scaling/template.py

@@ -0,0 +1,38 @@
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from heat.common import short_id
+
+
+def resource_templates(old_resources, resource_definition,
+                       num_resources, num_replace):
+    """
+    Create the template for the nested stack of existing and new instances
+    For rolling update, if launch configuration is different, the
+    instance definition should come from the existing instance instead
+    of using the new launch configuration.
+    """
+    old_resources = old_resources[-num_resources:]
+    num_create = num_resources - len(old_resources)
+    num_replace -= num_create
+
+    for i in range(num_resources):
+        if i < len(old_resources):
+            old_name, old_template = old_resources[i]
+            if old_template != resource_definition and num_replace > 0:
+                num_replace -= 1
+                yield old_name, resource_definition
+            else:
+                yield old_name, old_template
+        else:
+            yield short_id.generate_id(), resource_definition