Refactor Resource creation

Allow the Resource class to instantiate the correct type of object for each
resource.

Change-Id: I518f27fa27f675b9e497aac40962331833077aed
Signed-off-by: Zane Bitter <zbitter@redhat.com>

heat/engine/parser.py

@@ -18,38 +18,12 @@ import json
 import logging
 from heat.common import exception
 from heat.engine import checkeddict
-from heat.engine import cloud_watch
-from heat.engine import eip
-from heat.engine import escalation_policy
-from heat.engine import instance
-from heat.engine import resources
-from heat.engine import security_group
-from heat.engine import user
-from heat.engine import volume
-from heat.engine import wait_condition
+from heat.engine.resources import Resource
 from heat.db import api as db_api
 
 logger = logging.getLogger(__file__)
 
 
-(RESOURCE_CLASSES,) = ({
-    'AWS::EC2::Instance': instance.Instance,
-    'AWS::EC2::Volume': volume.Volume,
-    'AWS::EC2::VolumeAttachment': volume.VolumeAttachment,
-    'AWS::EC2::EIP': eip.ElasticIp,
-    'AWS::EC2::EIPAssociation': eip.ElasticIpAssociation,
-    'AWS::EC2::SecurityGroup': security_group.SecurityGroup,
-    'AWS::CloudWatch::Alarm': cloud_watch.CloudWatchAlarm,
-    'HEAT::Recovery::EscalationPolicy': escalation_policy.EscalationPolicy,
-    'AWS::CloudFormation::WaitConditionHandle':
-        wait_condition.WaitConditionHandle,
-    'AWS::CloudFormation::WaitCondition': wait_condition.WaitCondition,
-    'AWS::IAM::User': user.User,
-    'AWS::IAM::AccessKey': user.AccessKey,
-    'HEAT::HA::Restarter': instance.Restarter,
-},)
-
-
 class Stack(object):
     IN_PROGRESS = 'IN_PROGRESS'
     CREATE_FAILED = 'CREATE_FAILED'
@@ -94,12 +68,11 @@ class Stack(object):
             self._apply_user_parameters(parms)
 
         self.resources = {}
-        for rname, res in self.t['Resources'].items():
-            ResourceClass = RESOURCE_CLASSES.get(res['Type'],
-                                                 resources.GenericResource)
-            self.resources[rname] = ResourceClass(rname, res, self)
+        for rname, rdesc in self.t['Resources'].items():
+            res = Resource(rname, rdesc, self)
+            self.resources[rname] = res
 
-            self.calulate_dependencies(res, self.resources[rname])
+            self.calulate_dependencies(rdesc, res)
 
     def validate(self):
         '''

heat/engine/resource_types.py

@@ -0,0 +1,53 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#
+#    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.
+
+"""
+Register of resource types and their mapping to Resource classes.
+"""
+
+
+from heat.engine import resources
+
+from heat.engine import cloud_watch
+from heat.engine import eip
+from heat.engine import escalation_policy
+from heat.engine import instance
+from heat.engine import security_group
+from heat.engine import user
+from heat.engine import volume
+from heat.engine import wait_condition
+
+
+_resource_classes = {
+    'AWS::CloudFormation::WaitCondition': wait_condition.WaitCondition,
+    'AWS::CloudFormation::WaitConditionHandle':
+        wait_condition.WaitConditionHandle,
+    'AWS::CloudWatch::Alarm': cloud_watch.CloudWatchAlarm,
+    'AWS::EC2::EIP': eip.ElasticIp,
+    'AWS::EC2::EIPAssociation': eip.ElasticIpAssociation,
+    'AWS::EC2::Instance': instance.Instance,
+    'AWS::EC2::SecurityGroup': security_group.SecurityGroup,
+    'AWS::EC2::Volume': volume.Volume,
+    'AWS::EC2::VolumeAttachment': volume.VolumeAttachment,
+    'AWS::IAM::User': user.User,
+    'AWS::IAM::AccessKey': user.AccessKey,
+    'HEAT::HA::Restarter': instance.Restarter,
+    'HEAT::Recovery::EscalationPolicy': escalation_policy.EscalationPolicy,
+}
+
+
+def getClass(resource_type):
+    """Return the appropriate Resource class for the resource type."""
+    return _resource_classes.get(resource_type, resources.GenericResource)

heat/engine/resources.py

@@ -40,6 +40,18 @@ class Resource(object):
     UPDATE_FAILED = 'UPDATE_FAILED'
     UPDATE_COMPLETE = 'UPDATE_COMPLETE'
 
+    def __new__(cls, name, json, stack):
+        '''Create a new Resource of the appropriate class for its type.'''
+
+        if cls != Resource:
+            # Call is already for a subclass, so pass it through
+            return super(Resource, cls).__new__(cls, name, json, stack)
+
+        # Select the correct subclass to instantiate
+        import resource_types
+        ResourceClass = resource_types.getClass(json['Type'])
+        return ResourceClass(name, json, stack)
+
     def __init__(self, name, json_snippet, stack):
         self.t = json_snippet
         self.depends_on = []