Clean up helper methods in ResourceProvider

This change moves several of the module level methods that perform
database interaction back into the ResourceProvider class. They had
been created outside the class because of issues with the fixtures
python library when monkeypatching staticmethods and testing with
python3. Those issue have since been fixed in fixtures by
https://github.com/testing-cabal/fixtures/pull/30

Note that the methods that are associated with _update, _add and
_set_inventory have _not_ been moved because the changes involved
would have been more than a simple copy and paste.

Change-Id: I14395ba84cea9effe81e42f7615101ad9fab80e3
Partially-Implements: blueprint generic-resource-pools

nova/objects/resource_provider.py

@@ -25,48 +25,6 @@ _INV_TBL = models.Inventory.__table__
 _RP_TBL = models.ResourceProvider.__table__
 
 
-@db_api.api_context_manager.writer
-def _create_rp_in_db(context, updates):
-    db_rp = models.ResourceProvider()
-    db_rp.update(updates)
-    context.session.add(db_rp)
-    return db_rp
-
-
-@db_api.api_context_manager.writer
-def _delete_rp_from_db(context, _id):
-    # Don't delete the resource provider if it has allocations.
-    rp_allocations = context.session.query(models.Allocation).\
-                     filter(models.Allocation.resource_provider_id == _id).\
-                     count()
-    if rp_allocations:
-        raise exception.ResourceProviderInUse()
-    # Delete any inventory associated with the resource provider
-    context.session.query(models.Inventory).\
-        filter(models.Inventory.resource_provider_id == _id).delete()
-    result = context.session.query(models.ResourceProvider).\
-             filter(models.ResourceProvider.id == _id).delete()
-    if not result:
-        raise exception.NotFound()
-
-
-@db_api.api_context_manager.writer
-def _update_rp_in_db(context, id, updates):
-    db_rp = context.session.query(models.ResourceProvider).filter_by(
-        id=id).first()
-    db_rp.update(updates)
-    db_rp.save(context.session)
-
-
-@db_api.api_context_manager.reader
-def _get_rp_by_uuid_from_db(context, uuid):
-    result = context.session.query(models.ResourceProvider).filter_by(
-        uuid=uuid).first()
-    if not result:
-        raise exception.NotFound()
-    return result
-
-
 def _get_current_inventory_resources(conn, rp):
     """Returns a set() containing the resource class IDs for all resources
     currently having an inventory record for the supplied resource provider.
@@ -341,16 +299,37 @@ class ResourceProvider(base.NovaObject):
         self.obj_reset_changes()
 
     @staticmethod
+    @db_api.api_context_manager.writer
     def _create_in_db(context, updates):
-        return _create_rp_in_db(context, updates)
+        db_rp = models.ResourceProvider()
+        db_rp.update(updates)
+        context.session.add(db_rp)
+        return db_rp
 
     @staticmethod
-    def _delete(context, id):
-        _delete_rp_from_db(context, id)
+    @db_api.api_context_manager.writer
+    def _delete(context, _id):
+        # Don't delete the resource provider if it has allocations.
+        rp_allocations = context.session.query(models.Allocation).\
+                         filter(models.Allocation.resource_provider_id == _id).\
+                         count()
+        if rp_allocations:
+            raise exception.ResourceProviderInUse()
+        # Delete any inventory associated with the resource provider
+        context.session.query(models.Inventory).\
+            filter(models.Inventory.resource_provider_id == _id).delete()
+        result = context.session.query(models.ResourceProvider).\
+                 filter(models.ResourceProvider.id == _id).delete()
+        if not result:
+            raise exception.NotFound()
 
     @staticmethod
+    @db_api.api_context_manager.writer
     def _update_in_db(context, id, updates):
-        return _update_rp_in_db(context, id, updates)
+        db_rp = context.session.query(models.ResourceProvider).filter_by(
+            id=id).first()
+        db_rp.update(updates)
+        db_rp.save(context.session)
 
     @staticmethod
     def _from_db_object(context, resource_provider, db_resource_provider):
@@ -361,8 +340,13 @@ class ResourceProvider(base.NovaObject):
         return resource_provider
 
     @staticmethod
+    @db_api.api_context_manager.reader
     def _get_by_uuid_from_db(context, uuid):
-        return _get_rp_by_uuid_from_db(context, uuid)
+        result = context.session.query(models.ResourceProvider).filter_by(
+            uuid=uuid).first()
+        if not result:
+            raise exception.NotFound()
+        return result
 
 
 @base.NovaObjectRegistry.register