From 7cd0d244640c188e40448841af50352deee7c45a Mon Sep 17 00:00:00 2001
From: Crag Wolfe <cwolfe@redhat.com>
Date: Wed, 19 Oct 2016 17:59:41 -0700
Subject: [PATCH] Allow lazy load of raw_template but log warning

To avoid hard-to-debug bugs, rather than represent a db_stack's
raw_template as None if it hasn't been eagerly loaded, lazy load
it. In the lazy loading case, log a warning so developers are aware
there is a non-eager loading query that needs to be fixed.

Change-Id: Ic06a4bd7afbd4838ca97be302d75dede5402ae6e
---
 heat/objects/stack.py    | 26 +++++++++++++++++++++++---
 heat/tests/test_stack.py | 22 ++++++++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/heat/objects/stack.py b/heat/objects/stack.py
index cd52cbd2c4..a6904865d3 100644
--- a/heat/objects/stack.py
+++ b/heat/objects/stack.py
@@ -15,6 +15,7 @@
 
 """Stack object."""
 
+from oslo_log import log as logging
 from oslo_versionedobjects import base
 from oslo_versionedobjects import fields
 import six
@@ -28,6 +29,8 @@ from heat.objects import fields as heat_fields
 from heat.objects import raw_template
 from heat.objects import stack_tag
 
+LOG = logging.getLogger(__name__)
+
 
 class Stack(
     heat_base.HeatObject,
@@ -53,7 +56,7 @@ class Stack(
         'action': fields.StringField(nullable=True),
         'status': fields.StringField(nullable=True),
         'status_reason': fields.StringField(nullable=True),
-        'raw_template': fields.ObjectField('RawTemplate'),
+        'raw_template_obj': fields.ObjectField('RawTemplate'),
         'convergence': fields.BooleanField(),
         'current_traversal': fields.StringField(),
         'current_deps': heat_fields.JsonField(),
@@ -65,7 +68,7 @@ class Stack(
     @staticmethod
     def _from_db_object(context, stack, db_stack):
         for field in stack.fields:
-            if field == 'raw_template':
+            if field == 'raw_template_obj':
                 raw_template_obj = db_stack.__dict__.get('raw_template')
                 if raw_template_obj is not None:
                     # Object is already lazy loaded
@@ -74,13 +77,30 @@ class Stack(
                             context,
                             raw_template.RawTemplate(),
                             raw_template_obj))
-                stack['raw_template'] = raw_template_obj
+                    stack._raw_template = raw_template_obj
             else:
                 stack[field] = db_stack.__dict__.get(field)
         stack._context = context
         stack.obj_reset_changes()
         return stack
 
+    @property
+    def raw_template(self):
+        if hasattr(self, '_raw_template'):
+            return self._raw_template
+
+        LOG.warning('Loading a raw_template that should have been '
+                    'eagerly loaded for stack id %s' % self.id)
+        self._raw_template = raw_template.RawTemplate.get_by_id(
+            self._context,
+            self['raw_template_id'])
+        return self._raw_template
+
+    @raw_template.setter
+    def raw_template(self, value):
+        self['raw_template_obj'] = value
+        self._raw_template = value
+
     @classmethod
     def get_root_id(cls, context, stack_id):
         return db_api.stack_get_root_id(context, stack_id)
diff --git a/heat/tests/test_stack.py b/heat/tests/test_stack.py
index 94f42ea2c1..bae2f1d516 100644
--- a/heat/tests/test_stack.py
+++ b/heat/tests/test_stack.py
@@ -1710,6 +1710,28 @@ class StackTest(common.HeatTestCase):
                          self.stack.state)
         self.m.VerifyAll()
 
+    def test_stack_eager_or_lazy_load_templ(self):
+        self.stack = stack.Stack(self.ctx, 'test_stack_eager_or_lazy_tmpl',
+                                 self.tmpl)
+        self.stack.store()
+
+        ctx1 = utils.dummy_context()
+        s1_db_result = db_api.stack_get(ctx1, self.stack.id, eager_load=True)
+        s1_obj = stack_object.Stack._from_db_object(ctx1, stack_object.Stack(),
+                                                    s1_db_result)
+        self.assertIsNotNone(s1_obj._raw_template)
+        self.assertIsNotNone(s1_obj.raw_template)
+
+        ctx2 = utils.dummy_context()
+        s2_db_result = db_api.stack_get(ctx2, self.stack.id, eager_load=False)
+        s2_obj = stack_object.Stack._from_db_object(ctx2, stack_object.Stack(),
+                                                    s2_db_result)
+        # _raw_template has not been set since it not eagerly loaded
+        self.assertFalse(hasattr(s2_obj, "_raw_template"))
+        # accessing raw_template lazy loads it
+        self.assertIsNotNone(s2_obj.raw_template)
+        self.assertIsNotNone(s2_obj._raw_template)
+
     def test_preview_resources_returns_list_of_resource_previews(self):
         tmpl = {'HeatTemplateFormatVersion': '2012-12-12',
                 'Resources': {'AResource': {'Type': 'GenericResourceType'}}}