Removes redundant validation of template (1)

As part of stack create and preview, template is being
validated twice, first at service._validate_new_stack()
and second at stack.validate() by self.t.validate().
This patch fixes this issue.
It also improves code readability by using
proper indentation.

NOTE: second part, will have dogpile cache backend
integration

Change-Id: I86649752cadcd145760d482d07313881183b02b0
Closes-bug: #1444316

heat/engine/template.py

@@ -15,6 +15,7 @@ import abc
 import collections
 import copy
 import functools
+import hashlib
 
 from oslo_log import log as logging
 import six
@@ -115,8 +116,10 @@ class Template(collections.Mapping):
         self.files = files or {}
         self.maps = self[self.MAPPINGS]
         self.env = env or environment.Environment({})
+
         self.version = get_version(self.t,
                                    list(six.iterkeys(_template_classes)))
+        self.t_digest = None
 
     def __deepcopy__(self, memo):
         return Template(copy.deepcopy(self.t, memo), files=self.files,
@@ -226,6 +229,18 @@ class Template(collections.Mapping):
         sections (e.g. parameters are check by parameters schema class).
 
         '''
+        t_digest = hashlib.sha256(six.text_type(self.t)).hexdigest()
+
+        # TODO(kanagaraj-manickam) currently t_digest is stored in self. which
+        # is used to check whether already template is validated or not.
+        # But it needs to be loaded from dogpile cache backend once its
+        # available in heat (http://specs.openstack.org/openstack/heat-specs/
+        # specs/liberty/constraint-validation-cache.html). This is required
+        # as multiple heat-engines may process the same template at least
+        # in case of instance_group. And it fixes partially bug 1444316
+
+        if t_digest == self.t_digest:
+            return
 
         # check top-level sections
         for k in six.iterkeys(self.t):
@@ -243,6 +258,7 @@ class Template(collections.Mapping):
                 message = _('Resources must contain Resource. '
                             'Found a [%s] instead') % type(res)
                 raise exception.StackValidationFailed(message=message)
+        self.t_digest = t_digest
 
     @classmethod
     def create_empty_template(cls,

heat/tests/test_template.py

@@ -12,6 +12,7 @@
 #    under the License.
 
 import copy
+import hashlib
 import json
 
 import fixtures
@@ -271,6 +272,27 @@ class ParserTest(common.HeatTestCase):
 
 class TestTemplateValidate(common.HeatTestCase):
 
+    def test_template_validate_cfn_check_t_digest(self):
+        t = {
+            'AWSTemplateFormatVersion': '2010-09-09',
+            'Description': 'foo',
+            'Parameters': {},
+            'Mappings': {},
+            'Resources': {
+                'server': {
+                    'Type': 'OS::Nova::Server'
+                }
+            },
+            'Outputs': {},
+        }
+
+        tmpl = template.Template(t)
+        self.assertIsNone(tmpl.t_digest)
+        tmpl.validate()
+        self.assertEqual(hashlib.sha256(six.text_type(t)).hexdigest(),
+                         tmpl.t_digest,
+                         'invalid template digest')
+
     def test_template_validate_cfn_good(self):
         t = {
             'AWSTemplateFormatVersion': '2010-09-09',
@@ -328,15 +350,35 @@ class TestTemplateValidate(common.HeatTestCase):
 
     def test_template_validate_cfn_empty(self):
         t = template_format.parse('''
-AWSTemplateFormatVersion: 2010-09-09
-Parameters:
-Resources:
-Outputs:
-''')
+            AWSTemplateFormatVersion: 2010-09-09
+            Parameters:
+            Resources:
+            Outputs:
+            ''')
         tmpl = template.Template(t)
         err = tmpl.validate()
         self.assertIsNone(err)
 
+    def test_template_validate_hot_check_t_digest(self):
+        t = {
+            'heat_template_version': '2015-04-30',
+            'description': 'foo',
+            'parameters': {},
+            'resources': {
+                'server': {
+                    'type': 'OS::Nova::Server'
+                }
+            },
+            'outputs': {},
+        }
+
+        tmpl = template.Template(t)
+        self.assertIsNone(tmpl.t_digest)
+        tmpl.validate()
+        self.assertEqual(hashlib.sha256(six.text_type(t)).hexdigest(),
+                         tmpl.t_digest,
+                         'invalid template digest')
+
     def test_template_validate_hot_good(self):
         t = {
             'heat_template_version': '2013-05-23',
@@ -507,16 +549,16 @@ class TemplateTest(common.HeatTestCase):
 
     def test_invalid_template(self):
         scanner_error = '''
-1
-Mappings:
-  ValidMapping:
-    TestKey: TestValue
-'''
+            1
+            Mappings:
+              ValidMapping:
+                TestKey: TestValue
+            '''
         parser_error = '''
-Mappings:
-  ValidMapping:
-    TestKey: {TestKey1: "Value1" TestKey2: "Value2"}
-'''
+            Mappings:
+              ValidMapping:
+                TestKey: {TestKey1: "Value1" TestKey2: "Value2"}
+            '''
 
         self.assertRaises(ValueError, template_format.parse, scanner_error)
         self.assertRaises(ValueError, template_format.parse, parser_error)