[bug 1408981] Update bundle key generation. (#307)

* [bug 1408981] Update bundle key generation.

 - Use only startpage_version and locale used in the templates.

 - Include in the key either template for AS or for about:home, so that changes
   in one template does not affect the cached keys of the other.

* Hard-code date in template hash calculation.

Hard-code the date in template hash calculation to prevent getting new bundle
keys between deployments and also share the keys between the different cluster
regions.

snippets/base/models.py

@@ -41,6 +41,7 @@
     render_to_string(
         'base/fetch_snippets.jinja',
         {
+            'date': '',
             'snippet_ids': [],
             'snippets_json': '',
             'locale': 'xx',
@@ -54,6 +55,7 @@
     render_to_string(
         'base/fetch_snippets_as.jinja',
         {
+            'date': '',
             'snippet_ids': [],
             'snippets_json': '',
             'locale': 'xx',
@@ -152,21 +154,28 @@ def __init__(self, client):
     @cached_property
     def key(self):
         """A unique key for this bundle as a sha1 hexdigest."""
-        # Key should consist of snippets that are in the bundle plus any
-        # properties of the client that may change the snippet code
-        # being sent.
+        # Key should consist of snippets that are in the bundle. This part
+        # accounts for all the properties sent by the Client, since the
+        # self.snippets lists snippets are all filters and CMRs have been
+        # applied.
         key_properties = [
             '{id}-{date}-{templatedate}'.format(id=snippet.id,
                                                 date=snippet.modified.isoformat(),
                                                 templatedate=snippet.template.modified.isoformat())
             for snippet in self.snippets]
 
-        key_properties.extend(self.client)
+        # Additional values used to calculate the key are the templates and the
+        # variables used to render them besides snippets.
         key_properties.extend([
-            SNIPPET_FETCH_TEMPLATE_HASH,
-            SNIPPET_FETCH_TEMPLATE_AS_HASH,
+            self.client.startpage_version,
+            self.client.locale,
             util.current_firefox_major_version(),
+
         ])
+        if self.client.startpage_version == '5':
+            key_properties.append(SNIPPET_FETCH_TEMPLATE_AS_HASH)
+        else:
+            key_properties.append(SNIPPET_FETCH_TEMPLATE_HASH)
 
         key_string = u'_'.join(key_properties)
         return hashlib.sha1(key_string.encode('utf-8')).hexdigest()

snippets/base/templates/base/fetch_snippets.jinja

@@ -1,7 +1,11 @@
 {% include 'base/includes/snippet.css' %}
 <script type="text/javascript">
  //<![CDATA[
- // Generated on {{ utcnow() }}
+{#
+ The date variable gets populated when we calculate the template hash for caching
+ and gets the default utcnow() time otherwise.
+#}
+ // Generated on {{ date|default(utcnow()) }}
  // Included snippets:
      {% for id in snippet_ids %}
  //  - {{ id }}

snippets/base/templates/base/fetch_snippets_as.jinja

@@ -2,7 +2,11 @@
   {% include 'base/includes/snippet_as.css' %}
 </style>
 <script type="application/javascript">
- // Generated on {{ utcnow() }}
+{#
+ The date variable gets populated when we calculate the template hash for caching
+ and gets the default utcnow() time otherwise.
+#}
+ // Generated on {{ date|default(utcnow()) }}
  // Included snippets:
  {% for id in snippet_ids %}
  //  - {{ id }}

snippets/base/tests/test_models.py

@@ -417,18 +417,6 @@ def test_key_locale(self):
 
         self.assertNotEqual(bundle1.key, bundle2.key)
 
-    def test_key_name(self):
-        """
-        bundle.key must be different between bundles if they have
-        different names.
-        """
-        client1 = self._client(name='firefox')
-        client2 = self._client(name='firefox-test')
-        bundle1 = SnippetBundle(client1)
-        bundle2 = SnippetBundle(client2)
-
-        self.assertNotEqual(bundle1.key, bundle2.key)
-
     def test_key_equal(self):
         client1 = self._client(locale='en-US', startpage_version='4')
         client2 = self._client(locale='en-US', startpage_version='4')