Monkey patch django.db.models.options for faster cache expiry

cms/startup.py

@@ -9,7 +9,7 @@ settings.INSTALLED_APPS  # pylint: disable=pointless-statement
 
 from openedx.core.lib.django_startup import autostartup
 import django
-from monkey_patch import third_party_auth
+from monkey_patch import third_party_auth, django_db_models_options
 
 import xmodule.x_module
 import cms.lib.xblock.runtime
@@ -22,6 +22,7 @@ def run():
     Executed during django startup
     """
     third_party_auth.patch()
+    django_db_models_options.patch()
 
     # Comprehensive theming needs to be set up before django startup,
     # because modifying django template paths after startup has no effect.

common/djangoapps/monkey_patch/django_db_models_options.py

+"""
+Monkey patch implementation of the following _expire_cache performance improvement:
+
+https://github.com/django/django/commit/7628f87e2b1ab4b8a881f06c8973be4c368aaa3d
+
+Remove once we upgrade to a version of django which includes this fix natively!
+NOTE: This is on django's master branch but is NOT currently part of any django 1.8 or 1.9 release.
+"""
+
+from django.db.models.options import Options
+
+
+def patch():
+    """
+    Monkey-patch the Options class.
+    """
+    def _expire_cache(self, forward=True, reverse=True):
+        # pylint: disable=missing-docstring
+
+        # This method is usually called by apps.cache_clear(), when the
+        # registry is finalized, or when a new field is added.
+        if forward:
+            for cache_key in self.FORWARD_PROPERTIES:
+                if cache_key in self.__dict__:
+                    delattr(self, cache_key)
+        if reverse and not self.abstract:
+            for cache_key in self.REVERSE_PROPERTIES:
+                if cache_key in self.__dict__:
+                    delattr(self, cache_key)
+        self._get_fields_cache = {}  # pylint: disable=protected-access
+
+    # Patch constants as a set instead of a list.
+    Options.FORWARD_PROPERTIES = {'fields', 'many_to_many', 'concrete_fields',
+                                  'local_concrete_fields', '_forward_fields_map'}
+
+    Options.REVERSE_PROPERTIES = {'related_objects', 'fields_map', '_relation_tree'}
+
+    # Patch the expire_cache method to utilize constant's new set data structure.
+    Options._expire_cache = _expire_cache  # pylint: disable=protected-access

lms/startup.py

@@ -12,7 +12,7 @@ from openedx.core.lib.django_startup import autostartup
 import edxmako
 import logging
 import analytics
-from monkey_patch import third_party_auth
+from monkey_patch import third_party_auth, django_db_models_options
 
 
 import xmodule.x_module
@@ -29,6 +29,7 @@ def run():
     Executed during django startup
     """
     third_party_auth.patch()
+    django_db_models_options.patch()
 
     # To override the settings before executing the autostartup() for python-social-auth
     if settings.FEATURES.get('ENABLE_THIRD_PARTY_AUTH', False):