Change the central cache to store at two levels: first by scope, then by cache key

lms/djangoapps/courseware/model_data.py

@@ -84,7 +84,7 @@ class UserStateCache(object):
         self.course_id = course_id
 
     def cache_key_for_field_object(self, field_object):
-        return (Scope.user_state, field_object.module_state_key.map_into_course(self.course_id))
+        return field_object.module_state_key.map_into_course(self.course_id)
 
 
 class UserStateSummaryCache(object):
@@ -102,7 +102,7 @@ class UserStateSummaryCache(object):
         self.course_id = course_id
 
     def cache_key_for_field_object(self, field_object):
-        return (Scope.user_state_summary, field_object.usage_id.map_into_course(self.course_id), field_object.field_name)
+        return (field_object.usage_id.map_into_course(self.course_id), field_object.field_name)
 
 
 class PreferencesCache(object):
@@ -120,7 +120,7 @@ class PreferencesCache(object):
         )
 
     def cache_key_for_field_object(self, field_object):
-        return (Scope.preferences, field_object.module_type, field_object.field_name)
+        return (field_object.module_type, field_object.field_name)
 
 
 class UserInfoCache(object):
@@ -136,7 +136,7 @@ class UserInfoCache(object):
         )
 
     def cache_key_for_field_object(self, field_object):
-        return (Scope.user_info, field_object.field_name)
+        return field_object.field_name
 
 
 class FieldDataCache(object):
@@ -158,7 +158,12 @@ class FieldDataCache(object):
         select_for_update: True if rows should be locked until end of transaction
         asides: The list of aside types to load, or None to prefetch no asides.
         '''
-        self.cache = {}
+        self.cache = {
+            Scope.user_state: {},
+            Scope.user_info: {},
+            Scope.preferences: {},
+            Scope.user_state_summary: {},
+        }
         self.select_for_update = select_for_update
 
         if asides is None:
@@ -301,7 +306,7 @@ class FieldDataCache(object):
             return
 
         for field_object in cache._data:
-            self.cache[cache.cache_key_for_field_object(field_object)] = field_object
+            self.cache[scope][cache.cache_key_for_field_object(field_object)] = field_object
 
     def _fields_to_cache(self, descriptors):
         """
@@ -318,13 +323,13 @@ class FieldDataCache(object):
         Return the key used in the FieldDataCache for the specified KeyValueStore key
         """
         if key.scope == Scope.user_state:
-            return (key.scope, key.block_scope_id)
+            return key.block_scope_id
         elif key.scope == Scope.user_state_summary:
-            return (key.scope, key.block_scope_id, key.field_name)
+            return (key.block_scope_id, key.field_name)
         elif key.scope == Scope.preferences:
-            return (key.scope, BlockTypeKeyV1(key.block_family, key.block_scope_id), key.field_name)
+            return (BlockTypeKeyV1(key.block_family, key.block_scope_id), key.field_name)
         elif key.scope == Scope.user_info:
-            return (key.scope, key.field_name)
+            return key.field_name
 
     def find(self, key):
         '''
@@ -339,7 +344,7 @@ class FieldDataCache(object):
             # user we were constructed for.
             assert key.user_id == self.user.id
 
-        return self.cache.get(self._cache_key_from_kvs_key(key))
+        return self.cache[key.scope].get(self._cache_key_from_kvs_key(key))
 
     def find_or_create(self, key):
         '''
@@ -379,7 +384,7 @@ class FieldDataCache(object):
             )
 
         cache_key = self._cache_key_from_kvs_key(key)
-        self.cache[cache_key] = field_object
+        self.cache[key.scope][cache_key] = field_object
         return field_object
 
 

lms/djangoapps/courseware/tests/test_model_data.py

@@ -230,7 +230,7 @@ class TestMissingStudentModule(TestCase):
 
     def test_set_field_in_missing_student_module(self):
         "Test that setting a field in a missing StudentModule creates the student module"
-        self.assertEquals(0, len(self.field_data_cache.cache))
+        self.assertEquals(0, sum(len(cache) for cache in self.field_data_cache.cache.values()))
         self.assertEquals(0, StudentModule.objects.all().count())
 
         # We are updating a problem, so we write to courseware_studentmodulehistory
@@ -238,7 +238,7 @@ class TestMissingStudentModule(TestCase):
         with self.assertNumQueries(6):
             self.kvs.set(user_state_key('a_field'), 'a_value')
 
-        self.assertEquals(1, len(self.field_data_cache.cache))
+        self.assertEquals(1, sum(len(cache) for cache in self.field_data_cache.cache.values()))
         self.assertEquals(1, StudentModule.objects.all().count())
 
         student_module = StudentModule.objects.all()[0]