Merge performance fixes, and rename StudentModule.get_from_cache to get_with_caching

courseware/content_parser.py

@@ -168,17 +168,23 @@ def course_xml_process(tree):
     return tree
 
 def course_file(user):
-    ''' Given a user, return course.xml
-    '''
-    # TODO: Cache. 
+    ''' Given a user, return course.xml'''
     filename = user.profile_cache.courseware # UserProfile.objects.get(user=user).courseware
-
     groups = user_groups(user)
-
     options = {'dev_content':settings.DEV_CONTENT, 
                'groups' : groups}
 
+    
+    cache_key = filename + "_processed?dev_content:" + str(options['dev_content']) + "&groups:" + str(sorted(groups))
+    tree_string = cache.get(cache_key)
+    if not tree_string:
         tree = course_xml_process(etree.XML(render_to_string(filename, options, namespace = 'course')))
+        tree_string = etree.tostring(tree)
+        
+        cache.set(cache_key, tree_string, 60)
+    else:
+        tree = etree.XML(tree_string)
+
     return tree
 
 def section_file(user, section):

courseware/models.py

@@ -8,12 +8,19 @@ file and check it in at the same time as your model changes. To do that,
 2. ./manage.py schemamigration courseware --auto description_of_your_change
 3. Add the migration file created in mitx/courseware/migrations/
 
+
+ASSUMPTIONS: modules have unique IDs, even across different module_types
+
 """
 from django.db import models
+from django.db.models.signals import post_save, post_delete
+from django.core.cache import cache
 from django.contrib.auth.models import User
 
 from cache_toolbox import cache_model, cache_relation
 
+CACHE_TIMEOUT = 60 * 60 * 4 # Set the cache timeout to be four hours
+
 class StudentModule(models.Model):
     # For a homework problem, contains a JSON
     # object consisting of state
@@ -51,5 +58,35 @@ class StudentModule(models.Model):
     def __unicode__(self):
         return self.module_type+'/'+self.student.username+"/"+self.module_id+'/'+str(self.state)[:20]
 
+    @classmethod
+    def get_with_caching(cls, student, module_id):
+        k = cls.key_for(student, module_id)
+        student_module = cache.get(k)
+        if student_module is None:
+            student_module = StudentModule.objects.filter(student=student,
+                                                          module_id=module_id)[0]
+            # It's possible it really doesn't exist...
+            if student_module is not None:
+                cache.set(k, student_module, CACHE_TIMEOUT)
+
+        return student_module
+
+    @classmethod
+    def key_for(cls, student, module_id):
+        return "StudentModule-student_id:{0};module_id:{1}".format(student.id, module_id)
+
+
+def clear_cache_by_student_and_module_id(sender, instance, *args, **kwargs):
+    k = sender.key_for(instance.student, instance.module_id)
+    cache.delete(k)
+
+def update_cache_by_student_and_module_id(sender, instance, *args, **kwargs):
+    k = sender.key_for(instance.student, instance.module_id)
+    cache.set(k, instance, CACHE_TIMEOUT)
+
+
+post_save.connect(update_cache_by_student_and_module_id, sender=StudentModule, weak=False)
+post_delete.connect(clear_cache_by_student_and_module_id, sender=StudentModule, weak=False)
 
 cache_model(StudentModule)
+

courseware/module_render.py

@@ -48,13 +48,13 @@ def make_track_function(request):
 def modx_dispatch(request, module=None, dispatch=None, id=None):
     ''' Generic view for extensions. '''
     # Grab the student information for the module from the database
-    s = StudentModule.objects.filter(student=request.user, 
-                                     module_id=id)
-    if len(s) == 0:
+    #s = StudentModule.objects.filter(student=request.user, 
+    #                                 module_id=id)
+    s = StudentModule.get_with_caching(request.user, id)
+    if s is None:
         log.debug("Couldnt find module for user and id " + str(module) + " " + str(request.user) + " "+ str(id))
         raise Http404
 
-    s=s[0]
     oldgrade = s.grade
     oldstate = s.state