Fixed Celery Serialization Bug

CourseLocator is not JSON-serializable. Passing course keys as Unicode instead when scheduling tasks to update course structure.

lms/djangoapps/course_structure_api/v0/tests.py

@@ -299,7 +299,7 @@ class CourseStructureTests(CourseDetailMixin, CourseViewTestsMixin, ModuleStoreT
         super(CourseStructureTests, self).setUp()
 
         # Ensure course structure exists for the course
-        update_course_structure(self.course.id)
+        update_course_structure(unicode(self.course.id))
 
     def test_get(self):
         """

lms/djangoapps/course_structure_api/v0/views.py

@@ -192,7 +192,7 @@ class CourseStructure(CourseViewMixin, RetrieveAPIView):
             return super(CourseStructure, self).retrieve(request, *args, **kwargs)
         except models.CourseStructure.DoesNotExist:
             # If we don't have data stored, generate it and return a 503.
-            models.update_course_structure.delay(self.course.id)
+            models.update_course_structure.delay(unicode(self.course.id))
             return Response(status=503, headers={'Retry-After': '120'})
 
     def get_object(self, queryset=None):

openedx/core/djangoapps/content/course_structures/management/commands/generate_course_structure.py

@@ -39,7 +39,7 @@ class Command(BaseCommand):
 
         for course_key in course_keys:
             try:
-                update_course_structure(course_key)
+                update_course_structure(unicode(course_key))
             except Exception as e:
                 logger.error('An error occurred while generating course structure for %s: %s', unicode(course_key), e)
 

openedx/core/djangoapps/content/course_structures/models.py

@@ -4,7 +4,7 @@ import logging
 from celery.task import task
 from django.dispatch import receiver
 from model_utils.models import TimeStampedModel
-from opaque_keys.edx.locator import CourseLocator
+from opaque_keys.edx.keys import CourseKey
 from xmodule.modulestore.django import modulestore, SignalHandler
 
 from util.models import CompressedTextField
@@ -60,7 +60,7 @@ def generate_course_structure(course_key):
 def listen_for_course_publish(sender, course_key, **kwargs):
     # Note: The countdown=0 kwarg is set to to ensure the method below does not attempt to access the course
     # before the signal emitter has finished all operations. This is also necessary to ensure all tests pass.
-    update_course_structure.delay(course_key, countdown=0)
+    update_course_structure.delay(unicode(course_key), countdown=0)
 
 
 @task()
@@ -68,9 +68,12 @@ def update_course_structure(course_key):
     """
     Regenerates and updates the course structure (in the database) for the specified course.
     """
-    if not isinstance(course_key, CourseLocator):
-        logger.error('update_course_structure requires a CourseLocator. Given %s.', type(course_key))
-        return
+    # Ideally we'd like to accept a CourseLocator; however, CourseLocator is not JSON-serializable (by default) so
+    # Celery's delayed tasks fail to start. For this reason, callers should pass the course key as a Unicode string.
+    if not isinstance(course_key, basestring):
+        raise ValueError('course_key must be a string. {} is not acceptable.'.format(type(course_key)))
+
+    course_key = CourseKey.from_string(course_key)
 
     try:
         structure = generate_course_structure(course_key)