def _create_override(self, request_user, subsection_grade_model, **override_data):
        """
        Helper method to create a `PersistentSubsectionGradeOverride` object
        and send a `SUBSECTION_OVERRIDE_CHANGED` signal.
        """
        override = PersistentSubsectionGradeOverride.update_or_create_override(
            requesting_user=request_user,
            subsection_grade_model=subsection_grade_model,
            feature=grades_constants.GradeOverrideFeatureEnum.gradebook,
            **override_data
        )

        set_event_transaction_type(grades_events.SUBSECTION_GRADE_CALCULATED)
        create_new_event_transaction_id()

        recalculate_subsection_grade_v3.apply(
            kwargs=dict(
                user_id=subsection_grade_model.user_id,
                anonymous_user_id=None,
                course_id=text_type(subsection_grade_model.course_id),
                usage_id=text_type(subsection_grade_model.usage_key),
                only_if_higher=False,
                expected_modified_time=to_timestamp(override.modified),
                score_deleted=False,
                event_transaction_id=six.text_type(get_event_transaction_id()),
                event_transaction_type=six.text_type(get_event_transaction_type()),
                score_db_table=grades_constants.ScoreDatabaseTableEnum.overrides,
                force_update_subsections=True,
            )
        )
        # Emit events to let our tracking system to know we updated subsection grade
        grades_events.subsection_grade_calculated(subsection_grade_model)
        return override

    def undo_override_subsection_grade(self, user_id, course_key_or_id, usage_key_or_id):
        """
        Delete the override subsection grade row (the PersistentSubsectionGrade model must already exist)

        Fires off a recalculate_subsection_grade async task to update the PersistentSubsectionGrade table. If the
        override does not exist, no error is raised, it just triggers the recalculation.
        """
        # prevent circular imports:
        from .signals.handlers import SUBSECTION_OVERRIDE_EVENT_TYPE

        course_key = _get_key(course_key_or_id, CourseKey)
        usage_key = _get_key(usage_key_or_id, UsageKey)

        override = self.get_subsection_grade_override(user_id, course_key, usage_key)
        # Older rejected exam attempts that transition to verified might not have an override created
        if override is not None:
            override.delete()

        # Cache a new event id and event type which the signal handler will use to emit a tracking log event.
        create_new_event_transaction_id()
        set_event_transaction_type(SUBSECTION_OVERRIDE_EVENT_TYPE)

        # Signal will trigger subsection recalculation which will call PersistentSubsectionGrade.update_or_create_grade
        # which will no longer use the above deleted override, and instead return the grade to the original score from
        # the actual problem responses before writing to the table.
        SUBSECTION_OVERRIDE_CHANGED.send(
            sender=None,
            user_id=user_id,
            course_id=unicode(course_key),
            usage_id=unicode(usage_key),
            only_if_higher=False,
            modified=datetime.now().replace(tzinfo=pytz.UTC),  # Not used when score_deleted=True
            score_deleted=True,
            score_db_table=ScoreDatabaseTableEnum.overrides
        )

def compute_grades_for_course_v2(self, **kwargs):
    """
    Compute grades for a set of students in the specified course.

    The set of students will be determined by the order of enrollment date, and
    limited to at most <batch_size> students, starting from the specified
    offset.

    TODO: Roll this back into compute_grades_for_course once all workers have
    the version with **kwargs.

    Sets the ESTIMATE_FIRST_ATTEMPTED flag, then calls the original task as a
    synchronous function.

    estimate_first_attempted:
        controls whether to unconditionally set the ESTIMATE_FIRST_ATTEMPTED
        waffle switch.  If false or not provided, use the global value of
        the ESTIMATE_FIRST_ATTEMPTED waffle switch.
    """
    if 'event_transaction_id' in kwargs:
        set_event_transaction_id(kwargs['event_transaction_id'])

    if 'event_transaction_type' in kwargs:
        set_event_transaction_type(kwargs['event_transaction_type'])

    if kwargs.get('estimate_first_attempted'):
        waffle().override_for_request(ESTIMATE_FIRST_ATTEMPTED, True)

    try:
        return compute_grades_for_course(kwargs['course_key'], kwargs['offset'], kwargs['batch_size'])
    except Exception as exc:   # pylint: disable=broad-except
        raise self.retry(kwargs=kwargs, exc=exc)

def recalculate_subsection_grade_v2(**kwargs):
    """
    Updates a saved subsection grade.

    Arguments:
        user_id (int): id of applicable User object
        course_id (string): identifying the course
        usage_id (string): identifying the course block
        only_if_higher (boolean): indicating whether grades should
            be updated only if the new raw_earned is higher than the
            previous value.
        expected_modified_time (serialized timestamp): indicates when the task
            was queued so that we can verify the underlying data update.
        score_deleted (boolean): indicating whether the grade change is
            a result of the problem's score being deleted.
        event_transaction_id(string): uuid identifying the current
            event transaction.
        event_transaction_type(string): human-readable type of the
            event at the root of the current event transaction.
    """
    try:
        course_key = CourseLocator.from_string(kwargs['course_id'])
        if not PersistentGradesEnabledFlag.feature_enabled(course_key):
            return

        score_deleted = kwargs['score_deleted']
        scored_block_usage_key = UsageKey.from_string(kwargs['usage_id']).replace(course_key=course_key)
        expected_modified_time = from_timestamp(kwargs['expected_modified_time'])

        # The request cache is not maintained on celery workers,
        # where this code runs. So we take the values from the
        # main request cache and store them in the local request
        # cache. This correlates model-level grading events with
        # higher-level ones.
        set_event_transaction_id(kwargs.pop('event_transaction_id', None))
        set_event_transaction_type(kwargs.pop('event_transaction_type', None))

        # Verify the database has been updated with the scores when the task was
        # created. This race condition occurs if the transaction in the task
        # creator's process hasn't committed before the task initiates in the worker
        # process.
        if not _has_database_updated_with_new_score(
                kwargs['user_id'], scored_block_usage_key, expected_modified_time, score_deleted,
        ):
            raise _retry_recalculate_subsection_grade(**kwargs)

        _update_subsection_grades(
            course_key,
            scored_block_usage_key,
            kwargs['only_if_higher'],
            kwargs['user_id'],
        )

    except Exception as exc:   # pylint: disable=broad-except
        if not isinstance(exc, KNOWN_RETRY_ERRORS):
            log.info("tnl-6244 grades unexpected failure: {}. kwargs={}".format(
                repr(exc),
                kwargs
            ))
        raise _retry_recalculate_subsection_grade(exc=exc, **kwargs)

def grade_updated(**kwargs):
    """
    Emits the appropriate grade-related event after checking for which
    event-transaction is active.

    Emits a problem.submitted event only if there is no current event
    transaction type, i.e. we have not reached this point in the code via
    an outer event type (such as problem.rescored or score_overridden).
    """
    root_type = get_event_transaction_type()

    if not root_type:
        root_id = get_event_transaction_id()
        if not root_id:
            root_id = create_new_event_transaction_id()
        set_event_transaction_type(PROBLEM_SUBMITTED_EVENT_TYPE)
        tracker.emit(
            unicode(PROBLEM_SUBMITTED_EVENT_TYPE),
            {
                'user_id': unicode(kwargs['user_id']),
                'course_id': unicode(kwargs['course_id']),
                'problem_id': unicode(kwargs['usage_id']),
                'event_transaction_id': unicode(root_id),
                'event_transaction_type': unicode(PROBLEM_SUBMITTED_EVENT_TYPE),
                'weighted_earned': kwargs.get('weighted_earned'),
                'weighted_possible': kwargs.get('weighted_possible'),
            }
        )

    elif root_type in [GRADES_RESCORE_EVENT_TYPE, GRADES_OVERRIDE_EVENT_TYPE]:
        current_user = get_current_user()
        instructor_id = getattr(current_user, 'id', None)
        tracker.emit(
            unicode(root_type),
            {
                'course_id': unicode(kwargs['course_id']),
                'user_id': unicode(kwargs['user_id']),
                'problem_id': unicode(kwargs['usage_id']),
                'new_weighted_earned': kwargs.get('weighted_earned'),
                'new_weighted_possible': kwargs.get('weighted_possible'),
                'only_if_higher': kwargs.get('only_if_higher'),
                'instructor_id': unicode(instructor_id),
                'event_transaction_id': unicode(get_event_transaction_id()),
                'event_transaction_type': unicode(root_type),
            }
        )

    elif root_type in [SUBSECTION_OVERRIDE_EVENT_TYPE]:
        tracker.emit(
            unicode(root_type),
            {
                'course_id': unicode(kwargs['course_id']),
                'user_id': unicode(kwargs['user_id']),
                'problem_id': unicode(kwargs['usage_id']),
                'only_if_higher': kwargs.get('only_if_higher'),
                'override_deleted': kwargs.get('score_deleted', False),
                'event_transaction_id': unicode(get_event_transaction_id()),
                'event_transaction_type': unicode(root_type),
            }
        )

    def override_subsection_grade(
            self, user_id, course_key_or_id, usage_key_or_id, earned_all=None, earned_graded=None
    ):
        """
        Creates a PersistentSubsectionGradeOverride corresponding to the given
        user, course, and usage_key.
        Will also create a ``PersistentSubsectionGrade`` for this (user, course, usage_key)
        if none currently exists.

        Fires off a recalculate_subsection_grade async task to update the PersistentCourseGrade table.
        Will not override ``earned_all`` or ``earned_graded`` value if they are ``None``.
        Both of these parameters have ``None`` as their default value.
        """
        course_key = _get_key(course_key_or_id, CourseKey)
        usage_key = _get_key(usage_key_or_id, UsageKey)

        try:
            grade = PersistentSubsectionGrade.read_grade(
                user_id=user_id,
                usage_key=usage_key
            )
        except PersistentSubsectionGrade.DoesNotExist:
            grade = self._create_subsection_grade(user_id, course_key, usage_key)

        override = PersistentSubsectionGradeOverride.update_or_create_override(
            requesting_user=None,
            subsection_grade_model=grade,
            feature=GradeOverrideFeatureEnum.proctoring,
            earned_all_override=earned_all,
            earned_graded_override=earned_graded,
        )

        # Cache a new event id and event type which the signal handler will use to emit a tracking log event.
        create_new_event_transaction_id()
        set_event_transaction_type(SUBSECTION_OVERRIDE_EVENT_TYPE)

        # This will eventually trigger a re-computation of the course grade,
        # taking the new PersistentSubsectionGradeOverride into account.
        SUBSECTION_OVERRIDE_CHANGED.send(
            sender=None,
            user_id=user_id,
            course_id=text_type(course_key),
            usage_id=text_type(usage_key),
            only_if_higher=False,
            modified=override.modified,
            score_deleted=False,
            score_db_table=ScoreDatabaseTableEnum.overrides
        )

    def override_subsection_grade(self, user_id, course_key_or_id, usage_key_or_id, earned_all=None,
                                  earned_graded=None):
        """
        Override subsection grade (the PersistentSubsectionGrade model must already exist)

        Fires off a recalculate_subsection_grade async task to update the PersistentSubsectionGrade table. Will not
        override earned_all or earned_graded value if they are None. Both default to None.
        """
        course_key = _get_key(course_key_or_id, CourseKey)
        usage_key = _get_key(usage_key_or_id, UsageKey)

        grade = PersistentSubsectionGrade.objects.get(
            user_id=user_id,
            course_id=course_key,
            usage_key=usage_key
        )

        # Create override that will prevent any future updates to grade
        override, _ = PersistentSubsectionGradeOverride.objects.update_or_create(
            grade=grade,
            earned_all_override=earned_all,
            earned_graded_override=earned_graded
        )

        _ = PersistentSubsectionGradeOverrideHistory.objects.create(
            override_id=override.id,
            feature=PersistentSubsectionGradeOverrideHistory.PROCTORING,
            action=PersistentSubsectionGradeOverrideHistory.CREATE_OR_UPDATE
        )

        # Cache a new event id and event type which the signal handler will use to emit a tracking log event.
        create_new_event_transaction_id()
        set_event_transaction_type(SUBSECTION_OVERRIDE_EVENT_TYPE)

        # Signal will trigger subsection recalculation which will call PersistentSubsectionGrade.update_or_create_grade
        # which will use the above override to update the grade before writing to the table.
        SUBSECTION_OVERRIDE_CHANGED.send(
            sender=None,
            user_id=user_id,
            course_id=unicode(course_key),
            usage_id=unicode(usage_key),
            only_if_higher=False,
            modified=override.modified,
            score_deleted=False,
            score_db_table=ScoreDatabaseTableEnum.overrides
        )

def _emit_event(kwargs):
    """
    Emits a problem submitted event only if there is no current event
    transaction type, i.e. we have not reached this point in the code via a
    rescore or student state deletion.

    If the event transaction type has already been set and the transacation is
    a rescore, emits a problem rescored event.
    """
    root_type = get_event_transaction_type()

    if not root_type:
        root_id = get_event_transaction_id()
        if not root_id:
            root_id = create_new_event_transaction_id()
        set_event_transaction_type(PROBLEM_SUBMITTED_EVENT_TYPE)
        tracker.emit(
            unicode(PROBLEM_SUBMITTED_EVENT_TYPE),
            {
                'user_id': unicode(kwargs['user_id']),
                'course_id': unicode(kwargs['course_id']),
                'problem_id': unicode(kwargs['usage_id']),
                'event_transaction_id': unicode(root_id),
                'event_transaction_type': unicode(PROBLEM_SUBMITTED_EVENT_TYPE),
                'weighted_earned': kwargs.get('weighted_earned'),
                'weighted_possible': kwargs.get('weighted_possible'),
            }
        )

    if root_type in [GRADES_RESCORE_EVENT_TYPE, GRADES_OVERRIDE_EVENT_TYPE]:
        current_user = get_current_user()
        instructor_id = getattr(current_user, 'id', None)
        tracker.emit(
            unicode(GRADES_RESCORE_EVENT_TYPE),
            {
                'course_id': unicode(kwargs['course_id']),
                'user_id': unicode(kwargs['user_id']),
                'problem_id': unicode(kwargs['usage_id']),
                'new_weighted_earned': kwargs.get('weighted_earned'),
                'new_weighted_possible': kwargs.get('weighted_possible'),
                'only_if_higher': kwargs.get('only_if_higher'),
                'instructor_id': unicode(instructor_id),
                'event_transaction_id': unicode(get_event_transaction_id()),
                'event_transaction_type': unicode(root_type),
            }
        )

    def handle(self, *args, **options):
        if 'modified_start' not in options:
            raise CommandError('modified_start must be provided.')

        if 'modified_end' not in options:
            raise CommandError('modified_end must be provided.')

        modified_start = utc.localize(datetime.strptime(options['modified_start'], DATE_FORMAT))
        modified_end = utc.localize(datetime.strptime(options['modified_end'], DATE_FORMAT))
        event_transaction_id = create_new_event_transaction_id()
        set_event_transaction_type(PROBLEM_SUBMITTED_EVENT_TYPE)
        kwargs = {'modified__range': (modified_start, modified_end), 'module_type': 'problem'}
        for record in StudentModule.objects.filter(**kwargs):
            task_args = {
                "user_id": record.student_id,
                "course_id": unicode(record.course_id),
                "usage_id": unicode(record.module_state_key),
                "only_if_higher": False,
                "expected_modified_time": to_timestamp(record.modified),
                "score_deleted": False,
                "event_transaction_id": unicode(event_transaction_id),
                "event_transaction_type": PROBLEM_SUBMITTED_EVENT_TYPE,
                "score_db_table": ScoreDatabaseTableEnum.courseware_student_module,
            }
            recalculate_subsection_grade_v3.apply_async(kwargs=task_args)

        kwargs = {'created_at__range': (modified_start, modified_end)}
        for record in Submission.objects.filter(**kwargs):
            task_args = {
                "user_id": user_by_anonymous_id(record.student_item.student_id).id,
                "anonymous_user_id": record.student_item.student_id,
                "course_id": unicode(record.student_item.course_id),
                "usage_id": unicode(record.student_item.item_id),
                "only_if_higher": False,
                "expected_modified_time": to_timestamp(record.created_at),
                "score_deleted": False,
                "event_transaction_id": unicode(event_transaction_id),
                "event_transaction_type": PROBLEM_SUBMITTED_EVENT_TYPE,
                "score_db_table": ScoreDatabaseTableEnum.submissions,
            }
            recalculate_subsection_grade_v3.apply_async(kwargs=task_args)

def compute_grades_for_course_v2(self, **kwargs):
    """
    Compute grades for a set of students in the specified course.

    The set of students will be determined by the order of enrollment date, and
    limited to at most <batch_size> students, starting from the specified
    offset.

    TODO: Roll this back into compute_grades_for_course once all workers have
    the version with **kwargs.
    """
    if 'event_transaction_id' in kwargs:
        set_event_transaction_id(kwargs['event_transaction_id'])

    if 'event_transaction_type' in kwargs:
        set_event_transaction_type(kwargs['event_transaction_type'])

    try:
        return compute_grades_for_course(kwargs['course_key'], kwargs['offset'], kwargs['batch_size'])
    except Exception as exc:
        raise self.retry(kwargs=kwargs, exc=exc)

    def _create_override(self, request_user, subsection_grade_model, **override_data):
        """
        Helper method to create a `PersistentSubsectionGradeOverride` object
        and send a `SUBSECTION_OVERRIDE_CHANGED` signal.
        """
        override, _ = PersistentSubsectionGradeOverride.objects.update_or_create(
            grade=subsection_grade_model,
            defaults=self._clean_override_data(override_data),
        )

        _ = PersistentSubsectionGradeOverrideHistory.objects.create(
            override_id=override.id,
            user=request_user,
            feature=PersistentSubsectionGradeOverrideHistory.GRADEBOOK,
            action=PersistentSubsectionGradeOverrideHistory.CREATE_OR_UPDATE,
        )

        set_event_transaction_type(SUBSECTION_GRADE_CALCULATED)
        create_new_event_transaction_id()

        recalculate_subsection_grade_v3.apply(
            kwargs=dict(
                user_id=subsection_grade_model.user_id,
                anonymous_user_id=None,
                course_id=text_type(subsection_grade_model.course_id),
                usage_id=text_type(subsection_grade_model.usage_key),
                only_if_higher=False,
                expected_modified_time=to_timestamp(override.modified),
                score_deleted=False,
                event_transaction_id=unicode(get_event_transaction_id()),
                event_transaction_type=unicode(get_event_transaction_type()),
                score_db_table=ScoreDatabaseTableEnum.overrides,
                force_update_subsections=True,
            )
        )
        # Emit events to let our tracking system to know we updated subsection grade
        subsection_grade_calculated(subsection_grade_model)

def _recalculate_subsection_grade(self, **kwargs):
    """
    Updates a saved subsection grade.

    Keyword Arguments:
        user_id (int): id of applicable User object
        anonymous_user_id (int, OPTIONAL): Anonymous ID of the User
        course_id (string): identifying the course
        usage_id (string): identifying the course block
        only_if_higher (boolean): indicating whether grades should
            be updated only if the new raw_earned is higher than the
            previous value.
        expected_modified_time (serialized timestamp): indicates when the task
            was queued so that we can verify the underlying data update.
        score_deleted (boolean): indicating whether the grade change is
            a result of the problem's score being deleted.
        event_transaction_id (string): uuid identifying the current
            event transaction.
        event_transaction_type (string): human-readable type of the
            event at the root of the current event transaction.
        score_db_table (ScoreDatabaseTableEnum): database table that houses
            the changed score. Used in conjunction with expected_modified_time.
    """
    try:
        course_key = CourseLocator.from_string(kwargs['course_id'])
        scored_block_usage_key = UsageKey.from_string(kwargs['usage_id']).replace(course_key=course_key)

        set_custom_metrics_for_course_key(course_key)
        set_custom_metric('usage_id', unicode(scored_block_usage_key))

        # The request cache is not maintained on celery workers,
        # where this code runs. So we take the values from the
        # main request cache and store them in the local request
        # cache. This correlates model-level grading events with
        # higher-level ones.
        set_event_transaction_id(kwargs.get('event_transaction_id'))
        set_event_transaction_type(kwargs.get('event_transaction_type'))

        # Verify the database has been updated with the scores when the task was
        # created. This race condition occurs if the transaction in the task
        # creator's process hasn't committed before the task initiates in the worker
        # process.
        has_database_updated = _has_db_updated_with_new_score(self, scored_block_usage_key, **kwargs)

        if not has_database_updated:
            raise DatabaseNotReadyError

        _update_subsection_grades(
            course_key,
            scored_block_usage_key,
            kwargs['only_if_higher'],
            kwargs['user_id'],
            kwargs['score_deleted'],
        )
    except Exception as exc:
        if not isinstance(exc, KNOWN_RETRY_ERRORS):
            log.info("tnl-6244 grades unexpected failure: {}. task id: {}. kwargs={}".format(
                repr(exc),
                self.request.id,
                kwargs,
            ))
        raise self.retry(kwargs=kwargs, exc=exc)

def override_score_module_state(xmodule_instance_args, module_descriptor, student_module, task_input):
    '''
    Takes an XModule descriptor and a corresponding StudentModule object, and
    performs an override on the student's problem score.

    Throws exceptions if the override is fatal and should be aborted if in a loop.
    In particular, raises UpdateProblemModuleStateError if module fails to instantiate,
    or if the module doesn't support overriding, or if the score used for override
    is outside the acceptable range of scores (between 0 and the max score for the
    problem).

    Returns True if problem was successfully overriden for the given student, and False
    if problem encountered some kind of error in overriding.
    '''
    # unpack the StudentModule:
    course_id = student_module.course_id
    student = student_module.student
    usage_key = student_module.module_state_key

    with modulestore().bulk_operations(course_id):
        course = get_course_by_id(course_id)
        instance = _get_module_instance_for_task(
            course_id,
            student,
            module_descriptor,
            xmodule_instance_args,
            course=course
        )

        if instance is None:
            # Either permissions just changed, or someone is trying to be clever
            # and load something they shouldn't have access to.
            msg = "No module {location} for student {student}--access denied?".format(
                location=usage_key,
                student=student
            )
            TASK_LOG.warning(msg)
            return UPDATE_STATUS_FAILED

        if not hasattr(instance, 'set_score'):
            msg = "Scores cannot be overridden for this problem type."
            raise UpdateProblemModuleStateError(msg)

        weighted_override_score = float(task_input['score'])
        if not (0 <= weighted_override_score <= instance.max_score()):
            msg = "Score must be between 0 and the maximum points available for the problem."
            raise UpdateProblemModuleStateError(msg)

        # Set the tracking info before this call, because it makes downstream
        # calls that create events.  We retrieve and store the id here because
        # the request cache will be erased during downstream calls.
        create_new_event_transaction_id()
        set_event_transaction_type(GRADES_OVERRIDE_EVENT_TYPE)

        problem_weight = instance.weight if instance.weight is not None else 1
        if problem_weight == 0:
            msg = "Scores cannot be overridden for a problem that has a weight of zero."
            raise UpdateProblemModuleStateError(msg)
        else:
            instance.set_score(Score(
                raw_earned=weighted_override_score / problem_weight,
                raw_possible=instance.max_score() / problem_weight
            ))

        instance.publish_grade()
        instance.save()
        TASK_LOG.debug(
            u"successfully processed score override for course %(course)s, problem %(loc)s "
            u"and student %(student)s",
            dict(
                course=course_id,
                loc=usage_key,
                student=student
            )
        )

        return UPDATE_STATUS_SUCCEEDED

def rescore_problem_module_state(xmodule_instance_args, module_descriptor, student_module, task_input):
    '''
    Takes an XModule descriptor and a corresponding StudentModule object, and
    performs rescoring on the student's problem submission.

    Throws exceptions if the rescoring is fatal and should be aborted if in a loop.
    In particular, raises UpdateProblemModuleStateError if module fails to instantiate,
    or if the module doesn't support rescoring.

    Returns True if problem was successfully rescored for the given student, and False
    if problem encountered some kind of error in rescoring.
    '''
    # unpack the StudentModule:
    course_id = student_module.course_id
    student = student_module.student
    usage_key = student_module.module_state_key

    with modulestore().bulk_operations(course_id):
        course = get_course_by_id(course_id)
        # TODO: Here is a call site where we could pass in a loaded course.  I
        # think we certainly need it since grading is happening here, and field
        # overrides would be important in handling that correctly
        instance = _get_module_instance_for_task(
            course_id,
            student,
            module_descriptor,
            xmodule_instance_args,
            grade_bucket_type='rescore',
            course=course
        )

        if instance is None:
            # Either permissions just changed, or someone is trying to be clever
            # and load something they shouldn't have access to.
            msg = "No module {location} for student {student}--access denied?".format(
                location=usage_key,
                student=student
            )
            TASK_LOG.warning(msg)
            return UPDATE_STATUS_FAILED

        if not hasattr(instance, 'rescore'):
            # This should not happen, since it should be already checked in the
            # caller, but check here to be sure.
            msg = "Specified module {0} of type {1} does not support rescoring.".format(usage_key, instance.__class__)
            raise UpdateProblemModuleStateError(msg)

        # We check here to see if the problem has any submissions. If it does not, we don't want to rescore it
        if not instance.has_submitted_answer():
            return UPDATE_STATUS_SKIPPED

        # Set the tracking info before this call, because it makes downstream
        # calls that create events.  We retrieve and store the id here because
        # the request cache will be erased during downstream calls.
        create_new_event_transaction_id()
        set_event_transaction_type(GRADES_RESCORE_EVENT_TYPE)

        # specific events from CAPA are not propagated up the stack. Do we want this?
        try:
            instance.rescore(only_if_higher=task_input['only_if_higher'])
        except (LoncapaProblemError, StudentInputError, ResponseError):
            TASK_LOG.warning(
                u"error processing rescore call for course %(course)s, problem %(loc)s "
                u"and student %(student)s",
                dict(
                    course=course_id,
                    loc=usage_key,
                    student=student
                )
            )
            return UPDATE_STATUS_FAILED

        instance.save()
        TASK_LOG.debug(
            u"successfully processed rescore call for course %(course)s, problem %(loc)s "
            u"and student %(student)s",
            dict(
                course=course_id,
                loc=usage_key,
                student=student
            )
        )

        return UPDATE_STATUS_SUCCEEDED