From 7127ab863fd3aa5845f2b25a5a35c6b291fbe326 Mon Sep 17 00:00:00 2001
From: "J. Cliff Dyer" <cdyer@edx.org>
Date: Tue, 16 May 2017 11:46:24 -0400
Subject: [PATCH] Use a stable ordering for shuffled tasks.

---
 .../management/commands/compute_grades.py       |  7 ++++---
 .../commands/tests/test_compute_grades.py       | 17 ++++++++++++++---
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/lms/djangoapps/grades/management/commands/compute_grades.py b/lms/djangoapps/grades/management/commands/compute_grades.py
index ee32f01809..dae2000080 100644
--- a/lms/djangoapps/grades/management/commands/compute_grades.py
+++ b/lms/djangoapps/grades/management/commands/compute_grades.py
@@ -4,8 +4,8 @@ Command to compute all grades for specified courses.
 
 from __future__ import absolute_import, division, print_function, unicode_literals
 
+import hashlib
 import logging
-from random import shuffle
 
 from django.core.management.base import BaseCommand
 import six
@@ -88,7 +88,8 @@ class Command(BaseCommand):
         Enqueue all tasks, in shuffled order.
         """
         task_options = {'routing_key': options['routing_key']} if options.get('routing_key') else {}
-        for kwargs in self._shuffled_task_kwargs(options):
+        for seq_id, kwargs in enumerate(self._shuffled_task_kwargs(options)):
+            kwargs['seq_id'] = seq_id
             result = tasks.compute_grades_for_course_v2.apply_async(kwargs=kwargs, **task_options)
             log.info("Grades: Created {task_name}[{task_id}] with arguments {kwargs}".format(
                 task_name=tasks.compute_grades_for_course.name,
@@ -116,7 +117,7 @@ class Command(BaseCommand):
                 # The dictionaries with their extra overhead will be created
                 # and consumed one at a time.
                 all_args.append((six.text_type(course_key), offset, batch_size))
-        shuffle(all_args)
+        all_args.sort(key=lambda x: hashlib.md5(b'{!r}'.format(x)))
         for args in all_args:
             yield {
                 'course_key': args[0],
diff --git a/lms/djangoapps/grades/management/commands/tests/test_compute_grades.py b/lms/djangoapps/grades/management/commands/tests/test_compute_grades.py
index 76cffdf084..064c7a2296 100644
--- a/lms/djangoapps/grades/management/commands/tests/test_compute_grades.py
+++ b/lms/djangoapps/grades/management/commands/tests/test_compute_grades.py
@@ -27,6 +27,14 @@ def _sorted_by_batch(calls):
     return sorted(calls, key=lambda x: (x[1]['kwargs']['course_key'], x[1]['kwargs']['offset']))
 
 
+class Any(object):
+    """
+    Dummy object that compares equal to all other objects.
+    """
+    def __eq__(self, other):
+        return True
+
+
 @ddt.ddt
 class TestComputeGrades(SharedModuleStoreTestCase):
     """
@@ -100,7 +108,8 @@ class TestComputeGrades(SharedModuleStoreTestCase):
             'course_key': course_key,
             'batch_size': 2,
             'offset': offset,
-            'estimate_first_attempted': estimate_first_attempted
+            'estimate_first_attempted': estimate_first_attempted,
+            'seq_id': Any(),
         }
         self.assertEqual(
             _sorted_by_batch(mock_task.apply_async.call_args_list),
@@ -136,7 +145,8 @@ class TestComputeGrades(SharedModuleStoreTestCase):
                         'course_key': self.course_keys[1],
                         'batch_size': 2,
                         'offset': 0,
-                        'estimate_first_attempted': True
+                        'estimate_first_attempted': True,
+                        'seq_id': Any(),
                     },
                 },),
                 ({
@@ -144,7 +154,8 @@ class TestComputeGrades(SharedModuleStoreTestCase):
                         'course_key': self.course_keys[1],
                         'batch_size': 2,
                         'offset': 2,
-                        'estimate_first_attempted': True
+                        'estimate_first_attempted': True,
+                        'seq_id': Any(),
                     },
                 },),
             ],