Allow null edited_timestamp

Some old mongo courses do not have this field, and the team has opted
to allow null values rather than inserting a default. This change
affects both course and subsection grades.

TNL-6408

lms/djangoapps/grades/migrations/0011_null_edited_time.py

@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('grades', '0010_auto_20170112_1156'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='persistentcoursegrade',
+            name='course_edited_timestamp',
+            field=models.DateTimeField(null=True, verbose_name='Last content edit timestamp', blank=True),
+        ),
+        migrations.AlterField(
+            model_name='persistentsubsectiongrade',
+            name='course_version',
+            field=models.CharField(max_length=255, verbose_name='Guid of latest course version', blank=True),
+        ),
+        migrations.AlterField(
+            model_name='persistentsubsectiongrade',
+            name='subtree_edited_timestamp',
+            field=models.DateTimeField(null=True, verbose_name='Last content edit timestamp', blank=True),
+        ),
+    ]

lms/djangoapps/grades/models.py

@@ -277,8 +277,8 @@ class PersistentSubsectionGrade(DeleteGradesMixin, TimeStampedModel):
     usage_key = UsageKeyField(blank=False, max_length=255)
 
     # Information relating to the state of content when grade was calculated
-    subtree_edited_timestamp = models.DateTimeField('last content edit timestamp', blank=False)
-    course_version = models.CharField('guid of latest course version', blank=True, max_length=255)
+    subtree_edited_timestamp = models.DateTimeField(u'Last content edit timestamp', blank=True, null=True)
+    course_version = models.CharField(u'Guid of latest course version', blank=True, max_length=255)
 
     # earned/possible refers to the number of points achieved and available to achieve.
     # graded refers to the subset of all problems that are marked as being graded.
@@ -529,7 +529,7 @@ class PersistentCourseGrade(DeleteGradesMixin, TimeStampedModel):
     course_id = CourseKeyField(blank=False, max_length=255)
 
     # Information relating to the state of content when grade was calculated
-    course_edited_timestamp = models.DateTimeField(u'Last content edit timestamp', blank=False)
+    course_edited_timestamp = models.DateTimeField(u'Last content edit timestamp', blank=True, null=True)
     course_version = models.CharField(u'Course content version identifier', blank=True, max_length=255)
     grading_policy_hash = models.CharField(u'Hash of grading policy', blank=False, max_length=255)
 

lms/djangoapps/grades/new/subsection_grade.py

@@ -32,7 +32,7 @@ class SubsectionGrade(object):
         self.graded = getattr(subsection, 'graded', False)
 
         self.course_version = getattr(subsection, 'course_version', None)
-        self.subtree_edited_timestamp = subsection.subtree_edited_on
+        self.subtree_edited_timestamp = getattr(subsection, 'subtree_edited_on', None)
 
         self.graded_total = None  # aggregated grade for all graded problems
         self.all_total = None  # aggregated grade for all problems, regardless of whether they are graded
@@ -341,6 +341,6 @@ class SubsectionGradeFactory(object):
             log_statement,
             self.course.id,
             getattr(subsection, 'course_version', None),
-            subsection.subtree_edited_on,
+            getattr(subsection, 'subtree_edited_on', None),
             self.student.id,
         ))

lms/djangoapps/grades/signals/handlers.py

@@ -27,7 +27,7 @@ from .signals import (
 from ..constants import ScoreDatabaseTableEnum
 from ..new.course_grade import CourseGradeFactory
 from ..scores import weighted_score
-from ..tasks import recalculate_subsection_grade_v3
+from ..tasks import recalculate_subsection_grade_v3, RECALCULATE_GRADE_DELAY
 
 log = getLogger(__name__)
 
@@ -192,7 +192,7 @@ def enqueue_subsection_update(sender, **kwargs):  # pylint: disable=unused-argum
             event_transaction_type=unicode(get_event_transaction_type()),
             score_db_table=kwargs['score_db_table'],
         ),
-        countdown=2,
+        countdown=RECALCULATE_GRADE_DELAY,
     )
     log.info(
         u'Grades: Request async calculation of subsection grades with args: {}. Task [{}]'.format(

lms/djangoapps/grades/tasks.py

@@ -33,6 +33,7 @@ from .transformer import GradesTransformer
 log = getLogger(__name__)
 
 KNOWN_RETRY_ERRORS = (DatabaseError, ValidationError)  # Errors we expect occasionally, should be resolved on retry
+RECALCULATE_GRADE_DELAY = 2  # in seconds, to prevent excessive _has_db_updated failures. See TNL-6424.
 
 
 @task(bind=True, base=PersistOnFailureTask, default_retry_delay=30, routing_key=settings.RECALCULATE_GRADES_ROUTING_KEY)

lms/djangoapps/grades/tests/test_models.py

@@ -231,14 +231,14 @@ class PersistentSubsectionGradeTest(GradesModelTestCase):
         with self.assertRaises(ValidationError):
             PersistentSubsectionGrade.create_grade(**self.params)
 
-    def test_optional_fields(self):
-        del self.params["course_version"]
+    @ddt.data('course_version', 'subtree_edited_timestamp')
+    def test_optional_fields(self, field):
+        del self.params[field]
         PersistentSubsectionGrade.create_grade(**self.params)
 
     @ddt.data(
         ("user_id", ValidationError),
         ("usage_key", KeyError),
-        ("subtree_edited_timestamp", ValidationError),
         ("earned_all", ValidationError),
         ("possible_all", ValidationError),
         ("earned_graded", ValidationError),
@@ -427,10 +427,11 @@ class PersistentCourseGradesTest(GradesModelTestCase):
         self.assertIsInstance(created_grade.passed_timestamp, datetime)
         self.assertEqual(created_grade, read_grade)
 
-    def test_course_version_optional(self):
-        del self.params["course_version"]
+    @ddt.data('course_version', 'course_edited_timestamp')
+    def test_optional_fields(self, field):
+        del self.params[field]
         grade = PersistentCourseGrade.update_or_create_course_grade(**self.params)
-        self.assertEqual("", grade.course_version)
+        self.assertFalse(getattr(grade, field))
 
     @ddt.data(
         ("percent_grade", "Not a float at all", ValueError),

lms/djangoapps/grades/tests/test_tasks.py

@@ -27,7 +27,7 @@ from xmodule.modulestore.tests.factories import CourseFactory, ItemFactory, chec
 from lms.djangoapps.grades.config.models import PersistentGradesEnabledFlag
 from lms.djangoapps.grades.constants import ScoreDatabaseTableEnum
 from lms.djangoapps.grades.signals.signals import PROBLEM_WEIGHTED_SCORE_CHANGED
-from lms.djangoapps.grades.tasks import recalculate_subsection_grade_v3
+from lms.djangoapps.grades.tasks import recalculate_subsection_grade_v3, RECALCULATE_GRADE_DELAY
 
 
 @patch.dict(settings.FEATURES, {'PERSISTENT_GRADES_ENABLED_FOR_ALL_TESTS': False})
@@ -114,7 +114,7 @@ class RecalculateSubsectionGradeTest(ModuleStoreTestCase):
             return_value=None
         ) as mock_task_apply:
             PROBLEM_WEIGHTED_SCORE_CHANGED.send(sender=None, **send_args)
-            mock_task_apply.assert_called_once_with(kwargs=local_task_args)
+            mock_task_apply.assert_called_once_with(countdown=RECALCULATE_GRADE_DELAY, kwargs=local_task_args)
 
     @patch('lms.djangoapps.grades.signals.signals.SUBSECTION_SCORE_CHANGED.send')
     def test_triggers_subsection_score_signal(self, mock_subsection_signal):