def add_user_to_cohorts_race_condition(self, mock_tracker):
"""
Makes use of before_after to force a race condition, in order to
confirm handling of such conditions is done correctly.
"""
course_user = UserFactory(username="******", email="*****@*****.**")
course = modulestore().get_course(self.toy_course_key)
CourseEnrollment.enroll(course_user, self.toy_course_key)
first_cohort = CohortFactory(course_id=course.id, name="FirstCohort")
second_cohort = CohortFactory(course_id=course.id, name="SecondCohort")
# This before_after contextmanager allows for reliable reproduction of a race condition.
# It will break before the first save() call creates an entry, and then run add_user_to_cohort again.
# Because this second call will write before control is returned, the first call will be writing stale data.
# This test confirms that the first add_user_to_cohort call can handle this stale read condition properly.
# Proper handling is defined as treating calls as sequential, with write time deciding the order.
with before_after.before_after('django.db.models.Model.save',
after_ftn=cohorts.add_user_to_cohort(
second_cohort,
course_user.username),
autospec=True):
# This method will read, then break, then try to write stale data.
# It should fail at that, then retry with refreshed data
cohorts.add_user_to_cohort(first_cohort, course_user.username)
mock_tracker.emit.assert_any_call(
"edx.cohort.user_add_requested", {
"user_id": course_user.id,
"cohort_id": first_cohort.id,
"cohort_name": first_cohort.name,
"previous_cohort_id": second_cohort.id,
"previous_cohort_name": second_cohort.name,
})
# Note that the following get() will fail with MultipleObjectsReturned if race condition is not handled.
self.assertEqual(first_cohort.users.get(), course_user)
def test_before_and_after(self):
def before_fn(*a):
test_functions.test_list.append(1)
def after_fn(*a):
test_functions.test_list.append(3)
with before_after('before_after.tests.test_functions.sample_fn',
before_fn=before_fn,
after_fn=after_fn):
test_functions.sample_fn(2)
self.assertEqual(test_functions.test_list, [1, 2, 3])
def add_user_to_cohorts_race_condition(self, mock_tracker):
"""
Makes use of before_after to force a race condition, in order to
confirm handling of such conditions is done correctly.
"""
course_user = UserFactory(username="******", email="*****@*****.**")
course = modulestore().get_course(self.toy_course_key)
CourseEnrollment.enroll(course_user, self.toy_course_key)
first_cohort = CohortFactory(course_id=course.id, name="FirstCohort")
second_cohort = CohortFactory(course_id=course.id, name="SecondCohort")
# This before_after contextmanager allows for reliable reproduction of a race condition.
# It will break before the first save() call creates an entry, and then run add_user_to_cohort again.
# Because this second call will write before control is returned, the first call will be writing stale data.
# This test confirms that the first add_user_to_cohort call can handle this stale read condition properly.
# Proper handling is defined as treating calls as sequential, with write time deciding the order.
with before_after.before_after(
'django.db.models.Model.save',
after_ftn=cohorts.add_user_to_cohort(second_cohort, course_user.username),
autospec=True
):
# This method will read, then break, then try to write stale data.
# It should fail at that, then retry with refreshed data
cohorts.add_user_to_cohort(first_cohort, course_user.username)
mock_tracker.emit.assert_any_call(
"edx.cohort.user_add_requested",
{
"user_id": course_user.id,
"cohort_id": first_cohort.id,
"cohort_name": first_cohort.name,
"previous_cohort_id": second_cohort.id,
"previous_cohort_name": second_cohort.name,
}
)
# Note that the following get() will fail with MultipleObjectsReturned if race condition is not handled.
self.assertEqual(first_cohort.users.get(), course_user)