Fixed #26804 -- Fixed a race condition in QuerySet.update_or_create().

This commit is contained in:
Jensen Cochran 2016-06-24 12:08:42 -05:00 committed by Tim Graham
parent 76e19da5b0
commit d44afd8892
3 changed files with 62 additions and 11 deletions

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@ -347,6 +347,7 @@ answer newbie questions, and generally made Django that much better:
Jeff Triplett <jeff.triplett@gmail.com>
Jens Diemer <django@htfx.de>
Jens Page
Jensen Cochran <jensen.cochran@gmail.com>
Jeong-Min Lee <falsetru@gmail.com>
Jérémie Blaser <blaserje@gmail.com>
Jeremy Carbaugh <jcarbaugh@gmail.com>

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@ -482,8 +482,9 @@ class QuerySet(object):
defaults = defaults or {}
lookup, params = self._extract_model_params(defaults, **kwargs)
self._for_write = True
with transaction.atomic(using=self.db):
try:
obj = self.get(**lookup)
obj = self.select_for_update().get(**lookup)
except self.model.DoesNotExist:
obj, created = self._create_object_from_params(lookup, params)
if created:

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@ -1,10 +1,14 @@
from __future__ import unicode_literals
import time
import traceback
from datetime import date
from datetime import date, datetime, timedelta
from threading import Thread
from django.db import DatabaseError, IntegrityError
from django.test import TestCase, TransactionTestCase, ignore_warnings
from django.test import (
TestCase, TransactionTestCase, ignore_warnings, skipUnlessDBFeature,
)
from django.utils.encoding import DjangoUnicodeDecodeError
from .models import (
@ -422,3 +426,48 @@ class UpdateOrCreateTests(TestCase):
)
self.assertIs(created, False)
self.assertEqual(obj.last_name, 'NotHarrison')
class UpdateOrCreateTransactionTests(TransactionTestCase):
available_apps = ['get_or_create']
@skipUnlessDBFeature('has_select_for_update')
@skipUnlessDBFeature('supports_transactions')
def test_updates_in_transaction(self):
"""
Objects are selected and updated in a transaction to avoid race
conditions. This test forces update_or_create() to hold the lock
in another thread for a relatively long time so that it can update
while it holds the lock. The updated field isn't a field in 'defaults',
so update_or_create() shouldn't have an effect on it.
"""
def birthday_sleep():
time.sleep(0.3)
return date(1940, 10, 10)
def update_birthday_slowly():
Person.objects.update_or_create(
first_name='John', defaults={'birthday': birthday_sleep}
)
Person.objects.create(first_name='John', last_name='Lennon', birthday=date(1940, 10, 9))
# update_or_create in a separate thread
t = Thread(target=update_birthday_slowly)
before_start = datetime.now()
t.start()
# Wait for lock to begin
time.sleep(0.05)
# Update during lock
Person.objects.filter(first_name='John').update(last_name='NotLennon')
after_update = datetime.now()
# Wait for thread to finish
t.join()
# The update remains and it blocked.
updated_person = Person.objects.get(first_name='John')
self.assertGreater(after_update - before_start, timedelta(seconds=0.3))
self.assertEqual(updated_person.last_name, 'NotLennon')