Django related objects are missing from celery task (race condition?)

Question

Strange behavior, that I don\'t know how to explain. I\'ve got a model, Track, with some related points. I call a celery task to performs some calculat

Answer 1

So, I've solved it using django-transaction-hooks. It still looks kinda scary to replace my DB backend, but django-celery-transactions seems to be broken in Django 1.6. Now my setup looks like this:

settings.py:

DATABASES = {
    'default': {
        'ENGINE': 'transaction_hooks.backends.postgresql_psycopg2',
        'NAME': 'foo',
        },
    }
SOUTH_DATABASE_ADAPTERS = {'default':'south.db.postgresql_psycopg2'}  # this is required, or South breaks

models.py:

from django.db import connection

@shared_task
def my_task(track):
    print 'in the task', track.id, track.points.all().count()

def some_method():
    t = Track()
    t.save()
    t = fill_with_points(t)  # creating points, attaching them to a Track
    t.save()
    print 'before the task', track.id, track.points.all().count()
    connection.on_commit(lambda: my_task.delay(t))

Results:

before the task, 21346, 2971
in the task, 21346, 2971

It still seems strange that such a common use case has no native celery or Django solution.