celery = Celery(broker='amqp://test:test@localhost:5672/test')
celery.conf.update(CELERY_RESULT_BACKEND='mongodb')

@celery.task
def task_a(result):
    print('task_a:', result)
return result

@celery.task
def task_b(result):
    print('task_b:', result)
return result

@celery.task
def task_c(result):
    print('task_c:', result)
return result

@celery.task
def notify_user(result):
    print(result)
return result
Celery: обратный вызов после иерархии задач