If you combine Celery with supervisord it's important to check the official config file[1]. At least two settings there are really important - `stopwaitsecs=600` and `killasgroup=true`. If you don't use them you might end up with a bunch of orphaned child Celery processes and your tasks might be executed more than once.

[1] https://github.com/celery/celery/blob/ee46d0b78d8ffc068d5b80...