Celery signal task_success executes in which process?

Question

If I hook up a callback to the celery task_success signal handler, which process does it get executed in? The child or the worker process?

The documentation does not explicitly list it. (It lists it for the signal task_sent, but not for the other signals: http://docs.celeryproject.org/en/latest/userguide/signals.html#task-sent)

thanks...

Answer 1

There's no such thing as a "child" process; there is the process sending the task (which can be any Python process, including a celery worker, or celery beat, or anything else) and there is the worker that processes the task.

All the task signals except task_sent are executed in the worker that processes the task; in fact they can't possibly execute anywhere else. Celery signals (like Django signals) are not like operating system events, or like Celery tasks, which can originate in one process and trigger something in another process; they get processed in the same process as that in which they originate. They have nothing to do with the Python standard library signal module.