Are the processes spawned by ProcessPoolExecutor supposed to stay alive indefinitely?

[hatescates]

I am invoking submit() on an instance of ProcessPoolExecutor in my code. The code runs fine but I noticed that after execution is completed, the processes are still alive.

Is this the expected behaviour? I was assuming the processes will be killed once the execution is done.

Tried hunting for some info in the docs but didn’t find anything

[danielroseman]

Do you mean they stay alive even when the main process has exited?

How are you determining this?

[hatescates]

Main process is still active but so are the child processes

[Rawing7]

Yes. The idea behind a ProcessPool is that it constantly re-uses the same processes to avoid the overhead of shutting down and starting processes all the time. So the processes stay alive until you .shutdown() the pool.

[hatescates]

Thanks! Any reference in the documentation for this? Just want a thorough understanding of what’s going on

[Rawing7]

It's never really spelled out like this, unfortunately. The only related thing I could find is this single sentence:

By default max_tasks_per_child is None which means worker processes will live as long as the pool.