Tomorrow prevents script from terminating

[Slater-Victoroff]

When tomorrow is used the python script won't end. Ctrl+C won't stop it, only closing the process alltogether will stop it. Needless to say, this is pretty frustrating.

[muatik]

just hitting ctrl+c twice terminates it.

[madisonmay]

Hitting ctrl+c twice should not terminate a python script that is multithreaded and has long running child threads (if it does the child threads have already terminated). This is a problem that is not specific to tomorrow -- it's a general issue you run into when writing multithreaded code.

One of the main problems is this: the parent thread will not catch any exceptions if program execution is stuck in the child thread. I'm guessing that in the majority of circumstances this is the case -- a child thread hangs and the parent never even gets the chance to execute code.

I can work around this issue to enable this behavior (exit program when ctrl-c is pressed) but this isn't necessarily desirable behavior because it deviates from the norm of python's stdlib. Typically, pressing ctrl-c causes the main thread to exit as soon as any child threads have been joined (useful if you need things running in the background to exit cleanly, but want to terminate program execution immediately afterward).

Practically speaking I bet most users want programs to exit immediately, though. I've put up a PR which has the behavior your looking for. The caveat is that you'll need to set a timeout in order to make sure execution periodically returns to the main thread (where the ctrl-c signal can be caught). It can be an arbitrarily long timeout, but there needs to be a timeout. There's likely a way to work around this restriction as well, but it likely involves digging into the internals of the concurrent.futures library

[Slater-Victoroff]

So, maybe solvable by having something like a:

"this may cancel long-running child processes, do you wish to continue?"

When you hit control-c?