[ckuehl]

Good question! The problem is trying to signal it from outside the Docker container.

If your container has a process tree like

    PID 1: /bin/sh
    +--- PID 2: <your Python server>

then if you use `docker signal` from the host, it will only send a signal to PID 1, which is the shell. However the shell won't forward it on to your Python server, so nothing happens (in most cases).

dumb-init basically replaces the shell in that diagram, but forwards signals when it receives them. So when you use `docker signal`, the Python process receives the signal.

Alternatively, just eliminating the shell (so your Python app is PID 1) works for some cases, but you get special kernel behavior applied to PID 1 which you usually don't want. This is the main purpose of dumb-init.

[vikiomega9]

Ah that makes sense. I did not realize how docker-signal forwarded signals. From its perspective using PID 1 makes sense because that's where the "application" should run as specified in your dockerfile.