[Fix] Handle more POSIX signals on UNIX systems

[ljedrz]

This PR extends the signal handler on UNIX; in addition to SIGINT, it now also supports SIGTERM, SIGQUIT, and SIGHUP.

[iamalwaysuncomfortable]

Is it possible to bump up the number of seconds waiting for the shutdown? Even if there are SIGINT signals, a 3 second wait time might not be enough to clean everything up.

Maybe something like

tokio::time::sleep(Duration::from_secs(10)).await;

[ljedrz]

@iamalwaysuncomfortable what cleanups do you have in mind? Anything that's not (persistent) storage-related doesn't really require any special treatment.

[howardwu]

Adding a note for context here:

SIGTERM terminates the process gracefully
SIGQUIT terminates the process with a core dump
SIGKILL immediately and forcefully terminates the process; it can't be caught
SIGSTP suspends execution
SIGSTOP suspends execution and can't be caught
SIGHUP can be received when the owning terminal is shut down; it can be worked around on UNIXes with nohup or disown
SIGABRT terminates the process as if it was done from within the process