`nf` claims to have delivered `SIGINT` to all children on exit from one, but does not actually about node-foreman

[benweint]

Turns out I had misdiagnosed this!

nf really was delivering SIGINT to all direct children, but because it doesn't use process groups for each spawned child, if the child processes spawned their own children and didn't respond to SIGINT by exiting or forwarding to their children, then nf would just hang when one child exited.

In the repro case that I gave, the process tree looks like this after a exits:

❯ pstree -s nf.js
... snip ...
     \-+= 83622 ben node nf.js start
       \-+- 83628 ben /bin/bash ./wait-for-sigint.sh
         \--- 83632 ben sleep 1000000

The bash process (pid 83628) actually has received the SIGINT, but per the bash manual:

When Bash receives a signal for which a trap has been set while waiting for a command to complete, the trap will not be executed until the command completes.

So in this example:

1. a exited
2. nf sent SIGINT to the direct child process for b (bash, pid=83628)
3. bash got the SIGINT, but was waiting to invoke the trap handler until the sleep command (pid=83632) exited
4. The sleep command itself never received the SIGINT

The way that goreman solves this is by creating a process group for each spawned child, and then delivering the SIGINT signals to the group, rather than the direct child.

[benweint]

I've implemented support for using process groups in my fork (benweint@5cb9ee5) and can PR it if there's interest, but it looks like this project might be dead.