Supervisor: Sending SIGKILL to supervisord does not terminate children

SIGKILL can't be trapped. This demonstrates it:

$ python
>>> import signal
>>> def handler(signum, frame):
...   pass
... 
>>> signal.signal(signal.SIGKILL, handler)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: (22, 'Invalid argument')
>>>

There's nothing we can add or change in our code to change that.

Certainly, but why killing the parent process doesn't kill the child ones? I mean at the Linux level, not through supervisord intercepting SIGKILL and killing its children.

https://github.com/Supervisor/supervisor/blob/3.0b1/supervisor/process.py#L274

FWIW, if supervisor is pid 19285:

  kill -9 -19285

Negating the pid sends the kill signal to the whole process group.

I was trying to achieve the same thing. Sending SIGTERM instead of SIGKILL worked for me.
I would prefer the "SIGTERM" over "SIGKILL with negated process ID" since it allows graceful shutdown.