From: Ohad Lutzky <lutzky@...>
Date: 2007-05-28T20:31:20+09:00
Subject: Killing sons (Linux)

Maybe this isn't strictly a Ruby question, but I hope someone here can
help:

I have a job-management application, with a central daemon which
receives job requests. Upon receiving this request, it forks and then
runs "system" to run bash, which in turn runs the Matlab job. I use bash
for this in order to redirect the input and output from Matlab. pstree
output looks like this:

  init-+-apache2---8*[apache2]
       |-atd
      ...
       |-ruby-+-4*[ruby---bash---MATLAB-+-matlab_helper]
       |      |                         `-15*[{MATLAB}]]
       |      `-{ruby}
      ...

  Legend:
   daemon ^        ^ daemon fork

Now, my system also allows a 'kill' command, intended to stop the job in
progress. This has been causing me a lot of trouble, and I suddenly
(after quite a while the system has been in production, how embarassing)
realized why - the PID I'm keeping is of the daemon fork. Killing it
doesn't kill all of its sons - it causes bash to get reparented to init!

Any idea of a clean, quick way to fix this?

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