From: ara.t.howard@...
Date: 2006-06-05T00:14:11+09:00
Subject: Re: Please kill the children as you're leaving

On Sun, 4 Jun 2006, Francis Cianfrocca wrote:

> How does your parent process die unexpectedly? If it catches signal 9, for
> example, your atexit handlers won't run. You could try something dramatic
> like open a socketpair between parent and child processes (don't forget to
> turn off CLOEXEC for forking) and then have the child processes periodically
> send a byte to the parent. If you lose the parent, then the write from the
> child should catch SIGPIPE. Also possible is for the children to
> periodically to check the status of the parent process (getppid).

indeed.  this is exactly what my slave library does - it sets up a heartbeat
pipe between parent and child.  this way, even if the parent dies via 'kill
-9', which no code can handle, the child will die.  eg.

   harp:~ > cat a.rb
   # http://codeforpeople.com/lib/ruby/slave/
   require 'slave'

   class Child
     def initialize
       @pid = Process.pid
       Thread.new{loop{warn "child <#{ @pid }> @ <#{ Time.now }>"; sleep 1}}
     end
   end

   class Parent
     def initialize
       @pid = Process.pid
       @child = Slave.new(Child.new)
       sleep 3
       Process.kill -9, @pid
     end
   end

   Parent.new


   harp:~ > ruby a.rb
   child <26196> @ <Sun Jun 04 09:11:17 MDT 2006>
   child <26196> @ <Sun Jun 04 09:11:19 MDT 2006>
   child <26196> @ <Sun Jun 04 09:11:20 MDT 2006>
   Killed


ps.  the gem for slave is on rubyforge but, for some reason, a 'gem install
slave' does not work.  you can download the gem manually here:

   http://rubyforge.org/frs/?group_id=1024&release_id=5464

pss.  this is setup exactly like all the other projects under codeforopeople -
if anyone has any ideas on why slave installs fail please contact me offline.

cheers.

-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama