Re: poe wheel run question (sending the signal to the process group id instead of PID)

On Mon, Mar 02, 2009 at 11:47:09AM +0100, jorge sanchez wrote:
> Hi list,
> 
> I have one question regarding the POE::Wheel::Run kill method,
> according to the cpan.org page this method delivers signal to the
> child process.
> We are using the POE::Wheel::Run to spawn child which then spawns
> another childs in the chain. We also are using sort of watchdog timer
> which sends SIGKILL  signal to the child if it takes too long to
> accomplish its task to take it down.
> 
> The problem is that if we kill the child which has spawn other childs
> and if we send SIGKILL signal to this child then the spawned childs
> are reaped by init and are there  outside of our controll.
> 
> It would be very convenient to have also method to send the signal to
> the process group id to take down all the processes within the same
> process group.

Since version 1.0001 of POE, POE::Wheel::Run will use setpgrp() to change
the process group of the spawned process ( but only if the Conduit type isn't
'Pty' or 'Pty-pipe' which uses setsid() to change the process group ).

POE::Wheel::Run's kill() method basically uses perl's kill function under
the hood so the advice from there stands (http://p3rl.org/kill).

"Unlike in the shell, if SIGNAL is negative, it kills process groups instead of processes"

$wheel->kill(9); # Send KILL signal to the wheel PID

$wheel->kill(-9); # Send KILL signal to the wheel process group.

On SystemV (like Solaris) you can also use negative process IDs

kill( 9, $wheel->PID ); # Send KILL signal to the wheel PID

kill( 9, '-' . $wheel->PID ); # Send KILL signal to the wheel process group.

With the caveat from 'kill' documentation:

"(On System V, a negative PROCESS number will also kill process groups, 
but that's not portable.)"

Cheers,

-- 
Chris Williams
aka BinGOs
PGP ID 0x4658671F
http://www.gumbynet.org.uk
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