PERL POE - POE - Catching INT Signals

Author

POE - Catching INT Signals

Michael Collins

2007-02-22, 4:29 am

Here is a question I also posed on perlmonks.org...
(http://www.perlmonks.org/?node_id=601464)

I am searching for a way to catch and handle a Control-C when using
multiple POE sessions. I have successfully used the snippet from the POE
Cookbook to actually catch the INT signal in each of my Sessions:

inline_states => {

_connected => sub {

my ($kernel, $session) = @_[KERNEL, SESSION];

## Handle control-C

$kernel->sig( INT => 'event_sigint' );

... } # inline_states

....

event_sigint => sub {

my ($kernel, $session) = @_[KERNEL, SESSION];

print STDERR "Caught Control-C, shutting down gracefully.\ +n";

$kernel->yield("Shutdown",2,'Received break from user');

}, # event_sigint

In all but one of my sessions I simply catch the signal and print to
STDERR a simple message giving the session alias. The above snippet is
in only one of my sessions and I want to use it to do the graceful
shutdown.

However, I am using POE::Component::SimpleDBI, which uses
POE::Wheel::Run to fork a child process that does the 'heavy-lifting' as
the POD puts it. What is happening is that somewhere in POE's reaping of
the child process(es) created by POE::Component::SimpleDBI, the POE
kernel itself is (or seems to be) stopping in its tracks, that is, it
ends without any fanfare. The last thing I see on the screen before the
kernel ends is this:

!!! Child process PID:6326 reaped:

Things I have tried:

#1 - manually adding an INT handler to SimpleDBI.pm

#2 - perusing kernel.pm and signals.pm for clues

I confess to the monks that this challenge is beyond me and I humbly
submit the question for your review: is there a way to have POE reap the
child process without dying immediately thereafter, allowing me to yield
a shutdown subroutine to do the cleanup and exit?

Many thanks,

-MC

Rocco Caputo

2007-02-22, 7:24 pm

On Feb 22, 2007, at 01:52, Michael Collins wrote:

> I am searching for a way to catch and handle a Control-C when using
> multiple POE sessions. I have successfully used the snippet from
> the POE
> Cookbook to actually catch the INT signal in each of my Sessions:
>
> event_sigint => sub {
>
> my ($kernel, $session) = @_[KERNEL, SESSION];
>
> print STDERR "Caught Control-C, shutting down gracefully.\ +n";
>
> $kernel->yield("Shutdown",2,'Received break from user');
>
> }, # event_sigint
>
> In all but one of my sessions I simply catch the signal and print to
> STDERR a simple message giving the session alias. The above snippet is
> in only one of my sessions and I want to use it to do the graceful
> shutdown.

After reading this a second time, it occurs to me that you aren't
calling $kernel->sig_handled() in your SIGINT handler. If no session
does, then POE will not know you've handled the signal. It'll
continue on to reap your sessions prematurely.

--
Rocco Caputo - rcaputo@pobox.com

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