POE is a good choice for the parent. It makes it easy to write event-driven code that handles state changes and timed events.

POE is single threaded, however, so you definitely need to fork() any workers that might block. There's some example start/stop code at Re: Perl Background processes in Windows. Remove the setsid() call from that and the children will stay in the parent process group and die when it does. You should also consider what you're doing with Stdin/Stdout/Stderr in the child processes - going to parent's tty, or to log file or /dev/null? Also if you interrupt with CTRL-C you probably need tidy up code.

Following is an example of using POE to control start/stop. You would need to make it more sophisticated to handle your rules for the list of parameters and the respawn intervals. E.g. stash the date/time of last exit against entries in your list and take account of that in the spawner.

#!/usr/bin/perl

use strict;
use warnings;

# POE checking/debug levels
sub POE::Kernel::ASSERT_DEFAULT { 0 } # DATA, EVENTS, FILES, RETVALS, 
+USAGE
sub POE::Kernel::ASSERT_EVENTS  { 1 }
sub POE::Kernel::ASSERT_USAGE   { 1 }
sub POE::Session::ASSERT_STATES { 1 }

use POE;
use POSIX;

my $num_kids = 8;
my %kid_pids;

main();


END { do_end(); }

sub do_end
{
  # FILL HERE
  exit(0);
}

sub main
{
  # catch CTRL-C interrupt to tidy up cleanly
  $SIG{QUIT} = $SIG{INT} = $SIG{HUP} = \&do_end;

  POE::Session->create
  (
    inline_states =>
    {
      _start => sub
      {
        print "Starting\n";
        $_[KERNEL]->sig('INT', 'signal_handler');
        $_[KERNEL]->delay(reaper => 1 );
        $_[KERNEL]->delay(spawner => 1 );
      },
      _stop => sub {},
      signal_handler => sub {
        my ($kernel, $sig) = @_[KERNEL, ARG0];
        print "caught SIG$sig\n";
        do_end();
      },
      reaper => sub
      {
        $_[KERNEL]->delay(reaper => 1);
        while ( (my $pid = waitpid(-1, POSIX::WNOHANG)) > -1 )
        {
          my $exit_status = $? / 256;
          delete $kid_pids{$pid};
          print "child $pid died status $exit_status\n";
        }
      },
      spawner => sub
      {
        $_[KERNEL]->delay(spawner => 1);
        # start new kid if slot free
        if (scalar keys %kid_pids < $num_kids)
        {
          my $pid = start_child();
          if ($pid > 0)
          {
            $kid_pids{$pid} = 1;
            print "child $pid started\n";
          }
        }
      },
    },
  );

  $poe_kernel->run();
}

sub start_child
{
  # FILL HERE
  return $pid;
}
[download]

Regards, Peter

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.