use strict;
use warnings;

use POSIX qw( _exit );
use Time::HiRes qw( sleep time );

use constant PERIOD => 10.0;

use Parallel::ForkManager;

my @servers =  (
	       {
		   id   => "1",
		   name => "srv1",
	       },
	       {
		   id   => "2",
		   name => "srv2",
	       },
	       {
		   id   => "3",
		   name => "srv3",
	       }
     );


sub tick {

    my $MAX_PROCESSES	= 1000;
    my $pm = new Parallel::ForkManager($MAX_PROCESSES);

    my @ping_cmd = ("ping", "testhost", "-s 5", "-c 1");

    $pm->run_on_finish(
		       sub { 
			   my ($pid, $exit_code, $ident) = @_;
			   my ($check_id, $host) = $ident =~ /^(.*?) on (.*)/s;
			   print "^^^^^^^^^^^run_on_finish: $ident (pid: $pid) exited with code: [$exit_code] host: [$host]\n";
		       }
		       );
    
    $pm->run_on_start(
		      sub {
			  my ($pid,$ident)=@_;
			  print "** $ident started, pid: $pid\n";
		      }
		      );

    for(my $i=0; $i< @servers; $i++){
        my $srv_id	= $servers[$i]{id};
        my $srv_name	= $servers[$i]{name};

        $ping_cmd[1] = $servers[$i]{name};
	
        print "$srv_name:\n";
	    
        $pm->start("ping on $srv_id") and next;
        exec(@ping_cmd);
        print(STDERR "ping on $srv_name exec failed: $!\n");
        _exit($!);	
    }
}


sub sleep_till {
    my ($sleep_till) = @_;
    for (;;) {
        my $duration = $sleep_till - time();
        last if $duration <= 0;
        sleep($duration);
    }
}

{
    $SIG{CHLD} = 'IGNORE';  # Autoreap children
    my $time = time();

    for (;;) {
        $time += PERIOD;
        sleep_till($time);
        my $pid = fork();
        if (!defined($pid)) {
            warn("fork: $!\n");
        }
        elsif (!$pid) {
            $SIG{CHLD} = 'DEFAULT';
            _exit(0) if eval { tick(); 1 };
            print STDERR $@;
            _exit($! || ($?>>8) || 255);
        }
    }
}