#!/usr/bin/perl -w

use strict;

############################################################################
## Load the neccesary modules
############################################################################
use POSIX 'setsid';
use strict;
use POSIX ":sys_wait_h";

#################################################################
# Global variables used in the script                           #
#################################################################
my $SLEEP_TIME=120;
my $pid = 0;
my $counter = 0;
my $MAX_PROCESS = 75;
my $STOP_FILE = 'stopfile';
my $num_processes = 0;
my $process_name = $0;

################################################################
# Handle any zombies                                           #
################################################################
$SIG{CHLD} = \&REAPER;

sub REAPER {
    my $stiff;
    while (($stiff = waitpid(-1, &WNOHANG)) > 0) {
        # do something with $stiff if you want
    }
    $SIG{CHLD} = \&REAPER;                  # install *after* calling waitpid
}


###############################################################
# This subroutine stops the processes gracefully allowing the #
# processes that are running to complete and then it shuts    #
# down the script.                                            #
###############################################################
sub stopGraceful()
{
        while(-e $STOP_FILE && ($num_processes > 1))
        {
                $num_processes = `ps -ef | grep $process_name | grep -v grep | wc -l`;
                chomp($num_processes);
                print "Process number $num_processes.\n";

                if($num_processes == 1)
                {
                        exit(0);
                }
        }
}

sub mainLoop()
{
        while(!(-e $STOP_FILE))
        {
                $counter++;
                $num_processes = `ps -ef | grep $process_name | grep -v grep | wc -l`;
                chomp($num_processes);

                if($num_processes <= $MAX_PROCESS)
                {
                        $pid = fork();
                        die "Cannot fork: $!" unless defined($pid);
                        if ($pid == 0)
                        {
                                # Child process
                                # Insert database_worker script here.
                                print $counter . " : Process number $num_processes.\n";
                                sleep(int(rand($SLEEP_TIME)));
                                exit(0);   # Child process exits when it is done.
                        } # else 'tis the parent process
                }
        }

        if (-e $STOP_FILE)
        {
                stopGraceful();
                exit(0);
        }
}

#############################
##                         ##
##                         ##
##  Execution Begins Here  ##
##     Begin Main Loop     ##
##                         ##
##                         ##
#############################
mainLoop();

##</code><code>##

$num_processes = `ps -ef | grep $process_name | grep -v grep | wc -l`;