Hi Folks, I have a script to update the RRD databases with latency values to 5 different locations.The script forks 5 different process where each process will run the ping command to their respective location for 15 seconds and sleep for remaining 45 seconds & update the rrd databases after that with the values.

What i intend to by this is to update the RRD databases exactly at every 1 minute interval (i.ee 12:40:00 ,12:41:00,12:42:00 and so on...) The breakup is as follows:

12:40:00 - 12:40:15 (ping for 15 seconds) 12:40:15 - 12:40:59 (sleep for 45 seconds) 12:41:00 - update the rrd db

The problem i am facing is that the values dont arrive exactly at the right interval after some time..i.ee the values start to drift.

Instead of getting the value at 16:50:00 or 16:51:00 ..16:52:00 i am getting the values 3-4 seconds late i.ee 16:50:04 ..16:51:04..16:52:04
So,how do i make sure that i input the values in the db exactly at 1 minute interval ?? 
 #!/usr/bin/perl

use strict;
use warnings;
use Carp;
use POSIX;
use IO::Handle;
use IPC::Open3;
use Data::Dumper;

sub _Forked {
    my $ip = shift;
    #
    croak "Couldn't fork" unless defined (my $pid = fork());
    if ($pid == 0) {
        #CHILD 
        while (1) {
            #
            sleep 45;
            my @data    = `/bin/ping -w 15 -q $ip`;;
            my @values = ($data[4] =~ m{(\d+).\d+}g);
            my $time  = scalar localtime();
            print "$time - $ip - @values\n";
            #
       }
    }
    #
    return ($pid);
}

sub main {
   
    my $DSname  = {                                      
                    can   => 'vfs.edu',
                    us    => 'ucla.edu',
                    aus   => 'cdu.edu.au',
                    mal   => 'um.edu.my',
                    uk    => 'imperial.ac.uk',
                  };
    #
    foreach my $host (keys %{$DSname}) {
        my $cpid = _Forked($DSname->{$host});
    }
    #
   my $dpid   = POSIX::waitpid(-1,WUNTRACED); 
}
main();

[download]
The script will just print the values as of now
Output 
Wed Nov 30 12:27:00 2011 - cdu.edu.au - 241 246 255 5
Wed Nov 30 12:27:00 2011 - vfs.edu - 251 254 260 3
Wed Nov 30 12:27:00 2011 - ucla.edu - 216 223 233 6
Wed Nov 30 12:27:00 2011 - um.edu.my - 112 119 124 3
Wed Nov 30 12:27:00 2011 - imperial.ac.uk - 171 178 185 6

[download]

After few hours,the values are: 
Wed Nov 30 15:28:04 2011 - cdu.edu.au - 241 246 255 5
Wed Nov 30 15:28:04 2011 - vfs.edu - 251 254 260 3
Wed Nov 30 15:28:04 2011 - ucla.edu - 216 223 233 6
Wed Nov 30 15:28:04 2011 - um.edu.my - 112 119 124 3
Wed Nov 30 15:28:04 2011 - imperial.ac.uk - 171 178 185 6

[download]

In reply to RRD-Ping getting values on right interval by hello_world

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