Measure latency of DNS requests

dnsdeplay.pl

#!/usr/bin/perl -w

use strict;
use Net::DNS::Resolver;
use Time::HiRes qw(gettimeofday tv_interval);
use Getopt::Long;

my $nameserver;
my $query;
my $duration = 10;
my $type = "A";

my $options = GetOptions
(
    "n|ns=s"        => \$nameserver,
    "q|query=s"     => \$query,
    "d|duration:i"  => \$duration,
    "t|type=s"      => \$type
);

my @elapsed;
my $i = 0;

my $res = Net::DNS::Resolver->new(nameservers => [$nameserver]);
my $starttime = [gettimeofday];

while((tv_interval($starttime, [gettimeofday])) < $duration) {
    my $now = [gettimeofday];
    my $query = $res->query($query, $type);
    if($query) {
        $elapsed[$i] = int(tv_interval($now, [gettimeofday]) * 1000);
        $i++;
    } else {
        print STDERR "OMGWTFBBQ\n";
    }
}

my @sorted = sort {$a <=> $b} @elapsed;

my $median;
my $mid = scalar(@elapsed) >> 1;

if ($mid & 1) {
    $median = $elapsed[$mid];
} else {
    $median = ($elapsed[$mid - .5] + $elapsed[$mid + .5]) / 2;
}

my $average = int mean(\@elapsed);

print "min:$sorted[0] med:$median avg:$average max:$sorted[$#sorted] iter:$i\n";

sub mean {
    my ($arrayref) = shift;
    my $result;
    foreach (@$arrayref) { $result += $_ }
    return $result / @$arrayref;
}