Munin contributed plugins

#!/usr/bin/perl -w

=head1 NAME

dnsresponse - Plugin to monitor DNS resolution times.

"Poor man's smokeping" :)

=head1 APPLICABLE SYSTEMS

Any unix system.

=head1 CONFIGURATION

The following shows the default configuration.

  [dnsresponse_*]

    env.site www.google.com

    env.times 20

=head1 INTERPRETATION

The plugin shows the average and median times taken to resolve a site.

=head1 MAGIC MARKERS

  #%# family=auto

  #%# capabilities=autoconf,suggest

=head1 BUGS

None known.

=head1 VERSION

$Id: dnsresponse_ 61 2009-04-14 09:11:00Z stsimb $

=head1 AUTHOR

Copyright (c) 2009 by Sotiris Tsimbonis.

=head1 LICENSE

GPLv2

=cut

#%# family=auto

#%# capabilities=autoconf suggest

use strict;

use warnings;

my $DEBUG=0;

my $site = exists $ENV{'site'} ? $ENV{'site'} : "www.google.com";

my $times = exists $ENV{'times'} ? $ENV{'times'} : "20";

my $resconf="/etc/resolv.conf";

use File::Basename;

my $basename=basename($0);

my $scriptname;

my $dnsip;

($scriptname, $dnsip) = split("_", $basename);

print "DBG: target dns ip $dnsip\n" if ($DEBUG>0);

if ( defined $ARGV[0] and $ARGV[0] eq "config" ) {

	print "graph_title $dnsip DNS response time\n";

	print "graph_vlabel milliseconds\n";

	print "graph_scale no\n";

	print "graph_category Other\n";

	print "graph_info Time taken by $dnsip to resolve $site $times times.\n";

	#my @val = ("min", "avg", "median", "max");

	my @val = ("avg", "median", "stddev");

	my $value;

	foreach $value ( @val ) {

		if ($value eq "stddev") {

			print "$value.info Standard deviation (variance).\n";

		} else {

			print "$value.info $value time taken by $dnsip to resolve $site $times times.\n";

		}

		print "$value.label $value\n";

#		print "$value.type DERIVE\n";

#		print "$value.min 0\n";

#		print "$value.warning 100\n";

#		print "$value.critical 600\n";

	}

	exit 0;

}

if ( defined $ARGV[0] and $ARGV[0] eq "autoconf" ) {

	my $ret;

	if (! eval "require Net::DNS;") { $ret .= "Net::DNS not found. "; }

	if (! eval "require Time::HiRes;") { $ret .= "Time::HiRes not found. "; }

	if (! -s $resconf) { $ret .= "$resconf not found. "; }

	if ($ret) {

		print "no ($ret)\n";

		exit 1;

	} else {

		print "yes\n";

		exit 0;

	}

}

if ( defined $ARGV[0] and $ARGV[0] eq "suggest" ) {

	if (-s $resconf) {

		open (FILE, "< $resconf") || die "Could not open $resconf: $!\n";

		my $line;

		while ($line = <FILE>) {

			if ($line =~ /^nameserver/) {

				my $ns; my $ip;

				($ns, $ip) = split(" ", $line);

				print "$ip\n";

			}

		}

		exit 0;

	} else {

		print "ERROR reading $resconf\n";

		exit 1;

	}

}

use Time::HiRes qw ( gettimeofday tv_interval );

use Net::DNS;

my $res = Net::DNS::Resolver->new(

	nameservers => [$dnsip],

	recurse     => 1,

	debug       => $DEBUG,

);

my $i;

my @restimes;

for ($i=1; $i<=$times; $i++) {

	my $t0 = [gettimeofday];

	my $answer = $res->send($site);

	my $elapsed = tv_interval ($t0);

	push(@restimes, $elapsed);

	print "DBG: count $i elapsed $elapsed\n" if ($DEBUG>0);

}

@restimes=sort(@restimes);

#my $min=$restimes[0]*1000;

my $average=mean(@restimes)*1000;

my $median=median(@restimes)*1000;

my $stddev=std_dev_ref_sum(@restimes)*1000;

#my $max=$restimes[$times-1]*1000;

#print "min.value $min\n";

print "avg.value $average\n";

print "median.value $median\n";

print "stddev.value $stddev\n";

#print "max.value $max\n";

sub mean {

	my $result;

	foreach (@_) { $result += $_ }

	return $result / @_;

}

sub median {

	my @ar = @_;

	my $elements = scalar(@ar);

	return $ar[(int($elements-1)/2)];

#	if ($elements % 2) {

#		return $ar[($elements-1)/2];

#	} else {

#	return ($ar[($elements-1)/2-0.5]+$ar[($elements-1)/2+0.5])/2;

#	}

}

# Standard Deviance function from http://www.linuxjournal.com/article/6540

sub std_dev_ref_sum {

	my @ar = @_;

	my $elements = scalar @ar;

	my $sum = 0;

	my $sumsq = 0;

	foreach (@ar) {

		$sum += $_;

		$sumsq += ($_ **2);

	}

	return sqrt( $sumsq/$elements - (($sum/$elements) ** 2));

}