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debian/smokeping/usr/share/perl5/Smokeping/matchers/Avgratio.pm

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+package Smokeping::matchers::Avgratio;
+
+=head1 NAME
+
+Smokeping::matchers::Avgratio - detect changes in average median latency
+
+=head1 OVERVIEW
+
+The Avgratio matcher establishes a historic average median latency over
+several measurement rounds. It compares this average, against a second
+average latency value again build over several rounds of measurement.
+
+=head1 DESCRIPTION
+
+Call the matcher with the following sequence:
+
+ type = matcher
+ pattern =  Avgratio(historic=>a,current=>b,comparator=>o,percentage=>p)
+
+=over
+
+=item historic
+
+The number of median values to use for building the 'historic' average.
+
+=item current
+
+The number of median values to use for building the 'current' average.
+
+=item comparator
+
+Which comparison operator should be used to compare current/historic with percentage.
+
+=item percentage
+
+Right hand side of the comparison.
+
+=back
+
+  old <--- historic ---><--- current ---> now
+
+=head1 EXAMPLE
+
+Take build the average median latency over 10 samples, use this to divide the
+current average latency built over 2 samples and check if it is bigger than
+150%.
+
+ Avgratio(historic=>10,current=>2,comparator=>'>',percentage=>150);
+
+ avg(current)/avg(historic) > 150/100
+
+This means the matcher will activate when the current latency average is
+more than 1.5 times the historic latency average established over the last
+10 rounds of measurement.
+
+=head1 COPYRIGHT
+
+Copyright (c) 2004 by OETIKER+PARTNER AG. All rights reserved.
+
+=head1 SPONSORSHIP
+
+The development of this matcher has been sponsored by Virtela Communications, L<http://www.virtela.net/>.
+
+=head1 LICENSE
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+=head1 AUTHOR
+
+Tobias Oetiker <tobi@oetiker.ch>
+
+=cut
+
+use vars qw($VERSION);
+
+
+$VERSION = 1.0;
+
+use strict;
+use base qw(Smokeping::matchers::base);
+use Carp;
+
+sub new(@)
+{
+    my $class = shift;
+    my $rules = {
+                historic=>'\d+',
+                current=>'\d+',
+                comparator=>'(<|>|<=|>=|==)',
+                percentage=>'\d+(\.\d+)?' };
+
+    my $self  = $class->SUPER::new($rules,@_);
+    $self->{param}{sub} = eval "sub {\$_[0] ".$self->{param}{comparator}." \$_[1]}";
+    croak "compiling comparator $self->{param}{comparator}: $@" if $@;
+    $self->{param}{value} = $self->{param}{percentage}/100;
+    return $self;
+}
+
+sub Length($)
+{
+    my $self = shift;
+    return $self->{param}{historic} + $self->{param}{current};
+}
+
+sub Desc ($) {
+    croak "Detect changes in average median latency";
+}    
+
+sub avg(@){
+    my $sum=0;
+    my $cnt=0;
+    for (@_){
+	next unless defined $_;
+ 	$sum += $_;
+	$cnt ++;
+    }
+    return $sum/$cnt if $cnt;
+    return undef;
+}
+
+sub Test($$)
+{   my $self = shift;
+    my $data = shift; # @{$data->{rtt}} and @{$data->{loss}}    
+    my $len =  $self->Length;
+    my $rlen = scalar @{$data->{rtt}};
+    return undef 
+	if $rlen < $len
+           or (defined $data->{rtt}[-$len] and $data->{rtt}[-$len] eq 'S');
+    my $ac = $self->{param}{historic};
+    my $bc = $self->{param}{current};
+    my $cc = $ac +$bc;
+    my $ha = avg(@{$data->{rtt}}[-$cc..-$bc-1]);
+    my $ca = avg(@{$data->{rtt}}[-$bc..-1]);
+    return undef unless $ha and $ca;
+    return &{$self->{param}{sub}}($ca/$ha,$self->{param}{value});
+}