119 lines
3.2 KiB
Perl
119 lines
3.2 KiB
Perl
package Smokeping::matchers::Medratio;
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=head1 NAME
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Smokeping::matchers::Medratio - detect changes in the latency median
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=head1 OVERVIEW
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The Medratio matcher establishes a historic median latency over
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several measurement rounds. It compares this median, against a second
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median latency value again build over several rounds of measurement.
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By looking at the median value this matcher is largely immune against spikes
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and will only react to long term developments.
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=head1 DESCRIPTION
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Call the matcher with the following sequence:
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type = matcher
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pattern = Medratio(historic=>a,current=>b,comparator=>o,percentage=>p)
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=over
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=item historic
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The number of values to use for building the 'historic' median.
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=item current
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The number of values to use for building the 'current' median.
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=item comparator
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Which comparison operator should be used to compare current/historic with percentage.
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=item percentage
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Right hand side of the comparison.
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=back
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old <--- historic ---><--- current ---> now
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=head1 EXAMPLE
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Take the 12 last median values. Build the median out of the first 10
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and the median from the other 2 values. Divide the results and decide
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if it is bigger than 150 percent.
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Medratio(historic=>10,current=>2,comparator=>'>',percentage=>150);
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med(current)/med(historic) > 150/100
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This means the matcher will activate when the current latency median is
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more than 1.5 times the historic latency median established over the last
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10 rounds of measurement.
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=head1 COPYRIGHT
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Copyright (c) 2006 by OETIKER+PARTNER AG. All rights reserved.
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=head1 SPONSORSHIP
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The development of this matcher has been paid for by Virtela
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Communications, L<http://www.virtela.net/>.
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=head1 LICENSE
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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=head1 AUTHOR
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Tobias Oetiker <tobi@oetiker.ch>
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=cut
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use vars qw($VERSION);
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$VERSION = 1.0;
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use strict;
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use base qw(Smokeping::matchers::Avgratio);
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use Carp;
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sub Desc ($) {
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croak "Detect changes in median latency";
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}
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sub Test($$)
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{ my $self = shift;
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my $data = shift; # @{$data->{rtt}} and @{$data->{loss}}
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my $len = $self->Length;
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my $rlen = scalar @{$data->{rtt}};
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return undef
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if $rlen < $len
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or (defined $data->{rtt}[-$len] and $data->{rtt}[-$len] eq 'S');
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my $ac = $self->{param}{historic};
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my $bc = $self->{param}{current};
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my $cc = $ac +$bc;
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my $hm = (sort {$a <=> $b} @{$data->{rtt}}[-$cc..-$bc-1])[int($ac/2)];
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my $cm = (sort {$a <=> $b} @{$data->{rtt}}[-$bc..-1])[int($bc/2)];
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return undef unless $hm and $cm;
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return &{$self->{param}{sub}}($cm/$hm,$self->{param}{value});
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}
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