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.\"
.IX Title "Smokeping::matchers::Medratio 3"
.TH Smokeping::matchers::Medratio 3 "2006-12-12" "2.4.2" "SmokePing"
.SH "NAME"
Smokeping::matchers::Medratio \- detect changes in the latency median
.SH "OVERVIEW"
.IX Header "OVERVIEW"
The Medratio matcher establishes a historic median latency over
several measurement rounds. It compares this median, against a second
median latency value again build over several rounds of measurement.
.PP
By looking at the median value this matcher is largly imune against spikes
and will only react to long term developments.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Call the matcher with the following sequence:
.PP
.Vb 2
\& type = matcher
\& pattern =  Medratio(historic=>a,current=>b,comparator=>o,percentage=>p)
.Ve
.IP "historic" 4
.IX Item "historic"
The number of values to use for building the 'historic' median.
.IP "current" 4
.IX Item "current"
The number of values to use for building the 'current' median.
.IP "comparator" 4
.IX Item "comparator"
Which comparison operator should be used to compare current/historic with percentage.
.IP "percentage" 4
.IX Item "percentage"
Right hand side of the comparison.
.PP
.Vb 1
\&  old <\-\-\- historic \-\-\-><\-\-\- current \-\-\-> now
.Ve
.SH "EXAMPLE"
.IX Header "EXAMPLE"
Take  the 12 last median values. Build the median out of the first 10
and the median from the other 2 values. Divide the results and decide
if it is bigger than 150 percent.
.PP
.Vb 1
\& Medratio(historic=>10,current=>2,comparator=>\(aq>\(aq,percentage=>150);
.Ve
.PP
.Vb 1
\& med(current)/med(historic) > 150/100
.Ve
.PP
This means the matcher will activate when the current latency median is
more than 1.5 times the historic latency median established over the last
10 rounds of measurement.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (c) 2006 by \s-1OETIKER+PARTNER\s0 \s-1AG\s0. All rights reserved.
.SH "SPONSORSHIP"
.IX Header "SPONSORSHIP"
The development of this matcher has been paied for by Virtela
Communications, <http://www.virtela.net/>.
.SH "LICENSE"
.IX Header "LICENSE"
This program is free software; you can redistribute it and/or modify
it under the terms of the \s-1GNU\s0 General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
.PP
This program is distributed in the hope that it will be useful,
but \s-1WITHOUT\s0 \s-1ANY\s0 \s-1WARRANTY\s0; without even the implied warranty of
\&\s-1MERCHANTABILITY\s0 or \s-1FITNESS\s0 \s-1FOR\s0 A \s-1PARTICULAR\s0 \s-1PURPOSE\s0.  See the
\&\s-1GNU\s0 General Public License for more details.
.PP
You should have received a copy of the \s-1GNU\s0 General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, \s-1MA\s0 02139, \s-1USA\s0.
.SH "AUTHOR"
.IX Header "AUTHOR"
Tobias Oetiker <tobi@oetiker.ch>