NAME

       Smokeping::matchers::Medratio - detect changes in the latency median

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.

       By looking at the median value this matcher is largly imune against spikes and will only
       react to long term developments.

DESCRIPTION

       Call the matcher with the following sequence:

        type = matcher
        pattern =  Medratio(historic=>a,current=>b,comparator=>o,percentage=>p)

       historic
           The number of values to use for building the 'historic' median.

       current
           The number of values to use for building the 'current' median.

       comparator
           Which comparison operator should be used to compare current/historic with percentage.

       percentage
           Right hand side of the comparison.

         old <--- historic ---><--- current ---> now

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.

        Medratio(historic=>10,current=>2,comparator=>'>',percentage=>150);

        med(current)/med(historic) > 150/100

       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.

COPYRIGHT

       Copyright (c) 2006 by OETIKER+PARTNER AG. All rights reserved.

SPONSORSHIP

       The development of this matcher has been paied for by Virtela Communications,
       <http://www.virtela.net/>.

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.

AUTHOR

       Tobias Oetiker <tobi@oetiker.ch>