Medratio

# 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>