NAME

       Smokeping::matchers::Avgratio - detect changes in average median latency

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.

DESCRIPTION

       Call the matcher with the following sequence:

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

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

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

       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 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.

COPYRIGHT

       Copyright (c) 2004 by OETIKER+PARTNER AG. All rights reserved.

SPONSORSHIP

       The development of this matcher has been sponsored 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>