Name:
trend.cgi: Trending analysis extension. GPL. v0.6

Author:
Steve Shipway 2003

Requires:
rrdtool executable

Example:
routers.cgi*Extension[targetname]: "Trending analysis" /cgi-bin/trend.cgi graph-sm.gif

Description:

This is the prototype of the routers.cgi graph trending analysis plugin.  It
works as a routers2.cgi plugin extension (you cannot run it independently).

Install instructions are at the beginning of the script.  Remember you need to
give the path to your rrdtool EXECUTABLE, not its directory.

A reported bug in many windows versions of rrdtool will result in your
trending graph having unexplained spikes and negative values.  If this
happens, then you need to install an earlier (<1.0.33) version of rrdtool in a
separate directory, and use that rrdtool executable for trend.cgi.

**************************************************************************
NOTE THAT THIS IS A PROTOTYPE, ALPHA CODE, AND NOT SUPPORTED.  THIS IS
NEITHER AS POLISHED NOR AS RELIABLE AS THE MAIN CODE.  YOU ARE WELCOME TO 
TRY IT OUT, BUT ASSUME YOU ARE ON YOUR OWN!  USE THE DISCUSSION BOARD 
TO REPORT BUGS OR PROBLEMS.
**************************************************************************

This works by using a decayed average to create a first order curve (ie, a
line) approximation for the data.  You can set different decay factors to 
change the importance of historical data.  I find that about .95 or .9 works
the best.  It does not predict patterns or curves.  It does not work with 
userdefined graphs or stack or range graphtype.

This will work with speedycgi if you change the initial variable definitions
to 'our()' instead of 'my()'.  This requires perl 5.8 or later.

# routers2.conf

trend.cgi will read configuration from routers2.conf in the [trend.cgi]
section.  You can also set 'trendurl = /cgi-bin/trend.cgi' in the
[routers.cgi] section if you want trending to be automatically added to all
targets (this is experimental).  Note that this can also be put in a per-user
section, so you can offer trending to only particular users.

[trend.cgi]
debug = 1
logfile = /tmp/trend.log
#  set the debugging log on to the debug file.

decay = 0.95
# set the default decay rate for the averages

fgcolour = #ffffff
bgcolour = #000000
linkcolour = #8080ff
# set default colours for the page to match what you set in [routers.cgi]