graph the ratio of two data sources

[Hashar]

Hello ! )

I have cacti working and collecting lot of datas with some standards graphs (cpu temp / load / network use). Now I would like to reuse the existents datasources and produce a graph showing the ratio between them.

A simple example: I would like to graph is the actual bytes / second of an interface vs the number of unicast packets / second.

I firstly created a divide function ( a,b,/ ). Then I created a graph, added the two datasources as Line1 & Line2 then a dummy source that just call the divide function.

The trouble I am facing now is that I am not able to hide the graphing of the two data sources to only keep my special divide function. I tried the comments / gprint / legend statements but then they aren't def= by cacti .

Any idea / howto welcome )


Then it could also be used to graphs cpu usage / cpu temp or load / process and hopefully produce some cool graphs )

[Hashar]

And here is a rrdtool call that does that:

/usr/bin/rrdtool graph - \
--imgformat=PNG --start=-86400 --end=-300 \
--title="Localhost - Traffic vs Packets" \
--base=1000 --height=120 --width=500 \
--alt-autoscale-max --lower-limit=0 --vertical-label="" \
DEF:b="/usr/share/cacti/rra/localhost_unicast_in_75.rrd":unicast_in:AVERAGE \
DEF:a="/usr/share/cacti/rra/localhost_traffic_in_24.rrd":traffic_in:AVERAGE \
CDEF:cdefc=a,b,/ \
AREA:cdefc#FF3932:""


Attached is the output of the script.

[Lux]

Set the color of the other data sources to none in your graph template. They should disappear from the graph then.

Mike

[Hashar]

Yup they disappear but the Y axis still get scaled according to the not showing datas. I am going to look if Y axis can be scaled only according to one data.

[Lux]

You can always force the scale of the Y axis in the graph template.

Mike

[o_dupuis]

Instead of setting the Y-axis scale.
Create a CDEF that multiplies the Current-data-rouce-item by zero.
Then apply the CDEF to the data you don't want to graph.
Hence you still can use auto scaling, which is handy if what you graph is not a percentage but a rate for example