Using Data Sources in a CDEF without having to graphing them

[bodgit]

Hi,

I want to graph just a CDEF using some Data Sources, this is easy to do with rrdtool directly:

Code: Select all

...
DEF:a='/var/www/cacti/rra/....rrd':foo:AVERAGE \
DEF:b='/var/www/cacti/rra/....rrd':bar:AVERAGE \
CDEF:c=a,b,+ \
AREA:c#ff0000:'baz'

However I can't work out to get cacti to do that without drawing them in some way on the graph. The best I have managed is to plot the Data Sources using no colour:

Code: Select all

...
DEF:a='/var/www/cacti/rra/....rrd':foo:AVERAGE \
DEF:b='/var/www/cacti/rra/....rrd':bar:AVERAGE \
CDEF:c=a,b,+ \
LINE1:a:'' \
LINE1:b:'' \
AREA:c#ff0000:'baz'

This seems to work ok except when the resulting CDEF output produces smaller values than the Data Sources as the Data Source values then influence the scaling of the Y-axis and can make the CDEF look like line noise.

Any idea how to accomplish this?

[gandalf]

You are close: Now add a new CDEF to those invisible DEFs that look like CDEF=CURRENT_DATA_SOURCE,0,*.
Reinhard

[bodgit]

Thanks, that sorted it.