RRD Tool Graph Highlight NAN value

Question

Is there a way that I can have rrdGraph create a graph that highlights any missing data, rather than just leaving that space blank?

Answer 1

You could create a CDEF using the UN and IF commands to detect unknown data and turn it into INF which you could then paint using the AREA function to fill the background of the chart. Smokeping uses this trick.

Answer 2

Test the variable for unknown, and set a CDEF to be infinity if it is and 0 otherwise.

DEF:in=myfile.rrd:ds0
LINE1:in#0000ff:My_data
CDEF:unavailable=in,UN,INF,0,IF
AREA:unavailable#d0d0d0

Make sure your AREA comes after the LINE if you want it to blank out the graph when things are unknown. Expand the CDEF if you want to check multiple variables for unknown-ness.