I have multiple RRD databases each with incomplete data about the availability of a service as observed from different locations. They just record 100
if the service is up, or 0
if it is down.
I want to make a graph showing whether the service was available from any location, simply by checking whether I have any data in one of the RRDs for the time period in question.
I'm trying to do this with a CDEF which uses MAXNAN to find the maximum value of my averaged data sources - here's a simplified example:
rrdtool graph /tmp/graph.png -a PNG \
--start=1427213255 \
--end=1427224055 \
--upper-limit=100 \
--lower-limit=0 \
--rigid \
DEF:d0=/tmp/location1.rrd:available:AVERAGE \
DEF:d1=/tmp/location2.rrd:available:AVERAGE \
CDEF:agg=d0,d1,MAXNAN \
AREA:agg#00DD00:availability
This produces the error
ERROR: invalid rpn expression in: d0,d1,MAXNAN
Where am I going wrong?