rrdtool – Ryan Schulze

rrdtool tricks / tips

May 28, 2009May 13, 2013Ryan1 Commentbash, rrdtool

There are various different ways to generate rrdtool images. And most people will probably be generating elaborate ones out of perl or php scripts. The ones I am currently generating are built in a shell script (bash) and I was really having a problem with quotes and white space here for a while. If you generate the query and save it in a variable, the quotes go to hell and your white space (e.g. a space in a COMMENT) starts causing problems. my solution may not be the best, but it works without any trouble: Throw the whole command line into a temporary file and then use eval to create the graph. The following is not a complete statement, just a few lines as an example.

TmpFile="$(mktemp)"
echo -n "--vertical-label example --title \"Title with spaces\"  " &gt;&gt; ${TmpFile}
echo -n 'COMMENT:"           Comment with spaces\l" ' &gt;&gt; ${TmpFile}
eval "/usr/bin/rrdtool graph output.png $(cat ${TmpFile}) &gt;/dev/null"

TmpFile="$(mktemp)"

echo -n "--vertical-label example --title \"Title with spaces\" " >> ${TmpFile}

echo -n 'COMMENT:" Comment with spaces\l" ' >> ${TmpFile}

eval "/usr/bin/rrdtool graph output.png $(cat ${TmpFile}) >/dev/null"

rrdtool magic

April 9, 2008Ryanrrd, rrdtool

I upgraded some rrdtool graphs today (in the examples below, I was using weekly graphs). First I smoothed out some of the data with TREND. That was pretty easy, you just specify which data and the timeframe it should use to smooth out: CDEF:trend_data=data,21600,TREND smooths out data by 6 hours (21600 seconds). trend_data can be used afterwards (for LINE, AREA, ….) The DEF will have to be expanded a bit so that enough data is available for the TREND, I just added a days woth of data to begining and end by adding the following to the end of my DEF statement :start=now-8d:end=now+1d

The whole trend would look kinda like this:
rrdtool graph image.png \
–width 500 –height 200 \
–end now –start now-7d \
–vertical-label “data” \
DEF:data=some.rrd:data:AVERAGE:start=now-8d:end=now+1d \
CDEF:trend_data=data,21600,TREND \
LINE1:trend_data#000000:”smoothed out data”

The next thing I played around with, was extrapolating the data and drawing a projection. Fist thing to do, is open up the graph to end a few days in the future, easy to do with the –start and –end options: –end now+3d –start now-7d Now lets make DEF over the time range we want to use for the projection, this example will use the data of the last two weeks: DEF:data=some.rrd:data:AVERAGE:start=now-2w:end=now+3d All we need now is a little rrd magic I found in the depths of the internet:
VDEF:D=data,LSLSLOPE \
VDEF:H=data,LSLINT \
CDEF:projection=data,POP,D,COUNT,*,H,+ \
LINE1:projection#BB2030:”2 week projection”

Ok, if we throw both trend and projection together we end up with a cute little rrd mess that looks something like this:
rrdtool graph image.png \
–width 500 –height 200 \
–end now –start now-7d \
–vertical-label “data” \
DEF:data1=some.rrd:data:AVERAGE:start=now-8d:end=now+1d \
DEF:data2=some.rrd:data:AVERAGE:start=now-2w:end=now+3d \
CDEF:trend_data=data1,21600,TREND \
LINE1:trend_data#000000:”smoothed out data” \
VDEF:D=data2,LSLSLOPE \
VDEF:H=data2,LSLINT \
CDEF:projection=data2,POP,D,COUNT,*,H,+ \
LINE1:projection#BB2030:”2 week projection”