[rrd-users] Help - probably a really stupid mistake somewhere ...

Philip Peake philip at vogon.net
Tue Aug 17 20:23:05 CEST 2010

 I am trying to get my first RDD database going.
I think that I understand the doc/tutorial, so tried a really simple

The database:

    rrdtool create test.rrd --start N --step 5 DS:value:GAUGE:5:-1:101

What I think this does:

    * Creates a database called test.rrd (it does).
    * Has a step time of 5 seconds (don't want to wait forever to see data).
    * Starts from "now".
    * Has a single data source called "value", which is a GUAGE (keeps
      the value presented)
    * Data must be greater than -1 and less than 101
    * Has a single value stored, which is the AVERAGE of one "record",
      so will be equivalent to the value stored.
    * Keeps 12 x 5 = 60 seconds of data.

My data producer:


    my $random_number;

    while (sleep(5)) {
            $random_number = rand(100);
            print "Adding $random_number\n";
            @cmd = ("rrdtool", "update", "test.rrd", "N:$random_number");
            system(@cmd) == 0 or die "Failed: $?";

Once every 5 seconds call "rddtool update test.rrd N:<random number in
range 0 to 100>"

The database does change after each update.

My graph:

    rrdtool graph mygraph.png -a PNG --start -240 --title="Test"
    'DEF:v1=test.rrd:value:AVERAGE' 'LINE1:v1#0400ff:Rnd Value'

What it produces:

Database doesn't seem to be getting the values:

    $ rrdtool fetch test.rrd AVERAGE -s -30

    1282069345: nan
    1282069350: nan
    1282069355: nan
    1282069360: nan
    1282069365: nan
    1282069370: nan
    1282069375: nan

I am obviously doing something wrong ... but what???

Any help appreciated.

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