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

Tue, 17 Aug 2010 11:52:52 -0700

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

The database:
rrdtool create test.rrd --start N --step 5 DS:value:GAUGE:5:-1:101 RRA:AVERAGE:0.5:1:12
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:
#!/usr/bin/perl

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" --vertical-label="Random"\
'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
                          value

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.

Philip
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