I found it, well, at least I found a way to make it work, and have a
theory as to why.
The problem seemed to be the "timeout" value of 5: DS:value:GAUGE:5:-1:101
This didn't seem to play well with trying to enter data exactly on 5
seconds.
I re-created the DB, changing the "timeout" value to 10, and data
started to appear in my DB.
So what I learned is "do not set the timeout to be exactly the same
as the update rate".
Now I have another question that I can't see the answer to anywhere.
In some examples, I find multiple CFs being defined. For example:
rrdtool create test.rrd --start N --step 5 \
DS:value:GAUGE:10:-1:101 \
RRA:AVERAGE:0.5:1:30 \
RRA:AVERAGE:0.5:5:6
So we are keeping two averages, averaged over different periods.
When graphing, how do I select which of these AVERAGEs to use?
------------------------
On 8/17/2010 11:23 AM, Philip Peake wrote:
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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