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

[Philip Peake]

 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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