[rrd-users] not being able to get exactly updates made

Alceu R. de Freitas Jr. glasswalk3r at yahoo.com.br
Wed Oct 8 07:39:51 CEST 2014


My name is Alceu and I'm a newbie with RRDTool.

I'm trying to create a POC by using RRDTool::OO Perl module (available on CPAN).

I'm not sure where I'm doing a mistake, but it seems I'm not being able to set the database as desired.

For testing, I don't want any interpolation in the update data.

To create the database, I chose a step of 600 seconds (10 min). The data that I have is exactly 600 seconds after each other. In total, I have 1319 lines of data, so I also set the rows parameter to 1319. Also, to be sure, set the heartbeat to 600 seconds.

My first row of sample data starts at 1408735271. I've already tried several combinations of the start parameter (1408735270, (1408735271 - 600)) but I'm always getting the following result with fetch:

1408756800: 8.65

When in fact it should be:

1408735271: 9.75

This is how I'm fetching the data:

$rrd->fetch_start( start => 1408735271, end => 1409547002 );
while ( my ( $time, $value ) = $rrd->fetch_next() ) {
    print "$time: ", defined $value ? $value : "[undef]", "\n";

The start and end are using the timestamps from the first and last sample of data.

Am I not following the concepts of RRDTool or there is possibly a bug with RRDTool::OO?

Thank you,
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