[collectd] Problem configuring snmp plugin.

[Florian Forster]

Hi Krist,

On Mon, Sep 24, 2007 at 12:09:22PM +0200, Krist van Besien wrote:
>    <Host "M0n0Wall_router_2">
>        Interval 120
>    </Host>
> 
> Using "rrdtool info" I looked at what got put in to the rrd, and found
> out that rrd updates did take place, but the problem was that the
> rrd's created had a heartbeat of 20. Since the rrd was updated only
> every 120 seconds or so (as this is the interval set in the snmp
> plugin config) all data points remained "unknown".

when the interval of the SNMP plugin is set to 120 and the configuration
of the rrdtool plugin is left at the default values, the `step' of newly
created RRD-files should be 120 seconds and the minimal heartbeat should
be 240 seconds.

However, this only applies to newly created files - existing files are
used as-is, i. e. if they were created with a 10 second step (and 20
second heartbeat) und you later changed the step to 120 seconds, they
won't work anymore. You can use rrdtool to change the heartbeat to a
useable timespan (e. g. 180 seconds), see the rrdtune(1) manpage.

If you did set the interval to 120 before the files were created with a
wrong step and heartbeat setting, that could be a problem with a too
specific configuration of the rrdtool plugin.

If you left the rrdtool plugin at the default values and deleted all
RRD-files and the new files still end up wrong, that's most likely a
bug. But since everything worked fine for me I'd need more detailed
instructions on how to reproduce the problem to bugfix this..

> Where does this 130 seconds come from? Is the "interval" setting in
> the snmp config being ignored?

If the ``global'' `Interval' setting is set to the default 10 seconds,
it could be that the SNMP plugin collects data every 12 iterations when
it should collect data every 11 iterations. Can you verify if the same
problem occurs with other intervals, i. e. I'd expect that when you set
the global interval to 42 seconds and the SNMP-host interval to 210
seconds the RRD-file should be updated every 252 seconds..

> Is there a way to get the snmp plugin to sample more often?

Sure, set the `Interval' setting to a shorter interval - I often use 30
seconds, for example..

Regards,
-octo
-- 
Florian octo Forster
Hacker in training
GnuPG: 0x91523C3D
http://verplant.org/
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