[collectd] On $Interval differences between hosts

Sebastian Harl sh at tokkee.org
Wed Jun 22 10:50:00 CEST 2011


On Wed, Jun 22, 2011 at 06:01:10PM +1000, Trent W. Buck wrote:
> Sebastian Harl wrote:
> > On Wed, Jun 22, 2011 at 02:07:29PM +1000, Trent W. Buck wrote:
> > > Suppose I have centralized monitoring (i.e. hub-and-spoke), similar to
> > > centralized syslogging.  On the central host (accepts UDP and writes
> > > RRD), I have
> > > 
> > >     Interval 60
> > > 
> > > On the nodes (collectd data and write to UDP), I have
> > > 
> > >     Interval 10
> > > 
> > > Is a given RRD file updated every ten seconds, or every minute?
> > 
> > All RRD files are updated in "the right" interval. I.e., RRDs containing
> > data from some node are updated using a ten seconds interval and those
> > belonging to the central server are updated using a 60 seconds interval.
> >
> > Each plugin "knows" the interval with which it's queried and passes that
> > information along when dispatching data to collectd. This information is
> > also transferred over the network and, thus, available on the server as
> > well.
> OK, that makes sense.  So a follow-on question: if I define thresholds
> in the central hub collectd, do all thresholds apply/check every sixty
> seconds, or do they "do the right thing"?

Thresholds are checked whenever a value is dispatched to the daemon,
i.e. that's done "live" and depending on the specific interval of some
data-set (i.e., "the right thing" ;-)).

> If I happened to have it the other way around (leaves update each
> minute, hub updates even ten seconds), I can imagine the thresholds
> all freaking out (when $Important is set) because they haven't seen an
> update for five intervals (50s)...

The timeout used to check for missing values depends on the interval of
the data-sets as well (see the "Timeout" config option in


Sebastian "tokkee" Harl +++ GnuPG-ID: 0x8501C7FC +++ http://tokkee.org/

Those who would give up Essential Liberty to purchase a little Temporary
Safety, deserve neither Liberty nor Safety.         -- Benjamin Franklin

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