[collectd] interval in network packets?

Sebastian Harl sh at tokkee.org
Fri May 21 13:52:16 CEST 2010

Hi Thorsten,

On Thu, May 20, 2010 at 09:03:17AM -0700, Thorsten von Eicken wrote:
> On 5/19/2010 3:22 AM, Florian Forster wrote:
> > Hi Thorsten,
> >
> > On Fri, May 07, 2010 at 11:26:09AM -0700, Thorsten von Eicken wrote:
> >    
> >> Stupid question: what is the interval in network packets used for? I
> >> would think that the only interval that matters in the end is the one
> >> defined in the RRDs.
> >>      
> > the interval is used to set the correct "step" setting when creating new
> > RRD files, for instance. Another use is to detect values that have timed
> > out: By default values that are collected every 10 seconds time out
> > after 20 seconds while values that are collected once a minute time out
> > after two minutes.
> >    
> Can you point me at the code that does this "timing out"? I'm not sure I 
> understand what it means. Does it mean that values get dropped? If they 
> are too far in the past (compared to "now")? Or if there are newer 
> values that show up? Is it at the receiving end or is it in the output 
> end that they get dropped in collectd?

Have a look at uc_check_timeout() (in utils_cache; called from
plugin_read_all()). If some value has not been updated for 2 * interval
and that value is "interesting" (i.e., a threshold has been defined),
then a notification is dispatched by the daemon. All of that happens at
the server. No values get dropped in the daemon (well, unless that's
specified as a filter rule ;-)) -- that kind of stuff might happen in
output plugins only (e.g., RRDtool drops old values in case a newer
value has been stored already).


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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