[rrd-users] Re: RRDtool "GMT-centric" problem?

[Owen DeLong]

I solved this by using the entry_time=(now - (now % interval)).

My capture script does this before calling the rrd update routine.

Owen

> steve rader wrote:
> >                  I've found that the heartbeat of exactly one day
> > can generate NaN for a full day if the updates are 1day+2sec or
> > more apart.  So the best rrdtool create would be something like:
> > 
> >  rrdtool create page.rrd --start 946788800 --step 3600 \
> >  DS:pages:GAUGE:86520:0:1000 \
> >  RRA:AVERAGE:0.958:1:240
> > 
> > which allows for updates up to 1day+2min (86520) apart.
> > 
> 
> This would lead you back to the previous problem.  If you update the
> database on times that are not *exactly* on the boundaries that rrdtool
> keeps, you won't find the entered values in the RRD.
> 
> Consider intervals I1 and I2.  Interval I1 starts on boundary B1 and
> ends on boundary B2.  I2 goes from B2 to B3.
> 
> You update the database at B1, B2 + 1 minute and at B2.  Interval I1
> will have the value you've entered at time B2 + 1 minute (assuming it is
> a gauge value).  Interval I2 is also influenced by this update.  The
> remaining part of interval I2 is determined by the value you enter when
> updating at time B3.
> 
> Interval 2 will show a value that is mostly the value at time B3 but
> has a part of the value from the update at time B2 in it.
> It will be (60/86400)*V2 + ((86400-60)/86400)*V3.
> 
> Given the following input:
> 
>    rrdtool update page.rrd \
>       946789200:75 \
>       946875600:2 \
>       946962060:31 \
>       947048400:8 \
>       947134800:31
> 
> it will be approximately 8.0159722204 which is rounded to 8.02 ...
> In this example:
> B1 == 946875600
> B2 == 946962000
> B3 == 947048400
> V1 == 2
> V2 == 31
> 
> If you want to see the values you enter, you must use the correct times.
> Should RRDtool do it otherwise, it would not represent the true situation.
> It is showing you the value from B2 to B3, and you entered two different
> readings during that interval.
> 
> regards,
> -- 
>    __________________________________________________________________
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