[rrd-users] weird behaviour of rrd graph

[Tobias Oetiker]

Today Roland Kletzing wrote:

> Hello,
>
> thanks for the hints!
>
> > yes, that is the 'old' solution ... and it does work. but since
> > rrdtool is not even looking at coverage at the future end of the
> > range this does not matter any more ...
>
> that refers to actual versions of rrdtool!?

yes ... not quite sure when I changed it ... 1.3.x I think ...

> unfortunately i`m locked to 1.2.23 , as i don`t have a clue how to get
> a more recent version for that platform. maybe i can update to 1.2.30
> by switching to more recent openWRT build.  (which is embedded linux
> for routers). Would that help,too?

no I don't think so
>
> Anyway, regarding the modulo trick - i`m not sure if i got that right
>
> You mean like this ?
>
> export now=$(( `date +"%s"` - $((`date +"%s"` % 21600)) ))
> rrdtool .... --start end-1y  --end $now ....
>
> (i`m using busybox date, where date +"%s" means seconds since epoch.)

a simple way to solve the problem is to draw your charts 1 step
short ... so if your highest resolution rra is 300 seconds, always
set the end of the graph to now-300 seconds

cheers
tobi

> regards
> Roland
>
>
> --------------------------------------------------
> From: "Tobias Oetiker" <tobi at oetiker.ch>
> Sent: Tuesday, September 28, 2010 11:12 PM
> To: "Alex van den Bogaerdt" <alex at vandenbogaerdt.nl>
> Cc: <rrd-users at lists.oetiker.ch>
> Subject: Re: [rrd-users] weird behaviour of rrd graph
>
> > Today Alex van den Bogaerdt wrote:
> >
> > > > also note that recent rrdtool versions have become more 'stable' in
> > > > their choices ... by only looking to the past and not to the
> > > > present since all RRAs by definition cover the present to the best
> > > > of their abilities ...
> > >
> > >
> > > I'm not sure, but isn't this the same difference?
> > >
> > > now-1y will still sometimes be exactly on one RRA boundary, but usually
> > > not.
> > > Just as now does.
> > >
> > > I suggest Roland tries to compute current_time - (current_time modulo
> > > 21600)
> > > and use that instead of  "now" to see if that makes a difference. I'm not
> > > going to bet on it, but it would sure be my first try.
> > >
> > > 2nd and 3rd try would be 262800 and 2628000 where I wrote 21600.
> >
> > yes, that is the 'old' solution ... and it does work. but since
> > rrdtool is not even looking at coverage at the future end of the
> > range this does not matter any more ...
> >
> > cheers
> > tobi
> >
> > >
> > >
> > >
> >
> > --
> > Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
> > http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900
> >
> > _______________________________________________
> > rrd-users mailing list
> > rrd-users at lists.oetiker.ch
> > https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900