[rrd-users] Re: Unable to store integer values in RRD

[Tobias Oetiker]

Monday you sent me mail regarding [rrd-users] Re: Unable to store integer...:

*> 
*> Yusuf Goolamabbas <yusufg at outblaze.com> writes:
*> 
*> > 964420410:  3.2000000000e+01 
*> > 964420440:  3.2266666667e+01 
*> > 964420470:  3.9966666667e+01 
*> > 964420500:  3.8933333333e+01 
*> > 964420530:  3.2200000000e+01 
*> > 964420560:  3.0633333333e+01 
*> > 964420590:  3.7966666667e+01 
*> > 964420620:  3.8200000000e+01 
*> > 964420650:  3.7900000000e+01 
*> > 964420680:  NaN 
*> > 
*> > I am at a loss to understand how to get integer values stored in the
*> > database
*> 
*> You don't; rrdtool will average the values for you unless they are
*> stored exactly on the time points in the RRD. This issue was up here
*> recently; this is part of the reply from Tobi:
*> 
*>     if you updates arrived EXACTLY at the points in thime rrdtool
*>     stores data in its database (963600900,963600960,963601020,...)
*>     then exactly these values would be stored ... but because your data
*>     does not arrive exactly at these points in time rrdtool integrates
*>     the space below the curve created by the datapoints you supplied
*>     and then uses the --step size to calculate the value of the data
*>     source at the points in time which havbe to go to the log file.
*> 
*> I suppose you wil have to work out your own integer values, but this
*> may not *always* be correct. It is a bit early for me, but it seems
*> to me that the only value where you can get it wrong, is exactly
*> 3.5000000000e+01 which can be either 3 or 4.

the point is that you DO NO WANT to have integers there ... 

* you count your webserver processe a 5:02pm
* you count them again at 5:08pm 

your rrd stores data at 5pm and 5:05pm and then again at 5:10pm

* it tries to figure out how many processes have been running at
  the time the data gets stored ... unfortunately there is not
  exact data available ... so it creates an intermediate taeing the
  data provided into account ... this value can be non integer but
  this is no problem because you can not know how many processes
  there were a 5:05pm sharp unless you counted them. But you can
  know how many processes there were on average arround that time.

cheers
tobi

*> 

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