[rrd-users] Re: stuck building RRD

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Oct 25 22:46:50 MEST 2005

On Tue, Oct 25, 2005 at 02:57:21PM -0400, Craig Packard wrote:

> !Build table to store ticket opens in last 5 minutes and
> c:\py\rrdtool create TicketOandC.rrd --start N --step 300
> DS:NonClosed:GAUGE:300:0:5000
> DS:Closed:GAUGE:300:0:5000
> RRA:AVERAGE:0.5:1:288 !1 Day of Actuals
> RRA:AVERAGE:0.5:48:186 !31 Days of 4Hr Averages
> RRA:AVERAGE:0.5:288:365 !1 Yr or 1Day Averages
> This seems to be close. But now I get odd breaks in the graph every so
> often. I want the line from each datapoint (correct term?) to be connected
> to the next. To draw a constant line across the graph. I'm guess that these
> breaks mean for some reason every now-and-then I'm not getting a result
> pushed into the RRD file so the unknown is 'drawn' as a blank? How do I
> avoid that? Should I change the 0.5 to 0.1? But the 1 Days of actuals line
> only takes one data point so the 0.5 thing is pointless? I did have the DS
> as 300:0:U but changed it incase that was doing something screwy.

Your heartbeat equals your step size.  You must update every 300 seconds,
301 seconds is not good enough.  Do you really want that?  Don't get me
wrong, this may be OK if you choose to do so.  But if you run from some
kind of schedular, it is very likely that you run this script not at 300
seconds exactly but rather approximately every 300 seconds.  In other words,
15:10:00, 15:15:01, 15:20:00, 15:25:02 and so on.  Each time an interval
is more than 300 seconds, you have instructed rrdtool to reject the data
and substitute NaN.

You have xff==0.5 so you need to have two unknown intervals in a row to
see one blank spot in your data.  I think you may need to reconsider
your feeding script and/or your rrd parameters.  Modifying xff would
only mask the problem (and besides, it should allow more unknowns, not
less, so you'd need to go to 0.9, not to 0.1)

Alex van den Bogaerdt

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