[rrd-users] Question regarding missing data points

[Alex van den Bogaerdt]

> Hi,
>
> we use rrd to get an overview of our server farm. Every data point that is
> monitored (disk usage, cpu, mem, temp., iops, bandwidth and so on) gets
> written to rrd (and then gets visualized via drraw).
>
> Every now and then we get some timeout from the monitoring system (read: a
> missing data point), but i’m unable to implement this in RRD.
>
> Minimal compiling sample:
>
> -------------------------------------------------------------------------------
> rm test.rrd
> rrdtool create test.rrd --step 300 --start 1477432800
> DS:testds:GAUGE:300:U:U RRA:LAST:0:1:10
> rrdtool update test.rrd 1477433100:12
> rrdtool update test.rrd 1477433400:13
> rrdtool update test.rrd 1477433700:15
> # rrdtool update test.rrd 1477434000:NaN   # here is a missed measuring
> point
> rrdtool update test.rrd 1477434300:8
> rrdtool update test.rrd 1477434600:12
> -------------------------------------------------------------------------------
>
> As you can see, the data point for the timestamp 1477434000 will not be
> written to rrd, but the following data point is available, again.

You are not writing points, you are writing rates which are measured
during some interval.
The rate "8" is for time 1477433700..1477434300. This is however not
allowed because of your heartbeat setting and gets lost.

What happens if you do update at time 1477434000, using value U  ?