[Xymon] [xymon]repair rrd data

[Jeremy Laidman]

Hi Diffusion

This is most likely a problem with the data source feeding into Xymon, in
which case the RRD file will have times with no data, shown as "nan" (not a
number) in "rrdtool fetch <filename> AVERAGE" output. Note that it's common
for one or two "NaN" records at the end of each timescale in the RRD file
(and a bunch at the start also, if the host has been added relatively
recently), but it's less common to have numbers intermingled with NaN
lines. Here's an example:

$ *rrdtool fetch disk,root.rrd AVERAGE*
                            pct                used

1718868300: 8.6000000000e+01 6.1474990000e+06
1718868600: 8.6000000000e+01 6.1474990000e+06
1718868900: -nan -nan
1718869200: -nan -nan
1718869500: -nan -nan
1718869800: 8.6000000000e+01 6.1474990000e+06
1718870100: 8.6000000000e+01 6.1474990000e+06
1718870400: 8.6000000000e+01 6.1474990000e+06
1718870700: 8.6000000000e+01 6.1474990000e+06
...

This example is a sequence of data samples with numbers, then nan due to
missing samples and then more numbers. If you find this in your RRD files,
then the data doesn't exist, and there's no way to repair. The first column
is epoch time, which can be converted to local time using (on Linux or with
GNU date) "date --date @<epochtime>". This might be helpful in correlating
the nan entries with the gaps in your graphs.

In my experience, this is often caused by a connectivity problem between
the client and the server. You may find that data from the client (eg disk,
cpu) has gaps, but data from xymonnet probes (eg conn, http, dns) have no
gaps. This is consistent with missing client data samples.

You might find log messages in xymond.log that help identify a problem.
Also on the client, the xymonclient.log file might be worth a look.

Cheers
Jeremy

On Fri, 21 Jun 2024 at 01:16, <diffusion at bulot-fr.com> wrote:

> Hello
>
> I have many ncv graph and they often "dotted" instead made of lines
> It's like some data left in rrd : see attachment
>
> * How to correct without loosing all data ?
> * how it's happened ?
>
> I had search for "rrd repair tools" but nothing seems works on my
> server or PEBCAK ;-)
>
> (hope my english is not too bad)
>
> _______________________________________________
> Xymon mailing list
> Xymon at xymon.com
> http://lists.xymon.com/mailman/listinfo/xymon
>
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