[Xymon] How to setup a back-up xymon server

[Wim Nelis]

Xymon is also used to monitor my home-network. One of the clients is a raspberry 
pi 0 (rpi0, IP address 192.168.178.71), which controls the home ventilation unit 
and which will monitor more in the near future as sensors are added. Sometimes 
the Wifi-connection is not operational for some time. The obvious results are 
that status messages do not reach the xymon server (IP address 192.168.178.72), 
and that the associated graphs (RRD's) are not updated.

I would like to be able to check the graphs once the network connection is 
operational again. The current solution is to install a (secondary) xymon server, 
version 4.3.28, on rpi0 as well. (Note that there is no intention to use this 
xymon server for other purposes: there is no web server active on the rpi0, nor 
would I like to have a web server on this tiny computer.) The configuration file 
/etc/default/xymon-client on rpi0, which is included in file 
/usr/lib/xymon/client/etc/xymonclient.cfg, is modified to contain the addresses 
of both xymon servers:

XYMONSERVERS="127.0.0.1 192.168.178.72"

The default section and the host section for rpi0 in configuration file 
/usr/lib/xymon/server/etc/analysis.cfg is the same on both xymon servers. The 
client data arrives at the primary xymon server, resulting in tests and their 
associated graphs. When the need arise, the RRD files are copied from rpi0 to the 
primary xymon server, and can then be inspected. However, it seems that the data 
arrives twice at the primary xymon server. Xymond reports:

Multi-source statuses
   rpi0:conn                 reported by 192.168.178.71 and 127.0.0.1
   rpi0:cpu                  reported by 192.168.178.71 and 127.0.0.1
   rpi0:disk                 reported by 192.168.178.71 and 127.0.0.1
   rpi0:files                reported by 192.168.178.71 and 127.0.0.1
   rpi0:inode                reported by 192.168.178.71 and 127.0.0.1
   rpi0:memory               reported by 192.168.178.71 and 127.0.0.1
   rpi0:msgs                 reported by 192.168.178.71 and 127.0.0.1
   rpi0:ports                reported by 192.168.178.71 and 127.0.0.1
   rpi0:procs                reported by 192.168.178.71 and 127.0.0.1

The associated graphs one the primary xymon server are not complete: quite often 
de measurements of 2 or 3 consecutive periods of 5 minutes are missing. The xymon 
logfile rrd-status.log shows that multiple RRD updates, with slightly different 
values at about the same time, are the root cause of the incomplete graphs.

In this situation I would like to stop the secondary xymon server from sending 
the test results to the primary xymon server. How can one achieve that?

Regards,

   Wim Nelis.