On Wed, June 22, 2016 10:56 am, Junaid Shahid wrote:
Hello Xymon Gurus!
I have searched the interwebs for it but could not find anything useful.
My question is how are the values calculated for the Clock offset graph, displayed at the bottom of the "Trends" column. I have seen some posts (and my experience also confirms this) that Xymon's ntp check (specified in the hosts.cfg) is only to see if NTP daemon on a client is up (responsive). While the clock offset is plotted via some internal logic (client feeds data to the server).
Would really appreciate if some one can throw some light on it!
Some links that I have gone through: http://osdir.com/ml/monitoring.hobbit/2007-03/msg00361.html http://lists.xymon.com/oldarchive/2009/01/msg00417.html
Hi,
The "clock" value is computed from the timestamp of the client message (as seen at the end of generation by the client) to the timestamp of the "cpu" status message generation by the xymond_client on the server. (It's thus dependent on your xymon server having the time set correcty.) The client isn't doing a comparison itself against anything externally.
This is subject to skew if: a) your xymon server itself is wrong b) you have a xymonproxy in the middle and messages are delayed getting to xymond c) your xymond_client process is backlogged with [client] messages d) your xymon server is overloaded and has a long period between transmission and TCP processing by xymond
For b) and c) the 4.4 version (and the Terabithia RPMS, IIRC) use receipt time for the first proxy encountered, and xymond parsing/separation time otherwise, for comparison, which fixes both of those things. Local ntp problems and "raw" TCP lag until connection receipt will still affect things, however.
One "feature" of this in 4.3 though is that if you see clock skew rising and times are correct on both sides, then you can easily tell that your xymon server is having performance problems.
HTH, -jc