[Xymon] How is clock graph in "trends" column generated

[Jeremy Laidman]

On Tue, 28 Jun 2016, 23:27 Junaid Shahid <shahid.junaid at gmail.com> wrote:

> Thanks JC!
>
> Now that makes it very clear how CPU stats contain server's timestamp (and
> why).
>
> I have checked we are running version 4.3.21.
>
> Now lets look at the reasons of skew:
> a) your xymon server itself is wrong
> Our server's time is correct (as I have manually checked it multiple times
> manually and also with "ntpstats"). Plus, we have some 300+ clients under
> Xymon monitoring, and none of them exhibit any time skew in their CLOCK
> Offset trends
>
> b) you have a xymonproxy in the middle and messages are delayed getting to
> xymond
> We don't use any xymon proxy
>
> c) your xymond_client process is backlogged with [client] messages
> This also can't be the reason because all other clients don't exhibit any
> noticeable skew in their respective Clock Offset trends
>
> d) your xymon server is overloaded and has a long period between transmission
> and TCP processing by xymond
> This also must not be the case as no other client show any noticeable
> Clock Offset trend.
>
>
> In our case there is one specific server (out of 300+) that has a
> clock offset trend that alternates b/w 2-15 secs (like a sinusoidal wave).
> This machine's time is in perfect sync with our NTP server though (no
> clock drift exists actually). This machine has a little complicated network
> topology though (behind various layers such as firewalls, load balancers
> etc). My only guess now is that this is because of its weird network
> location, what do you think JC?
>

I tend to agree. If it takes a few seconds to make a TCP connection to the
xymon server and transmit the client message, you will see such a delay.

Try manually sending a client message and see how long it takes. Something
like:

$ time $XYMON $XYMSRV "client/timetest $MACHINE.$SERVEROSTYPE"

(run within a xymoncmd shell on the client)

J
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.xymon.com/pipermail/xymon/attachments/20160628/547bcaa1/attachment.html>