LVS / NAT with MON hanging after some days

Joseph Mack NA3T jmack at
Tue Oct 24 12:41:57 BST 2006

On Tue, 24 Oct 2006, Grames, Gernot wrote:

> I have configured a LVS/NAT with mon on 2 directors (Major and Backup).

what is mon monitoring on the director? (I've only used mon 
on the realservers to monitor services.)

> Behind the director i have 4 clients running.

4 realservers?

> The lvs with the nat and the mon is working perfectly for some time.
> After around 5 or 6 days (i have it seen also one time after one day)
> the server (director) freezes completly.

keyboard at the console does nothing?

> I made some scripts (cron) to write logfiles with the info of the
> running process, memory and hard disc space.
> But there i cannot find a special behavior.

usually when something dies hard, there's nothing to write 
to log files.

> I can`t also say if the ipvs is the problem or the mon??
> Is there a possibility to debug these things?

The mon scripts are quite simple, which means that there's 
not much to go wrong. The alert is a little complicated, but 
there's nothing there that can cause a freeze - none of it 
is kernel code. You should be able to send anything to ip_vs
vi the sysctl/ipvsadm and not freeze the machine.

What happens if you run the directors without mon for a 
while, i.e. you assume that none of the services are going 
to fail, and you just have one director running (at a time)?

Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at
Homepage It's GNU/Linux!

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