Antwort: Re: [Nagiosplug-devel] check_dns: DNS WARNING - nslookup returned error status

[Ton Voon]

On 2 Sep 2005, at 16:08, srunschke at abit.de wrote:
> If it is of any help, I would like to offer to escalate this issue
> to the RedHat Support. Since we have a dozen support subscribtions
> for RH Enterprise, I can easily create a ticket and let them solve
> it for us ;-)
> I just need some technical description of the problem so that
> someone not into Nagios would be able to understand it. I'm not
> sure I could word it properly myself.

Sascha,

I would like to take you up on this offer.

I've managed to reduce the test case down to the included tar file,  
so there are no nagios plugins involved. Instructions are:

gunzip and untar and cd
make
./run_tests 10

On my RHEL4 server (Red Hat Enterprise Linux version 4 Update 1,  
2.6.9-11.EL) , this will fail anywhere between 40% to 70% of the  
time. Running the same on MacOS10.4.1 and Debian 3.1 gives me 100%  
success.

In child_test.c, you can amend the command that is executed. These  
were the results I got (after 100 runs):

   - /bin/date 100%
   - /bin/cat /etc/hosts 100%
   - /usr/bin/dig redhat.com 69%
   - /bin/sleep 1 100%
   - /usr/bin/nslookup redhat.com 90% (after 100 runs), 40% (after 10  
runs)
   - /bin/ping -c 1 localhost 100%
   - /bin/ping -c 1 192.168.10.32 100%

So it looks like only DNS resolution stuff is causing problems. Using  
Peter's trick of waiting for childtermd to be set by the SIGCHLD  
handler (commented in child_test.c) changes it to 100% success at all  
times.

Definitely looks like a Redhat problem. Can you escalate to them. I  
think a technical summary could be: "wait() sometimes fails if child  
executes nslookup/dig command".

I'm happy for you to contact me if you need more information.

Ton


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