Antwort: Re: [Nagiosplug-devel] check_dns: DNS WARNING - nslookup returned error status
Andreas Ericsson
ae at op5.se
Mon Sep 5 04:10:35 CEST 2005
Ton Voon wrote:
> On 2 Sep 2005, at 16:08, srunschke at abit.de <mailto: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".
>
More likely, it fails if the child sets any of its filedescriptors to
non-blocking (including sockets). I remember seeing something about that
somewhere.
--
Andreas Ericsson andreas.ericsson at op5.se
OP5 AB www.op5.se
Lead Developer
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