FreeBSD 7.2-RELEASE amd64 hangs

[krad]

On 16 December 2010 17:42, Matej Šerc <matej.serc at gmail.com> wrote:

> Hi,
>
> I am experiencing a strange issue that has never occurred to me in all the
> years of using different versions of FreeBSD.
>
> One of our servers, which was running without any issues until yesterday,
> stopped responding for two times now - yesterday and today. About three
> days
> ago another process of pulling out SNMP data from devices was added, but I
> was looking the system load and the system was working normally and also
> processes were cmpleting successfully within the timeframe of 5 minutes
> (much faster, they completed in about 2 minutes). I also want to mention
> that those SNMP pulling processes were already working about a month or so
> on the same server (no hardware was changed in the meantime) and I am
> pretty
> sure that it should work normally as it did.
>
> My main problem is, that there is abcolutely nothing in log files - no
> errors, no warnings, nothing. No strange messages, every process just stops
> logging at one time and then continues after the reboot. Another
> interesting
> issue is that both hangs occured at approximately the same time, but there
> was nobody in the server room and also no one was logged into the server at
> that time except me. About 10 minutes before hang I was investigating
> processes and everything was very normal - no large CPU eating or memory
> eating processes. This might be interesting, even after every process stops
> responding, I was still able to ping the network interfaces and receive
> ICMP
> replies back.
>
> Of course my idea about it is that it must be connected to some hardware
> problems - my suggestion was to make some memory tests. But I would like to
> hear some your oppinions about the entire situation. Could some power
> supply
> issues be doing it? The server is about a year old and has, as I already
> mentioned, worked like a charm until now. How come there is no kernel panic
> since no daemon seems to be working? Why is network interface still up and
> working?
>
> I was unable to go to the co-location facility so I can't say what was on
> the screen at both times, but I suppose there was nothing else than
> messages
> I can read from log files.
>
> I know that 7.2 is pretty old version, but it was working until now on the
> same hardware and we had no reason to change that. Now the system is after
> reboot again running smoothly and without any issues at all.
>
> Thank you very much for any information regarding the issue.
>
> BR, Matej
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I'm not a huge fan of letting snmp spawn heavy weight scripts and processes
as it is to easy for a remote machine to effectively dos the machine. I
realise you are fairly sure the scripts arent an issue, but try croning them
every 5 minutes, and writing the results to a file. SNMP can then simply
retrieve the results from the file. This safeguard to to a certain extent,
in that it stops many processes being spawned. All you have to watch after
that is the job run time