High Latency with service checks

Assaf Flatto nagios at flatto.net
Wed Feb 16 09:57:41 CET 2011


Yu Watanabe wrote:
> Hello All.
>
> I would like to get an advice with nagios latency issue.
>
> In nagios 3.0.6 with RHEL 4, would there be a possibility 
> that service check latency hikes even though the sar or iostat
> usage is not in relatively high load usage? (I am planning to upgrade to v 3.2.3 soon.)
>
> SAR average cpu usage were 40% and iowait was lying 0%. Swaping were not occuring.
>
> I have more than 1000 ping checks and average latency are 20 min. Check execution time for ping is
> all below 1 sec. Plugin I am using is check_icmp. 
>
> CPU I am using is ,
> Intel(R) Xeon(TM) CPU 2.80GHz
> Memory is 8GB
> OS is RHEL 4.4
>
> Are there any possiblity that Nagios gets locked up with the service check scheduling?
>
> Thanks,
> Yu
>
>
>   
have you tried throttling the amount of concurrent checks ?
could it be that the 1000 pings is flooding your network ?

I've encountered a similar issue with a  a setup I had ( granted the 
latency wasn't that extreme ) , and from what you describe the symptoms 
sound the same .

We tried several solutions (DNX , Mod_gearman) to reduce the latency , 
the solution that worked int he end was adding extra RAM to the machine 
and that solved it - I know that is not the best method , but non of the 
"regular" methods of tweaking nagios (large install , ramfs etc` ) 
worked , the boost in ram reduced the latency from 6+ minutes to 3 sec.

Assaf


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