Nagios service latency

[Thomas Guyot-Sionnest]

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On 04/11/07 12:55 PM, Andreas Ericsson wrote:
> 
> That's not strictly true. Each check run by Nagios needs three fork()'s
> and two exec()'s. For your case, you can achieve exactly the same thing,
> but with 6 fork()'s and 4 exec()'s less by using
> 
> check_host -H $HOSTADDRESS$ -w <warn> -c <crit> -n 3
> 
> except that check_host will be a lot faster for the cases where the host
> has turned unreachable due to routing problems.
> 
> OTOH, it'll be less work for you *not* to change it, so so long as that
> works.

I agree, but with Nagios, check_latency is usually *not* caused by
system resources usage but rather by time spent waiting for hosts checks.

In other words I do *not* care about system resources utilization if
Nagios can't use them up which is currently the case. The way I do hosts
checks is IMHO the fastest one from Nagios point of view, despite the
fact that it can take more CPU cycles to get performed. My check send
only one ICMP ping in most cases. If it's isn't answered it will retry
up to two mote times (3 * 500 ms timeout max). That is tunable of
course. Also I believe the packet interval in your test makes it take
actually longer for the same number of unanswered packet with the same
timeout.

For Nagios 3 with host check caching your method is probably the best
one though.


BTW, this is probably tunable but for the records:

$ time bash -c './check_host -H 1.1.1.1 -w 300.00,80% -c 500.00,100% -n 3'
CRITICAL - 1.1.1.1: rta nan, lost 100%|rta=0.000ms;300.000;500.000;0;
pl=100%;80;100;;

real    0m4.517s
user    0m0.004s
sys     0m0.004s

$ time bash -c 'for i in 1 2 3; do ./check_icmp -H 1.1.1.1 -w 300.00,80%
- -c 500.00,100% -n 1 -t 10; done'
CRITICAL - 1.1.1.1: rta nan, lost 100%|rta=0.000ms;300.000;500.000;0;
pl=100%;80;100;;
CRITICAL - 1.1.1.1: rta nan, lost 100%|rta=0.000ms;300.000;500.000;0;
pl=100%;80;100;;
CRITICAL - 1.1.1.1: rta nan, lost 100%|rta=0.000ms;300.000;500.000;0;
pl=100%;80;100;;

real    0m2.830s
user    0m0.008s
sys     0m0.000s

Overall it's still faster to run 3 of my commands than one of yours on
an unreachable host.


Thomas

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