Performance tuning a host returning results via NSCA

[Oliver Hookins]

Hi all,

I guess performance is a constant problem for everyone but what I'm seeing
doesn't seem to make sense. I have two servers running Nagios, one that is
more or less just a frontend and another doing the checks and returning
results via send_nsca. Constantly I see the frontend light up with criticals
due to the passive results not being received in time (the service
freshness timeout is 120 seconds).

I only have 120 passive service checks and 45 passive host checks, so I can
assume if none of the hosts are down it is only doing one check per second.
The host performing the checks is under very little load so I can't see why
it is being held up. Here are some facts that may shed some light on the
situation:

On the host doing the checking:
 * as per docs/tuning.html:
  - 1. aggregate_status_updates = 1
  - 3. max_concurrent_checks = 0
  - 7. using check_icmp for host checks, and 'ping' service checks
  - 8. not using regularly scheduled host checks
  - 9. not using aggressive host checking
 * service_inter_check_delay_method=s (have tried 0.01)
 * service_interleave_factor=s
 * host_inter_check_delay_method=s (have tried 0.01)
 * service_reaper_frequency=1
 * sleep_time=1 (have tried 0.01)

OCSP and OCHP are both enabled and send through commands that look like
this:

/bin/echo -e "$HOSTNAME$\t$SERVICEDESC$\t$SERVICESTATEID$\t$SERVICEOUTPUT$"
| /usr/sbin/send_nsca -H nagios-server -c /etc/nagios/send_nsca.cfg

If I check the processes running by the nagios user with 'ps uf -U nagios' I
frequently see just the main nagios process and a forked command for
send_nsca. I'm wondering if sending the passive results is the bottleneck in
this case, and what I could do to improve it? Perhaps write each result to a
file and have a separate process sending multiple passive results back to
the master nagios server?

I'm interested to see anyone else's performance values on a system where
they are using send_nsca.

-- 
Regards,
Oliver Hookins

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