how is "Service check Latency" defined in nagios?

[Rahul Nabar]

On Mon, Feb 9, 2009 at 3:58 PM, Max <perldork at webwizarddesign.com> wrote:

> Rahul,
>
> On Mon, Feb 9, 2009 at 2:53 PM, Rahul Nabar <rpnabar at gmail.com> wrote:
> > Thanks Marc. I have: max_concurrent_checks=0
>
> Our experience has been that with max_concurrent_checks set to 0 and
> inter-check delay and nagios sleep set very low we get high reported
> service check latencies as we are basically asking Nagios to try and
> run everything as soon as possible ... 1000s of checks over a few
> seconds in essence ... which it can't do.   As far as 'real life'
> negative impact the high latency in this singular case hasn't meant
> much; it initially really worried me until i realized that the high
> service latency is just happening because we are basically telling
> nagios to pause / sleep / wait for as little time as possible and run
> things as quickly as possible.  We have around a 146 second service
> check latency but from our detailed Nagios metrics we see that check
> runs are completing in right around 4 minutes, under our 5 minute
> hard-ceiling (around 6000 checks).  our PNP performance graphs prove
> our suspicions .. our reporting server receives 6000 metrics in 4
> minutes or less and we have no gaps in our graphs or major under or
> over sampling problems with the data we retrieve from our remote
> agents.
>
> I only bring that up because if you not only have
> max_concurrent_checks set to 0 but also have tuned way down
> inter-check delay settings and sleep time you might be encountering
> the same situation and the high latency might not be something to
> worry about .. but only IF you have all your delays tuned very low and
> no ceiling on max checks.  for any other situation it is definitely
> something to investigate.



Thanks Max. That is a pretty intricate issue that I had no idea about! I'm
still trying to figure out the exact implications of what you describe.
Maybe I need to visit the Nagios manual again to re-read nagios's scheduling
logic. It's especially important to me now that I also have PnP running
performance stats.

Meanwhile this is a dump of the relevant parameters you speak about. I don't
recall changing any from their defaults.
Maybe I ought to in the light of what you mentioned?

service_inter_check_delay_method=s
host_inter_check_delay_method=s
sleep_time=0.25

#Timeouts:
service_check_timeout=60
host_check_timeout=30
event_handler_timeout=30
notification_timeout=30
ocsp_timeout=5
perfdata_timeout=5

-- 
Rahul
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