Increase the efficiency of passive checks

[Marc Powell]

Andrew_Hoying at blm.gov <mailto:Andrew_Hoying at blm.gov> wrote:
> Hello,
> 
> I'm currently running a Nagios server which is processing a little
> over 2000 passive checks every 10 minutes. I know the server has the
> memory and processing power to handle that many checks in half that
> time, however the bottle neck seems to be the size of the named pipe
> file and the speed at which it is read. I have Nagios set to check
> the file every second, which works fine, and it processes around 5
> passive checks a second, however the server Nagios is running on is
> still only using around 4% of it's processing power and it's disk
> access is nominal. What can I do to increase the size of the named
> pipe, or move to shared memory, a Unix socket, or some other method
> of accepting passive checks that would speed it up without
> significantly rewriting Nagios? Does anyone have a patch for 1.2 that
> would solve this problem? Is 2.0 significantly better in this regard?


FWIW, I'm receiving ~2600 passive checks every 5 minutes and Nagios
(1.1) is able to keep up just fine. The only modification I've made is
to set command_check_interval=-1 which tells Nagios to check the command
file as often as possible, not just every second. The command file is 0
length about 30-40% of the time and very rarely maxed out so I believe
that I can scale to at least double that number of checks and probably
more with no changes.

Also possibly related are the status update intervals and retention
values (as they will take time away from nagios processing external
commands). Mine are set as follows --

aggregate_status_updates=1
status_update_interval=15 (this affects GUI 'freshness')
retain_state_information=1
retention_update_interval=5

The _interval times above could probably be increased to squeeze out
more performance and should be set to whatever your expections for
freshness are. I haven't done any benchmarking to determine just how
much of an effect different values have but my feeling from using
Nagios/Netsaint for a couple of years is that they do have a measureable
effect, especially if they are very low and you have a high number of
devices/services you are monitoring.

--
Marc



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