dont check service when host down

Andreas Ericsson ae at op5.se
Wed Sep 19 09:00:13 CEST 2007


Hari Sekhon wrote:
> Andreas Ericsson wrote:
> 
>>> Could we make this a feature request?
>> I think you just did, and I think I just shot it down for nagios 2.x.
>>
> To be fair, I wasn't asking for this for Nagios 2.x. Nagios 3.x is the 
> development branch, is it not?
> 
> Also I still think it's a good idea, since there is no point in wasting 
> resources sending out checks for things
> that can't answer by definition...
> 
> I can't see the harm in this feature, only good in that it saves some 
> service checks when the host(s) are down.
> 

Patches speak louder than feature requests. Send the code and I'll have a
peek at it. Until then, I'll file it under "something to do on a rainy day".

Currently there are two other improvements that can be done in Nagios which
will improve performance quite a lot more than to stop executing service-
checks when the host they belong to are down.

The first is to rewrite the command execution logging to use a multiplexer.
That would get rid of one fork() call per executed command, which would be
a *huge* net gain in performance (it would double Nagios' capacity). It
would also mean that we can get rid of the threading code, which complicates
the expression of some of the algorithms in nagios (locking issues, primarily).

The second is to rewrite the config reading stuff to be module-loaded, so
that the code can be unloaded once the config is read. The data section
of the nagios binary is quite bloated with all the hardcoded strings, and
they need to be copied for every fork(). Since nagios does a lot of forking
today, that all adds up to quite a lot of cpu time. This change would also
(eventually) allow nagios to read config from external sources, as config
reading modules can be added later, without having to recompile the nagios
core.

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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