[Nagiosplug-devel] check_snmp multiplier / divisor

[Andreas Ericsson]

On 08/17/2012 03:41 AM, Eric Schoeller wrote:
> Hello list,
> 
> We have a fair number of checks using check_snmp, and it is very common
> that an INTEGER is reported in 'tenths' or even 'hundredths'. To use
> check_snmp natively against these OIDs we are forced to set thresholds
> such as '700' to represent '70.0' Fahrenheit. This isn't too big of a
> problem except when tired admins get pages about temperatures reaching
> (what appears to be) 700 degrees Fahrenheit.
> 
> In such cases we could simply write our own plugins, but there are a lot
> of these cases. It would be far more desirable to just use check_snmp. I
> was considering developing and submitting a patch for options such as
> --multiplier or --divisor ... or even perhaps --mangle where in you
> could perform a bit of math on any values returned from the SNMP agent.
> Thresholds would then be applied to the "mangled" value of the OID.
> 
> Would there be support for such a change if we submitted a patch? Is
> there a reason why it would be unnecessary?
> 

I would love such a patch. Sounds like a generally awesome idea. In order
to sanely implement it, I suggest supporting only simple math that can be
parsed easily and unambiguously. It's likely to cover 99% of the cases,
and for the rest, people will have to write their own plugins.

You'd possibly want some "power of 2 to percent" thing though, since a
lot of snmp-capable devices use all available precision to report
some available resource, so "--formula=pct(256)" would transform "128"
into "50".

I'd implement the math part as macros if I were you. That way they'll be
type-agnostic and work well in a wide range of scenarios.

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

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