check_icmp

[Andreas Ericsson]

Bergström Sebastian wrote:
> Thanks! That truly answers most of my questions.
> 
> What is the reason that you made check_icmp a drop-in replacement for
> _ping? Is it that much better?
> 

Yes. It's a lot faster (especially for detecting down hosts), more 
portable ("unable to parse ping output" goes away), it requires less 
memory (fewer fork()'s = fewer PTE's and fewer task-structures) and has 
more features. You can f.e. set TTL on outgoing packets, meaning you can 
monitor which of several redundant routes is being used, and if BGP 
fucks up and starts routing your traffic through a nearby continent 
you'll know it soon enough.

Also, it's a very common plugin to use, as nearly everybody use ping to 
find out if their hosts are up (and usually as a service as well). Even 
a minor speed increase in this plugin can make a dramatic change in 
nagios performance. Especially with network outages, where the usual 
check_ping would get ICMP_HOSTUNREACH several times, whereas check_icmp 
drops the target immediately upon such a reply and deemes it dead (saves 
roughly 12 seconds per hostcheck with identical default configurations).

> I know that check_ping has a weird problem of timing out everynow and
> then, even with increased host_check_timeout values...
> 

I don't know about that. I've been using check_icmp since version 0.6.

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Lead Developer


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