Host/Ping check and Nagios performance.

[Wil Schultz]

check_ping is a pig :)

It's okay for services since they can run in parallel but host checks  
are serialized which can b0rk your whole system if many hosts go down  
at the same time.

A faster way to do this is to use check_icmp, which does 5 pings at  
the same time (concurrently) as opposed to 5 in a row (consecutive)  
like check_ping does.
An even faster check is using check_host as a symlink to check_icmp,  
which still sends the 5 concurrent pings but only requires one to be  
okay, which is great for hostchecks IMHO.

There is a slight security hit using check_icmp or check_host as you  
must SetUID it.

Read the docs, this is all from memory but should be correct, hope  
this helps!

Here is an example:
######################################################################## 
###
bash-3.1# time ./check_ping -H 192.168.22.1 -w 100.0,20% -c 500.0,60%, 
100
PING OK - Packet loss = 0%, RTA = 0.31 ms

real    0m4.009s
user    0m0.000s
sys     0m0.000s
######################################################################## 
###
bash-3.1# time ./check_icmp -H 192.168.22.1 -w 100.0,20% -c 500.0,60%, 
100
OK - 192.168.22.1: rta 0.225ms, lost 0%|rta=0.225ms; 
100.000;500.000;0; pl=0%;20;100;;

real    0m0.004s
user    0m0.000s
sys     0m0.004s
######################################################################## 
###
bash-3.1# time ./check_host -H 192.168.22.1 -w 100.0,20% -c 500.0,60%, 
100
OK - 192.168.22.1 responds to ICMP. Packet 1, rta 0.666ms|pkt=1;;0;5  
rta=0.666;100.000;500.000;;

real    0m0.003s
user    0m0.000s
sys     0m0.004s
######################################################################## 
###


On Jun 7, 2007, at 8:07 AM, Jonathan Call wrote:

> Is there any reason why Nagios stops running all service checks  
> while it
> executes check-host-alive/ping on hosts? Can I change that? I cannot
> find a setting to do it.
>
> With the large number of service checks I'm running (1300+) whenever a
> host goes down (or in some cases just stops answering ICMP) it kills
> performance on the Nagios server.
>
>
> Jonathan Call
>
>
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