Why not make service depend upon host?

Tom Welsh twelsh at square-box.com
Mon Aug 16 18:39:41 CEST 2004


Hi Leonardo,

I think your missing the point. 

In the simplest terms....

Ff a service is UP the host is up. 
If the service is down the host may still be up. 
If the host is down there is definitely NO services running.

It makes sense to only check services, You only execute a HOST check if a
service check fails.

Your mimimizing your network traffic just slightly as a ping dosent take
that much bandwidth. (Unless I want to be cruel)

The way you said it you'd do a Ping check first to see if the host is there
and then do all your service checks. By default Nagios spreads its service
checks over all your servers so that none of them are hit by a big
monitoring load. Using your scenario almost every second or 3 check would be
a host check to see if the host was there. 

Now if you have 100 hosts with 10 services each that's 1000 service checks
and 100 possible ping checks if all 100 hosts were down.  

Your way of working would mean this would increase to approximately 1333
host and service checks if it checked 3 services per server per host ping
check.

Your increasing your scheduling queue by 1/3

I hope that makes sense. Im not sure it does 

Cheers

Tom Welsh
squareBOX technologies ltd


-----Original Message-----
From: nagios-users-admin at lists.sourceforge.net
[mailto:nagios-users-admin at lists.sourceforge.net] On Behalf Of
leoh at dcc.ufmg.br
Sent: 16 August 2004 15:58
To: nagios-users at lists.sourceforge.net
Subject: [Nagios-users] Why not make service depend upon host?

Hi Sirs,

I think that it's a good idea to let services checks depend on host checks.

In Nagios, hosts depends on hosts (just for notification failures) and
services checks depends on services checks (notifications and executions
failures).

If I want to tell nagios to check a service just if the host is up, I have
to define a PING service. Doing that I can depend on PING. But it's
redundant! Host checks should be enought to tell me that the host is up.

The solution is to make services checks to depend on host checks. Ex.:

#Check service B if Host B is UP
define hostservicedependency{
	host_name			Host B
	dependent_service_description	Service B
	execution_failure_criteria	w,u,c
	notification_failure_criteria	w,u,c
}


Will it be avaible in the next release? Is there any disavantage the I
have not spotted?

--
Leonardo Henrique Machado
Universidade Federal de Minas Gerais



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-------------------------------------------------------
SF.Net email is sponsored by Shop4tech.com-Lowest price on Blank Media
100pk Sonic DVD-R 4x for only $29 -100pk Sonic DVD+R for only $33
Save 50% off Retail on Ink & Toner - Free Shipping and Free Gift.
http://www.shop4tech.com/z/Inkjet_Cartridges/9_108_r285
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::: Please include Nagios version, plugin version (-v) and OS when reporting any issue. 
::: Messages without supporting info will risk being sent to /dev/null





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