Clarification (was: service that has no associated host...)

[Andreas Ericsson]

prosolutions at gmx.net wrote:
> 
> I will try to clarify this a little bit:
> 
> 
>               _____________
>              |  monitoring |
>              |  system     |
>              |             |
>              | (nagios)    |
>               -------------
>                    |
>                    |
>                    |  MYAPP    (test MYAPP, send request through
>                    |  test      external gateway to load-balanced
>                    |  script    cluster)
>                    |
>                routed through
>                 external 
> 		gateway
>                    |
>                    |
>              ______|___________
>             |  load-balancing  |
>             | cluster director |
>             |__________________|
>              |       |        |
>              |       |        |
>            __|_    __|_     __|_
>           |    |  |    |   |    |  application servers
>            ----    ----     ----    (running MYAPP)
>                                     
> 
> I want to define two instances of service MYAPP: MYAPP_peak_hours and
> MYAPP_off_peak both of which run at different times of day.  The
> event_handler will be my custom script which is configured to connect to
> an external gateway.

Do you mean check_command rather than event_handler?


>  The requests get routed to a load-balancing
> cluster director and answered by one of several servers in a pool.  I am
> not sure what host_name is supposed to be

The host_name of the cluster director, ofcourse. That's the host 
providing the service you're checking (even though it's just a proxy of 
sorts, it has to be up for the service check to succeed).

> or why I even need to
> configure one in nagios.

Because nagios requires services to be attached to hosts. It's a 
programmatic thing which can't be changed without rewriting nagios from 
the ground up.

>  In this instance, it doesn't seem to make
> sense to me.

I take it you're on a fairly green limb in the network management tree 
then. Services in a network are provided by one or more devices. Those 
devices are referred to as "hosts" in nagios, which is usually a fairly 
accurate term.

>  I am not checking a host.  I am checking a service which
> is handled by a cluster of hosts.  The IP address that the actual test
> script connects to has nothing to do with my app.

That ip-address is the ip-address of the host that the service-check 
belongs to. If you pull the plug to the device listening to that IP the 
check will fail.

>  There is no need to
> ping any specific server here to see if it is alive.

Bah!

>  I just want to run
> the test script at regular intervals.
> 

Nagios can do this for you, provided you follow nagios' rules.


If you post any more nonsense on this subject claiming that the check 
doesn't really belong to a host, I think you'll be pretty thoroughly 
flamed. I'll even go so far as to provide the flaming myself if no-one 
else feels up to it. ;)

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


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