[op5-users] Merlin

[Andreas Ericsson]

Tom Welsh wrote:
> Morning List,
> 
> I have just started playing about with Merlin in my Nagios setup. I
> was wondering if there is more documentation around apart from the
> config files?
> 
> # address to listen to. 0.0.0.0 is default
> #address = 0.0.0.0;
> 
> I take it i can set this to the IP address of my other Nagios instance
> and i would then get data replication between the two servers over
> port 15551?
> 

No, the "address" directive is there to protect you from listening
on multiple interfaces in case you have more than one, where one is
public and the other one is internal. Since Merlin has no protection
itself from malicious connecting hosts (other than the built-in peer
configuration things), it's sometimes desirable to limit it to one
interface. Leave it commented out while testing.

> How can i go about setting up an agregated and load balanced system
> something like the following
> 
>      NagiosS1Z1  <------------------> NagiosS2Z2
>                       \                       /
>                        \                     /
>                         \                  /
>                          v               v
>                           Nagios0Z0
> 


Assuming S1Z1 and S2Z2 are peers (ie, they monitor the same things)
and Nagios0Z0 is the aggregation server that can take over checks
for the other two but should, by default, monitor absolutely nothing,
you'll achieve that with *something* like the following config
snippets:

On NagiosS1Z1:
-%<--%<--%<-
mode = poller
peer NagiosS2Z2 {
	address = ip-of-nagiosS2Z2
}
noc Nagios0Z0 {
	address = ip-of-Nagios0Z0
}
-%<--%<--%<-

For NagiosS2Z2 I guess you can figure out what microscopic changes
are necessary in the merlin.conf file.

On Nagios0Z0:
-%<--%<--%<-
mode = noc
poller NagiosS2Z2 {
	address = ip-of-NagiosS2Z2
	hostgroup = all_hosts
}
poller NagiosS1Z1 {
	address = ip-of-Nagios1Z1
	hostgroup = all_hosts
}
-%<--%<--%<-

You'll have to create the hostgroup "all_hosts", which should contain
all the hosts you want the pollers to monitor. Config syncing doesn't
work at the moment, so it needs to be done manually.

> Does this make sense
> 

It does indeed, but please be aware that database updates won't happen
on Nagios0Z0 for events that occur on the two poller nodes. I haven't
gotten around to adding support for that yet, even though it would be
quite astonishingly simple :-)

> Stand by for more stupid questions soon.
> 

Hey, I know documentation is lacking so "stupid" questions are quite
expected, really. Doc patches are most welcome, so if you do some
short writeup to use internally, feel free to send it along and I'll
include it with future Merlin releases.

Thanks :-)

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

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