Empty hostgroups ok, but not if services defined?

[Thomas Guyot-Sionnest]

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On 09/04/08 04:13 AM, Marcus Fleige wrote:
> Hi again,
> 
> Marcus Fleige schrieb am 27.03.2008 15:35 Uhr:
>> Hi Ethan, hi list,
>>
>> i got a little problem with empty hostgroups in my config.
>>  From Nagios Version 3.0rc3 and up, empty hostgroups are
>> ignored by default. So far, so good, but when i define a
>> service for an empty hostgroup, i get an error:
>>
>> Error: Could not expand hostgroups and/or hosts specified
>> in service (config file '/etc/nagios/hostgroup-templates/
>> services-hardware-accesspoint.cfg', starting on line 1)
>>
>> Is it possible to circumvent this error? My initial idea was
>> to define a dummy host and make it a member of every hostgroup.
>> But i think this is not the most elegant way to deal with this...
>>
> 
> As this is bothering me, I'll try to make things clearer:
> 
> I'm using hostgroups to inherit services to hostgroup members, the 
> hostgroups are globally defined. Now, as i am building distributed 
> monitoring, some of these hostgroups are only used on the first 
> monitoring node and unknown to the second. This leads to a configuration 
> error on the second node, as the hostgroup is empty but there are still 
> services defined for it.
> 
> Per Definition, it is ok for Nagios if there is an empty hostgroup, it 
> is no problem if you define a hostgroup in your config without any 
> members ("0 Warnings, 0 Errors").
> 
> But if you define a service for that empty hostgroup, Nagios complains 
> about being unable to expand the hostgroup:
> Error: Could not expand hostgroups and/or hosts specified in service 
> (config file 
> '/etc/nagios/hostgroup-templates/services-hardware-accesspoint.cfg', 
> starting on line 1)

Just for correctness here's it fails on setting up the service here not
on expanding the hostsgroup.

If you look at the configuration, host_name is required for any service:
http://nagios.sourceforge.net/docs/3_0/objectdefinitions.html#service
By assigning an empty housgroup you are doing the same as omitting
host_name and this is why Nagios refuses to start.


> For me, this is somewhat inconsistent behaviour. From my understanding, 
> Nagios should ignore the empty hostgroup completely including its 
> services instead of complaining.
> 
> What do you think about that? Thanks for your time,

I don't believe it's inconsistent... If you have some C skills you could
 certainly patch that part of the code for yourself - I believe it's
pretty trivial. However I'm wondering if you really need "global
hostsgroups" in your distributed setup.

I built my servers to be distributed and, in doing so, I made them all
with a cfg_dir with:
1. server-local templates
2. server-local hosts/hostsgroups
3. server-local services/servicegroups

all that in sub dirs so it's easily manageable. Every template,
hostsgroup and servicegroup has a site prefix if front of it so there is
no possible name conflicts.

The idea is to eventually have a main dashboard using all the remote
files unmodified and change the base templates on which all these
services are built (passive, etc...)


I hope this helps...

Thomas
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