More config file madness add intersection to group operations

[John P. Rouillard]

In message <45D0C6E5.50907 at nagios.org>,
Ethan Galstad writes:

>John Rouillard wrote:
>> Is 3.0 going to support the intersection operation between hostgroups?
>> Currently you can do:
>> 
>>    web_servers,!boston
>> 
>> to get web servers that are not in boston, but trying to get web
>> servers that are in boston means adding every host to a site (e.g. boston,
>> miami, london, orlando) and then:
>> 
>>   web_servers, !orlando, !miami, !london
>> 
>> this is a maintenance nightmare when adding new sites and doesn't
>> express what you want. (I chose a simple example here. In some of my
>> configs I have 10 or 15 different hostgroups.)
>> 
>> What I would like to see is support for the intersection operation.
>> So web_servers in boston would be:
>> 
>>    web_servers, &boston
>> 
>> and production tier 1 web servers in boston that are not dns servers
>> would be
>> 
>>    web_servers, &boston, &production_tier_1, !dns_servers
>> 
>> The addition of intersection provides all the standard operations of
>> set theory: intersection, difference and union.
>I don't have any plans to add intersection support, as it would increase 
>the complexity of the code quite a bit.

I agree the code is more complex, but it greatly reduces the complexity
of setting up services based on the characteristics of the systems for
every user.

>You can accomplish what you 
>need by using smaller hostgroups (that don't get registered) that 
>contain distinct sets of hosts and then use the new subgroup feature in 
>Nagios 3 to define larger hostgroups that contain members of the smaller 
>groups you defined.

That is better than what we have, but is still a major maintainence
burden due to the proliferation of hostgroups. Having to explain to a
new admin (or even an older admin) that they have to select 1
hostgroup from each of three lists is a lot easier than having to
select 20 or 30 subgroups that are derived from the base sets of host
characteristics.

Plus the proliferation of hostgroups leads to a lot of errors in the
configurations that means people don't monitor what they think they
were monitoring.

I think:

     web_servers, &production_tier_1, &boston, &https_server

is a lot clearer than:

     web_servers, !production_tier_2, !production_tier_3, !test_tier_any, !dev_tier_any, !orlando, !miami, !london, !http_only

In any case, does the subgroup feature in nagios 3 allow:

  hostgroup boston_servers_AND_web_servers_AND_https {
     hostgroup_name  web_servers, !orlando, !miami, !london, !http_only
     register      0
  }

  hostgroup boston_servers_AND_web_servers_AND_https {
     hostgroup_name  web_servers, !boston, !miami, !london, !http_only
     register      0
  }

so at least I only have one place to change the intersection like
hostgroup. Then can I use these as:

  define service{
        service_description     HttpsCheck
        hostgroup_name          orlando_servers_AND_web_servers_AND_https
        use                     generic-service
        check_command           check_http!-p 443 -w 5 -c 12
        }
  define service{
        service_description     HttpsCheck
        hostgroup_name          boston_servers_AND_web_servers_AND_https
        use                     generic-service
        check_command           check_http!-p 443 -w 10 -c 20
        }
define serviceextinfo{
        service_description     HttpsCheck
        hostgroup_name          boston_servers_AND_web_servers_AND_https 
        notes   Basic check of https service at port 443.
        use                     generic-service
        }

Thanks for your feedback.

				-- rouilj
John Rouillard
===========================================================================
My employers don't acknowledge my existence much less my opinions.

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