Re: [Nagios-users] hostgroups and service dependencies?
Frost, Mark {PBG} wrote:
> I'm just starting to get into service dependencies. My problem is that
> I don't quite see how I can get around doing it individually for each
> and every service and host needed.
>
> An example is if I've got 100 Windows servers all configured to be part
> of a hostgroup. Then I've got a
>
>
> define service {
> hostgroup_name
> prod_windows_servers
> service_description NRPE Service
> check_command NRPE Service
> use Production
> Windows Service
> }
>
> define service {
> hostgroup_name
> prod_windows_servers
> service_description CPU Load
> check_command
> check_windows_load!90%!90%
> use Production
> Windows Service
> }
>
> define service {
> hostgroup_name
> prod_windows_servers
> service_description C: Drive
> check_command
> check_windows_disk!C:!90%!90%
> use Production
> Windows Service
> }
>
> where the 100 servers are all part of the 'prod_windows_servers"
> hostgroup. Here I can list the checks nice and compactly and add new
> hosts/checks merely by putting them in that hostgroup.
>
> I would like to make service checks on these boxes dependent on the
> "NRPE Service" check above. So if the NRPE service was not responding,
> Nagios wouldn't bother sending me alerts about all the other things on
> that box it could not reach.
>
> The object definitions seem to say that I can do
>
> define servicedependency {
> hostgroup_name
> prod_windows_servers
> service_description NRPE Service
> dependent_hostgroup_name
> prod_windows_servers
> dependent_service_description C: Drive
> execution_failure_criteria n
> notification_failure_criteria w,u,c
> }
>
> I'm assuming that this is supposed to match up each
> 'prod_windows_servers' entry with its matching entry rather than making
> each server dependent on this servers from *every* other hostgroup
> member?
>
You assume wrong. This makes it depend on each hostgroup member. In order
to do "same-host" dependencies, you can leave out one of the "hostgroup_name"
or "dependent_hostgroup_name". I can't remember which, so go browse the docs
to find out. Do note that same-host dependencies only work in Nagios 3.
> Just to see, I tried this out and when I did a pre-flight check it took
> 53 seconds (checking the host and service dependencies) when it normally
> runs instantly.
>
Right. I'll try to apply the depth first search to host and service
dependencies too. It was originally a patch from Jean Gabès, and it
speeds up parent/child relations for hosts by a *huge* amount, so it's
probably worth adding it to dependencies too.
Even so, I'm guessing you actually added 100 (or more) times the number of
dependencies you expected to add, so it's not surprising this eats a lot
of CPU.
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Re: [Nagios-users] hostgroups and service dependencies?
The 53 second delay is natural - as nagios is calculating the dependencies and
what it
calls "circular dependencies " - meaning it check that the definition is
correct and the logic you
defined is fine .
the delay will be there as long as you have the dependencies - as you are
adding more complexity to
the nagios operations and work logic - so it takes more time to prepare and
create
the "understanding " of the logic and requirements.
creating 100 definitions of service dependencies will not reduce the
calculation time , and will
only make you have a more "mess" in the configuration , the way you set it up
is correct , and more
elegant to read and understand by the next guy that will need to take care of
the system (if that
ever happens ).
On Wednesday 20 May 2009 19:35:20 Frost, Mark {PBG} wrote:
> I'm just starting to get into service dependencies. My problem is that
> I don't quite see how I can get around doing it individually for each
> and every service and host needed.
>
> An example is if I've got 100 Windows servers all configured to be part
> of a hostgroup. Then I've got a
>
>
> define service {
> hostgroup_name
> prod_windows_servers
> service_description NRPE Service
> check_command NRPE Service
> use Production
> Windows Service
> }
>
> define service {
> hostgroup_name
> prod_windows_servers
> service_description CPU Load
> check_command
> check_windows_load!90%!90%
> use Production
> Windows Service
> }
>
> define service {
> hostgroup_name
> prod_windows_servers
> service_description C: Drive
> check_command
> check_windows_disk!C:!90%!90%
> use Production
> Windows Service
> }
>
> where the 100 servers are all part of the 'prod_windows_servers"
> hostgroup. Here I can list the checks nice and compactly and add new
> hosts/checks merely by putting them in that hostgroup.
>
> I would like to make service checks on these boxes dependent on the
> "NRPE Service" check above. So if the NRPE service was not responding,
> Nagios wouldn't bother sending me alerts about all the other things on
> that box it could not reach.
>
> The object definitions seem to say that I can do
>
> define servicedependency {
> hostgroup_name
> prod_windows_servers
> service_description NRPE Service
> dependent_hostgroup_name
> prod_windows_servers
> dependent_service_description C: Drive
> execution_failure_criteria n
> notification_failure_criteria w,u,c
> }
>
> I'm assuming that this is supposed to match up each
> 'prod_windows_servers' entry with its matching entry rather than making
> each server dependent on this servers from *every* other hostgroup
> member?
>
> Just to see, I tried this out and when I did a pre-flight check it took
> 53 seconds (checking the host and service dependencies) when it normally
> runs instantly.
>
> I'm not sure this does what I want. Even so, I don't know that I can
> handle the 53 second wait which I imagine would escalate for each
> service I defined in this way). The only other route I can think of is
> to create a unique servicedepency definition for each of these. That's
> 100 x n dependency definitions, where n is the number of other services
> I'm checking on each of these boxes.
>
> Am I looking at this the wrong way? Is there an easier way to do this?
>
> Thanks
>
> Mark
>
>
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