Setting up service dependencies

[Carroll, Jim P [Contractor]]

Agreed, creating these dependencies is slow and painful (made less painful
with the help of a sample block of code that I add after each service that I
want to set up a dependency for, then run through each host's config file to
replace this and that).  I've barely shown you much of a single config file
for a given host.  Make no mistake, I'm monitoring some 1100+ services, and
a large chunk of those (ie, the majority) are NRPE-related.  I'm *still*
working on building out the dependencies, and expect to be adding quite a
few more NRPE services (say, 5-10 NRPE services per host for another ~60
hosts) before too long.  (I could possibly write a Perl script to add the
missing dependencies, but I like your XML suggestion for easing the pain.)
 
The only other suggestion/wish list item I would have, would be to be able
to create a system template which would encompass an integrated
host-and-multiple-services definition, something which would make subsequent
definitions relatively brief.  :)  Perhaps someday, but I'm keen to see if
there are other areas of Nagios which would reap greater rewards in a
shorter time with less effort, given the time/effort.
 
Jeff, I'm not sure if this should be moved over to the nagios-devel mailing
list (which I should think about subscribing to), but if you would care to
constructively hash out an approach/design which could be integrated without
too much grief, then check into it.  :)
 
jc

-----Original Message-----
From: Jeff Boulter [mailto:jboulter at yahoo-inc.com]
Sent: Thursday, January 09, 2003 1:52 PM
To: Nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Setting up service dependencies


yeah, I'm willing to deal with the fact that the host may not be really down
if I'm checking HTTP.
 
Your example is similar to what I tried. But almost all my services use
hostgroup_name rather than host_name to keep things manageable. Otherwise I
would have over 500 service objects to manage. servicedependency doesn't
seem to work right when you substitute hostgroup_name for host_name like it
works for all other object definitions. I would have to create thousands of
service dependecies if I were to do everything on a host basis rather than
hostgroup. Oh well, but here's a vote for XML config files which would make
automatic generation of these files easier. 
 
Jeff

-----Original Message-----
From: Carroll, Jim P [Contractor] [mailto:jcarro10 at sprintspectrum.com] 
Sent: Thursday, January 09, 2003 7:29 AM
To: 'Jeff Boulter'; Nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Setting up service dependencies


It's not A Bad Thing per se; given the example of a host behind a firewall
with a hole at port 80 poked through it, it would certainly have merit.  But
in the case where your webserver fails but, say, sshd is still up, can the
host be said to be down?
 
Just to say that I gave you a servicedependency example, here it is:
 
define service{
        host_name                       itdmll01
        use                             icmp
        service_description             NRPE check
        contact_groups                  linux-admins
        check_command                   check_nrpe!check_nrpe_status
        }
 
define service{
        host_name                       itdmll01
        use                             icmp
        service_description             Total Users
        contact_groups                  linux-admins
        check_command                   check_nrpe!check_users
        }
define servicedependency{
        dependent_host_name             itdmll01
        dependent_service_description   Total Users
        host_name                       itdmll01
        service_description             NRPE check
        execution_failure_criteria      w,u,c
        notification_failure_criteria   w,u,c
        }

Explanation:  "NRPE check" is the basic 'is NRPE up' check.  "Total Users"
actually kicks off a plugin on the remote host.  "Total Users" is dependent
on "NRPE check".  If "Total Users" fails, it checks to make sure that "NRPE
check" is up/down.  If the latter is down, that's all I get alerted on.  If
it's still up, then I get alerted on the former.
 
Does this help?
 
jc
 

-----Original Message-----
From: Jeff Boulter [mailto:jboulter at yahoo-inc.com]
Sent: Wednesday, January 08, 2003 7:53 PM
To: Nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Setting up service dependencies


I think I found a workaround for this. For some servers, like webservers
most of the services are some form of HTTP request, so I changed the
check_command on the host to do a simple http request. If that fails, then
the host is considered 'down' rather than just using the standard ping
check. If this is 'bad' for some reason, please let me know.
 
second question: is it possible to pass arbitrary ssh parameters to
check_ssh, like "-1" for ssh v1? Doesn't appear so, but maybe there's a
trick?
 
Jeff  

-----Original Message-----
From: Jeff Boulter [mailto:jboulter at yahoo-inc.com] 
Sent: Wednesday, January 08, 2003 10:12 AM
To: 'Nagios-users at lists.sourceforge.net'
Subject: RE: [Nagios-users] Setting up service dependencies


I've looked at the examples that come with nagios and they don't seem to
address the problem of using hostgroups versus hosts. I'm not using NPRE,
but if you have examples using hostgroups, I'd love to see them.
 
Jeff

-----Original Message-----
From: nagios-users-admin at lists.sourceforge.net
[mailto:nagios-users-admin at lists.sourceforge.net] On Behalf Of Carroll, Jim
P [Contractor]
Sent: Tuesday, January 07, 2003 1:47 PM
To: 'Jeff Boulter'; Nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Setting up service dependencies


That's different.  You'll want to set up a service dependency, of course.
 
Er... do you absolutely need to check for static HTML?  I mean, if the PHP
fails because the webserver is down....  Oh, unless you just want to be
informed that there's a PHP problem but that the server itself it still up.
Okay, I can see that.
 
I've set up various NRPE dependencies at our site, so if you need a trivial
example, I can post one to the list.  Let me know.
 
jc

-----Original Message-----
From: Jeff Boulter [mailto:jboulter at yahoo-inc.com]
Sent: Tuesday, January 07, 2003 1:05 PM
To: Nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Setting up service dependencies


That's good to know. I still have this issue though because I have some
tests that aren't going work if simpler tests fail. For example, a simple
test to see if a webserver can serve a static HTML can fail, and if that's
the case then checking to see if the webserver will return a PHP page is
obviously not going to work. 
 
Jeff

-----Original Message-----
From: Carroll, Jim P [Contractor] [mailto:jcarro10 at sprintspectrum.com] 
Sent: Tuesday, January 07, 2003 10:41 AM
To: Jeff Boulter; Nagios-users at lists.sourceforge.net
Subject: RE: [Nagios-users] Setting up service dependencies


I'm not sure why you're taking this approach.  Out of the box, Nagios will
behave as you wish it to.
 
If a service check fails, then a host check is made.  If the host check
fails, it's flagged as down and, depending on your particular configuration,
you'll receive the notification for the host being down, not for the N
services you're monitoring on that host.  If the host check passes, then
you'll get an alert on the service.
 
jc

-----Original Message-----
From: Jeff Boulter [mailto:jboulter at yahoo-inc.com]
Sent: Monday, January 06, 2003 6:37 PM
To: Nagios-users at lists.sourceforge.net
Subject: [Nagios-users] Setting up service dependencies




Hello all, 

I'm trying to set up service dependencies in Nagios. For example, I don't
want alerts about an HTTP service being down on a host if the host isn't
pingable.

So far, the only way I've found to do this is to set it up for each host
individually. That would be difficult with the hundreds of hosts that my
nagios is currently monitoring.

I tried creating a servicedependency object with a hostgroup_name and a
dependent_hostgroup_name. This seems to make each host in hostgroup_name
dependent on EVERY host in dependent_hostgroup_name. For example, if my
hostgroup has 7 hosts in it, it seems it's making each of those 7 hosts
dependent on each other, making 7x7=49 dependencies. (Stragely, Nagios
reports 98 dependencies. Why 2x?) 

Any suggestions on how to make a service dependencies local to each host and
not a group of hosts without lots and lots of dependency objects?

Jeff 

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