notify_nagios.rb

I needed to find a way to let our Nagios know about any status change on any keepalived instances we run.

Requirements:

• nagios server with passive check support and a service definition, using check_dummy plugin
• at least one keepalived daemon running, pointing notify_master, notify_backup and notify_fault to the location where the notify_nagios.rb script is at.
• ruby 1.8.7, of course
• place keepalived.sh in /usr/local/bin (or the local of your preference). Create a cron job to run every minute or so.
• install nsca server on your nagios server and the nsca client on the hosts running keepalived.

How it works:

The idea is pretty straightforward. You must have a service definition on your nagios server set to passive mode. For example, look at the service definition below:

Nagios

# The host itself...
define host {
	use			gen-host
	host_name		lbre-lb2
	alias			LBRE LOAD BALANCER 2
	address			lbre-lb2.stanford.edu
	contacts		dummyuser
	contact_groups		null
    passive_checks_enabled  1
}

define service {
	**service_description	keepalived**
	host_name		lbre-lb2
	**check_command		check_dummy!3!"No data from Passive Check"**
    flap_detection_options	n
    active_checks_enabled	0
    max_check_attempts	1
	check_freshness		1
	**freshness_threshold     3600**
    contacts		user
	contact_groups		null
    passive_checks_enabled  1
	stalking_options	n
	flap_detection_options  n
}

The options in bold are the ones we need to look at.

• service_description keepalived : this is what tell nagios which service will receive the status information when running the script.
• check_command check_dummy!3!"No data from Passive Check" : this nagios plugin simply returns the status specified by its arguments. In this example, I tell nagios to report "UNKNOWN" status with the message "No data from Passive Check"
• freshness_threshold 3600: this is something important. Basically, it means that nagios will run an active check if it doesn't receive any activity (notification) from any machine running keepalived for one hour.

keepalived: