The famous Nagios open source monitoring system has become a de facto standard in recent years. Unlike commercial monitoring solutions Nagios does not come as a one-size-fits-all monitoring system with thousands of monitoring agents and monitoring functions. Nagios is rather a small, lightweight monitoring system reduced to the bare essential of monitoring: an event management and notification engine. Nagios is very lightweight and flexible, but it must be extended in order to become a solution which is valuable for your organization. Plugins are a very important part in setting up a Nagios environment. Though Nagios is extremely customizable, there are no plugins that capture OpenStack specific metrics like number of floating IPs or network packets entering a virtual machine (even if there are some Nagios plugins to check that OpenStack services are up and running).
Ceilometer is the OpenStack component that captures these metrics. OpenStack measures typical performance indices like CPU utilization, Memory allocation, disk space used etc. for all VM instances within OpenStack. When an OpenStack environment has to be metered and monitored, Ceilometer is the right tool to do the job. Though Ceilometer is a quite powerful and flexible metering tool for OpenStack, it lacks capabilities to visualize the collected data.
It can easily be seen that Nagios and Ceilometer are complementary products which can be used in an integrated solution. There are no Nagios plugins to integrate the Ceilometer API (though Enovance has developed plugins to check that OpenStack components alive) with the Nagios monitoring environment and therefore allow Nagios to monitor not only the OpenStack components, but also all the hosted VMs and other services.
The ICCLab has developed a Nagios plugin which can be used to capture metrics through the Ceilometer API. The plugin is available download on Github. The Ceilometer call plugin can be used to capture a Ceilometer metric and define thresholds for employing the nagios alerting system.
In order to use the plugin simply copy it into your Nagios plugins folder (e. g. /usr/lib/nagios/plugins/) and define a Nagios command in your commands.cfg file (in /etc/nagios/objects/commands.cfg). Don’t forget to make your Nagios plugin executable to the Nagios API (chmod u+x).
A command to monitor the CPU utilization could look like this:
define command {
command_name check_ceilometer-cpu-util
command_line /usr/lib/nagios/plugins/ceilometer-call -s "cpu_util" -t 50.0 -T 80.0
}
Then you have to define a service that uses this command.
define service {
check_command check_ceilometer-cpu-util
host_name
normal_check_interval 1
service_description OpenStack instances CPU utilization
use generic-service
}
Now Nagios can employ Ceilometer API to monitor VMs inside OpenStack.
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