A tutorial for writing a quick and simple Lua script which will turn check_cpu into a multi functional check which return top CPU consumers. In last weeks edition I introduced the various parts we need to make this a reality. And that idea I have with NSClient++ is to create a Lego box with small multi purpose functions which the users can combine in many different ways. Here I will show you how we can do that.

The biggest reason for Nagios success is the ability to extend it with custom scripts which makes it one of the most powerful monitoring systems. Now Nagios is not the only place where you can extend your monitoring! NSClient++ provides many ways to extend it with scripts and since I have gotten many questions about how to use scripts with NSClient++ lately I have decided to write this tutorial to help sort out the concepts.

Stateful scripts are a simple yet powerfully way to enhance your monitoring which I think is used far to little. Using stateful script you can easily add simple predictions and change management. This is very easy to accomplished using NSClient++ as its built-in scripting modules by default provides stateful scripts (in contrast to Nagios and Icinga which tends to be stateless). This tutorial will walk you through writing a simple stateful script in Lua. If you are still confused about stateful scripts the main benefit is that they remember things. Thus you can alert when something changes as well as predict the future. A good example of this is disk growth prediction but there are a lot of other scenarios where they are useful.