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.

An often requested feature is to include the top-5 consumers of high CPU load in the result from check_cpu (or checkCpu). I have often discarded this as a non-core feature since it is not something I think should be part of NSClient++ instead I think it should be a script. Since no-one has created such a script I figured it would make a nice blog post so here I describe in a step by step guide how to create such a script for NSClient++.

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.