Last time we mentioned two fundamental principles while monitoring any object:

1. The monitor should collect as much important information as possible that will allow to accurately evaluate the health state of an object.
2. The monitor should have little to no effect on the activity of the object.

Sure, these two principles work against each other in most of cases, but with Node.js they work together quite nicely because Node.js is based on event-driven technology and doesn’t use the traditional threads-driven approach. This technology allows to register many listeners for one event and process them in parallel almost independently. To avoid even a small effect on the production server, it was decided to separate the monitor into two parts – the first is the javascript module-plugin that listens to all server events and accumulates necessary information and the second is the Linux shell script that periodically runs the monitor-plugin by using the REST technique for collecting, processing, and sending information to the Monitis main server.
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