What is Nagios
Nagios is one of the most widely adopted Open Source IT infrastructure monitoring tool whose main interesting feature being the fact that it does not know how to monitor anything. Well, it can sound like a joke but actually Nagios can be defined as an evaluating core which takes some informations as input and reacting accordingly. How this information is gathered? It is not the main concern of this tool and this leads us to an interesting point: Nagios leave sthe task of getting the monitored data to an external plugin which:
- Knows how to connect to the monitored services
- Knows how to collect the data from the monitored services
- Knows how to evaluate the data
Inform Nagios if the values gathered are beyond or in the boundaries to raise an alarm.
So, a plugin does a lot of things and one would ask himself what does Nagios do then? Imagine it as an exchange pod where information is flowing in and out and decisions are taken based on the configurations set; the core triggers the plugin to monitor a service, the plugin itself returns some information and Nagios takes a decision about:
- If to raise an alarm
- Send a notification
- Whom to notify
- For how long
- Which, if any action is taken in order to get back into normality
The core Nagios program does everything except actually knock at the door of a service, ask for information and decide if this information shows some issues or not.
Planning must be done, but it can be fun.
