Nagios Core - Active Monitoring

Preface

In this document I'd like to explain meaning of Active Monitoring.

Active Monitoring - Explanation

The easiest way how to understand manning of Active Monitoring is to read next description:

Who is doing the polling?

- The polling is done at monitoring software itself, but not at monitored object. It can be agent based or agent less polling.

Who is doing validation of polled data?

- Validation of polled data (and comparing them to thresholds) is done at monitoring software, but not at monitored object.

Who is deciding if alarm will be created?

- This decision is taken at monitoring software, but not at monitored object.

Active Monitoring - Advantage

Polling Management

- In most of cases it’s possible to say that the polling is scheduled and managed from monitoring software itself.

Flexibility

- In case that you’ll need to use specific polling method. That isn’t natively supported at monitoring software. It’s possible to write polling script that will do the polling and provide result to monitoring software.

Active Monitoring - Disadvantage

Polling Interval

It’s important to understand that Active Monitoring is based on scheduled jobs.

According to this:

- It can happen that polling interval is too long and you can overlook event:
- - That isn’t taking long enough
- - And happened between two polling intervals

- It can happen that the polling interval is too short.
- - This can be root cause of overloading of monitoring system or monitored object with too many requests.

Utilization of resources

Active Monitoring:
- Is based on periodical polling of interesting parameters.
- Is done with help of software/script that are periodically running on monitoring server or monitored object.

According to mentioned points, it’s important to understand that polling is done periodically, even the issue isn't present. Each polling is causing additional utilization of resources, of monitoring system as well of monitored object.

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