There are many ways we could go about monitoring, but they largely fall into two main categories, that is, blackbox and whitebox monitoring.
In blackbox monitoring, the application or host is observed from the outside and, consequently, this approach can be fairly limited. Checks are made to assess whether the system under observation responds to probes in a known way:
- Does the host respond to Internet Control Message Protocol (ICMP) echo requests (more commonly known as ping)?
- Is a given TCP port open?
- Does the application respond with the correct data and status code when it receives a specific HTTP request?
- Is the process for a specific application running in its host?
On the other hand, in whitebox monitoring, the system under observation surfaces data about its internal state and the performance of critical sections. This type of introspection...