Monitors Inside the Monitoring Tree 

Definition

The monitoring infrastructure builds a tree of monitors (a monitoring tree). Each monitor presents an agent that communicates with a particular monitored resource and processes the collected data. A monitor represents a small amount of data. It contains a simple type value that gives information about a single aspect of a monitored object.

Use

A monitor can represent the name of an object or the number of successful transactions with an object, but not the object itself. That is why a resource that works with several objects and wants to provide information about them in the monitoring infrastructure has to define several monitors representing different aspects of each object and must then group them semantically so that the group represents the whole object.

In the case of a Java application that is responsible for the proper functioning of several banks, the resource that provides the monitoring data is the application; the logical objects that can be monitored are the different banks. In this context, the monitors representing the different aspects of the object are: the name of the bank, the number of transactions over a particular amount, and so on.

Structure

The monitor is always part of a group of monitors describing an object. The objects themselves can be logically grouped further inside the monitoring tree in summaries. The summaries can be grouped together with other summaries; objects in summaries again, and so on.

Thus, the hierarchical structure of the monitoring tree follows the semantics of the objects being monitored. In the monitoring tree, the leaves are always monitors, the nodes in the first level above the leaves are objects, and the nodes in the upper levels are summaries.

The summaries from the first level below the root are predefined. They are named Kernel, Services, Applications, System, and Performance. These predefined summaries denote different problematic areas that can be monitored inside the AS Java.

The application developer has to place her/his monitors and objects under Applications, since the others are reserved for data coming from the kernel of the server, for data describing configuration of the system (for instance, system properties), and for data coming from the services monitoring the performance of the system as a whole.

The monitoring infrastructure supports the following types of monitors: text, state, table, version, configuration, availability, integer, long, frequency, quality and duration monitors. For more information, see Types of Monitors and Their Usage.

Example

The graphic below gives an idea what the monitoring tree looks like in the Monitor Browser.