Expose Your MBeans in a Smart Agent

A Java Dynamic Management agent follows the client-server model: the agent responds to the management requests from any number of client applications that wish to access the resources it contains. The agent centralizes all requests, dispatches them to the target MBeans and returns any responses. The agent handles the communication issues involved with receiving and sending data, so that the MBeans don't have to.

The central component of an agent is the MBean server. It is a registry for MBean instances and it exposes a generic interface through which clients can issue requests on specific MBeans. Clients may ask for the description of an MBean's management interface, in order to know what resource is exposed through that MBean. Using this information, the manager can then formulate a request to the MBean server to get or set attributes, invoke operations or register for notifications.

MBeans are only accessible through requests to the MBean server. Manager applications never have the direct reference of an MBean, only a symbolic object name which identifies the MBean in the agent. This preserves the client-server model and is essential to the implementation of query and security features.

The MBean server also provides the framework that allows agent services to interact with MBeans. Services are themselves implemented as MBeans, which interact with resource MBeans to perform some task. For example, a manager could decide to monitor some MBean attribute: it instantiates the monitoring service MBean, configures the threshold, and registers to receive the alarms that may occur. The manager no longer needs to poll the agent, it will automatically be notified whenever the attribute exceeds the threshold.

The library of services contains the logic that is necessary for implementing advanced management policies: scheduling events, monitoring attributes, establishing and enforcing relations, discovering other agents, creating subagent hierarchies, and downloading of new MBean objects. You may also develop your own service MBeans to meet your management needs, such as logging and persistence services which are typically platform dependent.