Cascading

Cascading is the term used to describe a hierarchy of agents, where management requests are passed from a master agent to one of its subagents. A master agent connects to other agents, possibly remote, through their connector server components, much like a manager connects to an agent. In a set of cascading agents, all MBeans in a subagent are visible as if registered in their master agent. The master agent hides the physical location of subagents and provides client applications with a centralized access point.

The cascading service is an MBean that establishes a connection to one subagent. For each of the subagent's MBeans, the cascading service instantiates a mirror MBean that is registered in the master agent. The cascading service also defines a filter and query expression that together determine the set of MBeans in the subagent that is mirrored.

The mirror MBean is a sort of proxy that is specific to the cascading service. A mirror MBean exposes the same management interface as its corresponding MBean. All attributes, operations, and notifications can be accessed through the mirror MBean, which forwards all management requests through the cascading service to the corresponding MBean in the subagent.

You can define hierarchies of agents of arbitrary complexity and depth. Because mirrored MBeans are registered MBeans, they can be mirrored again in a higher master agent. The cascading service is dynamic, meaning that mirrored MBeans are added or removed as MBeans in a subagent are added or removed.

The cascading mechanism works only in one direction. While master agents can manipulate objects in their subagents, subagents have no visibility of their master agent and are not even aware of their master agent.

The cascading service relies on connector components internally and can therefore be used with the RMI, HTTP, or HTTPS protocols. The user specifies the protocol and the subagent's address when configuring the cascading service.