2.3 Distributed administration

Administration in a distributed server environment is by necessity more complex than administration in a stand-alone server environment. In a distributed server environment, multiple WAS nodes are managed from a single central location. This distributed administration of components is brought about by three tiers, or layers, of administration services, as shown in Figure 2-7.

Figure 2-7 Layers of distributed administration services

Between these tiers, communication is used to distribute configuration and application data updates from the deployment manager to the node agent, and in turn to the server instances.

The routing of administration messages between components makes use of the JMX ObjectName that identifies the target managed resource within the administrative cell. The ObjectName contains all of the information necessary to route a request targeted at the resource, to the appropriate node where the resource is executing.

An example is shown in Figure 2-8, where an operation on Node Y invokes a management method on a management bean (MBean) located on another node, Node X.

Figure 2-8 Distributed administration message routing

Where:

1.	An object running on server A of Node Y sends an operation request to the deployment manager AdminService located on the same machine.

2.	The deployment manager AdminService determines which node hosts the requested service (Node X) and passes the request to the MBean acting as the proxy of the node's node agent.

3.	The proxy MBean forwards the request to the AdminService of the Node X node agent.

4.	On Node X, the node agent AdminService receives the request and determines which managed server (process) the requested service is hosted on (process A).

5.	The AdminService passes the request to the MBean acting as the proxy of the managed server.

6.	The proxy MBean forwards the request to the AdminService of the managed server.

7.	The managed server AdminService invokes the requested service via the local MBeanServer, which is responsible for all direct communication with MBeans hosted in that JVM.