Remote Notification Mechanism

The ClientNotificationHandler public interface specifies the methods for a connector to allow a notification listener to receive notifications from a remote MBean in an agent. The ClientNotificationHandler interface is implemented by HTTP and RMI connector clients at the manager side. To forward a notification from the agent to the connector client you can configure the connector to use either push or pull mode. In pull mode, the connector server on the agent side buffers all notifications until the connector client requests, or pulls, them. The forwarding period can be set to control the frequency with which notifications are pulled from the connector server. In push mode, the connector server forwards every notification to the connector client as it is received. In the Java Dynamic Management Kit 4.1 the forwarding period is not used in push mode, notifications are forwarded immediately. Figure 1-5 illustrates this process in terms of the Pull mechanism and the Push mechanism.

The Push Mechanism

You can choose to use the Push Mechanism to push notifications from an agent to a manager. When the connectors run the Push Mechanism , the connector server forwards the notifications to the connector client as soon as they are emitted by the MBeans. For example, you can register an object at the manager side as a listener for notifications emitted by MBean A. Thus, when MBean A, at the agent side, emits a notification, the HTTP, HTTP/SSL or RMI connector forwards this notification to the connector client at the manager side.

The Pull Mechanism

You can choose to use the Pull Mechanism to forward notifications from an agent to a manager. This is useful, for instance, when the agent is unable to connect to a manager. For example, if there is a fire-wall in place between the agent side and the manager side. You can use the Pull Mechanism to pull notifications from the agent side to the manager side. When you create the remote MBean server you need to set the mechanism mode and the pull period. The pull period is the time period between pulls. Pulls occur when the HTTP, HTTP/SSL or RMI connector server at the agent side is instructed by the manager to attempt to pull notifications. Thus, the manager decides when, and how often, it wants to retrieve notifications . For example, the pull frequency could be set to try to get notifications every thirty seconds or every minute.

Figure 1-5 Remote Notification Mechanism