WebLogic: The Definitive Guide

Node Manager

WebLogic provides a standalone Java tool called the Node Manager, which is responsible for managing the availability of all Managed Servers running on a machine. It runs as a dedicated process on a machine, either as a daemon on a Unix machine or as a service on the Windows platform. It provides a way to automatically restart Managed Servers in the case of failure, and even handles servers that are in a “failed” state. A Node Manager also lets the Administration Server remotely start, kill, and monitor Managed Server instances. A single Node Manager process should run on every machine that hosts Managed Servers. When the Node Manager boots a server, it creates a separate process for that server, just as if you had run the startManagedWebLogic script on that machine.

Warning

A Node Manager does not control the starting and stopping of the Administration Server. The machine that hosts the Administration Server doesn’t need a Node Manager, unless it also hosts one or more Managed Servers.

Figure 13-5 illustrates the role of Node Managers in a domain.

Figure 13-5. Node Managers act as agents to the Administration Server

In order to control the life cycle of a Managed Server, using either the Administration Server or the weblogic.Admin tool, you must start the servers under the control of a Node Manager. For instance, if you restart a Managed Server remotely using the Administration ...