WLS Node Manager

Refer to:
http://docs.oracle.com/cd/E15051_01/wls/docs103/nodemgr/overview.html#wp1074880

Node Manager Versions

WebLogic Server provides two versions of Node Manager, Java-based and script-based, with similar functionality. However, each version has different configuration and security considerations.

Java-based Node Manager

Java-based Node Manager runs within a Java Virtual Machine (JVM) process. It is recommended that you run it as a Windows service on Windows platforms and as an operating system service on UNIX platforms, allowing it to restart automatically when the system is rebooted.

Oracle provides native Node Manager libraries for Windows, Solaris, HP UX, Linux on Intel, Linux on Z-Series, and AIX operating systems.

This version of Node Manager determines its configuration from the nodemanager.properties file. See Reviewing nodemanager.properties.

Java-based Node Manager provides more security than the script-based version. See Configuring Java-based Node Manager Security.

Script-based Node Manager

For UNIX and Linux systems, WebLogic Server provides a script-based version of Node Manager. This script is based on UNIX shell scripts, but uses SSH for increased security.

Accessing Node Manager

A Node Manager client can be local or remote to the Node Managers with which it communicates. You access either version of Node Manager—the Java version or the script-based (SSH) version—from the following clients:

• Administration Server
• Administration Console, from the EnvironmentsMachinesConfigurationNode Manager page.
• JMX utilities
  you can create JMX utilities that talk to the Administration Server and perform operations on the ServerLifeCycleRuntimeMBean which in turn uses Node Manager internally to perform operations.  
• WLST commands and scripts—WLST offline serves as a Node Manager command-line interface that can run in the absence of a running Administration Server. You can use WLST commands to start, stop, and monitor a server instance without connecting to an Administration Server. Starting the Administration Server is the main purpose of the stand-alone client. However, you can also use WLST to:
• Stop a server instance that was started by Node Manager.
• Start a Managed Server.
• Access the contents of a Node Manager log file.
• Obtain server status for a server that was started with Node Manager.
• Retrieve the contents of server output log.

What You Can Do with Node Manager

The following sections describe basic Node Manager functionality.

Start, Shut Down, and Restart an Administration Server

Using the WebLogic Scripting Tool (or SSH client for Script-based Node Manager only), you connect to the Node Manager process on the machine that hosts the Administration Server and issue commands to start, shut down, or restart an Administration Server. The relationship of an Administration Server to Node Manager varies for different scenarios.

• An Administration Server can be under Node Manager control—You can start it, monitor it, and restart it using Node Manager.
• An Administration Server can be a Node Manager client—When you start or stop Managed Servers from the Administration Console, you are accessing Node Manager using the Administration Server.
• An Administration Server supports the process of starting up a Managed Server with Node Manager—When you start a Managed Server with Node Manager, the Managed Server contacts the Administration Server to obtain outstanding configuration updates.

Start, Shut Down, Suspend, and Restart Managed Servers

From the WebLogic Server Scripting Tool (WLST) command line or scripts, you can issue commands to Node Manager to start, shut down, suspend, and restart Managed Server instances and clusters.

Node Manager can restart a Managed Server after failure even when the Administration Server is unavailable if Managed Server Independence (MSI) mode is enabled for that Managed Server instance. This is enabled by default.

Note:

Node Manager cannot start a Managed Server for the first time in MSI mode, because at the Administration Server for the domain must be available so the Managed Server can obtain its configuration settings.

Note:

Node Manager uses the same command arguments that you supply when starting a Managed Server with a script or at the command line. For information about startup arguments, see “weblogic.Server Command-Line Reference” in WebLogic Server Command Reference.

Restart Administration and Managed Servers

If a server instance that was started using Node Manager fails, Node Manager automatically restarts it.

Note:

Node Manager can only restart a server that was started using Node Manager.

The restart feature is configurable. Node Manager’s default behavior is to:

• Automatically restart server instances under its control that fail. You can disable this feature.
• Restart failed server instances no more than a specific number of times. You define the number of restarts by setting the RestartMax property in the Node Manager startup.properties file.

If Node Manager fails or is explicitly shut down, upon restart, it determines the server instances that were under its control when it exited. Node Manager can restart any failed server instances as needed.

Note:

It is advisable to run Node Manager as an operating system service, so that it restarts automatically if its host machine is restarted.

Monitor Servers and View Log Data

Node Manager creates a log file for the Node Manager process and a log file of server output for each server instance it controls. You can view these log files, as well as log files for a server instance using the Administration Console or WLST commands.

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How Node Manager Works in the WebLogic Server Environment

The following sections provide a “big picture” diagram of Node Manager’s role in the WebLogic Server environment, as well as illustrations and descriptions of the processes Node Manager uses to communicate with servers:

Diagram of Node Manager and Servers

Figure 2-1 illustrates the relationship between Node Manager, its clients, and the server instances it controls.

Figure 2-1 Node Manager in the WebLogic Server Environment