2 Node Manager Overview

Node Manager is a WebLogic Server utility that runs as a separate process and enables you to manage the WebLogic Server environment that hosts applications with high availability requirements. Using Node Manager, you can monitor the self-reported health of Administration and Managed Servers and perform the basic tasks remotely using the WebLogic Server Administration Console, Fusion Middleware Control (FMWC), or from the command line.

Introduction

Node Manager is a WebLogic Server utility that enables you to start, shut down, and restart Administration Server and Managed Server instances from a remote location.

Server instances in a WebLogic Server production environment are often distributed across multiple domains, machines, and geographic locations. Although Node Manager is optional, Oracle recommends using it if your WebLogic Server environment hosts applications with high availability requirements because Node Manager allows you to control the running state of distributed server instances from a centralized location.

Node Manager must run on each computer that hosts WebLogic Server instances—whether Administration Server or Managed Server—that you want to control with Node Manager. See Running Node Manager as a Startup Service.

For a basic tutorial demonstrating how to create a default per domain Node Manager instance in a single-machine domain to start and stop Managed Server, see Node Manager Tutorial.

What You Can Do with Node Manager

Node Manager controls the Administration and Managed Servers. Using Node Manager, you can start, shut down, restart the servers, and monitor the log data.

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 a 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 WebLogic Server Administration Console or FMWC, 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 or a start script, the Managed Server contacts the Administration Server to obtain pending configuration updates.

Start, Shut Down, Suspend, and Restart Managed Servers

From the WebLogic Server Scripting Tool (WLST) command line, WebLogic Server Administration Console, FMWC, 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:

If using the pack and unpack commands, Node Manager can start a Managed Server for the first time in MSI mode. However, if using nmEnroll, Node Manager cannot start a Managed Server for the first time in MSI mode, because 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 Command Reference for Oracle WebLogic Server.

Restart Administration and Managed Servers Automatically

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

Note:

Node Manager can only restart a server instance 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 a 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 a Node Manager process and a log file of server output for each server instance it controls. See Log Files.

Node Manager Implementations

WebLogic Server provides two implementations of Node Manager, Java-based and script-based, with similar functionality. Each implementation has different configuration and security considerations.

Java-based Node Manager

Java-based Node Manager runs within a Java Virtual Machine (JVM) process. Oracle recommends 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. You can configure Java-based Node Manager using the Configuration Wizard or WLST offline.

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

Note:

Node Manager is not supported on OpenVMS, OS/390, AS400, UnixWare, or Tru64 UNIX.

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

Java-based Node Manager provides a more fine-grained security model, and the administrator credentials for accessing Node Manager are separate from those of the domain administrator. See Configuring Java-based Node Manager Security.

Script-based Node Manager

For UNIX and Linux systems, WebLogic Server provides a script-based implementation of Node Manager. This script is based on UNIX shell scripts.

For information on configuring the script implementation of Node Manager, see Configuring Script-Based Node Manager.

Script-based Node Manager is not recommended for production environments. However, depending on the security requirements for the environment in which you are using Node Manager, the script-based implementation may be acceptable. The advantage of the script-based Node Manager is that it can remotely manage server instances over a network that has been configured to use SSH. No additional server installation is required. The scripts merely have to be copied to the remote machine.

Note:

Oracle recommends that you run script-based Node Manager as an operating system service, which allows it to restart automatically when the system is rebooted.

Determining Which Node Manager Implementation to Use

The implementation of Node Manager you should use depends on the requirements of your WebLogic Server environment. The following considerations can help you decide which implementation is ideal for your environment:

If you are installing WebLogic Server on a Windows system, you must use the Java implementation of Node Manager. The scripted implementation of Node Manager is not supported on Windows.
Java-based Node Manager can be configured at the time you create the domain. Script-based Node Manager is configured after the domain has been created
To use consensus leasing, you may see faster performance when using the Java implementation of Node Manager.
The script-based Node Manager requires a much simpler security configuration than the Java implementation. RSH and SSH are generally easier to configure than SSL, which is the only way to secure Java-based Node Manager. The script implementation of Node Manager also requires a smaller footprint than the Java implementation.
The Java implementation of Node Manager can be used in conjunction with inetd on supported UNIX systems. The inetd daemon allows Node Manager to be automatically restarted upon receiving a request on the configured port. You can also install the Java implementation of Node Manager as a Windows service.

Accessing Node Manager

Use the WebLogic Server Administration Console, FMWC, or WLST to access the Java-based and the script-based implementations of Node Manager.

In addition, you can access script-based Node Manager from a provided shell command template. You can also use JMX to communicate with the Administration Server.

WebLogic Server Administration Console and FMWC—Use the Environments > Machines > Configuration > Node Manager page.
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. For more information on using WLST and Node Manager to control server instances, see Using Node Manager to Control Servers.

How Node Manager Works in the WebLogic Server Environment

Node Manager uses the startup properties and remote startup arguments to start an Administration Server and Managed Server respectively. The nmConnect command provides a Node Manager user name and password that are used to authenticate the user with Node Manager. The nmStart command identifies the server instance and creates the Administration Server process. In the WebLogic Server Administration Console and FMWC, you can specify the startup arguments that Node Manager uses to start a Managed Server.

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 server instances:

Diagram of Node Manager and Servers

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

In this diagram, Machine A hosts the Administration Server, and Machine B and Machine C host Managed Servers. Each machine contains a Node Manager instance. Using Node Manager, you can start, monitor and restart the Administration Server in Machine A. By using the Administration Server as a Node Manager client, you can start or stop Managed Servers in Machine B and Machine C.

You can use the WebLogic Server Administration Console, FMWC, WLST, or a JMX client to access Node Manager. You can use WLST commands to start, stop, and monitor a server instance when WLST is either connected directly to the Node Manager instance, or when WLST is connected to the Administration Server. When using the WebLogic Server Administration Console and FMWC, you access Node Manager using the Administration Server. You can also use a JMX client to communicate with the Administration Server.

Figure 2-1 Node Manager in the WebLogic Server Environment

Description of "Figure 2-1 Node Manager in the WebLogic Server Environment"

How Node Manager Starts an Administration Server

Figure 2-2 illustrates the process of starting an Administration Server with Node Manager.

This section assumes that you have installed the Administration Server and created its domain directory using the Configuration Wizard.

Node Manager is running on Machine A, which hosts the Administration Server. The standalone Node Manager client is remote.

Figure 2-2 Starting an Administration Server

Description of "Figure 2-2 Starting an Administration Server"

An authorized user issues the WLST offline command nmConnect to connect to a Node Manager process on the machine that hosts the Administration Server. The nmConnect command provides a Node Manager user name and password that are used to authenticate the user with Node Manager.

Note:

If a Node Manager instance is the script-based implementation, the user can connect using the SSH client.

Then, the user issues the nmStart command and provides the credentials for starting the Administration Server. For example:
```
prps = makePropertiesObject(Username=username;Password=password")
nmStart("AdminServer",props=prps) 
```
Note:

A boot.properties file is generated if the user has already started the Administration Server and provided credentials.

The nmStart command identifies the server instance to start.
Node Manager looks up the domain directory in nodemanager.domains, and authenticates the user credentials using a local file that contains the encrypted user name and password.
Node Manager obtains the startup properties for the Administration Server.

The nmStart command can optionally pass properties that are used to start the Managed Server. When these properties are passed, they overwrite any previously stored properties that Node Manager may have used. If no properties are passed with the nmStart command, then Node Manager uses the values in the startup.properties file that have been persisted from a previous startup or from using the nmGenBootStartupProps WLST command.
Node Manager creates the Administration Server process.
The Administration Server obtains the domain configuration from its config directory.

Note:

After the Administration Server is running, you can update the user credentials and startup properties using the WLST online command, nmGenBootStartupProps.

Alternatively, when the Administration Server and Node Manager are running, you can update the user credentials and startup properties in the WebLogic Server Administration Console and FMWC, on the AdminServer > Configuration > Server Start page. The Administration Server then pushes the updates to the running Node Manager and Node Manager writes the information to the disk.

How Node Manager Starts a Managed Server

Figure 2-3 illustrates the process of starting a Managed Server with Node Manager using the WebLogic Server Administration Console. You can also use FMWC, WLST or a JMX client to connect to the Administration Server.

Node Manager is running on Machine B, which hosts Managed Server 1. The Administration Server for the domain is running on Machine A.

Figure 2-3 Starting a Managed Server

Description of "Figure 2-3 Starting a Managed Server"

From the WebLogic Server Administration Console, the user issues a start command for Managed Server 1.
The Administration Server issues a start command for Managed Server 1 to Node Manager on the Machine B, providing the remote start properties configured for Managed Server 1. See Configuring Remote Startup Arguments.
Node Manager starts Managed Server 1.

Node Manager starts the Managed Server in the domain directory.
Managed Server 1 contacts the Administration Server to check for updates to its configuration information.
If there are outstanding changes to the domain configuration, Managed Server 1 updates its local cache of configuration data.

How Node Manager Restarts an Administration Server

Figure 2-4 illustrates the process of restarting an Administration Server with Node Manager.

Node Manager is running on the machine that hosts the Administration Server. The Administration Server, which was initially started with Node Manager, has exited. The Administration Server's AutoRestart attribute is set to true.

Note:

If a server instance's AutoRestart attribute is set to false, Node Manager will not restart it. However, the CrashRecoveryEnabled property takes precedence over the AutoRestart property in a crash recovery scenario. For example, if a server instance has AutoRestart=false but CrashRecoveryEnabled=true, when Node Manager restarts, Node Manager tries to recover the server instance if the server instance failed when Node Manager was not running.

Figure 2-4 Restarting an Administration Server

Description of "Figure 2-4 Restarting an Administration Server"

Node Manager determines from the Administration Server process exit code that it requires restart.
Node Manager obtains the user name and password for starting the Administration Server from the boot.properties file, and the server startup properties from the server_name/data/nodemanager/startup.properties file.
Node Manager starts the Administration Server.
The Administration Server reads its configuration data and starts up.

How Node Manager Restarts a Managed Server

Figure 2-5 illustrates process of restarting a Managed Server with Node Manager.

Node Manager is running on Machine B, which hosts Managed Server 1. Managed Server 1, which was initially started with Node Manager, has exited. Managed Server 1's AutoRestart attribute is set to true.

Note:

Figure 2-5 Restarting a Managed Server

Description of "Figure 2-5 Restarting a Managed Server"

Node Manager determines from the Managed Server 1 process exit code that it requires restart.
Node Manager obtains the user name and password for starting Managed Server 1 from the boot.properties file, and the server startup properties from the startup.properties file. These server-specific files are located in the server_name/data/nodemanager/ directory for Managed Server 1.
Node Manager starts Managed Server 1.

Note:

Node Manager waits RestartDelaySeconds after a server instances fails before attempting to restart it.
Managed Server 1 attempts to contact the Administration Server to check for updates to its configuration data. If it contacts the Administration Server and obtains updated configuration data, it updates its local cache of the config directory.
If Managed Server 1 fails to contact the Administration Server, and if Managed Server Independence mode (MSI) is enabled, Managed Server 1 uses its locally cached configuration data.
Note:

Managed Server Independence (MSI) mode is enabled by default. MSI mode is also enabled when:
- an admin_url is not provided, where admin_url specifies the listen address (host name, IP address, or DNS name) and port number of the domain's Administration Server.
- an admin_url is provided, but the Administration Server cannot be reached for any reason.
MSI mode can be temporary as the Managed Server intermittently attempts to reconnect to the Administration Server.

How Node Manager Shuts Down a Server Instance

Figure 2-6 illustrates the communications involved in shutting down a Managed Server that is under Node Manager control. Depending on the state and availability of the Managed Server, Node Manager might need to forcefully shut down the Managed Server. Node Manager cannot gracefully shut down a Managed Server.

Node Manager is running on Machine B, which hosts Managed Server 1.

Figure 2-6 Shutting Down a Server Instance Under Node Manager Control

Description of "Figure 2-6 Shutting Down a Server Instance Under Node Manager Control"

Through the WebLogic Server Administration Console, an authorized user issues a shutdown command for Managed Server 1.
The Administration Server attempts to connect to Managed Server 1 and issues the shutdown command directly to Managed Server 1. If the Administration Server successfully contacts Managed Server 1, Managed Server 1 performs the shutdown sequence described in Shutting Down Instances of WebLogic Server in Administering Server Startup and Shutdown for Oracle WebLogic Server. For the Managed Server to gracefully shut down itself, it must be connected to the Administration Server.
If, in the previous step, the Administration Server fails to contact Managed Server 1, the Administration Server connects to Node Manager to issue a kill command for Managed Server 1.
Node Manager issues a request to the operating system to kill Managed Server 1.
The operating system ends the Managed Server 1 process.

Node Manager and System Crash Recovery

To ensure that Node Manager properly restarts server instances after a system crash, set the crash recovery properties and perform the other required tasks for Java-based or script-based Node Manager.

To ensure that Node Manager properly restarts server instances, you must perform the following:

For Java-based Node Manager, ensure that CrashRecoveryEnabled is set to true.

The CrashRecoveryEnabled configuration property allows Node Manager to restart server instances after a system crash. The property is not enabled by default.

Note:

If a server instance's AutoRestart attribute is set to false, Node Manager will not restart it. However, the CrashRecoveryEnabled configuration property takes precedence over the AutoRestart server startup property in a crash recovery scenario. For example, if a server instance has AutoRestart=false but CrashRecoveryEnabled=true, when Node Manager restarts, Node Manager tries to recover the server instance if the server instance failed when Node Manager was not running.
For script-based Node Manager, place this line in machine start scripts or, if desired, run periodically on a given schedule:
```
wlscontrol.sh -d domain_name CRASHRECOVERY
```
You should start the Administration Server using Node Manager.
All Managed Servers should be started using the Administration Server. You can accomplish this using WLST, FMWC, or the WebLogic Server Administration Console.

After the system is restarted, Node Manager checks each managed domain specified in the nodemanager.domains file to determine if there are any server instances that were not cleanly shutdown. This is determined by the presence of any lock files which are created by Node Manager when a WebLogic Server process is created. This lock file contains the process identifier for WebLogic Server startup script. If the lock file exists, but the process ID is not running, Node Manager will attempt to automatically restart the server instance.

If the process is running, Node Manager performs an additional check to access the management servlet running in the process to verify that the process corresponding to the process ID is a WebLogic Server instance.

Note:

When Node Manager performs a check to access the management servlet, an alert may appear in the server log regarding improper credentials.

Node Manager Configuration and Log Files

In managing multiple server instances, Node Manager uses multiple configuration files and outputs log files to multiple directories.

These files are shown in Figure 2-7.

Figure 2-7 Node Manager Configuration and Logging Environment

Description of "Figure 2-7 Node Manager Configuration and Logging Environment"

The following sections describe Node Manager configuration and log files:

Configuration Files

Except where noted, configuration files apply to both Java-based and script-based Node Manager.

nodemanager.properties

This is the configuration file used by the Java-based implementation of Node Manager. See Reviewing nodemanager.properties.

By default, this file is located in NodeManagerHome, typically, ORACLE_HOME\user_projects\domains\domain_name\nodemanager, where ORACLE_HOME is the location you specified as Oracle Home when you installed WebLogic Server.

nodemanager.domains

This file contains mappings between the names of domains managed by Node Manager and their corresponding directories. See Configuring nodemanager.domains File.

For the Java-based Node Manager, this file is located in NodeManagerHome, typically, ORACLE_HOME\user_projects\domains\domain_name\nodemanager.

For the script-based Node Manager, this file's default NodeManagerHome location is WL_HOME/common/nodemanager, where WL_HOME is the location in which you installed WebLogic Server, for example, ORACLE_HOME/wlserver.

nm_password.properties

This file stores the Node Manager user name and password. See Specifying Node Manager User Name and Password.

This file is located in DOMAIN_HOME/config/nodemanager, where DOMAIN_HOME is the location of your WebLogic domain, typically, ORACLE_HOME\user_projects\domains\domain_name.