Sun Java System Application Server Enterprise Edition 8.2 Quick Start Guide

Chapter 2 Quick Start for Setting Up High Availability Failover

With the configuration used in the previous chapter, if a server instance goes down, users lose session state. This section, the second of two advanced topics, provides the steps for installing the high-availability database (HADB), creating a highly available cluster, and testing HTTP session persistence.

Application Server supports both HTTP session persistence and persistence for Stateful Session Beans. The procedures in this chapter cover HTTP session persistence.

These steps assume you have already performed the steps in the previous sections of this Quick Start. The steps are presented in the order that you should complete them.


Note –

Completing this section may require additional hardware resources.


This chapter contains the following sections:

About High Availability Clusters and HADB

A high availability cluster inSun Java System Application Server Enterprise Edition integrates a state replication service with the clusters and load balancer created earlier, enabling failover of HTTP sessions.

HttpSession objects and Stateful Session Bean state is stored in HADB, a high-availability database for storing session state. This horizontally scalable state management service can be managed independently of the application server tier. It was designed to support up to 99.999% service and data availability with load balancing, failover, and state recovery capabilities.

Keeping state management responsibilities separated from Application Server has significant benefits. Application Server instances spend their cycles performing as scalable and high performance JavaTM 2 Platform, Enterprise Edition (J2EETM platform) containers delegating state replication to an external high availability state service. Due to this loosely coupled architecture, application server instances can be easily added to or deleted from a cluster. The HADB state replication service can be independently scaled for optimum availability and performance. When an application server instance also performs replication, the performance of J2EE applications can suffer and can be subject to longer garbage collection pauses.

Because each HADB node requires 512 Mbytes of memory, you need 1 Gbyte of memory to run two HADB nodes on the same machine. If you have less memory, set up each node on a different machine. Running a two-node database on only one host is not recommended for deployment since it is not fault tolerant.

HADB Preinstallation Steps

This procedure covers the most common preinstallation tasks. For information on other preinstallation topics, including prerequisites for installing HADB, configuring network redundancy, and file system support, see Chapter 2, Installing and Setting Up High Availability Database, in Sun Java System Application Server Enterprise Edition 8.2 High Availability Administration Guide.

The recommended system configuration values in this section are sufficient for running up to six HADB nodes and do not take into consideration other applications on the system that also use shared memory.

ProcedureTo Configure Your System for HADB

  1. Get root access.

  2. Define variables related to shared memory and semaphores.

    • On Solaris 9:

      1. Add these lines to the /etc/system file. If these lines are in the file as comments, uncomment them and make sure that the values match these:

        set shmsys:shminfo_shmmax=0x80000000

        set semsys:seminfo_semmnu=600

        Set shminfo_shmmax to the total memory in your system (in hexadecimal notation the value 0x80000000 shown is for 2 Gigabytes of memory).

        If the seminfo_* variables are already defined, increment them by the amounts shown. The default values for seminfo_semmni and seminfo_semmns do not need to be changed.

      2. Reboot, using this command:

        sync; sync; reboot

    • On Solaris 10, setting shared memory is not required. Shared memory segments grow to one quarter of physical memory by default. To override the default, set the shared memory segments as described above in the global zone /etc/system file.

    • On Linux:

      1. Add these lines to the /etc/sysctl.conf file (or if they are in the file as comments, uncomment them). Set the value to the amount physical memory on the machine. Specify the value as a decimal number of bytes. For example, for a machine having 2 GB of physical memory:

        echo 2147483648 > /proc/sys/shmmax

        echo 2147483648 > /proc/sys/shmall

      2. Reboot, using this command:

        sync; sync; reboot

    • On Windows: No special system settings are needed.

  3. If you used existing JDK software when you installed a standalone Application Server, check the JDK version.

    HADB requires Sun JDK 1.5 (for the latest information on JDK versions, see the HADB Requirements and Supported Platforms in Sun Java System Application Server Enterprise Edition 8.2 Release Notes). Check the version installed, and if it is not done already, set the JAVA_HOME environment variable to the directory where the JDK is installed.

  4. If necessary after the reboot, restart the domain, Web Server, and node agent.

    To restart the domain, use the command asadmin start-domain domain1.

    To restart the Web Server, execute the start program in one of the following directories (depending upon the Web Server version):

    • web-server-install-dir/https-hostname

    • web-server-install-dir/https-hostname/bin

    To restart the node agent, use the command asadmin start-node-agent hostname. Replace the variable hostname with the name of the host where the Application Server is running.

Installing HADB

This section provides the steps for installing the high-availability database (HADB).


Note –

If you plan to run the high-availability database on the Application Server machine, and if you installed HADB when you installed Application Server, skip to Starting HADB.


You can install the HADB component on the same machine as your Application Server system if you have 2 Gbytes of memory and 1-2 CPUs. If not, use additional hardware. For example:

ProcedureTo Install HADB

  1. Run the Application Server or Java Enterprise System installer.

  2. Choose the option to install HADB.

  3. Complete the installation on your hosts.

Starting HADB

This section describes starting the HADB management agent in most cases by running the ma-initd script. For a production deployment, start the management agent as a service to ensure its availability. For more information, see Starting the HADB Management Agent in Sun Java System Application Server Enterprise Edition 8.2 High Availability Administration Guide.

If starting a database with HADB nodes on several hosts, start the management agent on each host.

ProcedureTo Start HADB in a Java Enterprise System Installation on Solaris or Linux

  1. Change to the /etc/init.d directory:

    cd /etc/init.d

  2. Run the command to start the agent:

    ./ma-initd start

ProcedureTo Start HADB in a Java Enterprise System Installation on Windows

HADB is started by default when Sun Java System is configured and running. However, if you need to start it manually, follow these steps:

  1. Go to Start⇒Settings⇒Control Panel, and double-click Administrative Tools.

  2. Double-click Services shortcut.

  3. Select HADBMgmtAgent Service from the Services list.

  4. From the Action menu, select Start.

ProcedureTo Start HADB in a Stand-Alone Installation on Solaris or Linux

  1. Change to the HADB bin directory in the Application Serverinstallation: install-dir/hadb/4/bin

  2. Run the command to start the agent:

    ./ma-initd start

ProcedureTo Start HADB in a Stand-Alone Installation on Windows

  1. In a terminal window, change to the HADB bin directory in the Application Serverinstallation: install-dir\hadb\4.x\bin

    The x represents the release number of HADB.

  2. Run the command to start the agent:

    ma.exe -i ma.cfg

Configuring a Cluster and Application for High Availability

The FirstCluster cluster must be configured to use HADB and high-availability must be enabled for the clusterjsp application before you can verify HTTP session persistence.

ProcedureTo Configure a Cluster and Application for High Availability

  1. From the machine on which the Domain Administration Server is running, configure FirstCluster to use HADB using this command:

    asadmin configure-ha-cluster --hosts hadb-hostname,hadb-hostname --devicesize 256 FirstCluster

    Replace the hadb-hostname variable with the host name of the machine where HADB is to run. If you are using just one machine, you must name it twice.

    This simplified example runs two nodes of HADB on the same machine. In production settings, use more than one machine.


    Note –

    To reduce the memory footprint of HADB for demonstration purposes, execute the following hadbm command. You are prompted for the administration password.

    In Java Enterprise System installations:

    /opt/SUNWhadb/4/bin/hadbm set DataBufferPoolSize=64,LogBufferSize=25 FirstCluster

    In standalone Application Server installations:

    install-dir/hadb/4/bin/hadbm set DataBufferPoolSize=64,LogBufferSize=25 FirstCluster


  2. Configure the clusterjsp application for HTTP session persistence by enabling high availability:

    1. In the Admin Console, expand the Applications node.

    2. Expand Enterprise Applications.

    3. Click clusterjsp.

    4. In the right pane, on the General tab, click the Availability Enabled checkbox.

    5. Click Save.

      Availability is enabled at the server instance and container level by default.

Restarting the Cluster

Before the changes made in the previous section take effect, the cluster's instances must be restarted.

ProcedureTo Restart the Cluster

  1. In the Admin Console, expand the Clusters node.

  2. Click FirstCluster.

  3. In the right pane, click Stop Instances.

  4. Once the instances are stopped, click Start Instances.

Verifying HTTP Session Failover

The procedure for testing session data failover is similar to the procedure for testing load balancing as described in Verifying Load Balancing. Because HADB has been installed and configured, and the cluster and application have been configured for high availability, Session Data is now preserved after failure when you follow this procedure. Failover is transparent to the user because the sample application is configured for automatic retry after failure.

ProcedureTo Verify HTTP Session Failover

  1. To display the first page of the clusterjsp application, type this URL in your browser:

    http://localhost:web-server-port/clusterjsp

    Replace the localhost variable with the name of the system that the Web Server is running on.

    Replace the web-server-port variable with the value of the port attribute of the LS element in web-server-install-dir/https-hostname/config/server.xml. For this example, port 38000 is used.

    A page similar to what you saw in To Verify the Application Deployment appears.

  2. Examine the Session and Host information displayed. For example:

    • Executed From Server: localhost

    • Server Port Number: 38000

    • Executed Server IP Address: 192.18.145.133

    • Session ID: 41880f618e4593e14fb5d0ac434b1

    • Session Created: Wed Feb 23 15:23:18 PST 2005

  3. View the server access log files to determine which application server instance is serving the application. The log files are located here:

    • Solaris Java Enterprise System installation:

      /var/opt/SUNWappserver/nodeagents/nodeagent-name/i1/logs/access/server_access_log

      /var/opt/SUNWappserver/nodeagents/nodeagent-name/i2/logs/access/server_access_log

    • Linux Java Enterprise System installation:

      /var/opt/sun/appserver/nodeagents/nodeagent-name/i1/logs/access/server_access_log

      /var/opt/sun/appserver/nodeagents/nodeagent-name/i2/logs/access/server_access_log

    • Windows Java Enterprise System installation:

      install-dir\nodeagents\nodeagent-name\i1\logs\access\server_access_log

      install-dir\nodeagents\nodeagent-name\i2\logs\access\server_access_log

    • Standalone Application Server installations:

      install-dir/nodeagents/nodeagent-name/i1/logs/access/server_access_log

      install-dir/nodeagents/nodeagent-name/i2/logs/access/server_access_log

  4. Stop the Application Server instance that is serving the page.

    1. In the Admin Console, in the left pane, expand Clusters.

    2. Click FirstCluster.

    3. In the right pane, click the Instances tab.

    4. Select the server instance that served the request and click the Stop button.

  5. Reload the clusterjsp sample application page.

    The session ID and session attribute data are retained.

  6. Check the access log of the other Application Server instance, and notice that it is now servicing the request.

    The state failover features work because the HTTP session is stored persistently in the HADB. In addition to the HTTP session state, the Application Server also can store the state of EJBTM enterprise beans in the HADB. For more information, see Sun Java System Application Server Enterprise Edition 8.2 Developer’s Guide.

Cleaning Up

To clean up, you can uninstall the Application Server installation by completing the steps in To Uninstall Completely, or you can simply delete the sample cluster you have just created by completing the steps in To Remove the Sample Cluster.

ProcedureTo Uninstall Completely

  1. Stop the Application Server processes using these commands:

    asadmin stop-cluster FirstCluster

    asadmin remove-ha-cluster --hosts hadb-hostname,hadb-hostname FirstCluster

    Replace the hadb-hostname variable with the host name of the machine where HADB is to run. If you are using just one machine, you must name it twice.

    asadmin stop-node-agent hostname

    asadmin stop-domain domain1

  2. Stop the HADB Management Agent by one of the following methods:

    • In a Solaris or Linux Java Enterprise System installation:

      1. Change to the /etc/init.d directory:

        cd /etc/init.d

      2. Run the command to stop the agent:

        ./ma-initd stop

    • In a Windows Java Enterprise System installation:

      1. Go to Start⇒Settings⇒Control Panel, and double-click Administrative Tools.

      2. Double-click the Services shortcut.

      3. Select HADBMgmtAgent Service from the Services list.

      4. From the Action menu, select Stop.

    • In a stand-alone Solaris or Linux Application Server installation:

      1. Change to install-dir/hadb/4/bin.

      2. Run the command to stop the agent:

        ./ma-initd stop

    • In a stand-alone Windows Application Server Installation:

      1. Change to install-dir\hadb\4.x\bin.

        The x represents the release number of HADB.

      2. Run the command to stop the agent:

        ma.exe -r

    At this point, all processes related to Sun Java System Application Server are stopped.

  3. Uninstall the Application Server.

    • In a Solaris or Linux Java Enterprise System installation, run var/sadm/prod/entsys/uninstall and follow the steps in the uninstallation wizard.

    • In a Windows Java Enterprise System installation, use the Control Panel's Add/Remove Programs item. Choose Sun Java Enterprise Systems and click Change/Remove. Remove install-dir\bin from the PATH environment variable and delete the AS_ADMIN_USER variable.

    • In a Solaris or Linux standalone Application Server installation, run install-dir/uninstall and follow the steps in the uninstallation wizard.

    • In a Windows standalone Application Server instance, from the Start menu, choose Programs ⇒ Sun Microsystems ⇒ Application Server EE ⇒ Uninstall.

  4. If you created a new Web Server instance for this exercise, delete it:

    1. Log on to the Web Server’s Administration Console.

    2. Stop the instance.

    3. Delete the instance.

  5. To uninstall the Web Server product, run the uninstall program from the web-server-install-dir.

ProcedureTo Remove the Sample Cluster

Use this procedure to remove only the FirstCluster (the sample highly-available cluster) and the sample application used during this exercise.

  1. Stop the Application Server processes and clean up configuration:

    asadmin stop-cluster FirstCluster

    asadmin remove-ha-cluster --hosts hadb-hostname,hadb-hostname FirstCluster

    Replace the hadb-hostname variable with the host name of the machine where HADB is to run. If you are using just one machine, you must name it twice.

    asadmin disable-http-lb-server FirstCluster

    asadmin delete-http-lb-ref --config MyLbConfig FirstCluster

    asadmin delete-http-lb-config MyLbConfig

    asadmin delete-instance i1

    asadmin delete-instance i2

    asadmin delete-cluster FirstCluster

    asadmin undeploy clusterjsp

  2. Stop the web server instance acting as load balancer by running the stop program in one of the following directories (depending upon the Web Server version):

    • web-server-install-dir/https-hostname

    • web-server-install-dir/https-hostname/bin

  3. Rename the loadbalancer.xml file in web-server-install-dir/https-hostname/config to loadbalancer.xml.sav in the same directory.

  4. Stop the HADB Management Agent by one of the following methods:

    • In a Solaris or Linux Java Enterprise System installation:

      1. Change to the /etc/init.d directory:

        cd /etc/init.d

      2. Run the command to stop the agent:

        ./ma-initd stop

    • In a Windows Java Enterprise System installation:

      1. Go to Start⇒Settings⇒Control Panel, and double-click Administrative Tools.

      2. Double-click the Services shortcut.

      3. Select HADBMgmtAgent Service from the Services list.

      4. From the Action menu, select Stop.

    • In a stand-alone Solaris or Linux Application Server installation:

      1. Change to install-dir/hadb/4/bin.

      2. Run the command to stop the agent:

        ./ma-initd stop

    • In a stand-alone Windows Application Server Installation:

      1. Change to install-dir\hadb\4.x\bin.

        The x represents the release number of HADB.

      2. Run the command to stop the agent:

        ma.exe -r

Next Steps

Congratulations! You have now completed the Quick Start for Application Server.

In this section, you have installed, configured, and started HADB, and configured a cluster and an application to use high availability. You have also cleaned up so that your system is ready for other work. See Where to Go Next for additional information on Application Server.

Where to Go Next

Other resources for learning about and using Application Server are available. They include the following: