Save an old version of the application or back up the domain.
To back up the domain, use the asadmin backup-domain command.
Turn off dynamic reconfiguration (if enabled) for all clusters.
To do this with Admin Console:
Expand the Configurations node.
Click the name of one cluster’s configuration.
On the Configuration System Properties page, uncheck the Dynamic Reconfiguration Enabled box.
Repeat for the other clusters
Alternatively, use this command:
asadmin set --user user --passwordfile password-file cluster-name-config.dynamic-reconfiguration-enabled=false
Redeploy the upgraded application to the target domain.
If you redeploy using the Admin Console, the domain is automatically the target. If you use asadmin, specify the target domain. Because dynamic reconfiguration is disabled, the old application continues to run on the clusters.
Enable the redeployed application for the clusters using asadmin enable-http-lb-application.
Quiesce one cluster from the load balancer
Disable the cluster using asadmin disable-http-lb-server.
Export the load balancer configuration file using asadmin export-http-lb-config.
Copy the exported configuration file to the web server instance’s configuration directory.
For example, for Sun Java System Web Server, the location is web-server-install-dir/https-host-name/config/loadbalancer.xml. Dynamic reconfiguration must be enabled for the load balancer (by setting the reloadinterval in the load balancer configuration), so that the new load balancer configuration file is loaded automatically.
Wait until the timeout has expired.
Monitor the load balancer’s log file to make sure the instance is offline. If users see a retry URL, skip the quiescing period and restart the server immediately.
Restart the disabled cluster while the other clusters are still running.
Restarting causes the cluster to synchronize with the domain and update the application.
Test the application on the restarted cluster to make sure it runs correctly.
Enable the cluster in the load balancer:
Repeat steps 5 through 8 for the other clusters.
When all server instances have the new application and are running, you can enable dynamic reconfiguration for all clusters again.