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John A. Lewis
Unicon, Inc.
Introduction
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JSR-168 Portlet applications represent a special challenge when it comes to clustering within Tomcat (or any other servlet container, for that matter). In order to effectively cluster web applications, session data must be replicated or shared between the nodes in the cluster. Otherwise, the user experiences a complete loss of context during a node failover. While Tomcat has provided session replication for quite some time, it has not supported replication of session changes resulting from a cross-context call from one webapp to another. |
Portlets that are deployed as separate webapps from the portal webapp must be accessed by cross-context calls from the portal. This cross-context access creates a number of issues: servlet filters are not applied, session sharing between servlets and portlets is difficult, and session replication in Tomcat did not work.
At The University of Wisconsin-Madison (www.wisc.edu) and Pearson Education (www.pearsoned.com) both recently identified a need for full support of portlet session replication within Tomcat. They engaged with Unicon (www.unicon.net) , weto work with the Tomcat community to provide this capability. We've recently worked directly with the Tomcat developers to get Cross-Context Session Replication built into Tomcat 5.5 and we've demonstrated that portlet session data can now be properly replicated. I'd like to give a special thanks to Peter Rossbach from the Tomcat team for working on this with us and for getting this done so quickly. The changes for Tomcat are currently in the latest development codebase and will be included in version 5.5.16 and later.
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