I’ve had on my to-do list for awhile now to post about a recent investigation into a WLS  stuck thread issue I fixed. And I still will, as the way I got there is probably more useful to some than the end result. But, someone sent me a question that led straight to the solution today, so I thought I would post the email thread here to benefit my reader:

Q: Can we configure a cluster of WLS that is behind a F5 to use jdbc based persistence without the server affinity defined by load balancer?

A: By persistence, I would assume you mean user session. The limitation is on the applications deployed rather than WLS itself. All objects in session must be serializeable in order for WLS to properly manage persistence, regardless of whether it is database or file or in-memory persistence.

If your client has an issue where session data is lost unless server affinity is maintained it is because persistence has been manually turned off for the application. This is almost always done be developers or vendors when their application does not support serialization.

I’ve run across this situation twice this year. The first time was a sloppy, dishonest vendor (they clearly stated both that their product supported serialization and that they had never tested it…so I did, and it did not) that did not make their session objects serializable. The second time they had issues with a third party application that serialized PDF reports that were generated for a request and they had to turn off persistence to keep the disks from filling up every quarter.