The Troubleshooting Oracle WebCenter Portlets documentation lists two problems under the Portlet Displays a Remote Portlet Communication Error section. Both seem legitimate causes and solutions, and I have run across both of them in the past. I hit a new one this week. Number three is running out of available threads in the Managed Server that is handling the request. This one was fun to find, because OOM errors that do not cause the server to fall over eventually clear up, and with an adequately sized cluster (the memory errors were caused by a dependent service failing) the issue is very random.
The symptom to look for is the OOM error in the log, which looks like this:
oracle.portlet.client.container.PortletException: java.lang.OutOfMemoryError: unable to create new native thread at oracle.portlet.client.tech.common.PortletFutureUtils.get(Portlet FutureUtils.java:72) at oracle.portlet.client.tech.common.PortletSessionManager$InitSession CompletionListener.conditionChange(PortletSessionManager.java:340) at oracle.portlet.client.service.pipeline.FutureConditionTask.done (FutureConditionTask.java:168) at java.util.concurrent.FutureTask$Sync.innerSetException(Future Task.java:273) at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
Restarting the servers will give you temporary relief, though for the long-run you need to find the root cause. In this case, it was an undersized WebCenter Content cluster running on the same physical box sucking all the resources down. A larger cluster and load balancing corrected the issue for good (knock wood).
© Scott S. Nelson