I've created a small project that shows how to use JBoss Infinispan with Apache Camel and the Idempotent Consumer Pattern to guarantee a message will not be processed twice in a clustered environment.
Imagine you have an application that has to scale out easily by deploying it on multiple containers. But the application has to process each unique request only once across the cluster.
The solution is simple: use Idempotent Consumer Pattern in Camel with a repository that can scale out easily. This is where Infinispan comes into play. Infinispan is extremely scalable, highly available key/value store and data grid. If you use InfinispanIdempotentRepository with an idempotent consumer, it will create an in-memory cache to store the requests, and the moment you start another instance of the application, the cache instances will sync and the idempotent consumers in all applications will not process existing requests any longer.
The core of the application is the following route definition that finds a new free port number for each instance of the application:
Simple, isn't it.