Basically all one needs is
- a persistence service I called ClientStateStorage, which can be provided with an http session for production. Otherwise it uses a simple Map for testing.
- a service-model extending AbstractServiceModelImpl which works much like the PooledServiceModel
- six (!) lines of xml to configure the stuff
Cluster-Failover-Safety is of course an issue because, as I understood it, HiveMind serialises services in a stateless manner (just writing its Id and, upon reading, creating a fresh instance with that id). For my Apps, however, that's not a big enough problem to trouble me much. Server-crashes happen so seldomly ...