Hi Sanne,
thx for your reply.
When you say "enable master indexer" you are talking about hibernate.worker.backend=jgroupsMaster and jgroupsSlave. Right?
I did that. I also tried exclusive use only on the master node.

Anyway as I said it has nothing to do with clustering.
Using infinispan as directory provider and async workers with exclusive index use just doesn't work. No matter if there is a slave node or not.