Though I understand the reasoning behind using Collections.unmodifiableSet() for the deployments returned from Host.getDeployments(), as its backed by the underlying Set this can still be a problem.

In making GateIn work on Wildfly, I found that on occasion when iterating over Host.getDeployments() during container startup, I would encounter a ConcurrentModificationException if a new Deployment was added at the same point I was looping through the existing deployments by calling Iterator.next()

It would be great if the Collection returned from Host.getDeployments() could be a copy of the underlying collection to prevent possible ConcurrentModificationExceptions.