Agreed that you shouldn't mix concurrency models excessively, but many problems do call for a mix. I don't think Rich was referring to what I am. He was talking about the trouble composing Java concurrency using locks and such, which is just hard.
On the other hand with clojure, a standard mix is to use non blocking IO to multiplex a large number of connections, then delegate work to a threadpool (using clojure refs/atoms etc.). Such a system has a much smaller chance of deadlocks and other issues.
A great example of polyglot concurrency is the clojure reducers framework that lets you delegate work to a fork/join pool. Most people don't need it, but it's nice to have a safe, seamless interface to such an advanced concurrency tool.
On the other hand with clojure, a standard mix is to use non blocking IO to multiplex a large number of connections, then delegate work to a threadpool (using clojure refs/atoms etc.). Such a system has a much smaller chance of deadlocks and other issues.
A great example of polyglot concurrency is the clojure reducers framework that lets you delegate work to a fork/join pool. Most people don't need it, but it's nice to have a safe, seamless interface to such an advanced concurrency tool.