Callbacks, synchronous and asynchronous

In the end it works, but imag­ine what hap­pens if callback-based APIs become pop­u­lar and every jar you use with a call­back in its API has to have its own thread pool. Kind of sucks. That’s prob­a­bly why Netty punts on the issue. Too hard to make pol­icy deci­sions about this in a low-level net­work­ing library.

/cc Waffle, who said some of this before.