Motivation
It's cleaner to add listeners to returned Futures rather than provided Promises because the latter can have strange side effects in terms of listeners firing and called methods returning. Adding listeners preemtively may yield also to more OPS than necessary when there's an Exception in the to be called method.
Modifications
Add listener to returned ChannelFuture rather than given ChannelPromise
Result
Cleaner completion and exception handling
7460d90a67