Just to let you know that Kenton Varda an ex-Googler working on
Protocol buffer released CapNProto.

http://kentonv.github.io/capnproto

There are some really nice features like 'Time-traveling RPC'
(aka RPC with continuations) that allows several calls server
side without paying for the round trip.

Some ports are underway (C, Erlang, Go, Ruby, Rust) but no D for
now (just saying :) ).

Guillaume