Finagle: Protocol agnostic extensible RPC system for the JVM with Java & Scala APIs (via)

Finagle is an extensible RPC system for the JVM, used to construct high-concurrency servers. Finagle implements uniform client and server APIs for several protocols, and is designed for high performance and concurrency. Most of Finagle’s code is protocol agnostic, simplifying the implementation of new protocols.

Finagle is written in Scala, but provides both Scala and Java idiomatic APIs.