But FWIW we totally agree with you. Finagle itself is a JVM library, and that worked well enough at Twitter [insert caveats here], but a big part of the reason we built linkerd is extending that model to non-JVM / polyglot services. There's SO much good stuff in Finagle... it would be a pity to confine it just to the JVM.
So far all our work has been JSON-over-HTTP, which is not performant. We've looked at gRPC and Thrift, but we've been dreading the prospect of having to pre-declare IDL, generate language glue and write client/server setup glue for every app.
At the moment, we're closing in on using NATS as a routing proxy, fulfilling a role very similar to Linkerd. Turns out it's fast enough that you can do RPC with it, and it seems very reliable. Language bindings are good to the point where you have to write almost no glue code. You have to pick a serialization format, and I think Msgpack might work well here.
But we're slowly moving towards a setup where we'll likely rely on autoscaling, and where we will likely need a more robust architecture.
I loved the pitch, but then I discovered that this is Scala only, which was disappointing.
Sure, if your entire organization runs on the JVM (like Twitter presumably does), then something like this is going to be fine. But many/most organizations use multiple languages, for various reasons. At my company we are currently looking into replacing our current microservie RPC (JSON over HTTP) with something better, and we do need to support Ruby, Go and Node.js, as well as plain HTTP from browsers.
The only viable cross-platform RPC technologies right now are gRPC and Thrift, both of which are rather heavy-handed (lots of IDL + code generation + client/server setup code), and neither of which solve the really hard problems (discoverability, load balancing, fault tolerance, etc.). It's also doubtful that gRPC is really in a usable state yet. Thrift is by far the most mature solution in this space.
Maybe we'll be able to take some inspiration from this project when building our upcoming solution, whatever it will be.