GRPC. It's really the only practical choice if you have Go, Node.js, and PHP apps that need to consume one central service. It also has a lot of the benefits that Mux brings.

Luckily GRPC can downgrade to HTTP/1.1, so if you want some of linkerd's features it isn't a total non-starter; but this is obviously less-than-desirable. We're working with the finagle team to complete finagle's netty4 integration, which will enable us to transparently introduce netty's http/2 codec into linkerd. This is a high-priority feature.

that's a fair answer.

It seems like there's overlap beyond lack of HTTP/2 support, where some of Finagle's features are handled by GRPC in different ways. I'd quite like to use the GRPC way, since Google is maintaining the bindings to many languages, and doing a decent job.

Cool! Is HTTP/2.0 already there, or planned? I think HTTP/2.0 is important to get proper pipelining of asynchronous calls.

We agree 100% that multiplexing is vital.

HTTP/2 is absolutely on the roadmap. We're actively working with some of the folks at Twitter to get it integrated and tested before introducing it into linkerd.

That said, linkerd is able to provision multiple downstream connections to multiplex requests to other services; but we need to extend this to the serverside to get the best application integration.

You may also be interested in Twitter's mux protocol (https://twitter.github.io/finagle/guide/Protocols.html#mux), which provides this featureset internally at Twitter, primarily for Thrift.