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Comment by cespare | Hacker News Reader

What HTTP/2 features make it desirable for general RPC (no browser involved)?

In the past I've found HTTP (1.1) to be okay, but not great for server->server RPC. The semantics are fine (but overkill) and the overhead sort of sucks. With HTTP/2 I guess the performance should be a lot better (with a binary protocol); I'm still unsure about the HTTP semantics in a general RPC context. Anyone with deeper knowledge of HTTP/2 care to enlighten me?

(Following up on a twitter conversation I had with @bradfitz: https://twitter.com/calebspare/status/571049339541270529)

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gRPC uses the following features from HTTP/2: Framing (needed to multiplex different RPCs on the same TCP connection), Flow Control (both intra-stream and connection-wide), HPAC (for compressing metadata that tends to be common across requests), and GoAway (to gracefully drain backends).

Thanks! This is a good list.

Streaming RPCs in both directions (client to server, and server to client) is one big feature. It's not really possible to do client-side streaming with HTTP/1.1, especially if you have proxies in the way. Independently framed messages make it a lot more feasible to implement other important RPC features like flow control too.

Yeah, it's certainly more compelling than trying to build on HTTP 1.1. The alternative I had in mind was not using HTTP, though (for instance building some custom framed protocol on TCP, or open-sourcing some version of whatever Google uses internally for protobuf RPC.)

a11r pointed out several interesting features of HTTP/2 that are put to good use in gRPC, though.

gRPC is based on the internal Stubby RPC system, and that works over HTTP/1.1 based on CONNECT and switching to raw TCP. That works well enough, but the HTTP/2 goodies are too good to pass up.

Great context, thanks. I'm excited to start using it :)

And using HTTP/2 directly allows using HTTP/2-based load balancers and reverse proxies, which is a huge bonus.

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