WebSocket over HTTP2

[rahbari]

Now that node core has added websocket support over http2 nodejs/node#23284, It's nice to know when it will be added to WS?

[lpinca]

See nodejs/node#23284 (comment). To answer your question, when someone interested in having the feature, will implement it and open a PR.

[ayZagen]

@lpinca We rely on ws and want to upgrade our servers to http2. It would be great to have http2 support on ws.
Thanks

[lpinca]

@ayZagen you are welcome to experiment with it. ws is built on top of the upgrade mechanism for HTTP/1.1 and works with a raw (net.Socket) TCP socket.

The way WebSocket works over HTTP/2 is different, the HTTP/2 API is different so it's not trivial to add support for it. Here is a proof of concept: https://github.com/jasnell/http2ws/blob/master/http2ws.js. It might be easier to write a wrapper module with the eventual required additions in ws instead of adding support directly in ws.

I am personally not interested in having HTTP/2 support because I think there is no real benefit in using an HTTP/2 stream instead of a raw TCP socket as the transport layer. I understand that in some cases it might be desirable to support HTTP/2 and WebSocket on the same server but I think that in many cases having a separate HTTP/1.1 server only for WebSocket is a good and viable option.

[FallingSnow]

I'm using node's http2 framework with the allowHTTP1: true option. Then setting a ws server to listen on the http2 server just works.

Although I would like to see ws support for HTTP2 so it feels less hacky.

[josephg]

@FallingSnow does that do websockets over http2 or is that just falling back to websockets over http1.1?

[josephg]

@lpinca the big advantage (architecturally) is taking advantage of multiplexing. Right now using websockets sort of requires you to throw away any http-like abstractions (and indeed we often just open a single ws connection to ws://example.com/ws or something) and do our own multiplexing.

With ws over h2 it can start making sense again for applications / APIs to add per-URL websocket connections for specific change feeds / use cases. (Since all connections are multiplexed through the single h2 tcp socket anyway).

The other advantage is faster connection times, since if the page is loaded over h2 then we don't need to do another tcp/TLS handshake to open a websocket.

[lpinca]

WebSocket over HTTP2 has only one advantage that is as you said the use of a single TCP connection when the origin is the same. In all other cases there are only disadvantages especially on the server and with the Node.js HTTP2 implementation.

Node.js HTTP2 adds a lot of overhead over a plain {net,tls}.Socket. There are streams wrapping other streams and the whole HTTP2 machinery. I did not run any benchmark but I'm pretty sure it would perform way worse in terms of both speed and especially memory usage.

See also this discussion dotnet/aspnetcore#7801 and in particular this comment dotnet/aspnetcore#7801 (comment).

[FallingSnow]

@josephg I believe the connection comes in as an HTTP1.1 request. There is no actual HTTP2 as far as I'm aware.

[damianobarbati]

Check this out guys: https://nodejs.org/api/http2.html section "The Extended CONNECT Protocol"

[LongTengDao]

By read all source code of ws (as server side), and find each place using socket, it seems that we only need do small change to support HTTP2:

1. socket.write('HTTP/1.1 101 Switching Protocols\r\n...') change to socketOrStream.additionalHeaders ? socketOrStream.additionalHeaders({ ':status': 101, ... }) : socketOrStream.write('...');
2. socket.setNoDelay(); change to socketOrStream.setNoDelay && socketOrStream.setNoDelay();;
3. socket.on data end error close change to socketOrStream.on data end error close frameError aborted, and remember remove them at right time.

Because net.Socket and (Server)Http2Stream are both stream.Duplex.

[masx200]

Do any browsers support "websocket over http2" now?

[adelyte-chris]

HTTP/2 explicitly disallows WebSocket upgrades. See HTTP/2 Issue #386 for the current status of adding WebSockets semantics to HTTP/2.

[lpinca]

@adelyte-chris RFC 8441 describes how to run the WebSocket protocol over a single stream of an HTTP/2 connection and this is already supported by Node.js.

That said, I did not change my mind on this topic.