# netty-websocket-http2 Netty based implementation of [rfc8441](https://tools.ietf.org/html/rfc8441) - bootstrapping websockets with http/2 Library addresses two use cases: for application servers and clients, It is transparent use of existing http1 websocket handlers on top of http2 streams; for gateways/proxies, It is websockets-over-http2 support with no http1 dependencies and minimal overhead. [https://jauntsdn.com/post/netty-websocket-http2/](https://jauntsdn.com/post/netty-websocket-http2/) ### websocket channel API Intended for application servers and clients. Allows transparent application of existing http1 websocket handlers on top of http2 stream. * Server ```groovy EchoWebSocketHandler http1WebSocketHandler = new EchoWebSocketHandler(); Http2WebSocketServerHandler http2webSocketHandler = Http2WebSocketServerBuilder.create() .acceptor( (ctx, path, subprotocols, request, response) -> { switch (path) { case "/echo": if (subprotocols.contains("echo.jauntsdn.com") && acceptUserAgent(request, response)) { /*selecting subprotocol for accepted requests is mandatory*/ Http2WebSocketAcceptor.Subprotocol .accept("echo.jauntsdn.com", response); return ctx.executor() .newSucceededFuture(http1WebSocketHandler); } break; case "/echo_all": if (subprotocols.isEmpty() && acceptUserAgent(request, response)) { return ctx.executor() .newSucceededFuture(http1WebSocketHandler); } break; } return ctx.executor() .newFailedFuture( new WebSocketHandshakeException( "websocket rejected, path: " + path)); }) .build(); ch.pipeline() .addLast(sslHandler, http2frameCodec, http2webSocketHandler); ``` * Client ```groovy Channel channel = new Bootstrap() .handler( new ChannelInitializer() { @Override protected void initChannel(SocketChannel ch) { Http2WebSocketClientHandler http2WebSocketClientHandler = Http2WebSocketClientBuilder.create() .handshakeTimeoutMillis(15_000) .build(); ch.pipeline() .addLast( sslHandler, http2FrameCodec, http2WebSocketClientHandler); } }) .connect(address) .sync() .channel(); Http2WebSocketClientHandshaker handShaker = Http2WebSocketClientHandshaker.create(channel); Http2Headers headers = new DefaultHttp2Headers().set("user-agent", "jauntsdn-websocket-http2-client/1.1.2"); ChannelFuture handshakeFuture = /*http1 websocket handler*/ handShaker.handshake("/echo", headers, new EchoWebSocketHandler()); handshakeFuture.channel().writeAndFlush(new TextWebSocketFrame("hello http2 websocket")); ``` Successfully handshaked http2 stream spawns websocket subchannel, with provided http1 websocket handlers on its pipeline. Runnable demo is available in `netty-websocket-http2-example` module - [channelserver](https://github.com/jauntsdn/netty-websocket-http2/blob/develop/netty-websocket-http2-example/src/main/java/com/jauntsdn/netty/handler/codec/http2/websocketx/example/channelserver/Main.java), [channelclient](https://github.com/jauntsdn/netty-websocket-http2/blob/develop/netty-websocket-http2-example/src/main/java/com/jauntsdn/netty/handler/codec/http2/websocketx/example/channelclient/Main.java). ### websocket handshake only API Intended for intermediaries/proxies. Only verifies whether http2 stream is valid websocket, then passes it down the pipeline as `POST` request with `x-protocol=websocket` header. ```groovy Http2WebSocketServerHandler http2webSocketHandler = Http2WebSocketServerBuilder.buildHandshakeOnly(); Http2StreamsHandler http2StreamsHandler = new Http2StreamsHandler(); ch.pipeline() .addLast(sslHandler, frameCodec, http2webSocketHandler, http2StreamsHandler); ``` Works with both callbacks-style `Http2ConnectionHandler` and frames based `Http2FrameCodec`. ``` Http2WebSocketServerBuilder.buildHandshakeOnly(); ``` Runnable demo is available in `netty-websocket-http2-example` module - [handshakeserver](https://github.com/jauntsdn/netty-websocket-http2/blob/develop/netty-websocket-http2-example/src/main/java/com/jauntsdn/netty/handler/codec/http2/websocketx/example/handshakeserver/Main.java), [channelclient](https://github.com/jauntsdn/netty-websocket-http2/blob/develop/netty-websocket-http2-example/src/main/java/com/jauntsdn/netty/handler/codec/http2/websocketx/example/channelclient/Main.java). ### configuration Initial settings of server http2 codecs (`Http2ConnectionHandler` or `Http2FrameCodec`) should contain [SETTINGS_ENABLE_CONNECT_PROTOCOL=1](https://tools.ietf.org/html/rfc8441#section-9.1) parameter to advertise websocket-over-http2 support. Also server http2 codecs must disable built-in headers validation because It is not compatible with rfc8441 due to newly introduced `:protocol` pseudo-header. All websocket handlers provided by this library do headers validation on their own - both for websocket and non-websocket requests. Above configuration may be done with utility methods of `Http2WebSocketServerBuilder` ``` public static Http2FrameCodecBuilder configureHttp2Server( Http2FrameCodecBuilder http2Builder); public static Http2ConnectionHandlerBuilder configureHttp2Server( Http2ConnectionHandlerBuilder http2Builder) ``` ### compression & subprotocols Client and server `permessage-deflate` compression configuration is shared by all streams ```groovy Http2WebSocketServerBuilder.compression(enabled); ``` or ```groovy Http2WebSocketServerBuilder.compression( compressionLevel, allowServerWindowSize, preferredClientWindowSize, allowServerNoContext, preferredClientNoContext); ``` Client subprotocols are configured on per-path basis ```groovy EchoWebSocketHandler http1WebsocketHandler = new EchoWebSocketHandler(); ChannelFuture handshake = handShaker.handshake("/echo", "subprotocol", headers, http1WebsocketHandler); ``` On a server It is responsibility of `Http2WebSocketAcceptor` to select supported subprotocol with ```groovy Http2WebSocketAcceptor.Subprotocol.accept(subprotocol, response); ``` ### lifecycle Handshake events and several shutdown options are available when using `Websocket channel` style APIs. #### handshake events Events are fired on parent channel, also on websocket channel if one gets created * `Http2WebSocketHandshakeStartEvent(websocketId, path, subprotocols, timestampNanos, requestHeaders)` * `Http2WebSocketHandshakeErrorEvent(webSocketId, path, subprotocols, timestampNanos, responseHeaders, error)` * `Http2WebSocketHandshakeSuccessEvent(webSocketId, path, subprotocols, timestampNanos, responseHeaders)` #### close events Outbound `Http2WebSocketLocalCloseEvent` on websocket channel pipeline closes http2 stream by sending empty `DATA` frame with `END_STREAM` flag set. Graceful and `RST` stream shutdown by remote endpoint is represented with inbound `Http2WebSocketRemoteCloseEvent` (with type `CLOSE_REMOTE_ENDSTREAM` and `CLOSE_REMOTE_RESET` respectively) on websocket channel pipeline. Graceful connection shutdown by remote with `GO_AWAY` frame is represented by inbound `Http2WebSocketRemoteGoAwayEvent` on websocket channel pipeline. #### shutdown Closing websocket channel terminates its http2 stream by sending `RST` frame. #### validation & write error events Both API style handlers send `Http2WebSocketHandshakeErrorEvent` for invalid websocket-over-http2 and http requests. For http2 frame write errors `Http2WebSocketWriteErrorEvent` is sent on parent channel if auto-close is not enabled; otherwise exception is delivered with `ChannelPipeline.fireExceptionCaught` followed by immediate close. ### flow control Inbound flow control is done automatically as soon as `DATA` frames are received. Library relies on netty's `DefaultHttp2LocalFlowController` for refilling receive window. Outbound flow control is expressed as websocket channels writability change on send window exhaust/refill, provided by `DefaultHttp2RemoteFlowController`. ### websocket stream weight Initial stream weight is configured with ```groovy Http2WebSocketClientBuilder.streamWeight(weight); ``` it can be updated by firing `Http2WebSocketStreamWeightUpdateEvent` on websocket channel pipeline. ### performance Library relies on capabilities provided by netty's `Http2ConnectionHandler` so performance characteristics should be similar. [netty-websocket-http2-perftest](https://github.com/jauntsdn/netty-websocket-http2/tree/develop/netty-websocket-http2-perftest/src/main/java/com/jauntsdn/netty/handler/codec/http2/websocketx/perftest) module contains application that gives rough throughput/latency estimate. The application is started with `perf_server.sh`, `perf_client.sh`. On modern box one can expect following results for single websocket: To evaluate performance with multiple connections we compose an application comprised with simple echo server, and client sending batches of messages periodically over single websocket per connection (approximately models chat application) With 25k active connections each sending batches of 5-10 messages of 0.2-0.5 KBytes over single websocket every 15-30seconds, the results are as follows (measured over time spans of 5 seconds): ### examples `netty-websocket-http2-example` module contains demos showcasing both API styles, with this library/browser as clients. * `channelserver, channelclient` packages for websocket subchannel API demos. * `handshakeserver, channelclient` packages for handshake only API demo. * `lwsclient` package for client demo that runs against [https://libwebsockets.org/testserver/](https://libwebsockets.org/testserver/) which hosts websocket-over-http2 server implemented with [libwebsockets](https://github.com/warmcat/libwebsockets) - popular C-based networking library. ### browser example `Channelserver` example serves web page at `https://www.localhost:8099` that sends pings to `/echo` endpoint. Currently only `Mozilla Firefox` and latest `Google Chrome` support websockets-over-http2. ### build & binaries ``` ./gradlew ``` Releases are published on MavenCentral ```groovy repositories { mavenCentral() } dependencies { implementation 'com.jauntsdn.netty:netty-websocket-http2:1.1.2' } ```