Get response status from ChannelFuture

[smiera]

Here is a example server

package org.test;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.*;

public class ListenerExample {
    public static void main(String[] args) throws Exception {
        // Configure the server.
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.option(ChannelOption.SO_BACKLOG, 1024);
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            final ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new HttpServerCodec());
                            pipeline.addLast(new HttpObjectAggregator(Integer.MAX_VALUE));
                            pipeline.addLast(new HttpContentDecompressor(true));
                            pipeline.addLast(new ListenerExampleHandler());
                        }
                    });

            Channel ch = b.bind(8081).sync().channel();

            ch.closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    private static class ListenerExampleHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest msg) throws Exception {
            System.out.println("New HTTP message: " + msg.uri());
            // Emulate long request handler
            Thread.sleep(2000);
            //
            final var isKeepAlive = HttpUtil.isKeepAlive(msg);
            // Response
            final var content = "PONG".getBytes();
            final var response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, Unpooled.wrappedBuffer(content));
            response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
            response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.length);
            response.headers().set(HttpHeaderNames.CONNECTION, isKeepAlive ? HttpHeaderValues.KEEP_ALIVE : HttpHeaderValues.CLOSE);
            //
            ctx.writeAndFlush(response).addListener((ChannelFuture future) -> {
                if (!isKeepAlive || !future.isSuccess()) {
                    future.channel().close();
                }

                System.out.println("SUCCESS: " + (future.isDone() && future.isSuccess()));
                System.out.println("ERROR: " + (future.isDone() && future.cause() != null) + ". " + future.cause());
                System.out.println("CANCELED: " + (future.isDone() && future.isCancelled()));
            });
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            cause.printStackTrace();
            ctx.close();
        }
    }
}

I need to get message status after writeAndFlush.

I try to add listener, but it does't work when client reset connection.

For example: using curl I send get request to server. When in server console log I see message about new request(New HTTP message: /), then I terminate curl(Control+C).
As result server return:

SUCCESS: true
ERROR: false. null
CANCELED: false
java.net.SocketException: Connection reset
	at java.base/sun.nio.ch.SocketChannelImpl.throwConnectionReset(SocketChannelImpl.java:401)
	at java.base/sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:434)
	at io.netty.buffer.PooledByteBuf.setBytes(PooledByteBuf.java:258)
	at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1132)

Why I get SUCCESS: true and how I can get error inside listener?

same question here

[smiera]

Someone? :)

[chrisvest]

When you terminate curl like that, the client does not do a TCP termination handshake, so the server does not know that the peer has closed its connection. Thus, the connection state on the server is open and we successfully deliver our data to the kernel to be sent. A little while later, the data packets starts arriving at the client, but the client-side kernel has no open connection by that port number, so it responds with a TCP RST packet. When that packet is delivered on the server, it gets turned into a SocketException: Connection reset. Since we 1) have already completed our writes, and 2) have no idea which specific packet caused the TCP RST, we cannot possibly pick a future to fail.
This is why the futures succeed, and you get an exceptionCaught.