为什么当客户端被 SIGKILL 杀死时，服务器上的 channelInactive 被调用？

Question

有一个回显服务器和一个回显客户端。当我使用 kill -9 <client_pid> 终止客户端进程时，服务器上的 channelInactive 被调用。

客户端被SIGKILL杀死了，所以应该来不及主动关闭这个socket。因此，不应触发服务器上的 channelInactive，但确实发生了。

为什么当客户端被SIGKILL杀死时调用服务器上的channelInactive？

EchoServer class


public class EchoServer {
  private final int port;

  public EchoServer(int port) {
    this.port = port;
  }

  public static void main(String[] args) throws InterruptedException {
    int port = 9001;
    new EchoServer(port).start();
  }

  public void start() throws InterruptedException {
    EventLoopGroup group = new NioEventLoopGroup();

    try {
      ServerBootstrap bootstrap = new ServerBootstrap();
      bootstrap
          .group(group)
          .channel(NioServerSocketChannel.class)
          .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
              ch.pipeline()
                .addLast(new ChannelInboundHandlerAdapter() {
                  @Override
                  public void channelInactive(ChannelHandlerContext ctx) throws Exception {
                    System.out.println("channelInactive()");
                  }
                });
            }
          });

      ChannelFuture future = bootstrap.bind(new InetSocketAddress(port)).sync();
      future.channel().closeFuture().sync();
    } finally {
      group.shutdownGracefully().sync();
    }
  }
}

EchoClient class


public class EchoClient {
  private final String host;
  private final int port;

  public EchoClient(String host, int port) {
    this.host = host;
    this.port = port;
  }

  public void start() throws InterruptedException {
    EventLoopGroup group = new NioEventLoopGroup();
    try {
      Bootstrap bootstrap = new Bootstrap();
      bootstrap
          .group(group)
          .channel(NioSocketChannel.class)
          .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
            }
          });

      ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port)).sync();
      future.channel().closeFuture().sync();
    } finally {
      group.shutdownGracefully().sync();
    }
  }

  public static void main(String[] args) throws InterruptedException {
    new EchoClient("localhost", 9001).start();
  }
}

Answer 1

The client is killed by SIGKILL, so it should have no time to actively close this socket.

客户端应用程序没有主动关闭套接字。如果没有本地应用程序打开套接字，客户端 OS 内核会隐式关闭套接字。

为什么当客户端被 SIGKILL 杀死时，服务器上的 channelInactive 被调用？

Why channelInactive on server is called when the client is killed by SIGKILL?

java

sockets

tcp

netty