为什么Akka TCP流服务器在connection.handlewith没有流时断开客户端？

Question

我正在寻找对我在以下代码中看到的行为的解释。当
conn.handleWith 被注释掉，我用 netcat 建立的 TCP 客户端连接，连接，并在几秒钟内显示被对等方断开连接（即服务器断开连接）。当 conn.handleWith 出现在代码中时，我看不到断开连接。我最初虽然它与为服务器设置的空闲超时有关，但事实并非如此。

那么为什么服务器在没有流量处理连接的情况下断开客户端呢？

  
    package com.example;
    
    import java.util.concurrent.CompletionStage;
    
    import akka.Done;
    import akka.NotUsed;
    import akka.actor.typed.ActorSystem;
    import akka.actor.typed.javadsl.Behaviors;
    import akka.stream.javadsl.Sink;
    import akka.stream.javadsl.Source;
    import akka.stream.javadsl.Tcp;
    import akka.stream.javadsl.Tcp.IncomingConnection;
    import akka.stream.javadsl.Tcp.ServerBinding;
    
    
    public class SimpleStream00 {
    
        public static void main(String[] args) throws InterruptedException {
    
            ActorSystem actorSystem = ActorSystem.create(Behaviors.empty(), "actorSystem");
    
            final Sink<IncomingConnection, CompletionStage<Done>> handler = Sink.foreach(conn -> {
                System.out.println("Client connected from: " + conn.remoteAddress());
                // conn.handleWith(Flow.of(ByteString.class), actorSystem); 
                // Server does not drop the connection when previous line is uncommented
            });
    
            Source<IncomingConnection, CompletionStage<ServerBinding>> source = Tcp.get(actorSystem).bind("127.0.0.1",
                    8888); // .idleTimeout(Duration.ofSeconds(60));
    
            CompletionStage<ServerBinding> bindingFuture = source.to(handler).run(actorSystem);
    
            bindingFuture.handle((binding, throwable) -> {
                if (binding != null) {
                    System.out.println("Server started, listening on: " + binding.localAddress());
    
                } else {
                    System.err.println("Server could not bind to  : " + throwable.getMessage());
                    actorSystem.terminate();
                }
                return NotUsed.getInstance();
            });
        }
    
    }

Answer 1

Akka Streams 的一般原则是，如果没有需求，流应该消耗尽可能少的资源。由于没有 handleWith，您的流永远不会从连接发出对 ByteString 的需求信号，Akka 的 TCP 层断开连接以节省资源。

为什么Akka TCP流服务器在connection.handlewith没有流时断开客户端？

Why does Akka TCP stream server disconnect client when there is no flow for the connection.handlewith?

akka-stream