Question

我尝试使用Akka 2.4.3将TCP流重定向/转发到另一个Sink。该程序应该打开服务器套接字，侦听传入的连接，然后使用tcp流。我们的发件人不希望/接受我们的回复，所以我们永远不会发回任何东西 - 我们只是消费流。在构建tcp流之后，我们需要将字节转换为更有用的字节并将其发送到接收器。

到目前为止，我尝试了以下内容，但我特别努力解决如何不将tcp数据包发送回发送方以及正确连接接收器的问题。

import scala.util.Failure
import scala.util.Success

import akka.actor.ActorSystem
import akka.event.Logging
import akka.stream.ActorMaterializer
import akka.stream.scaladsl.Sink
import akka.stream.scaladsl.Tcp
import akka.stream.scaladsl.Framing
import akka.util.ByteString
import java.nio.ByteOrder
import akka.stream.scaladsl.Flow

object TcpConsumeOnlyStreamToSink {
  implicit val system = ActorSystem("stream-system")
  private val log = Logging(system, getClass.getName)    

  //The Sink
  //In reality this is of course a real Sink doing some useful things :-)
  //The Sink accept types of "SomethingMySinkUnderstand"
  val mySink = Sink.ignore;

  def main(args: Array[String]): Unit = {
    //our sender is not interested in getting replies from us
    //so we just want to consume the tcp stream and never send back anything to the sender
    val (address, port) = ("127.0.0.1", 6000)
    server(system, address, port)
  }

  def server(system: ActorSystem, address: String, port: Int): Unit = {
    implicit val sys = system
    import system.dispatcher
    implicit val materializer = ActorMaterializer()
    val handler = Sink.foreach[Tcp.IncomingConnection] { conn =>
      println("Client connected from: " + conn.remoteAddress)

      conn handleWith Flow[ByteString]
      //this is neccessary since we use a self developed tcp wire protocol
      .via(Framing.lengthField(4, 0, 65532, ByteOrder.BIG_ENDIAN)) 
      //here we want to map the raw bytes into something our Sink understands
      .map(msg => new SomethingMySinkUnderstand(msg.utf8String))
      //here we like to connect our Sink to the Tcp Source
      .to(mySink) //<------ NOT COMPILING
    }


    val tcpSource = Tcp().bind(address, port)
    val binding = tcpSource.to(handler).run()

    binding.onComplete {
      case Success(b) =>
        println("Server started, listening on: " + b.localAddress)
      case Failure(e) =>
        println(s"Server could not bind to $address:$port: ${e.getMessage}")
        system.terminate()
    }

  }

  class SomethingMySinkUnderstand(x:String) {

  }
}

更新：将其添加到build.sbt文件以获取必要的代码

libraryDependencies += "com.typesafe.akka" % "akka-stream_2.11" % "2.4.3"

Answer 1

handleWith需要一个Flow，即一个包含未连接入口和未连接插座的盒子。您有效地提供了Source，因为您使用Flow操作将Sink与to相关联。

我认为你可以做到以下几点：

conn.handleWith(
  Flow[ByteString]
    .via(Framing.lengthField(4, 0, 65532, ByteOrder.BIG_ENDIAN)) 
    .map(msg => new SomethingMySinkUnderstand(msg.utf8String))
    .alsoTo(mySink)
    .map(_ => ByteString.empty)
    .filter(_ => false) // Prevents sending anything back
)

使用TCP流并将其重定向到另一个接收器（使用Akka Streams）

1 个答案: