使用TCP流并将其重定向到另一个接收器(使用Akka流)

krcsximq  于 2022-11-05  发布在  其他
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我尝试用Akka 2.4.3将TCP流重定向/转发到另一个Sink。程序应该打开一个服务器套接字,监听传入的连接,然后使用TCP流。我们的发送方不期望/接受来自我们的回复,所以我们从不发回任何东西-我们只是使用流。在构造TCP流后,我们需要将字节转换为更有用的东西,并将其发送到Sink。
到目前为止,我尝试了以下方法,但我特别纠结于如何不将TCP包发送回发送方并正确连接接收器。

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:将其添加到您的build.sbt文件中,以获得必要的deps

libraryDependencies += "com.typesafe.akka" % "akka-stream_2.11" % "2.4.3"
zyfwsgd6

zyfwsgd61#

handleWith需要一个Flow,即一个盒子有一个未连接的入口和一个未连接的出口。您实际上提供了一个Source,因为您通过使用to操作将FlowSink连接起来。
我认为您可以执行以下操作:

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
)
kxe2p93d

kxe2p93d2#

另一种(在我看来更干净)的编码方式(AKKA 2.6.x),这也将强调一个事实,即你不做任何出站流,将:

val receivingPipeline = Flow
  .via(framing)
  .via(decoder)
  .to(mySink)

val sendingNothing = Source.never[ByteString]()

conn.handleWith(Flow.fromSinkAndSourceCoupled(receivingPiline, sendingNothing))

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