Scala和Akka HTTP：请求内的请求和线程问题

Question

我对学习Scala，Akka Streams和Akka HTTP并不陌生，因此如果问题太简单，请事先道歉。

我想在HTTP请求中执行一个HTTP请求，就像下面的代码一样：

  implicit val system = ActorSystem("ActorSystem")
  implicit val materializer = ActorMaterializer
  import system.dispatcher

  val requestHandler: Flow[HttpRequest, HttpResponse, _] = Flow[HttpRequest].map {
    case HttpRequest(HttpMethods.GET, Uri.Path("/api"), _, _, _) =>
      val responseFuture = Http().singleRequest(HttpRequest(uri = "http://www.google.com"))
      responseFuture.onComplete {
        case Success(response) =>
          response.discardEntityBytes()
          println(s"The request was successful")
        case Failure(ex) =>
          println(s"The request failed with: $ex")
      }
      //Await.result(responseFuture, 10 seconds)
      println("Reached HttpResponse")
      HttpResponse(
        StatusCodes.OK, // HTTP 200
      )
  }

  Http().bindAndHandle(requestHandler, "localhost", 8080)  

但是在上述情况下，结果看起来像这样，这意味着在完成请求之前首先到达Reached HttpResponse：

Reached HttpResponse
The request was successful

我尝试使用Await.result(responseFuture, 10 seconds)（当前已注释掉），但没有区别。

我在这里想念什么？任何帮助将不胜感激！

非常感谢！

Answer 1

挑战是responseFuture是Future的一种。因此，您需要一个处理它的函数。该函数接受HttpRequest并返回Future of something。

HttpRequest => Future[T]

瞧，mapAsync正是您所需要的：

val requestHandler: Flow[HttpRequest, HttpResponse, _] = Flow[HttpRequest].mapAsync(2) {
  case HttpRequest(HttpMethods.GET, Uri.Path("/api"), _, _, _) =>
    Http().singleRequest(HttpRequest(uri = "http://www.google.com")).map (resp => {
      resp.discardEntityBytes()
      println(s"The request was successful")
      resp
    })
}