Scala 和 Akka HTTP：请求内部请求和线程问题

Question

我刚开始学习 Scala、Akka Streams 和 Akka HTTP，如果问题太基础，请先道歉。

我想在 HTTP 请求中做一个 HTTP 请求，就像下面这段代码：

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

但在上面的例子中，结果看起来是这样的，这意味着在完成请求之前先达到 Reached HttpResponse：

Reached HttpResponse
The request was successful

我尝试使用 Await.result(responseFuture, 10 seconds)（目前已被注释掉），但没有任何区别。

我在这里错过了什么？任何帮助将不胜感激！

非常感谢！

Answer 1

map 是一个接受请求并产生响应的函数：

HttpRequest => HttpResponse

挑战在于响应是 Future 的一种类型。因此，您需要一个处理它的函数。采用 HttpRequest 和 returns HttpResponse 的未来的函数。

HttpRequest => Future[HttpResponse]

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")
      HttpResponse(StatusCodes.OK)
    })
}

Scala 和 Akka HTTP：请求内部请求和线程问题

Scala and Akka HTTP: Request inside a request & issue with threads

scala

httpresponse

httprequest

akka-stream

akka-http