Question

让我们想象一下基于akka-streams和akka-http的代理应用程序，该应用程序以某种本地格式接收（作为TCP服务器）消息，向它们发出http请求，询问其他http服务器，将http响应转换回home-格式增加并回复给客户。下面的简化代码：

// as Client part 
val connPool = Http().cachedHostConnectionPool[CustHttpReq](someHost, somePort)

val asClientFlow = Flow[CustHttpReq]
  .via (connPool)
  .map (procHttpResp)

def procHttpResp (p: (Try[HttpResponse], CustHttpReq)): Future[ByteString] = {
  val (rsp, src) = p
  rsp match {
    case Success(response: HttpResponse) =>
      for (buf <- cvtToHomeGrown (response, src)) 
          yield buf
    case Failure(ex) => ... 
  }
}

def cvtToHomeGrown (rsp: HttpResponse): Future[ByteString] = {
  rsp.entity.dataBytes.runWith (Sink.fold (ByteString.empty)(_ ++ _))
    .map (cvtToHomeGrownActually) // has signature String => ByteString
}

// as Server part
val parseAndAskFlow = Flow[ByteString]
  .via(Framing.delimiter(
    ByteString('\n'))
  .map (buf => cvtToCustHttpReq (buf))
  .via (asClientFlow)  // plug-in asClient part, the problem is here

val asServerConn: Source[IncomingConnection, Future[ServerBinding]] = Tcp().bind("localhost",port)

asServerConn.runForeach (conn => conn.handleWith(parseAndAskFlow)

问题是conn.handleWith需要Flow [ByteString，ByteString，]，但是http客户端代码（rsp.entity.dataBytes ...）返回Future [ByteSring]，所以parseAndAskFlow的Flow [ByteString，Future [ByteString] ，]类型，但我不知道在哪里可以更好地完成它。我什至认为，就所有这些都是流而言，这根本不是一个好主意，并且等待某处将停止良好的异步处理，但是代码未编译。

Answer 1

使用mapAsync而非map将asClientFlow的类型更改为Flow[CustHttpReq, ByteString]：

val asClientFlow: Flow[CustHttpReq, ByteString] =
  Flow[CustHttpReq]
    .via(connPool)
    .mapAsync(1)(procHttpResp)

然后，parseAndAskFlow的类型可以为Flow[ByteString, ByteString]：

val parseAndAskFlow: Flow[ByteString, ByteString] =
  Flow[ByteString]
    .via(Framing.delimiter(ByteString("\n"))
    .map(cvtToCustHttpReq)
    .via(asClientFlow)

什么时候在akka-http中实现http响应的内容？

1 个答案: