akka http with connecting http server to outgoing tcp server throught nginx - akka-stream

Question

Problem when try to using akka http like proxy to tcp.
Start http server, which responsibility only to get json request from the client and send message on Tcp server through nginx, take response from it and send response back to the client. So, only like proxy.
The problem is that server try to response before tcp server response. But when I remove nginx proxy between http and tcp servers everything all right. In tcp level akka http server send RST packet and right after that get RST from nginx and connection close. Tcp respond to nginx but connection already closed. With simple tcp server the same situation.
Akka version 2.4.17, akka http 10.0.10
The code below
val connections: Flow[ByteString, ByteString,
Future[Tcp.OutgoingConnection]] =
Tcp().outgoingConnection(new InetSocketAddress(settings.tcpServerHost,
settings.tcpServerPort))
def start(): Unit ={
val requestHandler: HttpRequest => Future[HttpResponse] = {
case HttpRequest(POST, uri#Uri.Path("/v1/doc"), _, entry, _) =>
proxyTcp(100, uri, entry)
case HttpRequest(POST, uri#Uri.Path("/v5/doc"), _, entry, _) =>
proxyTcp(105, uri, entry)
case _ => Future(HttpResponse(status = StatusCodes.NotFound))
}
Http().bind(settings.host, settings.port).runForeach(connection => {
connection.handleWithAsyncHandler(requestHandler)
}) }
private def proxyTcp(version: Short, uri: Uri, entry: RequestEntity):
Future[HttpResponse] = {
val transform = Transformations(connections, version)
entry.withoutSizeLimit().dataBytes
.via(transform.json2tlv)
.via(transform.connections)
.runWith(Sink.head)
.map(result => HttpResponse(status = StatusCodes.OK, entity =
HttpEntity(ContentTypes.`application/json`, result.get)))
}