Akka HTTP client closing connection early

[Tom Eccles]

I'm trying to use Akka HTTP to write an HttpClient to send a single request and receive a response. My current approach is the following method, having set up an OutgoingConnection:

  private def sendRequest(request: HttpRequest, connection: Http.OutgoingConnection): Future[HttpResponse] = {

    Source(List(request -> 'NoContext)).runWith(Sink(connection.requestSubscriber))

    Source(connection.responsePublisher).map(_._1).runWith(Sink.head[HttpResponse])

  }

In the resulting TCP stream, I see the client send the HTTP request as expected, immediately followed by a TCP [FIN, ACK] packet. This causes the server to immediately reply with its own [FIN, ACK], closing the connection without sending a response.

Am I using the OutgoingConnection wrong, or is this a problem with Akka HTTP?

Strangely, I do get an HttpResponse when making requests to servers running with Akka HTTP - they respond despite the early FIN.

[Akka Team]

Hi Tom,

There wasn't a fully operating Http Client in 0.11 only some initial parts. Please wait for the 1.0-M1 version which comes with a fresh new API and a proper client. The new version is just around the corner ;)

-Endre

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[Konrad 'ktoso' Malawski]

And one minute afterwards… 1.0-M1 released!

See details in the announcement email :-)

Happy hakking!

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Konrad 'ktoso' Malawski

hAkker @ typesafe

http://akka.io

[Joe Edwards]

I'm seeing similar behaviour in 1.0-M1, my client looks like this:

class SingleUseConnectionHttpClient()(implicit actorSystem: ActorSystem) {

  val http = Http()

  implicit val materializer = FlowMaterializer(namePrefix = Some("SingleUseConnectionHttpClient"))

  def sendRequest(request: HttpRequest): Future[HttpResponse] = {

    val connection = http.outgoingConnection(request.uri.authority.host.address(), request.uri.effectivePort)

 

    Source.singleton(request) via connection.flow runWith Sink.head

  }

}

 

My best guess is that the request source is terminating after the single request, and this causes the connection to signal a close even though it is still waiting for the response. I've tried putting more than one request in the Source, and it always sends the [FIN, ACK] as soon as the last request is sent, regardless of how many responses have arrived.

On a related note, is there a more fully featured client coming soon? For example I believe spray 1.3.1 had built-in support for connection pooling to a single host.

[Roland Kuhn]

Which server do you see this with? A priori it makes sense to close the sending side if no further requests will follow, but if relevant HTTP servers misinterpret this then we’ll have to fix it (whether or not it is broken is a different question).

Regards,

Roland

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Dr. Roland Kuhn
Akka Tech Lead
Typesafe – Reactive apps on the JVM.
twitter: @rolandkuhn

[Endre Varga]

On Mon, Dec 8, 2014 at 3:08 PM, Roland Kuhn <goo...@rkuhn.info> wrote:

Which server do you see this with? A priori it makes sense to close the sending side if no further requests will follow, but if relevant HTTP servers misinterpret this then we’ll have to fix it (whether or not it is broken is a different question).

Two scenarios are possible here:

 1. the server misinterprets half-closed connections

 2. The TCP implementation does not correctly half-close the connection. AFAIK we have tests for this, but we can double-check it.

-Endre

[Joe Edwards]

So is it valid to close your half of the TCP stream if you aren't sending more requests (even if you're waiting for a response)?

I'm seeing it close early consistently against a Spray 1.3.1 server, a Tomcat server and an akka-http 1.0-M1 server. (Interestingly not against a 0.11 server)

I can't find any publicly available servers that exhibit the same behaviour right now, but I can have a further look if you think it's helpful.

Joe

[Joe Edwards]

I've tried to look into it, and it seems unclear. There's an interesting discussion which explains the argument here:

http://lists.w3.org/Archives/Public/ietf-http-wg-old/2001JanApr/0037.html

My akka client behaves as a 'type 1', and so it doesn't work with servers of 'type B'.

I don't have a good list of 'type B' servers, but the few I listed above (noticeably all JVM based?) seem to exhibit it.

How easy would it be to implement a config option (say) to enable/disable this behaviour?

[Roland Kuhn]

The best way to find out is to create a ticket with the information gathered so far, that way it won’t be accidentally forgotten.

Thanks,

Roland

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[Joe Edwards]

-> https://github.com/akka/akka/issues/16510

[Roland Kuhn]

Thanks a lot! 

10 dec 2014 kl. 12:51 skrev Joe Edwards <joeyed...@googlemail.com>:

-> https://github.com/akka/akka/issues/16510

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[Peter Swift]

Seems like I'm having the same issue.

object TestClient {

  implicit val system = ActorSystem()

  implicit val fm = FlowMaterializer()

  val connection = Http().outgoingConnection("localhost", 8080)

  def request() = {

    val result = Source.singleton(HttpRequest(GET, Uri("/ping"))).via(connection.flow).runWith(Sink.head)

    Await.result(result, 10.seconds)

  }

}

object TestServer {

  implicit val system = ActorSystem()

  implicit val fm = FlowMaterializer()

  def bind() {

    val binding = Http().bind(interface = "localhost", port = 8080)

    binding startHandlingWithSyncHandler {

      case HttpRequest(GET, Uri.Path("/ping"), _, _, _) => HttpResponse(entity = "PONG!")

      case _: HttpRequest                               => HttpResponse(404, entity = "Unknown resource!")

    }

  }

}

In repl: 

Server.bind

In another repl (first request works. subsequent requests fail)

scala> TestClient.request

res0: akka.http.model.HttpResponse = HttpResponse(200 OK,List(Date: Wed, 10 Dec 2014 20:22:04 GMT, Server: akka-http/2.3.7),HttpEntity.Default(text/plain; charset=UTF-8,5,SourcePipe(PublisherSource(akka.stream.impl.MultiStreamOutputProcessor$SubstreamOutput@5656b4fa),List(Collect(<function1>,OperationAttributes(List(Name(collect))))),List(),OperationAttributes(List()))),HttpProtocol(HTTP/1.1))

scala> TestClient.request

java.util.NoSuchElementException: empty stream

at akka.stream.scaladsl.HeadSink$HeadSinkSubscriber.onComplete(ActorFlowSink.scala:108)

at akka.stream.impl.fusing.ActorOutputBoundary.complete(ActorInterpreter.scala:167)

at akka.stream.impl.fusing.ActorOutputBoundary.onUpstreamFinish(ActorInterpreter.scala:194)

But I can 'curl localhost:8080/ping' all day long without problems.