'Graph must be connected' with Flow created from Publisher+Subscriber actor.

[folex]

class ActorPubSub extends ActorSubscriber with ActorPublisher[Int] {
  var events = Seq.empty[Int]

  override protected def requestStrategy: RequestStrategy = OneByOneRequestStrategy
  override def receive: Actor.Receive = {
    case OnNext(e: Int) => events = e +: events
    case Request(cnt) => events.take(cnt.toInt).foreach(onNext)
  }
}

val pubsubRef = system.actorOf(Props(new ActorPubSub))
val pub = ActorPublisher[Int](pubsubRef)
val sub = ActorSubscriber[Int](pubsubRef)
val pubsubFlow = Flow(Sink(sub), Source(pub))

FlowGraph { implicit b =>
  import akka.stream.scaladsl.FlowGraphImplicits._

  Source((1 to 10).toList) ~> pubsubFlow ~> Sink.foreach[Int](e =>
    println("Got a number " + e)
  )
}.run()

According to Flow.apply(Sink, Source) doc: 

Create a Flow from a seemingly disconnected Source and Sink pair.

If that's true, why graph remains unconnected? 

[Endre Varga]

Hi, 

This is a known issue and will be fully fixed in M4. The underlying problem is that the underlying graph representation does not treat it as a flow but as a Sink/Source, since it flattens everything that contains a graph inside. 

-Endre

 

--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
---
You received this message because you are subscribed to the Google Groups "Akka User List" group.
To unsubscribe from this group and stop receiving emails from it, send an email to akka-user+...@googlegroups.com.
To post to this group, send email to akka...@googlegroups.com.
Visit this group at http://groups.google.com/group/akka-user.
For more options, visit https://groups.google.com/d/optout.

[folex]

I should add that original (and more complex) example doesn't throw an "Unconnected" exception though it's isomorphic to the one in OP. It just doesn't work without any complains: just nothing ever sent to subscriber+publisher actor.

I'll try to provide standalone example though I'm not sure if I succeed to reproduce this. 

Or maybe such a behaviour is also known and you don't need an example of it?

[Rauan Maemirov]

Hey folex. I was trying to make use of sink-to-source as well, you might need to do the following:

val in = Flow[Int].to(Sink(ActorSubscriber[Int](pubsubRef)))
val out = Source(ActorPublisher[Int](pubsubRef))

Flow.wrap(in, out)(Keep.none)

Enter code here...

Check out this useful peace: https://github.com/jrudolph/akka-http-scala-js-websocket-chat/blob/master/backend/src/main/scala/example/akkawschat/Chat.scala

I don't know your use case, but since you're doing a single PubSub, I think you need to create a demand. Otherwise you probably might end up trying to stream from an empty sequence. I.e: something like:

case Request(cnt) =>

  if (events.nonEmpty)
    events.take(cnt.toInt).foreach(onNext)
  else
    request(cnt)

[Rauan Maemirov]

Actually, never mind the last code block. I forgot you set up OneByOneRequestStrategy, which will constantly demand from upstream.