Ah, I re-discovered the async callback APIs... I'd forgotten about them. Thus, my code now becomes:
val (queue, ar) = Source .queue[ByteString](100, OverflowStrategy.backpressure) .prefixAndTail(0) .map { case (_, in) => in } .toMat(Sink.head)(Keep.both) .run val asyncTryPull = getAsyncCallback[Unit]( _ => if (!hasBeenPulled(in)) tryPull(in)) val asyncCancel = getAsyncCallback[Unit]( _ => cancel(in)) and... queue.offer(newBlockBuffer).andThen { case Success(QueueOfferResult.Enqueued) => asyncTryPull.invoke(()) case _ => asyncCancel.invoke(()) } Sanity check still appreciated. Thanks. Cheers, -C -- >>>>>>>>>> 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+unsubscr...@googlegroups.com. To post to this group, send email to akka-user@googlegroups.com. Visit this group at https://groups.google.com/group/akka-user. For more options, visit https://groups.google.com/d/optout.