onNext is not allowed when the stream has not requested elements

[martinstuder]

We're getting the following occassional exception in our logs:

java.lang.IllegalStateException: onNext is not allowed when the stream has not requested elements, totalDemand was 0
        at akka.stream.actor.ActorPublisher$class.onNext(ActorPublisher.scala:190) ~[com.typesafe.akka.akka-stream-experimental_2.11-1.0-RC3.jar:na]
        at com.softwaremill.react.kafka.KafkaActorPublisher.onNext(KafkaActorPublisher.scala:12) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at com.softwaremill.react.kafka.KafkaActorPublisher$$anonfun$com$softwaremill$react$kafka$KafkaActorPublisher$$readDemandedItems$1.apply(KafkaActorPublisher.scala:35) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at com.softwaremill.react.kafka.KafkaActorPublisher$$anonfun$com$softwaremill$react$kafka$KafkaActorPublisher$$readDemandedItems$1.apply(KafkaActorPublisher.scala:35) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at scala.Option.foreach(Option.scala:257) ~[org.scala-lang.scala-library-2.11.6.jar:na]
        at com.softwaremill.react.kafka.KafkaActorPublisher.com$softwaremill$react$kafka$KafkaActorPublisher$$readDemandedItems(KafkaActorPublisher.scala:35) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at com.softwaremill.react.kafka.KafkaActorPublisher$$anonfun$receive$1.applyOrElse(KafkaActorPublisher.scala:17) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at akka.actor.Actor$class.aroundReceive(Actor.scala:467) ~[com.typesafe.akka.akka-actor_2.11-2.3.11.jar:na]
        at com.softwaremill.react.kafka.KafkaActorPublisher.akka$stream$actor$ActorPublisher$$super$aroundReceive(KafkaActorPublisher.scala:12) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at akka.stream.actor.ActorPublisher$class.aroundReceive(ActorPublisher.scala:317) ~[com.typesafe.akka.akka-stream-experimental_2.11-1.0-RC3.jar:na]
        at com.softwaremill.react.kafka.KafkaActorPublisher.aroundReceive(KafkaActorPublisher.scala:12) ~[com.softwaremill.reactive-kafka_2.11-0.6.0.jar:0.6.0]
        at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516) ~[com.typesafe.akka.akka-actor_2.11-2.3.11.jar:na]
        at akka.actor.ActorCell.invoke(ActorCell.scala:487) ~[com.typesafe.akka.akka-actor_2.11-2.3.11.jar:na]
        at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238) ~[com.typesafe.akka.akka-actor_2.11-2.3.11.jar:na]
        at akka.dispatch.Mailbox.run(Mailbox.scala:220) ~[com.typesafe.akka.akka-actor_2.11-2.3.11.jar:na]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) ~[na:1.8.0_40]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) ~[na:1.8.0_40]
        at java.lang.Thread.run(Thread.java:745) ~[na:1.8.0_40]

It doesn't seem like the stream is suffering from this, probably due to the one-for-one actor recover strategy.

[dbuschman7]

I have added a PR #13 for this issue. We ran into as well.

[iamthiago]

I've been running on this =) Thanks @dbuschman7 for the PR. Waiting for that.

[gvd]

This fix is not present in version 0.6.0 I believe. When will this fix be available in the maven repo?