Akka Camel: Messages routed to incorrect SEDA route

Question

My simplified Akka Camel application is set up as follows:

AppleProducer -> seda:appleRoute -> AppleConsumer

OrangeProducer -> seda:orangeRoute -> OrangeConsumer

What I am seeing though is that Apple events are intermittently being consumed by the OrangeConsumer, and vice versa.

Running this example (perhaps a few times) below recreates it.

I don't understand how this only happens intermittently. What am I doing wrong?

object TestApp extends App {
  implicit val system = ActorSystem()
  val camel = CamelExtension(system)
  val appleProducer = system.actorOf(Props(classOf[MyProducer], "seda:appleRoute"), "AppleProducer")
  system.actorOf(Props(classOf[MyAppleConsumer], "seda:appleRoute"), "AppleConsumer")
  val orangeProducer = system.actorOf(Props(classOf[MyProducer], "seda:orangeRoute"), "OrangeProducer")
  system.actorOf(Props(classOf[MyOrangeConsumer], "seda:orangeRoute"), "OrangeConsumer")

  appleProducer ! new Apple("1")
  orangeProducer ! new Orange("1")
  appleProducer ! new Apple("2")
  orangeProducer ! new Orange("2")
  appleProducer ! new Apple("3")
  orangeProducer ! new Orange("3")
  appleProducer ! new Apple("4")
  orangeProducer ! new Orange("4")
  appleProducer ! new Apple("5")
  orangeProducer ! new Orange("5")
  appleProducer ! new Apple("6")
  orangeProducer ! new Orange("6")

}

class MyProducer(route: String) extends Actor with ActorLogging  {

  def receive = {
    case payload: Any =>
      val template = CamelExtension(context.system).template
      template.setDefaultEndpointUri(route)
      template.sendBody(payload)
  }
}

class MyAppleConsumer(route: String) extends Consumer with ActorLogging {
  override def endpointUri: String = route

  override def receive: Receive = {
    case event: CamelMessage if event.body.isInstanceOf[Apple] =>
      log.info("Received event {}", event.body)
    case _ => throw new IllegalArgumentException("Invalid entity")
  }
}

class MyOrangeConsumer(route: String) extends Consumer with ActorLogging {
  override def endpointUri: String = route

  override def receive: Receive = {
    case event: CamelMessage if event.body.isInstanceOf[Orange] =>
      log.info("Received event {}", event.body)
    case _ => throw new IllegalArgumentException("Invalid entity")
  }
}

class Apple(id: String)
class Orange(id: String)

score 0 · Accepted Answer · answered Jun 03 '16 at 21:29

I think I managed to figure this out eventually.

The issue has nothing to do with SEDA. Instead it seems that the same DefaultProducerTemplate is returned for multiple MyProducer instances.

Therefore, there is occasionally a race condition when setting the defaultEndpointUri

Solution, for me, was to create only one instance of the MyProducer actor to ensure that we do not encounter this race condition

hveiga · Answer 2 · 2016-06-05T19:28:18.377

I would recommend extending the trait Producer instead of using a template for your MyProducer the same way you are using Consumer for your MyAppleConsumer and MyOrangeConsumer.

class MyProducer(route: String) extends Producer with OneWay  {
  def endpointUri = route 
}

More info can be found here: http://doc.akka.io/docs/akka/snapshot/scala/camel.html

I believe you should be able to simplify your code like this (disclaimer: not compiled or tested!):

case class Apple(id: String)
case class Orange(id: String)

object TestApp extends App {
  implicit val system = ActorSystem()

  val appleProducer = system.actorOf(Props(classOf[MyProducer], "seda:appleRoute"), "AppleProducer")
  system.actorOf(Props(classOf[MyConsumer], "seda:appleRoute"), "AppleConsumer")
  val orangeProducer = system.actorOf(Props(classOf[MyProducer], "seda:orangeRoute"), "OrangeProducer")
  system.actorOf(Props(classOf[MyConsumer], "seda:orangeRoute"), "OrangeConsumer")

  appleProducer ! Apple("1")
  orangeProducer ! Orange("1")
  appleProducer ! Apple("2")
  orangeProducer ! Orange("2")
  appleProducer ! Apple("3")
  orangeProducer ! Orange("3")
  appleProducer ! Apple("4")
  orangeProducer ! Orange("4")
  appleProducer ! Apple("5")
  orangeProducer ! Orange("5")
  appleProducer ! Apple("6")
  orangeProducer ! Orange("6")

}

class MyProducer(route: String) extends Producer with OneWay with ActorLogging  {
  def endpointUri = route
}

class MyConsumer(route: String) extends Consumer with ActorLogging {
  override def endpointUri: String = route

  override def receive: Receive = {
    case CamelMessage(body : Apple, headers) =>
      log.info("Received event {}", body)
    case CamelMessage(body : Orange, headers) =>
      log.info("Received event {}", body)
    case _ => throw new IllegalArgumentException("Invalid entity")
  }
}

I need to add custom Message creation logic in my Producer (that I left out in the example) so that is why I used the template. — DJ180, Jun 06 '16 at 13:56

Akka Camel: Messages routed to incorrect SEDA route

2 Answers2