Networks and types - the future of Akka
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The document discusses Akka Typed Actors and Akka Streams. It provides an example of a typed actor implementation of a burglar alarm system and how it can be distributed across multiple nodes in an Akka cluster. It also discusses how Akka Streams allows data to flow asynchronously between nodes over a network using concepts like sources, sinks and flows and how stream references allow streams to connect across actor systems.
![• Not a trivial problem: Topic of multiple research papers
to bring type-safety to the Actor model
•“TAkka” 2014, Phillip Wadler et al, University of Edinburgh
•“Reactors, Channels and Event Streams …” 2015,
Aleksandar Prokopec, Martin Odersky, EPFL
•Typed Actors [RIP]
The need for strong/strict typing](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-13-320.jpg)
![// behavior
def enabled(pinCode: String): Behavior[AlarmMessage] =
Behaviors.receive[AlarmMessage] { (ctx, msg) =>
msg match {
case DisableAlarm(enteredCode) if enteredCode == pinCode =>
ctx.log.info("Disabling alarm")
disabled(pinCode) // change behavior
case ActivityEvent =>
ctx.log.warning("OEOEOEOEOEOE alarm, activity detected!")
Behaviors.same
case _ =>
Behaviors.ignore
}
}
def disabled(pinCode: String): Behavior[AlarmMessage] =
Behaviors.receive[AlarmMessage] {
case EnableAlarm(enteredCode) if enteredCode == pinCode =>
enabled(pinCode) // change behavior
case _ =>
Behaviors.ignore
}](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-17-320.jpg)
![// behavior
def enabled(pinCode: String): Behavior[AlarmMessage] =
Behaviors.receive[AlarmMessage] { (ctx, msg) =>
msg match {
case DisableAlarm(enteredCode) if enteredCode == pinCode =>
ctx.log.info("Disabling alarm")
disabled(pinCode) // change behavior
case ActivityEvent =>
ctx.log.warning("OEOEOEOEOEOE alarm, activity detected!")
Behaviors.same
case _ =>
Behaviors.ignore
}
}
def disabled(pinCode: String): Behavior[AlarmMessage] =
Behaviors.receive[AlarmMessage] {
case EnableAlarm(enteredCode) if enteredCode == pinCode =>
enabled(pinCode) // change behavior
case _ =>
Behaviors.ignore
}](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-18-320.jpg)
![// behavior
def enabled(pinCode: String): Behavior[AlarmMessage] =
Behaviors.receive[AlarmMessage] { (ctx, msg) =>
msg match {
case DisableAlarm(enteredCode) if enteredCode == pinCode =>
ctx.log.info("Disabling alarm")
disabled(pinCode) // change behavior
case ActivityEvent =>
ctx.log.warning("OEOEOEOEOEOE alarm, activity detected!")
Behaviors.same
case _ =>
Behaviors.ignore
}
}
def disabled(pinCode: String): Behavior[AlarmMessage] =
Behaviors.receive[AlarmMessage] {
case EnableAlarm(enteredCode) if enteredCode == pinCode =>
enabled(pinCode) // change behavior
case _ =>
Behaviors.ignore
}](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-19-320.jpg)
![// running it
val system = ActorSystem(enabled("0000"), "AlarmSystem")
// system is also reference to top level actor
val alarmRef: ActorRef[AlarmMessage] = system
alarmRef ! DisableAlarm("1234")
alarmRef ! ActivityEvent
alarmRef ! DisableAlarm("0000")
alarmRef ! ActivityEvent
alarmRef ! EnableAlarm("0000")](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-20-320.jpg)
![// running it
val system = ActorSystem(enabled("0000"), "AlarmSystem")
// system is also reference to top level actor
val alarmRef: ActorRef[AlarmMessage] = system
alarmRef ! DisableAlarm("1234")
alarmRef ! ActivityEvent
alarmRef ! DisableAlarm("0000")
alarmRef ! ActivityEvent
alarmRef ! EnableAlarm(“0000")
alarmRef ! ”0000” // compile error
Compile-time safety](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-21-320.jpg)
![Untyped Actors
Untyped Actors vs Akka Typed
Akka Typed Actors
• sender() propagated
automatically
• any message type can
be sent to any Actor
• actor returns nothing
upon processing a
message
• sender is optionally part
of the protocol
• only the right type of messages
can be sent:
ActorRef[MessageProtocol]
• behaviors always return the
next behavior](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-22-320.jpg)
![Receptionist
Typed Receptionist
Receptionist
Receptionist
Register(Key[AlarmMessage],
ActorRef[AlarmMessage])
ActorRef[AlarmMessage]
ActorRef[SensorEvent]
Subscribe(key, actorRef)](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-25-320.jpg)
![val receptionist = Receptionist(system).ref
val alarmKey = ServiceKey[AlarmMessage]("alarm")
def startAlarm(pinCode: String): Behavior[AlarmMessage] =
Behaviors.setup { ctx =>
receptionist ! Register(alarmKey, ctx.self, ctx.system.deadLetters)
enabled(pinCode)
}](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-26-320.jpg)
![val receptionist = Receptionist(system).ref
val alarmKey = ServiceKey[AlarmMessage]("alarm")
def startAlarm(pinCode: String): Behavior[AlarmMessage] =
Behaviors.setup { ctx =>
receptionist ! Register(alarmKey, ctx.self, ctx.system.deadLetters)
enabled(pinCode)
}](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-27-320.jpg)
![// protocol
trait SensorEvent
case object WindowOpened extends SensorEvent
// behavior
def sensorBehavior: Behavior[SensorEvent] =
Behaviors.setup { ctx =>
var alarms = Set.empty[ActorRef[AlarmMessage]]
Receptionist(ctx.system).ref ! Receptionist.Subscribe(
alarmKey, ctx.self.narrow[Listing[AlarmMessage]])
Behaviors.receive[Any]((ctx, msg) =>
msg match {
case Listing(_, updatedAlarms: Set[ActorRef[AlarmMessage]]) =>
// updated list of alarms known
alarms = updatedAlarms
Behaviors.same
case WindowOpened =>
// inform all known alarms about activity
alarms.foreach(_ ! ActivityEvent)](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-28-320.jpg)
![// protocol
trait SensorEvent
case object WindowOpened extends SensorEvent
// behavior
def sensorBehavior: Behavior[SensorEvent] =
Behaviors.setup { ctx =>
var alarms = Set.empty[ActorRef[AlarmMessage]]
Receptionist(ctx.system).ref ! Receptionist.Subscribe(
alarmKey, ctx.self.narrow[Listing[AlarmMessage]])
Behaviors.receive[Any]((ctx, msg) =>
msg match {
case Listing(_, updatedAlarms: Set[ActorRef[AlarmMessage]]) =>
// updated list of alarms known
alarms = updatedAlarms
Behaviors.same
case WindowOpened =>
// inform all known alarms about activity
alarms.foreach(_ ! ActivityEvent)](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-29-320.jpg)
![def sensorBehavior: Behavior[SensorEvent] =
Behaviors.setup { ctx =>
var alarms = Set.empty[ActorRef[AlarmMessage]]
Receptionist(ctx.system).ref ! Receptionist.Subscribe(
alarmKey, ctx.self.narrow[Listing[AlarmMessage]])
Behaviors.receive[Any]((ctx, msg) =>
msg match {
case Listing(_, updatedAlarms: Set[ActorRef[AlarmMessage]]) =>
// updated list of alarms known
alarms = updatedAlarms
Behaviors.same
case WindowOpened =>
// inform all known alarms about activity
alarms.foreach(_ ! ActivityEvent)
Behaviors.same
}
)
}.narrow // narrow Behavior[Any] down to Behavior[SensorEvent]](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-30-320.jpg)
![SourceRef sending side
Scala
class SendingActor extends Actor {
import context.dispatcher
implicit val mat = ActorMaterializer()(context)
val numbersSource = Source(1 to 100000)
def receive = {
case SendMeNumbers ⇒
val ref: Future[SourceRef[Int]] =
numbersSource.runWith(StreamRefs.sourceRef())
val reply: Future[SendMeNumbersReply] =
ref.map(ref => SendMeNumbersReply(ref))
reply pipeTo sender()
}
}](https://image.slidesharecdn.com/devoxxlondon2018-networksandtypes-thefutureofakka-180520100355/85/Networks-and-types-the-future-of-Akka-39-320.jpg)
Networks and types - the future of Akka
- 1. Networks & Types Johan Andrén, Akka Team Devoxx UK, London, 2018-05-11 The Future of Akka
- 2. Johan Andrén Akka Team Stockholm Scala User Group @apnylle markatta.com/codemonkey/ johan.andren@lightbend.com
- 3. Build powerful reactive, concurrent, and distributed applications more easily Akka
- 4. • Distributed programming made simple • High performance messaging (up to 1 million msgs/s over network on Artery, close to 40-50 million msgs/s locally) • Asynchronous and Reactive by default • Initiator of Reactive Streams initiative, now part of JDK9 • Productive development, with tuned type-safe tools What does Akka solve?
- 5. What are the tools? Actors – simple & high performance concurrency Cluster, Cluster tools – tools for building distributed systems Streams – reactive streams implementation Persistence – CQRS + Event Sourcing for Actors HTTP – fully async streaming HTTP Server Alpakka – Reactive Streams Integrations a’la Camel Complete Java & Scala APIs for all features
- 6. Actors – simple & high performance concurrency Cluster, Cluster tools – tools for building distributed systems Streams – reactive streams implementation Persistence – CQRS + Event Sourcing for Actors HTTP – fully async streaming HTTP Server Alpakka – Reactive Streams Integrations a’la Camel Complete Java & Scala APIs for all features. All modules ready for preview, final polish during Q2 2018 Typed Typed Typed (already type-safe) (already type-safe) (already type-safe) What is coming soon?
- 7. Actor Message Inbox MessageMessage actorRef ! message Akka Actor fundamentals
- 8. • mutate state (including spawning a child actor) • send messages to other actors • change its behavior Actor Message Inbox MessageMessage An Actor can…
- 11. class MyActor extends Actor { def receive: Any => Unit = { case Msg(a) => sender() ! “Hi there!” } } Reminder of Akka “Classic” Actors
- 12. • Discoverability, how are things related • More compile time type-safety, less runtime debugging Types helps productivity! (and results in more reliable systems in production) The need for strong/strict typing “Sending the wrong message to an actor is actually quite uncommon” – Myself, earlier this week
- 13. • Not a trivial problem: Topic of multiple research papers to bring type-safety to the Actor model •“TAkka” 2014, Phillip Wadler et al, University of Edinburgh •“Reactors, Channels and Event Streams …” 2015, Aleksandar Prokopec, Martin Odersky, EPFL •Typed Actors [RIP] The need for strong/strict typing
- 14. Typed Actors
- 15. Burglar Alarm • enabled/disabled with a pin code • accepts notifications about “activity” • if enabled on activity, sound the alarm Example DIY
- 16. // message protocol trait AlarmMessage case class EnableAlarm(pinCode: String) extends AlarmMessage case class DisableAlarm(pinCode: String) extends AlarmMessage case object ActivityEvent extends AlarmMessage
- 17. // behavior def enabled(pinCode: String): Behavior[AlarmMessage] = Behaviors.receive[AlarmMessage] { (ctx, msg) => msg match { case DisableAlarm(enteredCode) if enteredCode == pinCode => ctx.log.info("Disabling alarm") disabled(pinCode) // change behavior case ActivityEvent => ctx.log.warning("OEOEOEOEOEOE alarm, activity detected!") Behaviors.same case _ => Behaviors.ignore } } def disabled(pinCode: String): Behavior[AlarmMessage] = Behaviors.receive[AlarmMessage] { case EnableAlarm(enteredCode) if enteredCode == pinCode => enabled(pinCode) // change behavior case _ => Behaviors.ignore }
- 18. // behavior def enabled(pinCode: String): Behavior[AlarmMessage] = Behaviors.receive[AlarmMessage] { (ctx, msg) => msg match { case DisableAlarm(enteredCode) if enteredCode == pinCode => ctx.log.info("Disabling alarm") disabled(pinCode) // change behavior case ActivityEvent => ctx.log.warning("OEOEOEOEOEOE alarm, activity detected!") Behaviors.same case _ => Behaviors.ignore } } def disabled(pinCode: String): Behavior[AlarmMessage] = Behaviors.receive[AlarmMessage] { case EnableAlarm(enteredCode) if enteredCode == pinCode => enabled(pinCode) // change behavior case _ => Behaviors.ignore }
- 19. // behavior def enabled(pinCode: String): Behavior[AlarmMessage] = Behaviors.receive[AlarmMessage] { (ctx, msg) => msg match { case DisableAlarm(enteredCode) if enteredCode == pinCode => ctx.log.info("Disabling alarm") disabled(pinCode) // change behavior case ActivityEvent => ctx.log.warning("OEOEOEOEOEOE alarm, activity detected!") Behaviors.same case _ => Behaviors.ignore } } def disabled(pinCode: String): Behavior[AlarmMessage] = Behaviors.receive[AlarmMessage] { case EnableAlarm(enteredCode) if enteredCode == pinCode => enabled(pinCode) // change behavior case _ => Behaviors.ignore }
- 20. // running it val system = ActorSystem(enabled("0000"), "AlarmSystem") // system is also reference to top level actor val alarmRef: ActorRef[AlarmMessage] = system alarmRef ! DisableAlarm("1234") alarmRef ! ActivityEvent alarmRef ! DisableAlarm("0000") alarmRef ! ActivityEvent alarmRef ! EnableAlarm("0000")
- 21. // running it val system = ActorSystem(enabled("0000"), "AlarmSystem") // system is also reference to top level actor val alarmRef: ActorRef[AlarmMessage] = system alarmRef ! DisableAlarm("1234") alarmRef ! ActivityEvent alarmRef ! DisableAlarm("0000") alarmRef ! ActivityEvent alarmRef ! EnableAlarm(“0000") alarmRef ! ”0000” // compile error Compile-time safety
- 22. Untyped Actors Untyped Actors vs Akka Typed Akka Typed Actors • sender() propagated automatically • any message type can be sent to any Actor • actor returns nothing upon processing a message • sender is optionally part of the protocol • only the right type of messages can be sent: ActorRef[MessageProtocol] • behaviors always return the next behavior
- 23. Akka Cluster + Akka Typed ActorSystem ActorSystem ActorSystem
- 24. Distributed Burglar Alarm • we can have any number of nodes • a sensor on any node can report activity to the alarm Example, iteration 2 DYI Distributed
- 26. val receptionist = Receptionist(system).ref val alarmKey = ServiceKey[AlarmMessage]("alarm") def startAlarm(pinCode: String): Behavior[AlarmMessage] = Behaviors.setup { ctx => receptionist ! Register(alarmKey, ctx.self, ctx.system.deadLetters) enabled(pinCode) }
- 27. val receptionist = Receptionist(system).ref val alarmKey = ServiceKey[AlarmMessage]("alarm") def startAlarm(pinCode: String): Behavior[AlarmMessage] = Behaviors.setup { ctx => receptionist ! Register(alarmKey, ctx.self, ctx.system.deadLetters) enabled(pinCode) }
- 28. // protocol trait SensorEvent case object WindowOpened extends SensorEvent // behavior def sensorBehavior: Behavior[SensorEvent] = Behaviors.setup { ctx => var alarms = Set.empty[ActorRef[AlarmMessage]] Receptionist(ctx.system).ref ! Receptionist.Subscribe( alarmKey, ctx.self.narrow[Listing[AlarmMessage]]) Behaviors.receive[Any]((ctx, msg) => msg match { case Listing(_, updatedAlarms: Set[ActorRef[AlarmMessage]]) => // updated list of alarms known alarms = updatedAlarms Behaviors.same case WindowOpened => // inform all known alarms about activity alarms.foreach(_ ! ActivityEvent)
- 29. // protocol trait SensorEvent case object WindowOpened extends SensorEvent // behavior def sensorBehavior: Behavior[SensorEvent] = Behaviors.setup { ctx => var alarms = Set.empty[ActorRef[AlarmMessage]] Receptionist(ctx.system).ref ! Receptionist.Subscribe( alarmKey, ctx.self.narrow[Listing[AlarmMessage]]) Behaviors.receive[Any]((ctx, msg) => msg match { case Listing(_, updatedAlarms: Set[ActorRef[AlarmMessage]]) => // updated list of alarms known alarms = updatedAlarms Behaviors.same case WindowOpened => // inform all known alarms about activity alarms.foreach(_ ! ActivityEvent)
- 30. def sensorBehavior: Behavior[SensorEvent] = Behaviors.setup { ctx => var alarms = Set.empty[ActorRef[AlarmMessage]] Receptionist(ctx.system).ref ! Receptionist.Subscribe( alarmKey, ctx.self.narrow[Listing[AlarmMessage]]) Behaviors.receive[Any]((ctx, msg) => msg match { case Listing(_, updatedAlarms: Set[ActorRef[AlarmMessage]]) => // updated list of alarms known alarms = updatedAlarms Behaviors.same case WindowOpened => // inform all known alarms about activity alarms.foreach(_ ! ActivityEvent) Behaviors.same } ) }.narrow // narrow Behavior[Any] down to Behavior[SensorEvent]
- 31. // running it val system1 = ActorSystem(startAlarm("0000"), "AlarmSystem") val system2 = ActorSystem(sensorBehavior, "AlarmSystem") // programmatic cluster formation val node1 = Cluster(system1) val node2 = Cluster(system2) // node1 joins itself to form cluster node1.manager ! Join(node1.selfMember.address) // node2 joins the now existing cluster node2.manager ! Join(node1.selfMember.address) // a bit later the burglar comes after(1.day) { system2 ! WindowOpened }
- 33. Akka Stream fundamentals SinkSource Flow Elements
- 34. Akka Stream fundamentals SinkSource Flow potential asynchronous boundary potential asynchronous boundary
- 35. Akka Stream fundamentals SinkSource Flow 1 msg/s buffer size 3 10 msg/s 💥 💥 💥 🔥
- 36. Akka Stream fundamentals SinkSource Flow 1 msg/s buffer size 3 10 msg/s hand me 2 morehand me 2 more 1 msg/s
- 37. JVM 2 ActorSystem JVM 1 ActorSystem (special) SinkSource Flow Flow Sink SourceRef StreamRefs — new feature since Akka 2.5.10
- 38. JVM 2 ActorSystem JVM 1 ActorSystem (special) SinkSource Flow Flow SinkSourceRef This end controls the pace through backpressure StreamRefs — new feature since Akka 2.5.10
- 39. SourceRef sending side Scala class SendingActor extends Actor { import context.dispatcher implicit val mat = ActorMaterializer()(context) val numbersSource = Source(1 to 100000) def receive = { case SendMeNumbers ⇒ val ref: Future[SourceRef[Int]] = numbersSource.runWith(StreamRefs.sourceRef()) val reply: Future[SendMeNumbersReply] = ref.map(ref => SendMeNumbersReply(ref)) reply pipeTo sender() } }
- 40. SourceRef receiving side Scala class ReceivingActor(sendingActor: ActorRef) extends Actor { sendingActor ! SendMeNumbers override def receive: Receive = { case SendMeNumbersReply(sourceRef) => sourceRef.runWith(Sink.foreach(println)) } }
- 41. StreamRefs — new feature since Akka 2.5.10 By design NOT a“distributed automatic stream processing deployment and management framework”. (e.g. how Spark, Flink or Beam could be described). Ideal for combining Alpakka Enterprise Integration Data Processing or Ingestion Pipelines between ActorSystems