Advanced Akka For Architects
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The document discusses Akka's capabilities for multi-data center clustering, including features like cluster sharding and persistence, as well as handling node failures and network partitions. It emphasizes the importance of configuring seed nodes and data center roles for optimal operation and outlines the process for implementing replicated entities. Furthermore, it offers links for further learning and resources regarding Akka's use in distributed systems.
![Multiple Akka Clusters
Multi Data Center
akka.cluster {
# Change this to real hostname for production
seed-nodes = ["akka.tcp://ClusterSystem@host1:2552",
"akka.tcp://ClusterSystem@host2:2552"]
# Change this to the Akka data center this node belongs to
multi-data-center.self-data-center = DC-A
}
akka.persistence {
snapshot-store.plugin = "cassandra-snapshot-store"
multi-data-center {
all-data-centers = ["DC-A", “DC-B", “DC-C”]
}
}](https://image.slidesharecdn.com/advancedakkaforarchitects-171208130703/85/Advanced-Akka-For-Architects-9-320.jpg)
![import akka.persistence.multidc.scaladsl.ReplicatedEntity
final class Post1
extends ReplicatedEntity[BlogCommand, BlogEvent, BlogState] {
override def initialState: BlogState = BlogState.empty
override def commandHandler: CommandHandler =
CommandHandler { (ctx, state, cmd) => ??? }
override def eventHandler(state: BlogState, event: BlogEvent):
BlogState = ???
}](https://image.slidesharecdn.com/advancedakkaforarchitects-171208130703/85/Advanced-Akka-For-Architects-23-320.jpg)
![override def eventTrigger(
ctx: EventTriggerContext,
state: State, event: Event): Effect[Event, State] = {
event match {
case StepStarted(nr) =>
authority ! RequestApproval(nr)
ctx.actorContext.timers.startPeriodicTimer(ResendTick, ResendTick, resendInterval)
Effect.none
case StepApproved(_, _) =>
if (!state.denied && selfDc == "DC-A"
&& state.isCurrentStepApproved && state.currentStep < maxSteps) {
// approved by all, continue with next step
log.info("Step {} approved by all, continue", state.currentStep)
Effect.persist(StepStarted(state.currentStep + 1))
} else
Effect.none
case _ =>
Effect.none
}
}](https://image.slidesharecdn.com/advancedakkaforarchitects-171208130703/85/Advanced-Akka-For-Architects-31-320.jpg)
Advanced Akka For Architects
- 2. Akka Multi-Data Center Clustering Cluster Singletons Cluster Sharding Persistence
- 4. Akka Cluster Single Data Center
- 5. Akka Cluster Single Data Center Split Brain Unresponsive Member
- 6. Speed of light 300 km/ms, 186 mi/ms Small circle radius 3,000 km, 1,860 mi ~ 10 ms SOL distance
- 7. Single Akka Cluster Multi Data Center
- 8. Multiple Akka Clusters Multi Data Center
- 9. Multiple Akka Clusters Multi Data Center akka.cluster { # Change this to real hostname for production seed-nodes = ["akka.tcp://ClusterSystem@host1:2552", "akka.tcp://ClusterSystem@host2:2552"] # Change this to the Akka data center this node belongs to multi-data-center.self-data-center = DC-A } akka.persistence { snapshot-store.plugin = "cassandra-snapshot-store" multi-data-center { all-data-centers = ["DC-A", “DC-B", “DC-C”] } }
- 10. Multiple Akka Clusters Clusters within Clusters
- 11. Multiple Akka Clusters Clusters within Clusters Network Partition
- 12. Multiple Akka Clusters Clusters within Clusters Node Failure
- 13. Cluster Events Within Data Center MemberJoined MemberUp MemberExited MemberRemoved UnreachableMember ReachableMember Cross Data Center UnreachableMember ReachableMember
- 14. Multiple Akka Clusters Physical or Logical “Data Centers” Clusters within Clusters Microservice Microservice Microservice
- 15. Cluster Singleton One per Data Center
- 16. Cluster Sharding One per Data Center
- 18. Cluster Sharding ShardRegion Proxy val counterProxyDcB: ActorRef = ClusterSharding(system).startProxy( typeName = "Counter", role = None, dataCenter = Some(“C"), extractEntityId = extractEntityId, extractShardId = extractShardId)
- 19. Akka Persistence One per Data Center
- 20. Multi Data Center Persistence Commercial Add-on
- 23. import akka.persistence.multidc.scaladsl.ReplicatedEntity final class Post1 extends ReplicatedEntity[BlogCommand, BlogEvent, BlogState] { override def initialState: BlogState = BlogState.empty override def commandHandler: CommandHandler = CommandHandler { (ctx, state, cmd) => ??? } override def eventHandler(state: BlogState, event: BlogEvent): BlogState = ??? }
- 24. import akka.persistence.multidc.javadsl.CommandHandler; import akka.persistence.multidc.javadsl.EventHandler; import akka.persistence.multidc.javadsl.ReplicatedEntity; final class Post1 extends ReplicatedEntity<BlogCommand, BlogEvent, BlogState> { @Override public BlogState initialState() { return BlogState.EMPTY; } @Override public CommandHandler<BlogCommand, BlogEvent, BlogState> commandHandler() { throw new RuntimeException("Not implemented yet"); } @Override public EventHandler<BlogEvent, BlogState> eventHandler() { throw new RuntimeException("Not implemented yet"); } }
- 25. import akka.persistence.multidc.javadsl.CommandHandler; import akka.persistence.multidc.javadsl.EventHandler; import akka.persistence.multidc.javadsl.ReplicatedEntity; final class Post1 extends ReplicatedEntity<BlogCommand, BlogEvent, BlogState> { @Override public BlogState initialState() { return BlogState.EMPTY; } @Override public CommandHandler<BlogCommand, BlogEvent, BlogState> commandHandler() { throw new RuntimeException("Not implemented yet"); } @Override public EventHandler<BlogEvent, BlogState> eventHandler() { throw new RuntimeException("Not implemented yet"); } }
- 26. public CommandHandler<BlogCommand, BlogEvent, BlogState> commandHandler() { return commandHandlerBuilder(BlogCommand.class) .matchCommand(AddPost.class, (ctx, state, cmd) -> { final PostAdded evt = new PostAdded(cmd.postId, cmd.content, state.contentTimestamp.increase(currentTimeMillis(), getSelfDc())); return Effect().persist(evt).andThen((state2) -> // After persist is done additional side effects can be performed ctx.getSender().tell(new AddPostDone(cmd.postId), getSelf()) ); }) public EventHandler<BlogEvent, BlogState> eventHandler() { return eventHandlerBuilder(BlogEvent.class) .matchEvent(PostAdded.class, (state, postAdded) -> { if (postAdded.timestamp.isAfter(state.contentTimestamp)) { return state.withContent(postAdded.content, postAdded.timestamp); } else { return state; } })
- 27. Multi-DC Persistence Replication and handling of events
- 28. Multi-DC Persistence - Last writer wins
- 29. // eventHandler is used both when persisting new events, replaying // events, and consuming replicated events. override def eventHandler(state: BlogState, event: BlogEvent): BlogState = { event match { case PostAdded(postId, content, timestamp) => if (timestamp.isAfter(state.contentTimestamp)) state.withContent(content, timestamp) else state case BodyChanged(_, newContent, timestamp) => if (timestamp.isAfter(state.contentTimestamp)) state.withContent(newContent, timestamp) else state case Published(_) => state.copy(published = true) } }
- 30. // the returned event handler is used both when persisting new events, replaying // events, and consuming replicated events. @Override public EventHandler<BlogEvent, BlogState> eventHandler() { return eventHandlerBuilder(BlogEvent.class) .matchEvent(PostAdded.class, (state, postAdded) -> { if (postAdded.timestamp.isAfter(state.contentTimestamp)) { return state.withContent(postAdded.content, postAdded.timestamp); } else { return state; } }) .matchEvent(BodyChanged.class, (state, bodyChanged) -> { if (bodyChanged.timestamp.isAfter(state.contentTimestamp)) { return state.withContent(bodyChanged.content, bodyChanged.timestamp); } else { return state; } }) .matchEvent(Published.class, (state, publish) -> state.publish()) .matchAny((state, otherEvent) -> state); }
- 31. override def eventTrigger( ctx: EventTriggerContext, state: State, event: Event): Effect[Event, State] = { event match { case StepStarted(nr) => authority ! RequestApproval(nr) ctx.actorContext.timers.startPeriodicTimer(ResendTick, ResendTick, resendInterval) Effect.none case StepApproved(_, _) => if (!state.denied && selfDc == "DC-A" && state.isCurrentStepApproved && state.currentStep < maxSteps) { // approved by all, continue with next step log.info("Step {} approved by all, continue", state.currentStep) Effect.persist(StepStarted(state.currentStep + 1)) } else Effect.none case _ => Effect.none } }
- 32. @Override public Effect<Event, State> eventTrigger(EventTriggerContext ctx, State state, Event event) { if (event instanceof StepStarted) { StepStarted stepStarted = (StepStarted) event; authority.tell(new RequestApproval(stepStarted.stepNr), ctx.actorContext().getSelf()); ctx.actorContext().getTimers().startPeriodicTimer(ResendTick.INSTANCE, ResendTick.INSTANCE, resendInterval); return Effect().none(); } else if (event instanceof StepApproved) { StepApproved stepApproved = (StepApproved) event; if (!state.denied && getSelfDc().equals("DC-A") && state.isCurrentStepApproved() && state.currentStep < maxSteps) { // approved by all, continue with next step log().info("Step {} approved by all, continue", state.currentStep); return Effect().persist(new StepStarted(state.currentStep + 1)); } else return Effect().none(); } else { return Effect().none(); } }
- 33. Akka Multi-Data Center Clustering In summary
- 34. Want to learn more about Akka Multi Data Center? Cluster across multiple data centers - http://bit.ly/2iY8qLO Multi-DC Persistence (Akka Commercial Addons) - http://bit.ly/2zSN9GC
- 35. Get your team hooked on Akka with this comprehensive introduction by Hugh McKee: “Akka Revealed” GO TO VIDEO & SLIDES Next Steps - Introduce Your Team To Akka
- 36. Learn why Akka is so ideal for distributed systems with a free copy of Hugh McKee’s O’Reilly eBook: Designing Reactive Systems: The Role of Actors in Distributed Architecture GET A COPY Next Steps - Learn The “Why” Of Akka Actors
- 37. Are you a serious enterprise looking to run Akka and other Lightbend technologies in production? Let us know when it’s time for a chat! CONTACT US Next Steps - Enterprise Add-Ons & Support