The document provides an overview of advanced Akka features, discussing aspects such as local and remote actors, scheduling, clustering, routing, and persistence within actor systems. It highlights Akka's benefits, including its concurrency, scalability, fault tolerance, and ease of integration with other systems. The presentation concludes with a note on Akka's versatility across different programming languages and a mention of its experimental features.

1. A Tour of (Advanced)
Akka Features in 40
Minutes
Johan Janssen, Info Support
@johanjanssen42

2. Content
▪ Why Akka?
▪ Local actor
▪ Remote actor
▪ Scheduling
▪ Cluster
▪ Routing
▪ Cluster singleton
▪ Sharding
▪ Persistence
▪ Akka HTTP
▪ Finite State Machines
▪ Conclusion
▪ Questions

3. Why Akka?

4. Why Akka?
▪ Concurrent
▪ Scalable
▪ Fault tolerant
▪ More natural programming experience when connecting to other
systems
▪ Easy to use?

6. Local actor

7. Local actor
Actor on
JVM 1

8. Local actor
Coordinator Actor
Hello
conference

9. Local actor
Coordinator Actor
println("Hello conference")

10. class Worker extends Actor {
def receive = {
case x =>
println(x)
}
}
val system = ActorSystem("ExampleActorSystem")
val workerActorRef = system.actorOf(Props[Worker])
workerActorRef ! "Hello conference"
Scala

11. Remote actor

12. Remote actor
Actor on
JVM 1
Actor on
JVM 2

13. val workerActorRef = system.actorOf(Props[Worker])
workerActorRef ! "Hello conference"
val workerActorRef =
context.actorSelection("akka.tcp://
ExampleActorSystem@127.0.0.1:9005
/user/workerActor")
workerActorRef ! "Hello conference"

14. akka {
actor {
provider =
"akka.remote.RemoteActorRefProvider"
}
remote {
enabled-transports =
["akka.remote.netty.tcp"]
netty.tcp {
hostname = "127.0.0.1"
port = 9002

15. Remote actor
Coordinator
actor
Worker
actor
StartMessage
Hello
conference

16. Remote actor
Coordinator
actor
Worker
actor
WorkerMessage
Greetings from the
coordinator:
Hello Conference

17. Remote actor
Coordinator
actor
Worker
actor
WorkerResponse
Message
Item processed
successfully

18. Scheduling

19. Scheduling
Actor
Scheduled once after 1 second
Tick
Scheduled every 5 seconds
Tock
system.scheduler.scheduleOnce(1 seconds, scheduleReceiveActor, Tick)
system.scheduler.schedule(0 seconds, 5 seconds, scheduleReceiveActor, Tock)

20. Scheduling
▪ Does not work for fixed point in time like 17:00
– Use Quartz

21. Cluster

22. Cluster
ActorSystem
on JVM 1
ActorSystem
on JVM 3
ActorSystem
on JVM 2
ActorSystem
on JVM 4

23. Seed nodes
▪ Contact points for automatically joining a cluster

24. akka {
cluster {
seed-nodes = [
"akka.tcp://ClusterNode@127.0.0.1:2551",
"akka.tcp://ClusterNode@127.0.0.1:2552"
]
}
}

25. Cluster Worker
Node
Port 2551
Association failed with [akka.tcp://ClusterSystem@127.0.0.1:2552

26. Cluster Worker
Node
Port 2551
Worker
Node
Port 2552
Member Up with IP: 127.0.0.1 and port: 2551
Member Up with IP: 127.0.0.1 and port: 2552
Member Up with IP: 127.0.0.1 and port: 2551
Member Up with IP: 127.0.0.1 and port: 2552

27. Cluster Worker
Node
Port 2551
Worker
Node
Port 2552
Member Up with IP: 127.0.0.1 and port: 2550
Member Up with IP: 127.0.0.1 and port: 2550
Coordinator
Node
Port 2550

28. Cluster Worker
Node
Port 2551
Worker
Node
Port 2552
Coordinator
Node
Port 2550
RegisterWorker
RegisterWorker

29. Cluster Worker
Node
Port 2551
Worker
Node
Port 2552
Coordinator
Node
Port 2550
Worker registered with IP: 127.0.0.1 and port: 2551
Worker registered with IP: 127.0.0.1 and port: 2552

30. Routing

31. Routing
Actor on
JVM 1
Actor on
JVM 3
Actor on
JVM 4
Actor on
JVM 2
Loadbalancer

32. akka {
actor {
provider = "akka.cluster.ClusterActorRefProvider"
deployment {
/coordinator/router {
router = round-robin-pool
nr-of-instances = 10
routees.paths = ["/user/emptystringactor"]
cluster {
enabled = on
allow-local-routees = off
}
}
}
}
}

33. Routing
Coordinator
Actor on
JVM 1
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2""

34. Routing
Coordinator
Actor on
JVM 1
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2""
HashMap[hostname, counter]

35. Routing
Coordinator
Actor on
JVM 1
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2
""

36. Routing
Coordinator
Actor on
JVM 1
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2
""

37. Cluster singleton

38. Cluster singleton
▪ Only one instance of the actor in the cluster
▪ (Re)created on the oldest node
▪ Can be used for instance for scheduling/caching

39. Cluster singleton
Actor on
JVM 1
Other
actors on
JVM 3
Other
actors on
JVM 4
Singleton
actor and
other actors
on JVM 2

40. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2""

41. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2""
HashMap[hostname, counter]

42. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2""

43. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2""
HashMap[hostname, counter]

44. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
EmptyString
Actor on
JVM 2
Crash

45. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
""

46. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
""
HashMap[hostname, counter]

47. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
""

48. Cluster singleton
Coordinator
EmptyString
Actor on
JVM 3
EmptyString
Actor on
JVM 4
""
HashMap[hostname, counter]

49. Sharding

50. Sharding
▪ Dividing a set of actors over a cluster
▪ Actors will be divided into groups called shards
▪ It will divide based on a logical identifier

51. Sharding
Actor on
JVM 1
odd
Shard on
JVM 3
even
Shard on
JVM 2
0, 2, 4, 6, 8
1, 3, 5, 7, 9

52. Persistence

53. Persistence
▪ Store actor information
▪ Recover after crash
▪ Possibility to take snapshots

54. Example without persistence
Actor
Cobol

55. Example without persistence
Actor
Cobol

56. Example without persistence
Cobol
Actor

57. Example without persistence
Actor
Java Cobol

58. Example without persistence
Cobol
Java
Actor
Crash
Restart

59. Example without persistence
Actor

60. Example without persistence
Actor
Scala

61. Example without persistence
Scala
Actor

62. Persistence
PersistentActor
Cobol
Command
Journal

63. Persistence
Journal
Cobol
Event
PersistentActor

64. Persistence
Journal
ACK
PersistentActor
Cobol
Event

65. Persistence
Cobol
Journal
Cobol
Event
PersistentActor

66. Persistence
Cobol
Journal
Cobol
Event
PersistentActor
Java
Event

67. Persistence
Cobol
Java
Journal
Cobol
Event
PersistentActor
Crash
Restart Java
Event

68. Persistence
Journal
Cobol
Event
PersistentActor
Java
Event

69. Persistence
Cobol
Java
Journal
Cobol
Event
PersistentActor
Java
Event
Scala

70. Persistence
Cobol
Java
Scala
Journal
Cobol
Event
PersistentActor
Java
Event

71. Snapshots
Journal
PersistentActor
Snapshot store
State until
Event C++
C++
Cobol

72. Snapshots
Journal
PersistentActor
Snapshot store
State until
Event C++
C++
Cobol

73. Snapshots
Journal
PersistentActor
Snapshot store
State until
Event C++ C++
Cobol

74. Snapshots
Journal
PersistentActor
Snapshot store
State until
Event C++
Java
C++
Cobol

75. Snapshots
Journal
PersistentActor
Snapshot store
State until
Event C++
Crash
Restart
C++
Cobol
Java

76. Snapshots
Journal
PersistentActor
Snapshot store
State until
Event C++ C++
Cobol
Java

77. Snapshots
Cobol
C++
Journal
PersistentActor
Snapshot store
State until
Event C++ C++
Cobol
Java

78. Snapshots
Cobol
C++
Java
Journal
PersistentActor
Snapshot store
State until
Event C++ C++
Cobol
Java

79. Snapshots
Cobol
C++
Java
Scala
Journal
PersistentActor
Snapshot store
State until
Event C++ C++
Cobol
Java

80. Akka HTTP

81. Akka HTTP
Actor on
JVM 1
Actor on
JVM 2

82. Finite State Machine

83. Finite State Machine
▪ State
▪ Event

84. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Progress, iteration
Progress, iteration
Progress, iteration
NoProgress
Progress, 2

85. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Work harder
Iteration: 0

86. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Good job!
Iteration: 0

87. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Wrong direction
Iteration: 0

88. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Use Akka
Iteration: 0

89. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Good job!
Iteration: 1

90. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Wrong direction
Iteration: 1

91. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project
Use Akka
Iteration: 1

92. Finite State Machines (FSM)
Inprogress
Project
Crappy
Project
New
Project Get another job!
Iteration: 2

93. Conclusion

94. Conclusion
▪ Akka can be used with Scala or Java
▪ There is even a .NET version of Akka
▪ Akka is really powerful
▪ Akka is quite easy to use
▪ Some features are still experimental

95. Questions
Johan Janssen @johanjanssen42
GitHub: https://github.com/johanjanssen/Akka-examples