Concurrent and Distributed Applications with Akka, Java and Scala
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The document discusses concurrency and distribution in applications using Akka, Java and Scala. It covers key concepts like actors, messages and message passing in Akka. It describes how actors encapsulate state and behavior, communicate asynchronously via message passing and provide built-in concurrency without shared state or locks. The document also discusses patterns for building distributed, fault tolerant and scalable applications using Akka actors deployed locally or remotely.
![Hello World Actor
Define
class HelloWorld extends Actor {
def receive = {
case msg =>
printf(“Received %sn”, msg)
}
}
Create
val system = ActorSystem(“MySystem”)
val hello = system.actorOf(Props[HelloWorld], “hello”)
Send Message
hello ! “World”](https://image.slidesharecdn.com/akkaapps-140916002149-phpapp01/85/Concurrent-and-Distributed-Applications-with-Akka-Java-and-Scala-59-320.jpg)
![Routing
Round Robin Router
val actor = system.actorOf(
Props[MyActor].withRouter(RoundRobinRouter(4)),
name = “myrouter”
)
Using actor with routers (no changes)
!
actor ! Message](https://image.slidesharecdn.com/akkaapps-140916002149-phpapp01/85/Concurrent-and-Distributed-Applications-with-Akka-Java-and-Scala-98-320.jpg)
![Routing Configuration
Configuration overrides code
akka.actor.deployment {
/myrouter {
router = round-robin
nr-of-instances = 8
}
}
Routers from Config
val actor = system.actorOf(
Props[MyActor].withRouter(FromConfig()),
name = “myrouter”
)](https://image.slidesharecdn.com/akkaapps-140916002149-phpapp01/85/Concurrent-and-Distributed-Applications-with-Akka-Java-and-Scala-100-320.jpg)
![Remote Deployment
Code without changes
val actor = system.actorOf(
Props[MyActor],
name = “myactor”
)
Configuration
!
akka.actor.deployment {
/myactor {
remote = “akka://sys@server:2553”
}
}](https://image.slidesharecdn.com/akkaapps-140916002149-phpapp01/85/Concurrent-and-Distributed-Applications-with-Akka-Java-and-Scala-102-320.jpg)
![Remote Deployment (routers)
akka.actor.deployment {
/myrouter {
router = round-robin
nr-of-instances = 8
!
target {
nodes = [“akka://sys@server1:2552”
“akka://sys@server2:2552”]
}
}
}
Routers from Config
val actor = system.actorOf(
Props[MyActor].withRouter(FromConfig()),
name = “myrouter”
)](https://image.slidesharecdn.com/akkaapps-140916002149-phpapp01/85/Concurrent-and-Distributed-Applications-with-Akka-Java-and-Scala-103-320.jpg)
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Concurrent and Distributed Applications with Akka, Java and Scala
- 1. Concurrent and Distributed Applications with Akka, Java and Scala ! Buenos Aires, Argentina, Oct 2012 ! @frodriguez
- 2. Moore’s law Moore's law says that every 18 months, the number of transistors that can fit within a given area on a chip doubles.
- 3. Moore’s law Moore's law says that every 18 months, the number of transistors that can fit within a given area on a chip doubles. Page's law says that every 18 months software becomes twice as slow
- 4. Modern CPUs intel ® Xeon ® processor
- 5. Modern CPUs intel ® Xeon ® processor Small improvements in execution speed
- 6. intel ® Xeon ® processor Small improvements in execution speed but... Modern CPUs
- 7. Modern CPUs Core Core Core Core Cor Core Core Core Core Core Core Core Core Core Core Core Small improvements in execution speed but... Improved parallelism support Multicore processors
- 8. Alternative Moore’s & Page’s laws Every 18 months, the number of cores per chip doubles.
- 9. Alternative Moore’s & Page’s laws Every 18 months, the number of cores per chip doubles. Every 18 months the number of IDLE cores doubles
- 11. Modern Applications Demands... Scalability
- 12. Modern Applications Demands... Scalability Vertical (scaling up) - Concurrency Horizontal (scaling out) - Distribution
- 13. Modern Applications Demands... Scalability Vertical (scaling up) - Concurrency Horizontal (scaling out) - Distribution Size (Resources, Users, ...) Geographically Admin / Management
- 15. Modern Applications Demands... High Availability Fault Tolerance (local & distributed)
- 16. Modern Applications Demands... High Availability Fault Tolerance (local & distributed) Performance & Low Latency Efficient Use of Resources (CPU & Memory) Asynchronous (reduced latency) Distributed (cheap machines, better performance / $)
- 17. How to Write Concurrent Applications for Multicore Processors ?
- 18. Traditional Approach Threads (pools processing tasks) Shared (and mutable) State Synchronization and Locking Concurrent Collections
- 20. Traditional Threads ? process(...){ }
- 21. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results }
- 22. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results }
- 23. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Blocked Updating State in the Heap Returning Results } Thread Suspended
- 24. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results }
- 25. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results }
- 26. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results } Add concurrency...
- 27. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results }
- 28. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results Requires Synchronization can be blocked Requires Synchronization can be blocked }
- 29. Traditional Threads ? process(...){ Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results Requires Synchronization can be blocked Requires Synchronization can be blocked } Bad for CPU caches
- 30. Traditional Threads ? How many threads ? Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results
- 31. Traditional Threads ? How many threads ? Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results
- 32. Traditional Threads ? How many threads ? Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results Improves with threads (Assuming blocking, non-async I/O is used...)
- 33. Traditional Threads ? How many threads ? Computing Reading State from Heap I/O (e.g: Disk, Network, DBs) Processing Results Updating State in the Heap Returning Results Degrades with more threads than cores Context Switching, Contention, L1 & L2 Caches
- 34. What About Latency ? Client Biz DB Fetching and Mapping N Items Latency (time to first item) Thread by task (instead of by layer). Sync Results
- 35. What About Latency ? Client Biz DB Fetching and Mapping N Items Latency (time to first item) Parallelism by Layer - Asynchronous and Partial Results From Request/Response to Request Stream/Response Stream
- 36. How to Write Distributed Applications ?
- 37. Traditional Approach RPC (WS, RMI, ...) Queues (JMS, AMQP, STOMP, etc), Raw Sockets
- 38. Traditional Approach RPC (WS, RMI, ...) Queues (JMS, AMQP, STOMP, etc), Raw Sockets Local != Remote Local should be an optimization, not a forced early decision...
- 39. Akka “Akka is a toolkit and runtime for building highly concurrent, distributed, and fault tolerant event-driven applications on the JVM. ” Based on the actor model
- 40. What is an Actor ? Actors are objects which encapsulate state and behavior Communicate exclusively by exchanging messages Conceptually have their own light-weight thread No Need for Synchronization
- 41. Actors Actor State Behavior
- 42. Actors Actor State Behavior Mailbox
- 43. Actors Actor State Behavior C B A Mailbox
- 44. Actors Actor State Behavior C B A Mailbox
- 45. Actors Actor State Behavior C B A Mailbox
- 46. Actors Actor State BehaAvior C B Mailbox
- 47. Actors Actor State Behavior C B Mailbox
- 48. Actors Actor State Behavior C B Mailbox
- 49. Actors Actor State Behavior C B Millions of Actors Mailbox One per Actor
- 50. Actors Actor State Behavior Number of Threads Proportional to number of Cores C B Millions of Actors Mailbox One per Actor
- 51. Actors: Processing Messages /myactor State Behavior A
- 52. Actors: Processing Messages /myactor State BehaAvior
- 53. Actors: Processing Messages /myactor New State State Behavior Change State
- 54. Actors: Processing Messages /myactor State NBeewh Baevhaioviorr Change State Change Behavior
- 55. Actors: Processing Messages /myactor State Behavior /someactor State B Behavior Change State Change Behavior Send a Message
- 56. Actors: Processing Messages /myactor State Behavior /someactor State Behavior B Change State Change Behavior Send a Message
- 57. Actors: Processing Messages /myactor State Behavior /someactor State BehaBvior Change State Change Behavior Send a Message
- 58. Actors: Processing Messages /myactor State Behavior /someactor State Behavior /myactor/child State Behavior Change State Change Behavior Send a Message Create Actors
- 59. Hello World Actor Define class HelloWorld extends Actor { def receive = { case msg => printf(“Received %sn”, msg) } } Create val system = ActorSystem(“MySystem”) val hello = system.actorOf(Props[HelloWorld], “hello”) Send Message hello ! “World”
- 60. Counter Actor Define class Counter extends Actor { var total = 0 ! def receive = { case Count(value) => total += value case GetStats => sender ! Stats(total) } } Protocol case class Count(n: Int) case class Stats(total: Int) case object GetStats
- 61. Sending a Message /actorB State Behavior /actorA State Behavior
- 62. Sending a Message /actorB State Behavior /actorA State Behavior actorB ! A
- 63. Sending a Message /actorB State Behavior /actorA State BehAavior actorB ! A
- 64. Sending a Message /actorB State Behavior /actorA State Behavior A actorB ! A
- 65. Sending a Message /actorB State Behavior /actorA State Behavior A actorB ! A
- 66. Sending a Message /actorB State Behavior /actorA State Behavior A actorB ! A sender ! B
- 67. Sending a Message /actorB State Behavior /actorA State Behavior B actorB ! A sender ! B
- 68. Sending a Message /actorB State Behavior /actorA State Behavior actorB ! A sender ! B B
- 69. Sending a Message /actorB State Behavior /actorA State Behavior B actorB ! A sender ! B
- 70. Sending a Message /actorB State Behavior /actorA State Behavior actorB ! A sender ! B
- 71. Sending a Message /actorB State Behavior /actorA State Behavior actorB ! A actorB tell A sender ! B sender tell B
- 72. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior
- 73. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB tell (A, actorC)
- 74. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State BehAavior actorB tell (A, actorC)
- 75. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior A actorB tell (A, actorC)
- 76. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior A actorB tell (A, actorC)
- 77. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior A actorB tell (A, actorC) sender ! B
- 78. Sending a Message /actorB State Behavior B /actorC State Behavior /actorA State Behavior actorB tell (A, actorC) sender ! B
- 79. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB tell (A, actorC) sender ! B B
- 80. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB tell (A, actorC) sender ! B B
- 81. Sending a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB tell (A, actorC) sender ! B
- 82. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior
- 83. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A
- 84. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State BehAavior actorB ! A
- 85. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior A actorB ! A
- 86. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior A actorB ! A
- 87. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior A actorB ! A actorC forward B
- 88. Forward a Message /actorB State Behavior B /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B
- 89. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B B
- 90. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B B
- 91. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B sender ! C B
- 92. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B sender ! C C
- 93. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B sender ! C C
- 94. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior C actorB ! A actorC forward B sender ! C
- 95. Forward a Message /actorB State Behavior /actorC State Behavior /actorA State Behavior actorB ! A actorC forward B sender ! C
- 96. Ask & Pipe Patterns Ask val response = actor ? Message ! response onSuccess { case Response(a) => printf(“Response %s”, a) } Pipe val response = actor ? Message ! response pipeTo actor2
- 97. Mailbox UnboundedMailbox (default) UnboundedPriorityMailbox BoundedMailbox (*) BoundedPriorityMailbox (*) * May produce deadlocks if used unproperly
- 98. Routing Round Robin Router val actor = system.actorOf( Props[MyActor].withRouter(RoundRobinRouter(4)), name = “myrouter” ) Using actor with routers (no changes) ! actor ! Message
- 99. Routing RoundRobinRouter RandomRouter SmallestMailboxRouter BroadcastRouter ScatterGatherFirstCompletedRouter
- 100. Routing Configuration Configuration overrides code akka.actor.deployment { /myrouter { router = round-robin nr-of-instances = 8 } } Routers from Config val actor = system.actorOf( Props[MyActor].withRouter(FromConfig()), name = “myrouter” )
- 101. Remoting Accessing remote actor val actor = system.actorFor( “akka://sys@server:2552/user/actor” ) Using remote actor (no changes) ! actor ! Message ! // Replies also work ok sender ! Response
- 102. Remote Deployment Code without changes val actor = system.actorOf( Props[MyActor], name = “myactor” ) Configuration ! akka.actor.deployment { /myactor { remote = “akka://sys@server:2553” } }
- 103. Remote Deployment (routers) akka.actor.deployment { /myrouter { router = round-robin nr-of-instances = 8 ! target { nodes = [“akka://sys@server1:2552” “akka://sys@server2:2552”] } } } Routers from Config val actor = system.actorOf( Props[MyActor].withRouter(FromConfig()), name = “myrouter” )
- 104. Fault Tolerance override val supervisorStrategy = OneForOneStrategy(...) { case _: ArithmeticException => Resume case _: NullPointerException => Restart case _: IllegalArgumentException => Stop case _: Exception => Escalate } Supervision Hierarchies across machines
- 105. Thanks @frodriguez frodriguez <at> gmail.com