![Remote actors
Creating 10 actors on 2 nodes with a router
akka
{
actor
{
deployment
{
/serviceA/aggregation
{
router
=
"round-‐robin"
nr-‐of-‐instances
=
10
target
{
nodes
=
["akka://app@10.0.0.2:2552",
"akka://app@10.0.0.3:2552"]
}
}
}
}
}
Looking up a remote actor
val
actor
=
context.actorFor("akka://actorSystemName@10.0.0.1:2552/user/actorName")](https://image.slidesharecdn.com/20120503bejugakka-120505143332-phpapp02/85/Akka-BeJUG-16-320.jpg)
Akka (BeJUG)
- 2. Akka Part of stack Written in Scala With officially supported Java API
- 3. Akka ‘s premise It’s too hard to write systems that are: Concurrent & Correct Highly scalable Fault-tolerant
- 4. Akka 2.0 Actors Software Transactional Memory Dataflow concurrency Futures
- 5. Akka who uses ? traffic management
- 6. Actors Inspired by : Asynchronous message passing Scale up, scale out Fault-tolerant (‘let it crash’)
- 7. Actors How to define an actor? ~400 bytes Local state Behavior mailbox
- 8. Actors How to define an actor? ~400 bytes Create more actors Send messages Modify state Local state Modify behavior Behavior mailbox
- 9. Actors How to define an actor? class MyFirstActor extends Actor { var total = 0 def receive = { case MyMessage(payload) => println(“Received: “ + payload”) case countMessage: Int => total += countMessage case _ => println("Unknown message") } }
- 10. Actors Dispatcher: contains executor strategy Local state Event-driven Behavior mailbox
- 11. Actors and Fork/Join Ping/pong messages (no processing) Improved 48 JSR-166 build ( ?) cores
- 12. Demo NearestCityActor NearestCityActor NearestCityActor NearestCityActor RoundRobin Result Router ListenerActor Messages with cities Print results
- 13. Supervision Hierarchical supervision Child actors supervised by parent Trap exceptions and apply recovery Error Kernel pattern Actor 1 create child actor Actor 2 dangerous operation critical state supervise Distinguish scratch and critical state
- 14. Supervision class GuardianActor extends Actor { def supervisorStrategy = OneForOneStrategy({ case _:CompanyBankruptException => Stop case _:InvalidStateException => Restart case _:ServiceUnavailableException => Resume case _ => Escalate }, maxNrOfRetries = 3, 5.seconds) def receive = { ... } } Actor may implement preRestart & postRestart
- 15. Remote actors Dispatchers for scale-up, remote actors for scala-out Machine A Machine B actor2 ! SomeMsg Actor 1 Actor 2 Netty, Protobuf Router Actor 3 Actor creation Supervision Remote deploy through config (no code change)
- 16. Remote actors Creating 10 actors on 2 nodes with a router akka { actor { deployment { /serviceA/aggregation { router = "round-‐robin" nr-‐of-‐instances = 10 target { nodes = ["akka://app@10.0.0.2:2552", "akka://app@10.0.0.3:2552"] } } } } } Looking up a remote actor val actor = context.actorFor("akka://actorSystemName@10.0.0.1:2552/user/actorName")
- 17. Blocking Actors lift some ForkJoin restrictions Remoting possible Recursive decomposition optional Fault-tolerant Still, there are restrictions similar to ForkJoin tasks No blocking IO No explicit locking No shared memory writes
- 18. Async IO Based on composable Futures Serve http mini akka-Spray Consume http async-http-client Persistence hammersmith
- 19. Async IO Based on Java NIO Akka IO Immutable abstractions on top of: Channels Streams (Iteratee based) Bridges (low-level) async IO and actors
- 20. Async IO Practical application: JMeter => 1 user, 1 thread Gatling => 1 user, 1 actor + blocking IO + async-http-client = OutOfMemory errors = or clustering necessary time drift in results
- 21. Async IO Practical application: JMeter => 1 user, 1 thread Gatling => 1 user, 1 actor + blocking IO + async-http-client = OutOfMemory errors = or clustering necessary time drift in results
- 22. Is that all? Finite State Machine Akka TestKit core Scheduler Event Bus modules
- 23. Is that all? Typesafe Console Commercial subscription
- 24. Questions? Code @ bit.ly/bejug-akka