Akka (BeJUG)

Akka (BeJUG)

• 1.
  Akka Actors @Sander_Mak
• 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 definean actor? ~400 bytes Local state Behavior mailbox
• 8.
  Actors How to definean actor? ~400 bytes Create more actors Send messages Modify state Local state Modify behavior Behavior mailbox
• 9.
  Actors How to definean 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 executorstrategy Local state Event-driven Behavior mailbox
• 11.
  Actors and Fork/Join Ping/pongmessages (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 Childactors 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 extendsActor { 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 forscale-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 10actors 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 someForkJoin 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 Basedon 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