Scaling Web Apps with Akka
29 likes5,482 views
This document summarizes a presentation about scaling web applications with Akka. It discusses how Akka uses an actor model of computation with message passing between lightweight processes to enable safe concurrency. Key features of Akka that help with scaling include fault tolerance through supervision, flexible dispatch strategies to leverage multiple cores, and support for NoSQL databases through pluggable storage backends. The presentation provides code examples of implementing actors in Akka and other frameworks and concludes by taking questions about Akka.
![Erlang Actors Example
-module(mypackage).
myErlangActor() ->
receive
{msgType, Msg} ->
io:format(" p n", [Msg]),
myErlangActor()
Other ->
io:format("wholy canoli, this is unmatched! n"),
myErlangActor()
end.
c(mypackage).
Pid = spawn(fun mypackage:myErlangActor/0).
Pid ! {msgType, "Erlang is for the discerning programmer"}.](https://image.slidesharecdn.com/akkalsugskillsmatter-100717164358-phpapp02/85/Scaling-Web-Apps-with-Akka-11-320.jpg)
![Akka Actors
import se.scalablesolutions.akka.actor.Actor
case class Message(msg: String)
class AnActor extends Actor {
def receive = {
case Message(m) => println(m)
case _ => println("unknown message")
}
}
class Director {
val myActor = Actor.actorOf[AnActor]
myActor.start
myActor ! Message("akkastic!")
}](https://image.slidesharecdn.com/akkalsugskillsmatter-100717164358-phpapp02/85/Scaling-Web-Apps-with-Akka-15-320.jpg)
spawnLinkRemote[MyActor](host, port)
startLinkRemote(myActor, host, port)](https://image.slidesharecdn.com/akkalsugskillsmatter-100717164358-phpapp02/85/Scaling-Web-Apps-with-Akka-17-320.jpg)
![Handle Failure Gracefully: Supervisor
val supervisor = Supervisor(
SupervisorConfig(
RestartStrategy(OneForOne, 3, 1000, List(classOf[Exception])),
Supervise(
actorOf[MyActor],
LifeCycle(Permanent)) ::
Nil))
supervisor.link(actorOf[MyActor])
class MyActor extends Actor {
self.lifeCycle = Some(LifeCycle(Permanent))
override def preRestart(reason: Throwable) {
// clean things up
}
}](https://image.slidesharecdn.com/akkalsugskillsmatter-100717164358-phpapp02/85/Scaling-Web-Apps-with-Akka-19-320.jpg)
Ad
More Related Content
What's hot (20)
Similar to Scaling Web Apps with Akka (20)
Ad
Recently uploaded (20)
Ad
Scaling Web Apps with Akka
- 1. Scaling Web Apps with Akka Maciej Matyjas London Scala User Group Skills Matter 2010 July 14
- 2. “ Simple Scalability, Fault-Tolerance, Concurrency & Remoting through Actors” akkasource.org
- 3. Scaling Web Apps with Akka Characteristics Techniques High Availability Hardware Quick Page Loads Load Balancing Fast Reads/Writes Caching Partitioning Queues/Messaging Replication CDN
- 4. Scaling Web Apps with Akka
- 5. Scaling Web Apps with Akka Range of mountains in Sweden Open Source Project Written in Scala with Scala/Java APIs
- 6. Scaling Web Apps with Akka Actors Model Multi-Core and Cloud Infrastructure Graceful Failure a la Erlang OTP Transactions a la Clojure NoSQL and Distributed Data Stores Flexible Dispatch Strategies
- 7. Actors Model of Computing Defined in 1963 by Carl Hewitt Used by Erlang to support reliability (99.9999999% uptime)
- 8. Actors Model of Computing "encapsulates state and behavior into a lightweight process/thread" - Jonas Bonér Asynchronous message passing between Actors Messages are immutable Synchronized mailbox Mailbox is read with pattern matching No shared state No locks Safe concurrency
- 9. No shared state + No locks = Safe concurrency
- 10. Actors Model Implementations Erlang Scala Thread based Scala Event based Lift Actors Akka
- 11. Erlang Actors Example -module(mypackage). myErlangActor() -> receive {msgType, Msg} -> io:format(" p n", [Msg]), myErlangActor() Other -> io:format("wholy canoli, this is unmatched! n"), myErlangActor() end. c(mypackage). Pid = spawn(fun mypackage:myErlangActor/0). Pid ! {msgType, "Erlang is for the discerning programmer"}.
- 12. Scala Thread Based Actors import scala.actor.Actor import scala.actor.Actor._ case class Message(msg: String) class AnActor extends Actor { def act() = receive { case Message(m) => println(m) case _ => println("unknown message") } } class Director { val myActor = new AnActor myActor.start myActor ! Message("threedz can haz block?") }
- 13. Scala Event Based Actors import scala.actor.Actor import scala.actor.Actor._ case class Message(msg: String) class AnActor extends Actor { def act() = loop { react { case Message(m) => println(m) case _ => println("unknown message") }}} class Director { val myActor = new AnActor myActor.start myActor ! Message("eventz iz lightweight?") }
- 14. Lift Actors case class Message(msg: String) class AnActor extends LiftActor { def messageHandler = { case Message(m) => println(m) case _ => println("unknown message") }} class Director { val myActor = new AnActor myActor ! Message("Lift Actors is lightest & rulz!") }
- 15. Akka Actors import se.scalablesolutions.akka.actor.Actor case class Message(msg: String) class AnActor extends Actor { def receive = { case Message(m) => println(m) case _ => println("unknown message") } } class Director { val myActor = Actor.actorOf[AnActor] myActor.start myActor ! Message("akkastic!") }
- 16. Leverage Multi-Core and Distributed Cloud Infrastructure Millions of lightweight actors on commodity hardware Safe Concurrency Remote Actors
- 17. Leverage Multi-Core and Distributed Cloud Infrastructure: Remote Actors import se.scalablesolutions.akka.remote.RemoteNode spawnRemote[MyActor](host, port) spawnLinkRemote[MyActor](host, port) startLinkRemote(myActor, host, port)
- 18. Handle Failure Gracefully "Let it Crash" Actor exceptions w/out supervision do not behave well Remote Actors w/out supervision are unmanaged Linking Actors Supervisor Manages linked Actors Notified when linked Actor crashes OneForOne AllForOne Works with Remote Actors
- 19. Handle Failure Gracefully: Supervisor val supervisor = Supervisor( SupervisorConfig( RestartStrategy(OneForOne, 3, 1000, List(classOf[Exception])), Supervise( actorOf[MyActor], LifeCycle(Permanent)) :: Nil)) supervisor.link(actorOf[MyActor]) class MyActor extends Actor { self.lifeCycle = Some(LifeCycle(Permanent)) override def preRestart(reason: Throwable) { // clean things up } }
- 20. Manage Transactions Software Transactional Memory (STM) Thanks Clojure! Addresses fundamental weakness of Actors Model Hello Shared State! Transactional but still no locks In memory Map, Vector, & Ref throw exceptions if modified outside of transaction ACI but no D Transactors Transactional Actors Actors + STM If Actor's writes clash, rollback memory and retried
- 21. Manage Transactions: Transactors import se.scalablesolutions.akka.actor.Transactor import se.scalablesolutions.akka.stm._ class MyActor extends Transactor { def receive = { case Increment(counter) => counter.swap(counter.get + 1) } } class Director { lazy val counter = Ref(0) //counter.swap(7) // blows up, cannot mutate outside transaction myActor ! Increment(counter) }
- 22. NoSQL & Distributed Data Stores Pluggable Storage Back Ends Cassandra Redis MongoDB Others... Brings the D in ACID Works with STM and Transactors
- 23. NoSQL & Distributed Data Stores: Casssandra import se.scalablesolutions.akka._ import stm.Transaction.Local._ import persistence.cassandra._ val map = CassandraStorage.newMap(myId) // map += "myKey" -> Value(someSuch) // exception atomic { map += "myKey" -> Value(someSuch) }
- 24. Flexible Dispatch Strategies Default is Single-threaded, Event-based dispatcher Work-stealing, Event-based Reactor-base, Event-driven Thread-based Event-based
- 25. Flexible Dispatch Strategies class MyActor extends Actor { self.dispatcher = Dispatchers. newExecutorBasedEventDrivenDispatche(name) dispatcher .withNewThreadPoolWithBoundedBlockingQueue(100) .setCorePoolSize(16) .setMaxPoolSize(128) .setKeepAliveTimeInMillis(60000) .setRejectionPolicy(new CallerRunsPolicy) .buildThreadPool }
- 26. Here Comes the Code Demo Time!
- 27. Versions Scala 2.8.0.RC6 Lift 2.0-scala2.8.0-SNAPSHOT Akka 2.8.0.RC3 0.9.1 sbt 0.7.4 ensime master on github.com
- 28. Alternatives Before Drinking the Kool-Aid or Flogging Your Fav Tool Other Actor Impls More Options scalaz JVM FunctionalJava Fork/Join GParallelizer ESB Kilim Netty ActorFoundry HawtDispatch Actors Guild Erlang Jetlang RabbitMQ Actorom Hadoop Fan Actors OpenMP MPI
- 29. Questions About Akka? http://akkasource.org http://groups.google.com/group/akka-user Course at Skills Matter Oct 13-14 LSUG talk on Oct 13 Ask me: @matyjas [email protected]