81 lines
2.2 KiB
Scala
81 lines
2.2 KiB
Scala
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/**
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* Copyright (C) 2009-2017 Lightbend Inc. <http://www.lightbend.com>
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*/
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package docs.actor
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class SharedMutableStateDocSpec {
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//#mutable-state
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import akka.actor.{ Actor, ActorRef }
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import akka.pattern.ask
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import akka.util.Timeout
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import scala.concurrent.Future
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import scala.concurrent.duration._
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import scala.language.postfixOps
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import scala.collection.mutable
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case class Message(msg: String)
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class EchoActor extends Actor {
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def receive = {
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case msg => sender() ! msg
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}
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}
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class CleanUpActor extends Actor {
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def receive = {
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case set: mutable.Set[_] => set.clear()
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}
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}
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class MyActor(echoActor: ActorRef, cleanUpActor: ActorRef) extends Actor {
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var state = ""
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val mySet = mutable.Set[String]()
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def expensiveCalculation(actorRef: ActorRef): String = {
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// this is a very costly operation
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"Meaning of live is 42"
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}
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def expensiveCalculation(): String = {
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// this is a very costly operation
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"Meaning of live is 42"
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}
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def receive = {
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case _ =>
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//Wrong ways
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implicit val ec = context.dispatcher
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implicit val timeout = Timeout(5 seconds) // needed for `?` below
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// Very bad, shared mutable state,
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// will break your application in weird ways
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Future { state = "This will race" }
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((echoActor ? Message("With this other one")).mapTo[Message])
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.foreach { received => state = received.msg }
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// Very bad, shared mutable object,
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// the other actor cand mutate your own state,
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// or worse, you might get weird race conditions
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cleanUpActor ! mySet
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// Very bad, "sender" changes for every message,
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// shared mutable state bug
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Future { expensiveCalculation(sender()) }
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//Right ways
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// Completely safe, "self" is OK to close over
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// and it's an ActorRef, which is thread-safe
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Future { expensiveCalculation() } foreach { self ! _ }
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// Completely safe, we close over a fixed value
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// and it's an ActorRef, which is thread-safe
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val currentSender = sender()
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Future { expensiveCalculation(currentSender) }
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}
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}
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//#mutable-state
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}
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