=act #3623 unsubscribe when actors terminate, instead of isTerminated
* Moved to removing actors proactively when they are terminated instead of checking `isTerminated` during publish. * Subscribers which have registered before initializing the unsubscriber will be aggregated in a Seq until one is registered and then it will take responsibility of unregistering them on termination. * Initialization of the unsubscriber can only be run once - attempting to initialize the event stream with another unsubscriber will fail, and init will return false. * Assumed having an init (mutable) method on the `EventBus` is fine, as it has such methods already and @patriknw's comment in the task for this. * since we must check if the subscriber has any subscribed channels left we had to expose this detail from SubchannelClassification via `hasSubscriptions`. Increases cost of ubsubscribe(actor, channel) a bit. * Evacuated the expensive `hasSubscription` call out of eventstream's `unsubscribe` call, and instead making the Unsubscriber check this before it stops watching an actor. If in the mean time the same actor got subscribed, there will be a new Subscribe message emited - so we're good on that side. Also, if it would terminate before the unsubscriber gets the Register message it will call `watch(actor)` on a dead actor, which results in getting Terminated for it, thus we'll stop watching it from the Unsubscriber as expected. Final squash and small cleanup. Please review again;
This commit is contained in:
Konrad Malawski
Konrad Malawski
parent
5982aab066
commit
f57470926e
5 changed files with 257 additions and 5 deletions
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@ -6,7 +6,7 @@ package akka.event
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import language.postfixOps
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import scala.concurrent.duration._
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import akka.actor.{ Actor, ActorRef, ActorSystemImpl, ActorSystem, Props, UnhandledMessage }
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import akka.actor._
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import com.typesafe.config.ConfigFactory
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import scala.collection.JavaConverters._
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import akka.event.Logging.InitializeLogger
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@ -28,11 +28,15 @@ object EventStreamSpec {
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akka {
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actor.serialize-messages = off
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stdout-loglevel = WARNING
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loglevel = DEBUG
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loglevel = WARNING
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actor.debug.unhandled = on
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}
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""")
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val configUnhandledWithDebug =
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ConfigFactory.parseString("akka.actor.debug.event-stream = on")
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.withFallback(configUnhandled)
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final case class M(i: Int)
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final case class SetTarget(ref: ActorRef)
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@ -274,6 +278,130 @@ class EventStreamSpec extends AkkaSpec(EventStreamSpec.config) {
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es.unsubscribe(a1.ref, classOf[AT]) should be(true)
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es.unsubscribe(a2.ref, classOf[BTT]) should be(true)
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}
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"unsubscribe an actor on its termination" in {
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val sys = ActorSystem("EventStreamSpecUnsubscribeOnTerminated", configUnhandledWithDebug)
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try {
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val es = sys.eventStream
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val a1, a2 = TestProbe()
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val tm = new A
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val target = sys.actorOf(Props(new Actor {
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def receive = { case in ⇒ a1.ref forward in }
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}), "to-be-killed")
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es.subscribe(a2.ref, classOf[Any])
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es.subscribe(target, classOf[A]) should be(true)
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es.subscribe(target, classOf[A]) should be(false)
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target ! PoisonPill
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fishForDebugMessage(a2, s"unsubscribing $target from all channels")
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fishForDebugMessage(a2, s"unwatching $target")
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es.publish(tm)
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a1.expectNoMsg(1 second)
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a2.expectMsg(tm)
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} finally {
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sys.shutdown()
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}
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}
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"unsubscribe the actor, when it subscribes already in terminated state" in {
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val sys = ActorSystem("EventStreamSpecUnsubscribeTerminated", configUnhandledWithDebug)
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try {
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val es = sys.eventStream
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val a1, a2 = TestProbe()
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val target = system.actorOf(Props(new Actor {
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def receive = { case in ⇒ a1.ref forward in }
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}), "to-be-killed")
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watch(target)
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target ! PoisonPill
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expectTerminated(target)
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es.subscribe(a2.ref, classOf[Any])
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// target1 is Terminated; When subscribing, it will be unsubscribed by the Unsubscriber right away
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es.subscribe(target, classOf[A]) should be(true)
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fishForDebugMessage(a2, s"unsubscribing $target from all channels")
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es.subscribe(target, classOf[A]) should be(true)
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fishForDebugMessage(a2, s"unsubscribing $target from all channels")
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} finally {
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sys.shutdown()
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}
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}
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"not allow initializing a TerminatedUnsubscriber twice" in {
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val sys = ActorSystem("MustNotAllowDoubleInitOfTerminatedUnsubscriber", config)
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// initializes an TerminatedUnsubscriber during start
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try {
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val es = sys.eventStream
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val p = TestProbe()
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val refWillBeUsedAsUnsubscriber = es.initUnsubscriber(p.ref)
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refWillBeUsedAsUnsubscriber should equal(false)
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} finally {
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sys.shutdown()
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}
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}
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"unwatch an actor from unsubscriber when that actor unsubscribes from the stream" in {
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val sys = ActorSystem("MustUnregisterDuringUnsubscribe", configUnhandledWithDebug)
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try {
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val es = sys.eventStream
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val a1, a2 = TestProbe()
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es.subscribe(a1.ref, classOf[Logging.Debug])
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es.subscribe(a2.ref, classOf[A])
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fishForDebugMessage(a1, s"watching ${a2.ref}")
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es.unsubscribe(a2.ref)
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fishForDebugMessage(a1, s"unwatching ${a2.ref}")
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} finally {
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sys.shutdown()
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}
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}
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"unwatch an actor from unsubscriber when that actor unsubscribes from channels it subscribed" in {
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val sys = ActorSystem("MustUnregisterWhenNoMoreChannelSubscriptions", configUnhandledWithDebug)
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try {
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val es = sys.eventStream
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val a1, a2 = TestProbe()
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es.subscribe(a1.ref, classOf[Logging.Debug])
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es.subscribe(a2.ref, classOf[A])
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es.subscribe(a2.ref, classOf[T])
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fishForDebugMessage(a1, s"watching ${a2.ref}")
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es.unsubscribe(a2.ref, classOf[A]) should equal(true)
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fishForDebugMessage(a1, s"unsubscribing ${a2.ref} from channel class akka.event.EventStreamSpec$$A")
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a1.expectNoMsg(1 second)
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es.unsubscribe(a2.ref, classOf[T]) should equal(true)
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fishForDebugMessage(a1, s"unsubscribing ${a2.ref} from channel interface akka.event.EventStreamSpec$$T")
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fishForDebugMessage(a1, s"unwatching ${a2.ref}, since has no subscriptions")
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a1.expectNoMsg(1 second)
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es.unsubscribe(a2.ref, classOf[T]) should equal(false)
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} finally {
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sys.shutdown()
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}
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}
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}
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private def verifyLevel(bus: LoggingBus, level: Logging.LogLevel) {
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@ -284,4 +412,11 @@ class EventStreamSpec extends AkkaSpec(EventStreamSpec.config) {
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msg foreach (expectMsg(_))
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}
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private def fishForDebugMessage(a: TestProbe, messagePrefix: String) {
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a.fishForMessage(3 seconds, hint = "expected debug message prefix: " + messagePrefix) {
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case Logging.Debug(_, _, msg: String) if msg startsWith messagePrefix ⇒ true
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case other ⇒ false
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}
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}
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}
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@ -618,6 +618,7 @@ private[akka] class ActorSystemImpl(val name: String, applicationConfig: Config,
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provider.init(this)
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if (settings.LogDeadLetters > 0)
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logDeadLetterListener = Some(systemActorOf(Props[DeadLetterListener], "deadLetterListener"))
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startEventStreamUnsubscriber(eventStream)
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registerOnTermination(stopScheduler())
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loadExtensions()
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if (LogConfigOnStart) logConfiguration()
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@ -662,6 +663,10 @@ private[akka] class ActorSystemImpl(val name: String, applicationConfig: Config,
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shutdown()
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}
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def startEventStreamUnsubscriber(eventStream: EventStream) {
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systemActorOf(Props(classOf[EventStreamUnsubscriber], eventStream, DebugEventStream), "eventStreamUnsubscriber")
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}
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//#create-scheduler
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/**
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* Create the scheduler service. This one needs one special behavior: if
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@ -175,6 +175,13 @@ trait SubchannelClassification { this: EventBus ⇒
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recv foreach (publish(event, _))
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}
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/**
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* INTERNAL API
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* Expensive call! Avoid calling directly from event bus subscribe / unsubscribe.
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*/
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private[akka] def hasSubscriptions(subscriber: Subscriber): Boolean =
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cache.values exists { _ contains subscriber }
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private def removeFromCache(changes: immutable.Seq[(Classifier, Set[Subscriber])]): Unit =
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cache = (cache /: changes) {
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case (m, (c, cs)) ⇒ m.updated(c, m.getOrElse(c, Set.empty[Subscriber]) -- cs)
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@ -184,6 +191,7 @@ trait SubchannelClassification { this: EventBus ⇒
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cache = (cache /: changes) {
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case (m, (c, cs)) ⇒ m.updated(c, m.getOrElse(c, Set.empty[Subscriber]) ++ cs)
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}
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}
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/**
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@ -5,9 +5,11 @@ package akka.event
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import language.implicitConversions
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import akka.actor.{ ActorRef, ActorSystem }
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import akka.actor._
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import akka.event.Logging.simpleName
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import akka.util.Subclassification
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import java.util.concurrent.atomic.AtomicReference
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import scala.annotation.tailrec
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object EventStream {
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//Why is this here and why isn't there a failing test if it is removed?
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@ -28,6 +30,9 @@ class EventStream(private val debug: Boolean = false) extends LoggingBus with Su
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type Event = AnyRef
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type Classifier = Class[_]
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/** Either the list of subscribed actors, or a ref to an [[akka.event.EventStreamUnsubscriber]] */
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private val initiallySubscribedOrUnsubscriber = new AtomicReference[Either[Set[ActorRef], ActorRef]](Left(Set.empty))
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protected implicit val subclassification = new Subclassification[Class[_]] {
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def isEqual(x: Class[_], y: Class[_]) = x == y
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def isSubclass(x: Class[_], y: Class[_]) = y isAssignableFrom x
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@ -36,13 +41,13 @@ class EventStream(private val debug: Boolean = false) extends LoggingBus with Su
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protected def classify(event: AnyRef): Class[_] = event.getClass
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protected def publish(event: AnyRef, subscriber: ActorRef) = {
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if (subscriber.isTerminated) unsubscribe(subscriber)
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else subscriber ! event
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subscriber ! event
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}
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override def subscribe(subscriber: ActorRef, channel: Class[_]): Boolean = {
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if (subscriber eq null) throw new IllegalArgumentException("subscriber is null")
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if (debug) publish(Logging.Debug(simpleName(this), this.getClass, "subscribing " + subscriber + " to channel " + channel))
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registerWithUnsubscriber(subscriber)
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super.subscribe(subscriber, channel)
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}
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@ -50,6 +55,7 @@ class EventStream(private val debug: Boolean = false) extends LoggingBus with Su
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if (subscriber eq null) throw new IllegalArgumentException("subscriber is null")
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val ret = super.unsubscribe(subscriber, channel)
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if (debug) publish(Logging.Debug(simpleName(this), this.getClass, "unsubscribing " + subscriber + " from channel " + channel))
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unregisterIfNoMoreSubscribedChannels(subscriber)
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ret
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}
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@ -57,6 +63,61 @@ class EventStream(private val debug: Boolean = false) extends LoggingBus with Su
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if (subscriber eq null) throw new IllegalArgumentException("subscriber is null")
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super.unsubscribe(subscriber)
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if (debug) publish(Logging.Debug(simpleName(this), this.getClass, "unsubscribing " + subscriber + " from all channels"))
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unregisterIfNoMoreSubscribedChannels(subscriber)
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}
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/**
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* INTERNAL API
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*/
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private[akka] def initUnsubscriber(unsubscriber: ActorRef): Boolean = {
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initiallySubscribedOrUnsubscriber.get match {
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case value @ Left(subscribers) ⇒
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if (initiallySubscribedOrUnsubscriber.compareAndSet(value, Right(unsubscriber))) {
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if (debug) publish(Logging.Debug(simpleName(this), this.getClass, "initialized unsubscriber to: " + unsubscriber + ", registering " + subscribers.size + " initial subscribers with it"))
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subscribers foreach registerWithUnsubscriber
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true
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} else {
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// recurse, because either new subscribers have been registered since `get` (retry Left case),
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// or another thread has succeeded in setting it's unsubscriber (end on Right case)
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initUnsubscriber(unsubscriber)
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}
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case Right(presentUnsubscriber) ⇒
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if (debug) publish(Logging.Debug(simpleName(this), this.getClass, s"not using unsubscriber $unsubscriber, because already initialized with $presentUnsubscriber"))
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false
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}
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}
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/**
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* INTERNAL API
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*/
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private[akka] def registerWithUnsubscriber(subscriber: ActorRef): Unit = {
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initiallySubscribedOrUnsubscriber.get match {
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case value @ Left(subscribers) ⇒
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if (!initiallySubscribedOrUnsubscriber.compareAndSet(value, Left(subscribers + subscriber)))
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registerWithUnsubscriber(subscriber)
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case Right(unsubscriber) ⇒
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unsubscriber ! EventStreamUnsubscriber.Register(subscriber)
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}
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}
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/**
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* INTERNAL API
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*
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* The actual check if the subscriber still has subscriptions is performed by the `EventStreamUnsubscriber`,
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* because it's an expensive operation, and we don want to block client-code for that long, the Actor will eventually
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* catch up and perform the apropriate operation.
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*/
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private[akka] def unregisterIfNoMoreSubscribedChannels(subscriber: ActorRef): Unit = {
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initiallySubscribedOrUnsubscriber.get match {
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case value @ Left(subscribers) ⇒
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if (!initiallySubscribedOrUnsubscriber.compareAndSet(value, Left(subscribers - subscriber)))
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unregisterIfNoMoreSubscribedChannels(subscriber)
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case Right(unsubscriber) ⇒
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unsubscriber ! EventStreamUnsubscriber.UnregisterIfNoMoreSubscribedChannels(subscriber)
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}
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}
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}
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@ -0,0 +1,43 @@
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/**
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* Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
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*/
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package akka.event
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import akka.actor._
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import akka.event.Logging.simpleName
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/**
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* Watches all actors which subscribe on the given event stream, and unsubscribes them from it when they are Terminated.
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*/
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class EventStreamUnsubscriber(eventStream: EventStream, debug: Boolean = false) extends Actor with ActorLogging {
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import EventStreamUnsubscriber._
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override def preStart() {
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if (debug) eventStream.publish(Logging.Debug(simpleName(getClass), getClass, s"registering unsubscriber with $eventStream"))
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eventStream initUnsubscriber self
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}
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def receive = {
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case Register(actor) ⇒
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if (debug) eventStream.publish(Logging.Debug(simpleName(getClass), getClass, s"watching $actor in order to unsubscribe from EventStream when it terminates"))
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context watch actor
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case UnregisterIfNoMoreSubscribedChannels(actor) if eventStream.hasSubscriptions(actor) ⇒
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// do nothing
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// hasSubscriptions can be slow, but it's better for this actor to take the hit than the EventStream
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case UnregisterIfNoMoreSubscribedChannels(actor) ⇒
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if (debug) eventStream.publish(Logging.Debug(simpleName(getClass), getClass, s"unwatching $actor, since has no subscriptions"))
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context unwatch actor
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case Terminated(actor) ⇒
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if (debug) eventStream.publish(Logging.Debug(simpleName(getClass), getClass, s"unsubscribe $actor from $eventStream, because it was terminated"))
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eventStream unsubscribe actor
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}
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}
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object EventStreamUnsubscriber {
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final case class Register(actor: ActorRef)
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final case class UnregisterIfNoMoreSubscribedChannels(actor: ActorRef)
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}
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