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/*
* Copyright (C) 2009-2020 Lightbend Inc.
*/
package akka.actor
import java.io.{ NotSerializableException, ObjectOutputStream }
import java.util.concurrent.ThreadLocalRandom
import scala.annotation.{ switch, tailrec }
import scala.collection.immutable
import scala.concurrent.ExecutionContextExecutor
import scala.concurrent.duration.Duration
import scala.util.control.NonFatal
import com.github.ghik.silencer.silent
import akka.actor.dungeon.ChildrenContainer
import akka.annotation.{ InternalApi, InternalStableApi }
import akka.dispatch.{ Envelope, MessageDispatcher }
import akka.dispatch.sysmsg._
import akka.event.Logging.{ Debug, Error, LogEvent }
import akka.japi.Procedure
import akka.util.unused
/**
* The actor context - the view of the actor cell from the actor.
* Exposes contextual information for the actor and the current message.
*
* There are several possibilities for creating actors (see [[akka.actor.Props]]
* for details on `props`):
*
* {{{
* // Java or Scala
* context.actorOf(props, "name")
* context.actorOf(props)
*
* // Scala
* context.actorOf(Props[MyActor])
* context.actorOf(Props(classOf[MyActor], arg1, arg2), "name")
*
* // Java
* getContext().actorOf(Props.create(MyActor.class));
* getContext().actorOf(Props.create(MyActor.class, arg1, arg2), "name");
* }}}
*
* Where no name is given explicitly, one will be automatically generated.
*/
trait ActorContext extends ActorRefFactory with ClassicActorContextProvider {
/**
* The ActorRef representing this actor
*
* This method is thread-safe and can be called from other threads than the ordinary
* actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def self: ActorRef
/**
* Retrieve the Props which were used to create this actor.
*
* This method is thread-safe and can be called from other threads than the ordinary
* actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def props: Props
/**
* Gets the current receive timeout.
* When specified, the receive method should be able to handle a [[akka.actor.ReceiveTimeout]] message.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def receiveTimeout: Duration
/**
* Defines the inactivity timeout after which the sending of a [[akka.actor.ReceiveTimeout]] message is triggered.
* When specified, the receive function should be able to handle a [[akka.actor.ReceiveTimeout]] message.
* 1 millisecond is the minimum supported timeout.
*
* Please note that the receive timeout might fire and enqueue the `ReceiveTimeout` message right after
* another message was enqueued; hence it is '''not guaranteed''' that upon reception of the receive
* timeout there must have been an idle period beforehand as configured via this method.
*
* Once set, the receive timeout stays in effect (i.e. continues firing repeatedly after inactivity
* periods). Pass in `Duration.Undefined` to switch off this feature.
*
* Messages marked with [[NotInfluenceReceiveTimeout]] will not reset the timer. This can be useful when
* `ReceiveTimeout` should be fired by external inactivity but not influenced by internal activity,
* e.g. scheduled tick messages.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def setReceiveTimeout(timeout: Duration): Unit
/**
* Changes the Actor's behavior to become the new 'Receive' (PartialFunction[Any, Unit]) handler.
* Replaces the current behavior on the top of the behavior stack.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def become(behavior: Actor.Receive): Unit = become(behavior, discardOld = true)
/**
* Changes the Actor's behavior to become the new 'Receive' (PartialFunction[Any, Unit]) handler.
* This method acts upon the behavior stack as follows:
*
* - if `discardOld = true` it will replace the top element (i.e. the current behavior)
* - if `discardOld = false` it will keep the current behavior and push the given one atop
*
* The default of replacing the current behavior on the stack has been chosen to avoid memory
* leaks in case client code is written without consulting this documentation first (i.e.
* always pushing new behaviors and never issuing an `unbecome()`)
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def become(behavior: Actor.Receive, discardOld: Boolean): Unit
/**
* Reverts the Actor behavior to the previous one on the behavior stack.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def unbecome(): Unit
/**
* Returns the sender 'ActorRef' of the current message.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def sender(): ActorRef
/**
* Returns all supervised children; this method returns a view (i.e. a lazy
* collection) onto the internal collection of children. Targeted lookups
* should be using `child` instead for performance reasons:
*
* {{{
* val badLookup = context.children find (_.path.name == "kid")
* // should better be expressed as:
* val goodLookup = context.child("kid")
* }}}
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def children: immutable.Iterable[ActorRef]
/**
* Get the child with the given name if it exists.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def child(name: String): Option[ActorRef]
/**
* Returns the dispatcher (MessageDispatcher) that is used for this Actor.
* Importing this member will place an implicit ExecutionContext in scope.
*
* This method is thread-safe and can be called from other threads than the ordinary
* actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
implicit def dispatcher: ExecutionContextExecutor
/**
* The system that the actor belongs to.
* Importing this member will place an implicit ActorSystem in scope.
*
* This method is thread-safe and can be called from other threads than the ordinary
* actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
implicit def system: ActorSystem
/**
* Returns the supervising parent ActorRef.
*
* This method is thread-safe and can be called from other threads than the ordinary
* actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def parent: ActorRef
/**
* Registers this actor as a Monitor for the provided ActorRef.
* This actor will receive a Terminated(subject) message when watched
* actor is terminated.
*
* `watch` is idempotent if it is not mixed with `watchWith`.
*
* It will fail with an [[IllegalStateException]] if the same subject was watched before using `watchWith`.
* To clear the termination message, unwatch first.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*
* @return the provided ActorRef
*/
def watch(subject: ActorRef): ActorRef
/**
* Registers this actor as a Monitor for the provided ActorRef.
* This actor will receive the specified message when watched
* actor is terminated.
*
* `watchWith` is idempotent if it is called with the same `msg` and not mixed with `watch`.
*
* It will fail with an [[IllegalStateException]] if the same subject was watched before using `watch` or `watchWith` with
* another termination message. To change the termination message, unwatch first.
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*
* @return the provided ActorRef
*/
def watchWith(subject: ActorRef, msg: Any): ActorRef
/**
* Unregisters this actor as Monitor for the provided ActorRef.
* @return the provided ActorRef
*
* *Warning*: This method is not thread-safe and must not be accessed from threads other
* than the ordinary actor message processing thread, such as [[java.util.concurrent.CompletionStage]] and [[scala.concurrent.Future]] callbacks.
*/
def unwatch(subject: ActorRef): ActorRef
/**
* ActorContexts shouldn't be Serializable
*/
final protected def writeObject(@unused o: ObjectOutputStream): Unit =
throw new NotSerializableException("ActorContext is not serializable!")
}
/**
* INTERNAL API
*/
@InternalApi
private[akka] trait Cell {
/**
* The “self” reference which this Cell is attached to.
*/
def self: ActorRef
/**
* The system within which this Cell lives.
*/
def system: ActorSystem
/**
* The system internals where this Cell lives.
*/
def systemImpl: ActorSystemImpl
/**
* Start the cell: enqueued message must not be processed before this has
* been called. The usual action is to attach the mailbox to a dispatcher.
*/
def start(): this.type
/**
* Recursively suspend this actor and all its children. Is only allowed to throw Fatal Throwables.
*/
def suspend(): Unit
/**
* Recursively resume this actor and all its children. Is only allowed to throw Fatal Throwables.
*/
def resume(causedByFailure: Throwable): Unit
/**
* Restart this actor (will recursively restart or stop all children). Is only allowed to throw Fatal Throwables.
*/
def restart(cause: Throwable): Unit
/**
* Recursively terminate this actor and all its children. Is only allowed to throw Fatal Throwables.
*/
def stop(): Unit
/**
* Returns “true” if the actor is locally known to be terminated, “false” if
* alive or uncertain.
*/
private[akka] def isTerminated: Boolean
/**
* The supervisor of this actor.
*/
def parent: InternalActorRef
/**
* All children of this actor, including only reserved-names.
*/
def childrenRefs: ChildrenContainer
/**
* Get the stats for the named child, if that exists.
*/
def getChildByName(name: String): Option[ChildStats]
/**
* Method for looking up a single child beneath this actor.
* It is racy if called from the outside.
*/
def getSingleChild(name: String): InternalActorRef
/**
* Enqueue a message to be sent to the actor; may or may not actually
* schedule the actor to run, depending on which type of cell it is.
* Is only allowed to throw Fatal Throwables.
*/
@InternalStableApi
def sendMessage(msg: Envelope): Unit
/**
* Enqueue a message to be sent to the actor; may or may not actually
* schedule the actor to run, depending on which type of cell it is.
* Is only allowed to throw Fatal Throwables.
*/
final def sendMessage(message: Any, sender: ActorRef): Unit =
sendMessage(Envelope(message, sender, system))
/**
* Enqueue a message to be sent to the actor; may or may not actually
* schedule the actor to run, depending on which type of cell it is.
* Is only allowed to throw Fatal Throwables.
*/
def sendSystemMessage(msg: SystemMessage): Unit
/**
* Returns true if the actor is local, i.e. if it is actually scheduled
* on a Thread in the current JVM when run.
*/
def isLocal: Boolean
/**
* If the actor isLocal, returns whether "user messages" are currently queued,
* “false” otherwise.
*/
def hasMessages: Boolean
/**
* If the actor isLocal, returns the number of "user messages" currently queued,
* which may be a costly operation, 0 otherwise.
*/
def numberOfMessages: Int
/**
* The props for this actor cell.
*/
def props: Props
}
/**
* Everything in here is completely Akka PRIVATE. You will not find any
* supported APIs in this place. This is not the API you were looking
* for! (waves hand)
*/
private[akka] object ActorCell {
val contextStack = new ThreadLocal[List[ActorContext]] {
override def initialValue: List[ActorContext] = Nil
}
final val emptyCancellable: Cancellable = new Cancellable {
def isCancelled: Boolean = false
def cancel(): Boolean = false
}
final val emptyBehaviorStack: List[Actor.Receive] = Nil
final val emptyActorRefSet: Set[ActorRef] = immutable.HashSet.empty
final val terminatedProps: Props = Props((throw IllegalActorStateException("This Actor has been terminated")): Actor)
final val undefinedUid = 0
@tailrec final def newUid(): Int = {
// Note that this uid is also used as hashCode in ActorRef, so be careful
// to not break hashing if you change the way uid is generated
val uid = ThreadLocalRandom.current.nextInt()
if (uid == undefinedUid) newUid()
else uid
}
final def splitNameAndUid(name: String): (String, Int) = {
val i = name.indexOf('#')
if (i < 0) (name, undefinedUid)
else (name.substring(0, i), Integer.valueOf(name.substring(i + 1)))
}
final val DefaultState = 0
final val SuspendedState = 1
final val SuspendedWaitForChildrenState = 2
}
//ACTORCELL is NOT 64 bytes aligned, unless it is demonstrated to have a large improvement on performance
//vars don't need volatile since it's protected with the mailbox status
//Make sure that they are not read/written outside of a message processing (systemInvoke/invoke)
/**
* Everything in here is completely Akka PRIVATE. You will not find any
* supported APIs in this place. This is not the API you were looking
* for! (waves hand)
*/
@silent("deprecated")
private[akka] class ActorCell(
val system: ActorSystemImpl,
val self: InternalActorRef,
_initialProps: Props,
val dispatcher: MessageDispatcher,
val parent: InternalActorRef)
extends AbstractActor.ActorContext
with Cell
with dungeon.ReceiveTimeout
with dungeon.Children
with dungeon.Dispatch
with dungeon.DeathWatch
with dungeon.FaultHandling {
private[this] var _props = _initialProps
def props: Props = _props
import ActorCell._
final def isLocal = true
final def systemImpl = system
protected final def guardian = self
protected final def lookupRoot = self
final def provider = system.provider
override final def classicActorContext: ActorContext = this
protected def uid: Int = self.path.uid
private[this] var _actor: Actor = _
def actor: Actor = _actor
var currentMessage: Envelope = _
private var behaviorStack: List[Actor.Receive] = emptyBehaviorStack
private[this] var sysmsgStash: LatestFirstSystemMessageList = SystemMessageList.LNil
// Java API
final def getParent() = parent
// Java API
final def getSystem() = system
// Java API
final override def getDispatcher(): ExecutionContextExecutor = dispatcher
// Java API
final override def getSelf(): ActorRef = self
// Java API
final override def getProps(): Props = props
protected def stash(msg: SystemMessage): Unit = {
assert(msg.unlinked)
sysmsgStash ::= msg
}
private def unstashAll(): LatestFirstSystemMessageList = {
val unstashed = sysmsgStash
sysmsgStash = SystemMessageList.LNil
unstashed
}
/*
* MESSAGE PROCESSING
*/
//Memory consistency is handled by the Mailbox (reading mailbox status then processing messages, then writing mailbox status
final def systemInvoke(message: SystemMessage): Unit = {
/*
* When recreate/suspend/resume are received while restarting (i.e. between
* preRestart and postRestart, waiting for children to terminate), these
* must not be executed immediately, but instead queued and released after
* finishRecreate returns. This can only ever be triggered by
* ChildTerminated, and ChildTerminated is not one of the queued message
* types (hence the overwrite further down). Mailbox sets message.next=null
* before systemInvoke, so this will only be non-null during such a replay.
*/
def calculateState: Int =
if (waitingForChildrenOrNull ne null) SuspendedWaitForChildrenState
else if (mailbox.isSuspended) SuspendedState
else DefaultState
@tailrec def sendAllToDeadLetters(messages: EarliestFirstSystemMessageList): Unit =
if (messages.nonEmpty) {
val tail = messages.tail
val msg = messages.head
msg.unlink()
provider.deadLetters ! msg
sendAllToDeadLetters(tail)
}
def shouldStash(m: SystemMessage, state: Int): Boolean =
(state: @switch) match {
case DefaultState => false
case SuspendedState => m.isInstanceOf[StashWhenFailed]
case SuspendedWaitForChildrenState => m.isInstanceOf[StashWhenWaitingForChildren]
}
@tailrec
def invokeAll(messages: EarliestFirstSystemMessageList, currentState: Int): Unit = {
val rest = messages.tail
val message = messages.head
message.unlink()
try {
message match {
case message: SystemMessage if shouldStash(message, currentState) => stash(message)
case f: Failed => handleFailure(f)
case DeathWatchNotification(a, ec, at) => watchedActorTerminated(a, ec, at)
case Create(failure) => create(failure)
case Watch(watchee, watcher) => addWatcher(watchee, watcher)
case Unwatch(watchee, watcher) => remWatcher(watchee, watcher)
case Recreate(cause) => faultRecreate(cause)
case Suspend() => faultSuspend()
case Resume(inRespToFailure) => faultResume(inRespToFailure)
case Terminate() => terminate()
case Supervise(child, async) => supervise(child, async)
case NoMessage => // only here to suppress warning
}
} catch handleNonFatalOrInterruptedException { e =>
handleInvokeFailure(Nil, e)
}
val newState = calculateState
// As each state accepts a strict subset of another state, it is enough to unstash if we "walk up" the state
// chain
val todo = if (newState < currentState) rest.reversePrepend(unstashAll()) else rest
if (isTerminated) sendAllToDeadLetters(todo)
else if (todo.nonEmpty) invokeAll(todo, newState)
}
invokeAll(new EarliestFirstSystemMessageList(message), calculateState)
}
//Memory consistency is handled by the Mailbox (reading mailbox status then processing messages, then writing mailbox status
final def invoke(messageHandle: Envelope): Unit = {
val msg = messageHandle.message
val timeoutBeforeReceive = cancelReceiveTimeoutIfNeeded(msg)
try {
currentMessage = messageHandle
if (msg.isInstanceOf[AutoReceivedMessage]) {
autoReceiveMessage(messageHandle)
} else {
receiveMessage(msg)
}
currentMessage = null // reset current message after successful invocation
} catch handleNonFatalOrInterruptedException { e =>
handleInvokeFailure(Nil, e)
} finally
// Schedule or reschedule receive timeout
checkReceiveTimeoutIfNeeded(msg, timeoutBeforeReceive)
}
def autoReceiveMessage(msg: Envelope): Unit = {
if (system.settings.DebugAutoReceive)
publish(Debug(self.path.toString, clazz(actor), "received AutoReceiveMessage " + msg))
msg.message match {
case t: Terminated => receivedTerminated(t)
case AddressTerminated(address) => addressTerminated(address)
case Kill => throw ActorKilledException("Kill")
case PoisonPill => self.stop()
case sel: ActorSelectionMessage => receiveSelection(sel)
case Identify(messageId) => sender() ! ActorIdentity(messageId, Some(self))
}
}
private def receiveSelection(sel: ActorSelectionMessage): Unit =
if (sel.elements.isEmpty)
invoke(Envelope(sel.msg, sender(), system))
else
ActorSelection.deliverSelection(self, sender(), sel)
final def receiveMessage(msg: Any): Unit = actor.aroundReceive(behaviorStack.head, msg)
/*
* ACTOR CONTEXT IMPLEMENTATION
*/
final def sender(): ActorRef = currentMessage match {
case null => system.deadLetters
case msg if msg.sender ne null => msg.sender
case _ => system.deadLetters
}
def become(behavior: Actor.Receive, discardOld: Boolean = true): Unit =
behaviorStack = behavior :: (if (discardOld && behaviorStack.nonEmpty) behaviorStack.tail else behaviorStack)
def become(behavior: Procedure[Any]): Unit = become(behavior, discardOld = true)
def become(behavior: Procedure[Any], discardOld: Boolean): Unit =
become({ case msg => behavior.apply(msg) }: Actor.Receive, discardOld)
def unbecome(): Unit = {
val original = behaviorStack
behaviorStack =
if (original.isEmpty || original.tail.isEmpty) actor.receive :: emptyBehaviorStack
else original.tail
}
/*
* ACTOR INSTANCE HANDLING
*/
//This method is in charge of setting up the contextStack and create a new instance of the Actor
protected def newActor(): Actor = {
contextStack.set(this :: contextStack.get)
try {
behaviorStack = emptyBehaviorStack
val instance = props.newActor()
if (instance eq null)
throw ActorInitializationException(self, "Actor instance passed to actorOf can't be 'null'")
// If no becomes were issued, the actors behavior is its receive method
behaviorStack = if (behaviorStack.isEmpty) instance.receive :: behaviorStack else behaviorStack
_actor = instance
instance
} finally {
val stackAfter = contextStack.get
if (stackAfter.nonEmpty)
contextStack.set(if (stackAfter.head eq null) stackAfter.tail.tail else stackAfter.tail) // pop null marker plus our context
}
}
protected def create(failure: Option[ActorInitializationException]): Unit = {
def failActor(): Unit =
if (_actor != null) {
clearActorFields(actor, recreate = false)
setFailedFatally()
_actor = null // ensure that we know that we failed during creation
}
failure.foreach { throw _ }
try {
val created = newActor()
created.aroundPreStart()
checkReceiveTimeout(reschedule = true)
if (system.settings.DebugLifecycle)
publish(Debug(self.path.toString, clazz(created), "started (" + created + ")"))
} catch {
case e: InterruptedException =>
failActor()
Thread.currentThread().interrupt()
throw ActorInitializationException(self, "interruption during creation", e)
case NonFatal(e) =>
failActor()
e match {
case i: InstantiationException =>
throw ActorInitializationException(
self,
"""exception during creation, this problem is likely to occur because the class of the Actor you tried to create is either,
a non-static inner class (in which case make it a static inner class or use Props(new ...) or Props( new Creator ... )
or is missing an appropriate, reachable no-args constructor.
""",
i.getCause)
case x => throw ActorInitializationException(self, "exception during creation", x)
}
}
}
private def supervise(child: ActorRef, async: Boolean): Unit =
if (!isTerminating) {
// Supervise is the first thing we get from a new child, so store away the UID for later use in handleFailure()
initChild(child) match {
case Some(_) =>
handleSupervise(child, async)
if (system.settings.DebugLifecycle)
publish(Debug(self.path.toString, clazz(actor), "now supervising " + child))
case None =>
publish(
Error(
self.path.toString,
clazz(actor),
"received Supervise from unregistered child " + child + ", this will not end well"))
}
}
// future extension point
protected def handleSupervise(child: ActorRef, async: Boolean): Unit = child match {
case r: RepointableActorRef if async => r.point(catchFailures = true)
case _ =>
}
@InternalStableApi
@silent("never used")
final protected def clearActorFields(actorInstance: Actor, recreate: Boolean): Unit = {
currentMessage = null
behaviorStack = emptyBehaviorStack
}
final protected def clearFieldsForTermination(): Unit = {
unstashAll()
_props = ActorCell.terminatedProps
_actor = null
}
// logging is not the main purpose, and if it fails there’s nothing we can do
protected final def publish(e: LogEvent): Unit =
try system.eventStream.publish(e)
catch { case NonFatal(_) => }
protected final def clazz(o: AnyRef): Class[_] = if (o eq null) this.getClass else o.getClass
}
