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/**
* Copyright (C) 2009-2014 Typesafe Inc.
*/
package akka.actor
import language.implicitConversions
import java.lang.{ Iterable ⇒ JIterable }
import java.util.concurrent.TimeUnit
import akka.japi.Util.immutableSeq
import scala.collection.mutable.ArrayBuffer
import scala.collection.immutable
import scala.concurrent.duration.Duration
import akka.event.Logging.LogEvent
import akka.event.Logging.Error
import akka.event.Logging.Warning
import scala.util.control.NonFatal
/**
* INTERNAL API
*/
private[akka] sealed trait ChildStats
/**
* INTERNAL API
*/
private[akka] case object ChildNameReserved extends ChildStats
/**
* ChildRestartStats is the statistics kept by every parent Actor for every child Actor
* and is used for SupervisorStrategies to know how to deal with problems that occur for the children.
*/
case class ChildRestartStats(child: ActorRef, var maxNrOfRetriesCount: Int = 0, var restartTimeWindowStartNanos: Long = 0L)
extends ChildStats {
def uid: Int = child.path.uid
//FIXME How about making ChildRestartStats immutable and then move these methods into the actual supervisor strategies?
def requestRestartPermission(retriesWindow: (Option[Int], Option[Int])): Boolean =
retriesWindow match {
case (Some(retries), _) if retries < 1 ⇒ false
case (Some(retries), None) ⇒ { maxNrOfRetriesCount += 1; maxNrOfRetriesCount <= retries }
case (x, Some(window)) ⇒ retriesInWindowOkay(if (x.isDefined) x.get else 1, window)
case (None, _) ⇒ true
}
private def retriesInWindowOkay(retries: Int, window: Int): Boolean = {
/*
* Simple window algorithm: window is kept open for a certain time
* after a restart and if enough restarts happen during this time, it
* denies. Otherwise window closes and the scheme starts over.
*/
val retriesDone = maxNrOfRetriesCount + 1
val now = System.nanoTime
val windowStart =
if (restartTimeWindowStartNanos == 0) {
restartTimeWindowStartNanos = now
now
} else restartTimeWindowStartNanos
val insideWindow = (now - windowStart) <= TimeUnit.MILLISECONDS.toNanos(window)
if (insideWindow) {
maxNrOfRetriesCount = retriesDone
retriesDone <= retries
} else {
maxNrOfRetriesCount = 1
restartTimeWindowStartNanos = now
true
}
}
}
/**
* Implement this interface in order to configure the supervisorStrategy for
* the top-level guardian actor (`/user`). An instance of this class must be
* instantiable using a no-arg constructor.
*/
trait SupervisorStrategyConfigurator {
def create(): SupervisorStrategy
}
final class DefaultSupervisorStrategy extends SupervisorStrategyConfigurator {
override def create(): SupervisorStrategy = SupervisorStrategy.defaultStrategy
}
final class StoppingSupervisorStrategy extends SupervisorStrategyConfigurator {
override def create(): SupervisorStrategy = SupervisorStrategy.stoppingStrategy
}
trait SupervisorStrategyLowPriorityImplicits { this: SupervisorStrategy.type ⇒
/**
* Implicit conversion from `Seq` of Cause-Directive pairs to a `Decider`. See makeDecider(causeDirective).
*/
implicit def seqCauseDirective2Decider(trapExit: Iterable[CauseDirective]): Decider = makeDecider(trapExit)
// the above would clash with seqThrowable2Decider for empty lists
}
object SupervisorStrategy extends SupervisorStrategyLowPriorityImplicits {
sealed trait Directive
/**
* Resumes message processing for the failed Actor
*/
case object Resume extends Directive
/**
* Discards the old Actor instance and replaces it with a new,
* then resumes message processing.
*/
case object Restart extends Directive
/**
* Stops the Actor
*/
case object Stop extends Directive
/**
* Escalates the failure to the supervisor of the supervisor,
* by rethrowing the cause of the failure, i.e. the supervisor fails with
* the same exception as the child.
*/
case object Escalate extends Directive
/**
* Java API: Returning this directive resumes message processing for the failed Actor
*/
def resume = Resume
/**
* Java API: Returning this directive discards the old Actor instance and replaces it with a new,
* then resumes message processing.
*/
def restart = Restart
/**
* Java API: Returning this directive stops the Actor
*/
def stop = Stop
/**
* Java API: Returning this directive escalates the failure to the supervisor of the supervisor,
* by rethrowing the cause of the failure, i.e. the supervisor fails with
* the same exception as the child.
*/
def escalate = Escalate
/**
* When supervisorStrategy is not specified for an actor this
* [[Decider]] is used by default in the supervisor strategy.
* The child will be stopped when [[akka.actor.ActorInitializationException]],
* [[akka.actor.ActorKilledException]], or [[akka.actor.DeathPactException]] is
* thrown. It will be restarted for other `Exception` types.
* The error is escalated if it's a `Throwable`, i.e. `Error`.
*/
final val defaultDecider: Decider = {
case _: ActorInitializationException ⇒ Stop
case _: ActorKilledException ⇒ Stop
case _: DeathPactException ⇒ Stop
case _: Exception ⇒ Restart
}
/**
* When supervisorStrategy is not specified for an actor this
* is used by default. OneForOneStrategy with decider defined in
* [[#defaultDecider]].
*/
final val defaultStrategy: SupervisorStrategy = {
OneForOneStrategy()(defaultDecider)
}
/**
* This strategy resembles Erlang in that failing children are always
* terminated (one-for-one).
*/
final val stoppingStrategy: SupervisorStrategy = {
def stoppingDecider: Decider = {
case _: Exception ⇒ Stop
}
OneForOneStrategy()(stoppingDecider)
}
/**
* Implicit conversion from `Seq` of Throwables to a `Decider`.
* This maps the given Throwables to restarts, otherwise escalates.
*/
implicit def seqThrowable2Decider(trapExit: immutable.Seq[Class[_ <: Throwable]]): Decider = makeDecider(trapExit)
type Decider = PartialFunction[Throwable, Directive]
type JDecider = akka.japi.Function[Throwable, Directive]
type CauseDirective = (Class[_ <: Throwable], Directive)
/**
* Decider builder which just checks whether one of
* the given Throwables matches the cause and restarts, otherwise escalates.
*/
def makeDecider(trapExit: immutable.Seq[Class[_ <: Throwable]]): Decider = {
case x ⇒ if (trapExit exists (_ isInstance x)) Restart else Escalate
}
/**
* Decider builder which just checks whether one of
* the given Throwables matches the cause and restarts, otherwise escalates.
*/
def makeDecider(trapExit: JIterable[Class[_ <: Throwable]]): Decider = makeDecider(immutableSeq(trapExit))
/**
* Decider builder for Iterables of cause-directive pairs, e.g. a map obtained
* from configuration; will sort the pairs so that the most specific type is
* checked before all its subtypes, allowing carving out subtrees of the
* Throwable hierarchy.
*/
def makeDecider(flat: Iterable[CauseDirective]): Decider = {
val directives = sort(flat)
{ case x ⇒ directives collectFirst { case (c, d) if c isInstance x ⇒ d } getOrElse Escalate }
}
/**
* Converts a Java Decider into a Scala Decider
*/
def makeDecider(func: JDecider): Decider = { case x ⇒ func(x) }
/**
* Sort so that subtypes always precede their supertypes, but without
* obeying any order between unrelated subtypes (insert sort).
*
* INTERNAL API
*/
private[akka] def sort(in: Iterable[CauseDirective]): immutable.Seq[CauseDirective] =
(new ArrayBuffer[CauseDirective](in.size) /: in) { (buf, ca) ⇒
buf.indexWhere(_._1 isAssignableFrom ca._1) match {
case -1 ⇒ buf append ca
case x ⇒ buf insert (x, ca)
}
buf
}.to[immutable.IndexedSeq]
private[akka] def withinTimeRangeOption(withinTimeRange: Duration): Option[Duration] =
if (withinTimeRange.isFinite && withinTimeRange >= Duration.Zero) Some(withinTimeRange) else None
private[akka] def maxNrOfRetriesOption(maxNrOfRetries: Int): Option[Int] =
if (maxNrOfRetries < 0) None else Some(maxNrOfRetries)
private[akka] val escalateDefault = (_: Any) ⇒ Escalate
}
/**
* An Akka SupervisorStrategy is the policy to apply for crashing children.
*
* IMPORTANT:
*
* You should not normally need to create new subclasses, instead use the
* existing [[akka.actor.OneForOneStrategy]] or [[akka.actor.AllForOneStrategy]],
* but if you do, please read the docs of the methods below carefully, as
* incorrect implementations may lead to “blocked” actor systems (i.e.
* permanently suspended actors).
*/
abstract class SupervisorStrategy {
import SupervisorStrategy._
/**
* Returns the Decider that is associated with this SupervisorStrategy.
* The Decider is invoked by the default implementation of `handleFailure`
* to obtain the Directive to be applied.
*/
def decider: Decider
/**
* This method is called after the child has been removed from the set of children.
* It does not need to do anything special. Exceptions thrown from this method
* do NOT make the actor fail if this happens during termination.
*/
def handleChildTerminated(context: ActorContext, child: ActorRef, children: Iterable[ActorRef]): Unit
/**
* This method is called to act on the failure of a child: restart if the flag is true, stop otherwise.
*/
def processFailure(context: ActorContext, restart: Boolean, child: ActorRef, cause: Throwable, stats: ChildRestartStats, children: Iterable[ChildRestartStats]): Unit
/**
* This is the main entry point: in case of a child’s failure, this method
* must try to handle the failure by resuming, restarting or stopping the
* child (and returning `true`), or it returns `false` to escalate the
* failure, which will lead to this actor re-throwing the exception which
* caused the failure. The exception will not be wrapped.
*
* This method calls [[akka.actor.SupervisorStrategy#logFailure]], which will
* log the failure unless it is escalated. You can customize the logging by
* setting [[akka.actor.SupervisorStrategy#loggingEnabled]] to `false` and
* do the logging inside the `decider` or override the `logFailure` method.
*
* @param children is a lazy collection (a view)
*/
def handleFailure(context: ActorContext, child: ActorRef, cause: Throwable, stats: ChildRestartStats, children: Iterable[ChildRestartStats]): Boolean = {
val directive = decider.applyOrElse(cause, escalateDefault)
directive match {
case d @ Resume ⇒
logFailure(context, child, cause, d)
resumeChild(child, cause)
true
case d @ Restart ⇒
logFailure(context, child, cause, d)
processFailure(context, true, child, cause, stats, children)
true
case d @ Stop ⇒
logFailure(context, child, cause, d)
processFailure(context, false, child, cause, stats, children)
true
case d @ Escalate ⇒
logFailure(context, child, cause, d)
false
}
}
/**
* Logging of actor failures is done when this is `true`.
*/
protected def loggingEnabled: Boolean = true
/**
* Default logging of actor failures when
* [[akka.actor.SupervisorStrategy#loggingEnabled]] is `true`.
* `Escalate` failures are not logged here, since they are supposed
* to be handled at a level higher up in the hierarchy.
* `Resume` failures are logged at `Warning` level.
* `Stop` and `Restart` failures are logged at `Error` level.
*/
def logFailure(context: ActorContext, child: ActorRef, cause: Throwable, decision: Directive): Unit =
if (loggingEnabled) {
val logMessage = cause match {
case e: ActorInitializationException if e.getCause ne null ⇒ e.getCause.getMessage
case e ⇒ e.getMessage
}
decision match {
case Resume ⇒ publish(context, Warning(child.path.toString, getClass, logMessage))
case Escalate ⇒ // don't log here
case _ ⇒ publish(context, Error(cause, child.path.toString, getClass, logMessage))
}
}
// logging is not the main purpose, and if it fails there’s nothing we can do
private def publish(context: ActorContext, logEvent: LogEvent): Unit =
try context.system.eventStream.publish(logEvent) catch { case NonFatal(_) ⇒ }
/**
* Resume the previously failed child: do never apply this to a child which
* is not the currently failing child. Suspend/resume needs to be done in
* matching pairs, otherwise actors will wake up too soon or never at all.
*/
final def resumeChild(child: ActorRef, cause: Throwable): Unit = child.asInstanceOf[InternalActorRef].resume(causedByFailure = cause)
/**
* Restart the given child, possibly suspending it first.
*
* IMPORTANT:
*
* If the child is the currently failing one, it will already have been
* suspended, hence `suspendFirst` must be false. If the child is not the
* currently failing one, then it did not request this treatment and is
* therefore not prepared to be resumed without prior suspend.
*/
final def restartChild(child: ActorRef, cause: Throwable, suspendFirst: Boolean): Unit = {
val c = child.asInstanceOf[InternalActorRef]
if (suspendFirst) c.suspend()
c.restart(cause)
}
}
/**
* Applies the fault handling `Directive` (Resume, Restart, Stop) specified in the `Decider`
* to all children when one fails, as opposed to [[akka.actor.OneForOneStrategy]] that applies
* it only to the child actor that failed.
*
* @param maxNrOfRetries the number of times a child actor is allowed to be restarted, negative value means no limit,
* if the limit is exceeded the child actor is stopped
* @param withinTimeRange duration of the time window for maxNrOfRetries, Duration.Inf means no window
* @param decider mapping from Throwable to [[akka.actor.SupervisorStrategy.Directive]], you can also use a
* [[scala.collection.immutable.Seq]] of Throwables which maps the given Throwables to restarts, otherwise escalates.
* @param loggingEnabled the strategy logs the failure if this is enabled (true), by default it is enabled
*/
case class AllForOneStrategy(
maxNrOfRetries: Int = -1,
withinTimeRange: Duration = Duration.Inf,
override val loggingEnabled: Boolean = true)(val decider: SupervisorStrategy.Decider)
extends SupervisorStrategy {
import SupervisorStrategy._
/**
* Java API
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, decider: SupervisorStrategy.JDecider, loggingEnabled: Boolean) =
this(maxNrOfRetries, withinTimeRange, loggingEnabled)(SupervisorStrategy.makeDecider(decider))
/**
* Java API
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, decider: SupervisorStrategy.JDecider) =
this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(decider))
/**
* Java API
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, trapExit: JIterable[Class[_ <: Throwable]]) =
this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(trapExit))
/**
* Java API: compatible with lambda expressions
* This is an EXPERIMENTAL feature and is subject to change until it has received more real world testing.
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, decider: SupervisorStrategy.Decider) =
this(maxNrOfRetries = maxNrOfRetries, withinTimeRange = withinTimeRange)(decider)
/**
* Java API: compatible with lambda expressions
* This is an EXPERIMENTAL feature and is subject to change until it has received more real world testing.
*/
def this(loggingEnabled: Boolean, decider: SupervisorStrategy.Decider) =
this(loggingEnabled = loggingEnabled)(decider)
/**
* Java API: compatible with lambda expressions
* This is an EXPERIMENTAL feature and is subject to change until it has received more real world testing.
*/
def this(decider: SupervisorStrategy.Decider) =
this()(decider)
/*
* this is a performance optimization to avoid re-allocating the pairs upon
* every call to requestRestartPermission, assuming that strategies are shared
* across actors and thus this field does not take up much space
*/
private val retriesWindow = (maxNrOfRetriesOption(maxNrOfRetries), withinTimeRangeOption(withinTimeRange).map(_.toMillis.toInt))
def handleChildTerminated(context: ActorContext, child: ActorRef, children: Iterable[ActorRef]): Unit = ()
def processFailure(context: ActorContext, restart: Boolean, child: ActorRef, cause: Throwable, stats: ChildRestartStats, children: Iterable[ChildRestartStats]): Unit = {
if (children.nonEmpty) {
if (restart && children.forall(_.requestRestartPermission(retriesWindow)))
children foreach (crs ⇒ restartChild(crs.child, cause, suspendFirst = (crs.child != child)))
else
for (c ← children) context.stop(c.child)
}
}
}
/**
* Applies the fault handling `Directive` (Resume, Restart, Stop) specified in the `Decider`
* to the child actor that failed, as opposed to [[akka.actor.AllForOneStrategy]] that applies
* it to all children.
*
* @param maxNrOfRetries the number of times a child actor is allowed to be restarted, negative value means no limit,
* if the limit is exceeded the child actor is stopped
* @param withinTimeRange duration of the time window for maxNrOfRetries, Duration.Inf means no window
* @param decider mapping from Throwable to [[akka.actor.SupervisorStrategy.Directive]], you can also use a
* [[scala.collection.immutable.Seq]] of Throwables which maps the given Throwables to restarts, otherwise escalates.
* @param loggingEnabled the strategy logs the failure if this is enabled (true), by default it is enabled
*/
case class OneForOneStrategy(
maxNrOfRetries: Int = -1,
withinTimeRange: Duration = Duration.Inf,
override val loggingEnabled: Boolean = true)(val decider: SupervisorStrategy.Decider)
extends SupervisorStrategy {
/**
* Java API
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, decider: SupervisorStrategy.JDecider, loggingEnabled: Boolean) =
this(maxNrOfRetries, withinTimeRange, loggingEnabled)(SupervisorStrategy.makeDecider(decider))
/**
* Java API
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, decider: SupervisorStrategy.JDecider) =
this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(decider))
/**
* Java API
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, trapExit: JIterable[Class[_ <: Throwable]]) =
this(maxNrOfRetries, withinTimeRange)(SupervisorStrategy.makeDecider(trapExit))
/**
* Java API: compatible with lambda expressions
* This is an EXPERIMENTAL feature and is subject to change until it has received more real world testing.
*/
def this(maxNrOfRetries: Int, withinTimeRange: Duration, decider: SupervisorStrategy.Decider) =
this(maxNrOfRetries = maxNrOfRetries, withinTimeRange = withinTimeRange)(decider)
/**
* Java API: compatible with lambda expressions
* This is an EXPERIMENTAL feature and is subject to change until it has received more real world testing.
*/
def this(loggingEnabled: Boolean, decider: SupervisorStrategy.Decider) =
this(loggingEnabled = loggingEnabled)(decider)
/**
* Java API: compatible with lambda expressions
* This is an EXPERIMENTAL feature and is subject to change until it has received more real world testing.
*/
def this(decider: SupervisorStrategy.Decider) =
this()(decider)
/*
* this is a performance optimization to avoid re-allocating the pairs upon
* every call to requestRestartPermission, assuming that strategies are shared
* across actors and thus this field does not take up much space
*/
private val retriesWindow = (
SupervisorStrategy.maxNrOfRetriesOption(maxNrOfRetries),
SupervisorStrategy.withinTimeRangeOption(withinTimeRange).map(_.toMillis.toInt))
def handleChildTerminated(context: ActorContext, child: ActorRef, children: Iterable[ActorRef]): Unit = ()
def processFailure(context: ActorContext, restart: Boolean, child: ActorRef, cause: Throwable, stats: ChildRestartStats, children: Iterable[ChildRestartStats]): Unit = {
if (restart && stats.requestRestartPermission(retriesWindow))
restartChild(child, cause, suspendFirst = false)
else
context.stop(child) //TODO optimization to drop child here already?
}
}
