Add 'replyWhileStopped' param to BackoffSupervisor

akka-actor-tests/src/test/scala/akka/pattern/BackoffSupervisorSpec.scala

@@ -174,5 +174,8 @@ class BackoffSupervisorSpec extends AkkaSpec with ImplicitSender {
             .withSupervisorStrategy(restartingStrategy)))
       }
     }
+
+    "Reply " in {
+    }
   }
 }

akka-actor/src/main/scala/akka/pattern/BackoffOnRestartSupervisor.scala

@@ -15,13 +15,14 @@ import akka.actor.SupervisorStrategy._
  * with ``akka.pattern.Backoff.onFailure``.
  */
 private class BackoffOnRestartSupervisor(
-  val childProps: Props,
-  val childName:  String,
-  minBackoff:     FiniteDuration,
-  maxBackoff:     FiniteDuration,
-  val reset:      BackoffReset,
-  randomFactor:   Double,
-  strategy:       OneForOneStrategy)
+  val childProps:        Props,
+  val childName:         String,
+  minBackoff:            FiniteDuration,
+  maxBackoff:            FiniteDuration,
+  val reset:             BackoffReset,
+  randomFactor:          Double,
+  strategy:              OneForOneStrategy,
+  val replyWhileStopped: Option[Any])
   extends Actor with HandleBackoff
   with ActorLogging {
 

akka-actor/src/main/scala/akka/pattern/BackoffOptions.scala

@@ -19,6 +19,7 @@ import akka.actor.{ Props, OneForOneStrategy, SupervisorStrategy }
  *                    case e: RetryableException => Restart
  *                 }
  *               )
+ *               .withReplyWhileStopped(TheSystemIsDown)
  *
  * }}}
  */
@@ -177,6 +178,15 @@ trait BackoffOptions {
    */
   def withDefaultStoppingStrategy: BackoffOptions
 
+  /**
+   * Returns a new BackoffOptions with a constant reply to messages that the supervisor receives while its
+   * child is stopped. By default, a message received while the child is stopped is forwarded to `deadLetters`.
+   * With this option, the supervisor will reply to the sender instead.
+   * @param replyWhileStopped The message that the supervisor will send in response to all messages while
+   *   its child is stopped.
+   */
+  def withReplyWhileStopped(replyWhileStopped: Any): BackoffOptions
+
   /**
    * Returns the props to create the back-off supervisor.
    */
@@ -191,14 +201,16 @@ private final case class BackoffOptionsImpl(
   maxBackoff:         FiniteDuration,
   randomFactor:       Double,
   reset:              Option[BackoffReset] = None,
-  supervisorStrategy: OneForOneStrategy    = OneForOneStrategy()(SupervisorStrategy.defaultStrategy.decider)) extends BackoffOptions {
+  supervisorStrategy: OneForOneStrategy    = OneForOneStrategy()(SupervisorStrategy.defaultStrategy.decider),
+  replyWhileStopped:  Option[Any]          = None) extends BackoffOptions {
 
   val backoffReset = reset.getOrElse(AutoReset(minBackoff))
 
   def withAutoReset(resetBackoff: FiniteDuration) = copy(reset = Some(AutoReset(resetBackoff)))
   def withManualReset = copy(reset = Some(ManualReset))
   def withSupervisorStrategy(supervisorStrategy: OneForOneStrategy) = copy(supervisorStrategy = supervisorStrategy)
   def withDefaultStoppingStrategy = copy(supervisorStrategy = OneForOneStrategy()(SupervisorStrategy.stoppingStrategy.decider))
+  def withReplyWhileStopped(replyWhileStopped: Any) = copy(replyWhileStopped = Some(replyWhileStopped))
 
   def props = {
     require(minBackoff > Duration.Zero, "minBackoff must be > 0")
@@ -212,9 +224,9 @@ private final case class BackoffOptionsImpl(
 
     backoffType match {
       case RestartImpliesFailure ⇒
-        Props(new BackoffOnRestartSupervisor(childProps, childName, minBackoff, maxBackoff, backoffReset, randomFactor, supervisorStrategy))
+        Props(new BackoffOnRestartSupervisor(childProps, childName, minBackoff, maxBackoff, backoffReset, randomFactor, supervisorStrategy, replyWhileStopped))
       case StopImpliesFailure ⇒
-        Props(new BackoffSupervisor(childProps, childName, minBackoff, maxBackoff, backoffReset, randomFactor, supervisorStrategy))
+        Props(new BackoffSupervisor(childProps, childName, minBackoff, maxBackoff, backoffReset, randomFactor, supervisorStrategy, replyWhileStopped))
     }
   }
 }

akka-actor/src/main/scala/akka/pattern/BackoffSupervisor.scala

@@ -170,13 +170,14 @@ object BackoffSupervisor {
  * with `Backoff.onStop`.
  */
 final class BackoffSupervisor(
-  val childProps: Props,
-  val childName:  String,
-  minBackoff:     FiniteDuration,
-  maxBackoff:     FiniteDuration,
-  val reset:      BackoffReset,
-  randomFactor:   Double,
-  strategy:       SupervisorStrategy)
+  val childProps:        Props,
+  val childName:         String,
+  minBackoff:            FiniteDuration,
+  maxBackoff:            FiniteDuration,
+  val reset:             BackoffReset,
+  randomFactor:          Double,
+  strategy:              SupervisorStrategy,
+  val replyWhileStopped: Option[Any])
   extends Actor with HandleBackoff {
 
   import BackoffSupervisor._
@@ -203,7 +204,7 @@ final class BackoffSupervisor(
     maxBackoff:         FiniteDuration,
     randomFactor:       Double,
     supervisorStrategy: SupervisorStrategy) =
-    this(childProps, childName, minBackoff, maxBackoff, AutoReset(minBackoff), randomFactor, supervisorStrategy)
+    this(childProps, childName, minBackoff, maxBackoff, AutoReset(minBackoff), randomFactor, supervisorStrategy, None)
 
   // for binary compatibility with 2.4.0
   def this(
@@ -229,6 +230,7 @@ private[akka] trait HandleBackoff { this: Actor ⇒
   def childProps: Props
   def childName: String
   def reset: BackoffReset
+  def replyWhileStopped: Option[Any]
 
   var child: Option[ActorRef] = None
   var restartCount = 0
@@ -274,9 +276,10 @@ private[akka] trait HandleBackoff { this: Actor ⇒
       // use the BackoffSupervisor as sender
       context.parent ! msg
 
-    case msg ⇒ child match {
-      case Some(c) ⇒ c.forward(msg)
-      case None    ⇒ context.system.deadLetters.forward(msg)
+    case msg ⇒ (child, replyWhileStopped) match {
+      case (Some(c), _) ⇒ c.forward(msg)
+      case (_, Some(r)) ⇒ sender ! r
+      case _            ⇒ context.system.deadLetters.forward(msg)
     }
   }
 }