Package org.apache.pekko.actor

Interface Stash

All Superinterfaces:

Actor, RequiresMessageQueue<DequeBasedMessageQueueSemantics>, StashSupport, UnrestrictedStash

All Known Subinterfaces:

AbstractPersistentActorLike, AsyncWriteProxy, AtLeastOnceDelivery, AtLeastOnceDeliveryLike, Eventsourced, PersistenceStash, PersistentActor, PersistentFSM<S,D,E>

All Known Implementing Classes:

AbstractActorWithStash, AbstractFSMWithStash, AbstractPersistentActor, AbstractPersistentActorWithAtLeastOnceDelivery, AbstractPersistentActorWithTimers, AbstractPersistentFSM, AbstractPersistentLoggingFSM, JournalPerfSpec.BenchActor, PersistencePluginProxy, PersistentShardCoordinator

public interface Stash
extends UnrestrictedStash, RequiresMessageQueue<DequeBasedMessageQueueSemantics>

The Stash trait enables an actor to temporarily stash away messages that can not or should not be handled using the actor's current behavior.

Example:

    class ActorWithProtocol extends Actor with Stash {
      def receive = {
        case "open" =>
          unstashAll()
          context.become({
            case "write" => // do writing...
            case "close" =>
              unstashAll()
              context.unbecome()
            case msg => stash()
          }, discardOld = false)
        case "done" => // done
        case msg    => stash()
      }
    }
  

Note that the Stash trait can only be used together with actors that have a deque-based mailbox. By default Stash based actors request a Deque based mailbox since the stash trait extends RequiresMessageQueue[DequeBasedMessageQueueSemantics]. You can override the default mailbox provided when DequeBasedMessageQueueSemantics are requested via config:

    pekko.actor.mailbox.requirements {
      "org.apache.pekko.dispatch.BoundedDequeBasedMessageQueueSemantics" = your-custom-mailbox
    }
  

Alternatively, you can add your own requirement marker to the actor and configure a mailbox type to be used for your marker.

For a Stash that also enforces unboundedness of the deque see pekko.actor.UnboundedStash. For a Stash that does not enforce any mailbox type see pekko.actor.UnrestrictedStash.

Note that the Stash trait must be mixed into (a subclass of) the Actor trait before any trait/class that overrides the preRestart callback. This means it's not possible to write Actor with MyActor with Stash if MyActor overrides preRestart.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.pekko.actor.Actor

Actor.emptyBehavior$, Actor.ignoringBehavior$

Method Summary

Methods inherited from interface org.apache.pekko.actor.Actor

aroundPostRestart, aroundPostStop, aroundPreRestart, aroundPreStart, aroundReceive, context, org$apache$pekko$actor$Actor$_setter_$context_$eq, org$apache$pekko$actor$Actor$_setter_$self_$eq, postRestart, preStart, receive, self, sender, supervisorStrategy, unhandled

Methods inherited from interface org.apache.pekko.actor.StashSupport

actorCell, clearStash, context, enqueueFirst, mailbox, org$apache$pekko$actor$StashSupport$_setter_$mailbox_$eq, prepend, self, stash, theStash_$eq, unstash, unstashAll, unstashAll

Methods inherited from interface org.apache.pekko.actor.UnrestrictedStash

postStop, preRestart, super$postStop, super$preRestart