Interface Processor

All Superinterfaces:
Actor, ProcessorImpl, Recovery, RequiresMessageQueue<DequeBasedMessageQueueSemantics>, Snapshotter, Stash, StashFactory, StashSupport, UnrestrictedStash
All Known Subinterfaces:
AtLeastOnceDelivery, EventsourcedProcessor
All Known Implementing Classes:
AbstractPersistentActorWithAtLeastOnceDelivery, AbstractProcessor, RequestWriter, UntypedPersistentActorWithAtLeastOnceDelivery, UntypedProcessor

public interface Processor
extends ProcessorImpl

An actor that persists (journals) messages of type Persistent. Messages of other types are not persisted.

 import akka.persistence.{ Persistent, Processor }

 class MyProcessor extends Processor {
   def receive = {
     case Persistent(payload, sequenceNr) => // message has been written to journal
     case other                           => // message has not been written to journal

 val processor = actorOf(Props[MyProcessor], name = "myProcessor")

 processor ! Persistent("foo")
 processor ! "bar"

During start and restart, persistent messages are replayed to a processor so that it can recover internal state from these messages. New messages sent to a processor during recovery do not interfere with replayed messages, hence applications don't need to wait for a processor to complete its recovery.

Automated recovery can be turned off or customized by overriding the preStart and preRestart life cycle hooks. If automated recovery is turned off, an application can explicitly recover a processor by sending it a Recover message.

Persistent messages are assigned sequence numbers that are generated on a per-processor basis. A sequence starts at 1L and doesn't contain gaps unless a processor (logically) deletes a message

During recovery, a processor internally buffers new messages until recovery completes, so that new messages do not interfere with replayed messages. This internal buffer (the ''processor stash'') is isolated from the ''user stash'' inherited by akka.actor.Stash. Processor implementation classes can therefore use the ''user stash'' for stashing/unstashing both persistent and transient messages.

Processors can also store snapshots of internal state by calling saveSnapshot. During recovery, a saved snapshot is offered to the processor with a SnapshotOffer message, followed by replayed messages, if any, that are younger than the snapshot. Default is to offer the latest saved snapshot.

See Also:
UntypedProcessor, Recover, PersistentBatch

Nested Class Summary
Nested classes/interfaces inherited from interface akka.persistence.Recovery
Nested classes/interfaces inherited from interface akka.actor.Actor
Method Summary
 java.lang.String persistenceId()
          Persistence id.
Methods inherited from interface akka.persistence.ProcessorImpl
_persistenceId, aroundPostStop, aroundPreRestart, aroundPreStart, deleteMessage, deleteMessage, deleteMessages, deleteMessages, flushJournalBatch, initializing, instanceId, nextSequenceNr, onRecoveryCompleted, onRecoveryFailure, onReplayFailure, onReplaySuccess, preRestart, preRestartDefault, preStart, processing, processorBatch, processorId, recoveryFinished, recoveryRunning, sequenceNr, snapshotterId, unhandled, unstashFilterPredicate
Methods inherited from interface akka.persistence.Recovery
_currentPersistent, _currentState, _lastSequenceNr, _recoveryFailureCause, _recoveryFailureMessage, aroundReceive, currentPersistentMessage, extension, getCurrentPersistentMessage, journal, lastSequenceNr, prepareRestart, receiverStash, recoveryPending, recoveryStarted, replayFailed, replayStarted, runReceive, snapshotSequenceNr, updateLastSequenceNr, updateLastSequenceNr, withCurrentPersistent
Methods inherited from interface akka.persistence.Snapshotter
deleteSnapshot, deleteSnapshots, loadSnapshot, saveSnapshot, snapshotStore
Methods inherited from interface akka.actor.UnrestrictedStash
Methods inherited from interface akka.actor.Actor
aroundPostRestart, context, postRestart, receive, self, sender, supervisorStrategy
Methods inherited from interface akka.actor.StashSupport
actorCell, capacity, clearStash, context, enqueueFirst, mailbox, prepend, self, stash, theStash, unstash, unstashAll, unstashAll
Methods inherited from interface akka.actor.StashFactory

Method Detail


java.lang.String persistenceId()
Persistence id. Defaults to this persistent-actors's path and can be overridden.

Specified by:
persistenceId in interface Recovery