akka.persistence
Interface PersistentView

All Superinterfaces:

Actor, Recovery, RequiresMessageQueue<DequeBasedMessageQueueSemantics>, Snapshotter, Stash, StashFactory, StashSupport, UnrestrictedStash

All Known Implementing Classes:

AbstractPersistentView, UntypedPersistentView

public interface PersistentView
extends Actor, Recovery

A view replicates the persistent message stream of a PersistentActor. Implementation classes receive the message stream directly from the Journal. These messages can be processed to update internal state in order to maintain an (eventual consistent) view of the state of the corresponding persistent actor. A persistent view can also run on a different node, provided that a replicated journal is used.

Implementation classes refer to a persistent actors' message stream by implementing persistenceId with the corresponding (shared) identifier value.

Views can also store snapshots of internal state by calling autoUpdate. The snapshots of a view are independent of those of the referenced persistent actor. During recovery, a saved snapshot is offered to the view with a SnapshotOffer message, followed by replayed messages, if any, that are younger than the snapshot. Default is to offer the latest saved snapshot.

By default, a view automatically updates itself with an interval returned by autoUpdateInterval. This method can be overridden by implementation classes to define a view instance-specific update interval. The default update interval for all views of an actor system can be configured with the akka.persistence.view.auto-update-interval configuration key. Applications may trigger additional view updates by sending the view Update requests. See also methods

- autoUpdate for turning automated updates on or off - autoUpdateReplayMax for limiting the number of replayed messages per view update cycle

Nested Class Summary

Nested classes/interfaces inherited from interface akka.persistence.Recovery

Recovery.State

Nested classes/interfaces inherited from interface akka.actor.Actor

Actor.emptyBehavior$

Method Summary

boolean	autoUpdate() If true, this view automatically updates itself with an interval specified by autoUpdateInterval.
scala.concurrent.duration.FiniteDuration	autoUpdateInterval() The interval for automated updates.
long	autoUpdateReplayMax() The maximum number of messages to replay per update.
Recovery.State	idle() When receiving an Update request, switches to replayStarted state and triggers an incremental message replay.
boolean	isPersistent() If true, the currently processed message was persisted (is sent from the Journal).
void	onReplayComplete(boolean await) Switches to idle state and schedules the next update if autoUpdate returns true.
void	onReplayFailure(scala.PartialFunction<java.lang.Object,scala.runtime.BoxedUnit> receive, boolean await, java.lang.Throwable cause) INTERNAL API.
void	onReplaySuccess(scala.PartialFunction<java.lang.Object,scala.runtime.BoxedUnit> receive, boolean await) INTERNAL API.
void	postStop() User overridable callback.
void	preRestart(java.lang.Throwable reason, scala.Option<java.lang.Object> message) User overridable callback: '''By default it disposes of all children and then calls postStop().'''
void	preStart() Triggers an initial recovery, starting form a snapshot, if any, and replaying at most autoUpdateReplayMax messages (following that snapshot).
java.lang.Object	replayStarted(boolean await) INTERNAL API.
void	runReceive(scala.PartialFunction<java.lang.Object,scala.runtime.BoxedUnit> receive, Persistent msg) INTERNAL API WARNING: This implementation UNWRAPS PERSISTENT() before delivering to the receive block.
scala.Option<Cancellable>	schedule()
java.lang.String	snapshotterId() Returns viewId.
java.lang.String	viewId() View id is used as identifier for snapshots performed by this PersistentView.
akka.persistence.PersistenceSettings.view$	viewSettings()

Methods inherited from interface akka.persistence.Recovery

_currentPersistent, _currentState, _lastSequenceNr, _recoveryFailureCause, _recoveryFailureMessage, aroundReceive, currentPersistentMessage, extension, getCurrentPersistentMessage, journal, lastSequenceNr, persistenceId, prepareRestart, processorId, receiverStash, recoveryPending, recoveryStarted, replayFailed, snapshotSequenceNr, updateLastSequenceNr, updateLastSequenceNr, withCurrentPersistent

Methods inherited from interface akka.persistence.Snapshotter

deleteSnapshot, deleteSnapshots, loadSnapshot, saveSnapshot, snapshotStore

Methods inherited from interface akka.actor.Actor

aroundPostRestart, aroundPostStop, aroundPreRestart, aroundPreStart, context, postRestart, receive, self, sender, supervisorStrategy, unhandled

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

createStash

Method Detail

replayStarted

java.lang.Object replayStarted(boolean await)

INTERNAL API.

Extends the replayStarted state of Recovery with logic to handle Update requests sent by users.

Specified by:

replayStarted in interface Recovery

Parameters:

await - (undocumented)

Returns:

(undocumented)

idle

Recovery.State idle()

When receiving an Update request, switches to replayStarted state and triggers an incremental message replay. Invokes the actor's current behavior for any other received message.

Returns:

(undocumented)

onReplaySuccess

void onReplaySuccess(scala.PartialFunction<java.lang.Object,scala.runtime.BoxedUnit> receive,
                     boolean await)

INTERNAL API.

Specified by:

onReplaySuccess in interface Recovery

Parameters:

receive - (undocumented)

await - (undocumented)

onReplayFailure

void onReplayFailure(scala.PartialFunction<java.lang.Object,scala.runtime.BoxedUnit> receive,
                     boolean await,
                     java.lang.Throwable cause)

INTERNAL API.

Specified by:

onReplayFailure in interface Recovery

Parameters:

receive - (undocumented)

await - (undocumented)

cause - (undocumented)

onReplayComplete

void onReplayComplete(boolean await)

Switches to idle state and schedules the next update if autoUpdate returns true.

Parameters:

await - (undocumented)

runReceive

void runReceive(scala.PartialFunction<java.lang.Object,scala.runtime.BoxedUnit> receive,
                Persistent msg)

INTERNAL API WARNING: This implementation UNWRAPS PERSISTENT() before delivering to the receive block.

Specified by:

runReceive in interface Recovery

Parameters:

receive - (undocumented)

msg - (undocumented)

viewSettings

akka.persistence.PersistenceSettings.view$ viewSettings()

schedule

scala.Option<Cancellable> schedule()

viewId

java.lang.String viewId()

View id is used as identifier for snapshots performed by this PersistentView. This allows the View to keep separate snapshots of data than the PersistentActor originating the message stream.

The usual case is to have a *different* id set as viewId than persistenceId, although it is possible to share the same id with an PersistentActor - for example to decide about snapshots based on some average or sum, calculated by this view.

Example:

    class SummingView extends PersistentView {
      override def persistenceId = "count-123"
      override def viewId        = "count-123-sum" // this view is performing summing,
                                                   // so this view's snapshots reside under the "-sum" suffixed id

      // ...
    }
 

Returns:

(undocumented)

snapshotterId

java.lang.String snapshotterId()

Returns viewId.

Specified by:

snapshotterId in interface Snapshotter

Returns:

(undocumented)

isPersistent

boolean isPersistent()

If true, the currently processed message was persisted (is sent from the Journal). If false, the currently processed message comes from another actor (from "user-land").

Returns:

(undocumented)

autoUpdate

boolean autoUpdate()

If true, this view automatically updates itself with an interval specified by autoUpdateInterval. If false, applications must explicitly update this view by sending Update requests. The default value can be configured with the akka.persistence.view.auto-update configuration key. This method can be overridden by implementation classes to return non-default values.

Returns:

(undocumented)

autoUpdateInterval

scala.concurrent.duration.FiniteDuration autoUpdateInterval()

The interval for automated updates. The default value can be configured with the akka.persistence.view.auto-update-interval configuration key. This method can be overridden by implementation classes to return non-default values.

Returns:

(undocumented)

autoUpdateReplayMax

long autoUpdateReplayMax()

The maximum number of messages to replay per update. The default value can be configured with the akka.persistence.view.auto-update-replay-max configuration key. This method can be overridden by implementation classes to return non-default values.

Returns:

(undocumented)

preStart

void preStart()

Triggers an initial recovery, starting form a snapshot, if any, and replaying at most autoUpdateReplayMax messages (following that snapshot).

Specified by:

preStart in interface Actor

preRestart

void preRestart(java.lang.Throwable reason,
                scala.Option<java.lang.Object> message)

Description copied from interface: Actor

User overridable callback: '''By default it disposes of all children and then calls postStop().'''

Specified by:

preRestart in interface Actor

Specified by:

preRestart in interface UnrestrictedStash

Parameters:

reason - the Throwable that caused the restart to happen

message - optionally the current message the actor processed when failing, if applicable

Is called on a crashed Actor right BEFORE it is restarted to allow clean up of resources before Actor is terminated.

postStop

void postStop()

Description copied from interface: Actor

User overridable callback.

Is called asynchronously after 'actor.stop()' is invoked. Empty default implementation.

Specified by:

postStop in interface Actor

Specified by:

postStop in interface UnrestrictedStash