Class AsyncWriteJournal

Abstract journal, optimized for asynchronous, non-blocking writes.

Inheritance

Object

ActorBase

WriteJournalBase

AsyncWriteJournal

AsyncWriteProxy

MemoryJournal

SqlJournal

Implements

IInternalActor

IAsyncRecovery

Inherited Members

WriteJournalBase.PreparePersistentBatch(IEnumerable<IPersistentEnvelope>)

WriteJournalBase.AdaptToJournal(IPersistentRepresentation)

ActorBase.Sender

ActorBase.Self

ActorBase.IInternalActor.ActorContext

ActorBase.Context

ActorBase.AroundReceive(Receive, Object)

ActorBase.EmptyReceive

ActorBase.Unhandled(Object)

ActorBase.Become(Receive)

ActorBase.BecomeStacked(Receive)

ActorBase.UnbecomeStacked()

ActorBase.SetReceiveTimeout(Nullable<TimeSpan>)

ActorBase.AroundPreRestart(Exception, Object)

ActorBase.AroundPreStart()

ActorBase.PreStart()

ActorBase.AroundPostRestart(Exception, Object)

ActorBase.PreRestart(Exception, Object)

ActorBase.PostRestart(Exception)

ActorBase.AroundPostStop()

ActorBase.PostStop()

ActorBase.SupervisorStrategy()

Object.Equals(Object)

Object.Equals(Object, Object)

Object.GetHashCode()

Object.GetType()

Object.MemberwiseClone()

Object.ReferenceEquals(Object, Object)

Object.ToString()

Namespace: Akka.Persistence.Journal

Assembly: Akka.Persistence.dll

Syntax

public abstract class AsyncWriteJournal : WriteJournalBase, IInternalActor, IAsyncRecovery

Constructors

AsyncWriteJournal()

Initializes a new instance of the AsyncWriteJournal class.

Declaration

protected AsyncWriteJournal()

Exceptions

Type	Condition
ArgumentException	This exception is thrown when the Persistence extension related to this journal has not been used in the current ActorSystem context.
ConfigurationException	This exception is thrown when an invalid replay-filter.mode is read from the configuration. Acceptable replay-filter.mode values include: off | repair-by-discard-old | fail | warn

Fields

CanPublish

Declaration

protected readonly bool CanPublish

Field Value

Type	Description
Boolean

Methods

DeleteMessagesToAsync(String, Int64)

Asynchronously deletes all persistent messages up to inclusive toSequenceNr bound.

Declaration

protected abstract Task DeleteMessagesToAsync(string persistenceId, long toSequenceNr)

Parameters

Type	Name	Description
String	persistenceId	TBD
Int64	toSequenceNr	TBD

Returns

Type	Description
Task	TBD

ReadHighestSequenceNrAsync(String, Int64)

Asynchronously reads the highest stored sequence number for provided persistenceId. The persistent actor will use the highest sequence number after recovery as the starting point when persisting new events. This sequence number is also used as toSequenceNr in subsequent calls to ReplayMessagesAsync(IActorContext, String, Int64, Int64, Int64, Action<IPersistentRepresentation>) unless the user has specified a lower toSequenceNr. Journal must maintain the highest sequence number and never decrease it.

This call is protected with a circuit-breaker.

Please also not that requests for the highest sequence number may be made concurrently to writes executing for the same persistenceId, in particular it is possible that a restarting actor tries to recover before its outstanding writes have completed.

Declaration

public abstract Task<long> ReadHighestSequenceNrAsync(string persistenceId, long fromSequenceNr)

Parameters

Type	Name	Description
String	persistenceId	Persistent actor identifier
Int64	fromSequenceNr	Hint where to start searching for the highest sequence number. When a persistent actor is recovering this fromSequenceNr will the sequence number of the used snapshot, or 0L if no snapshot is used.

Returns

Type	Description
Task<Int64>	TBD

Receive(Object)

Processor for user defined messages.

Declaration

protected sealed override bool Receive(object message)

Parameters

Type	Name	Description
Object	message	The message.

Returns

Type	Description
Boolean	TBD

Overrides

ActorBase.Receive(Object)

ReceivePluginInternal(Object)

Plugin API: Allows plugin implementers to use f.PipeTo(Self) and handle additional messages for implementing advanced features

Declaration

protected virtual bool ReceivePluginInternal(object message)

Parameters

Type	Name	Description
Object	message	TBD

Returns

Type	Description
Boolean	TBD

ReceiveWriteJournal(Object)

TBD

Declaration

protected bool ReceiveWriteJournal(object message)

Parameters

Type	Name	Description
Object	message	TBD

Returns

Type	Description
Boolean	TBD

ReplayMessagesAsync(IActorContext, String, Int64, Int64, Int64, Action<IPersistentRepresentation>)

Asynchronously replays persistent messages. Implementations replay a message by calling recoveryCallback. The returned task must be completed when all messages (matching the sequence number bounds) have been replayed. The task must be completed with a failure if any of the persistent messages could not be replayed.

The toSequenceNr is the lowest of what was returned by ReadHighestSequenceNrAsync(String, Int64) and what the user specified as recovery Recovery parameter. This does imply that this call is always preceded by reading the highest sequence number for the given persistenceId.

This call is NOT protected with a circuit-breaker because it may take a long time to replay all events. The plugin implementation itself must protect against an unresponsive backend store and make sure that the returned Task is completed with success or failure within reasonable time. It is not allowed to ignore completing the Task.

Declaration

public abstract Task ReplayMessagesAsync(IActorContext context, string persistenceId, long fromSequenceNr, long toSequenceNr, long max, Action<IPersistentRepresentation> recoveryCallback)

Parameters

Type	Name	Description
IActorContext	context	The contextual information about the actor processing replayed messages.
String	persistenceId	Persistent actor identifier
Int64	fromSequenceNr	Inclusive sequence number where replay should start
Int64	toSequenceNr	Inclusive sequence number where replay should end
Int64	max	Maximum number of messages to be replayed
Action<IPersistentRepresentation>	recoveryCallback	Called to replay a message, may be called from any thread.

Returns

Type	Description
Task	TBD

TryUnwrapException(Exception)

TBD

Declaration

protected static Exception TryUnwrapException(Exception e)

Parameters

Type	Name	Description
Exception	e	TBD

Returns

Type	Description
Exception	TBD

WriteMessagesAsync(IEnumerable<AtomicWrite>)

Plugin API: asynchronously writes a batch of persistent messages to the journal.

The batch is only for performance reasons, i.e. all messages don't have to be written atomically. Higher throughput can typically be achieved by using batch inserts of many records compared to inserting records one-by-one, but this aspect depends on the underlying data store and a journal implementation can implement it as efficient as possible. Journals should aim to persist events in-order for a given persistenceId as otherwise in case of a failure, the persistent state may be end up being inconsistent.

Each AtomicWrite message contains the single Akka.Persistence.Persistent that corresponds to the event that was passed to the Persist<TEvent>(TEvent, Action<TEvent>) method of the PersistentActor, or it contains several Akka.Persistence.Persistent that correspond to the events that were passed to the PersistAll<TEvent>(IEnumerable<TEvent>, Action<TEvent>) method of the PersistentActor. All Akka.Persistence.Persistent of the AtomicWrite must be written to the data store atomically, i.e. all or none must be stored. If the journal (data store) cannot support atomic writes of multiple events it should reject such writes with a NotSupportedException describing the issue. This limitation should also be documented by the journal plugin.

If there are failures when storing any of the messages in the batch the returned Task must be completed with failure. The Task must only be completed with success when all messages in the batch have been confirmed to be stored successfully, i.e. they will be readable, and visible, in a subsequent replay. If there is uncertainty about if the messages were stored or not the Task must be completed with failure.

Data store connection problems must be signaled by completing the Task with failure.

The journal can also signal that it rejects individual messages (AtomicWrite) by the returned Task. It is possible but not mandatory to reduce number of allocations by returning null for the happy path, i.e. when no messages are rejected. Otherwise the returned list must have as many elements as the input messages. Each result element signals if the corresponding AtomicWrite is rejected or not, with an exception describing the problem. Rejecting a message means it was not stored, i.e. it must not be included in a later replay. Rejecting a message is typically done before attempting to store it, e.g. because of serialization error.

Data store connection problems must not be signaled as rejections.

It is possible but not mandatory to reduce number of allocations by returning null for the happy path, i.e. when no messages are rejected.

Calls to this method are serialized by the enclosing journal actor. If you spawn work in asynchronous tasks it is alright that they complete the futures in any order, but the actual writes for a specific persistenceId should be serialized to avoid issues such as events of a later write are visible to consumers (query side, or replay) before the events of an earlier write are visible. A PersistentActor will not send a new WriteMessages request before the previous one has been completed.

Please not that the Sender of the contained Akka.Persistence.Persistent objects has been nulled out (i.e. set to NoSender in order to not use space in the journal for a sender reference that will likely be obsolete during replay.

Please also note that requests for the highest sequence number may be made concurrently to this call executing for the same persistenceId, in particular it is possible that a restarting actor tries to recover before its outstanding writes have completed. In the latter case it is highly desirable to defer reading the highest sequence number until all outstanding writes have completed, otherwise the PersistentActor may reuse sequence numbers.

This call is protected with a circuit-breaker.

Declaration

protected abstract Task<IImmutableList<Exception>> WriteMessagesAsync(IEnumerable<AtomicWrite> messages)

Parameters

Type	Name	Description
IEnumerable<AtomicWrite>	messages	TBD

Returns

Type	Description
Task<System.Collections.Immutable.IImmutableList<Exception>>	TBD

Implements

IInternalActor

IAsyncRecovery

Extension Methods

ObjectExtensions.IsDefaultForType<T>(T)

ObjectExtensions.AsOption<T>(T)

Extensions.AsInstanceOf<T>(Object)