akka.persistence

Channel

final class Channel extends Actor

A channel is used by Processors (and Views) for sending Persistent messages to destinations. The main responsibility of a channel is to prevent redundant delivery of replayed messages to destinations when a processor is recovered.

A channel is instructed to deliver a persistent message to a destination with the Deliver command. A destination is provided as ActorPath and messages are sent via that path's ActorSelection.

class ForwardExample extends Processor {
val destination = context.actorOf(Props[MyDestination])
val channel = context.actorOf(Channel.props(), "myChannel")

def receive = {
  case m @ Persistent(payload, _) =>
    // forward modified message to destination
    channel forward Deliver(m.withPayload(s"fw: ${payload}"), destination.path)
}
}

To reply to the sender of a persistent message, the sender reference should be used as channel destination.

class ReplyExample extends Processor {
val channel = context.actorOf(Channel.props(), "myChannel")

def receive = {
  case m @ Persistent(payload, _) =>
    // reply modified message to sender
    channel ! Deliver(m.withPayload(s"re: ${payload}"), sender.path)
}
}

Redundant delivery of messages to destinations is only prevented if the receipt of these messages is explicitly confirmed. Therefore, persistent messages that are delivered via a channel are of type ConfirmablePersistent. Their receipt can be confirmed by a destination by calling the confirm() method on these messages.

class MyDestination extends Actor {
def receive = {
  case cp @ ConfirmablePersistent(payload, sequenceNr, redeliveries) => cp.confirm()
}
}

If a destination does not confirm the receipt of a ConfirmablePersistent message, it will be redelivered by the channel according to the parameters in ChannelSettings. Redelivered messages have a redeliveries value greater than zero.

If the maximum number of redeliveries is reached for certain messages, they are removed from the channel and a redeliverFailureListener (if specified, see ChannelSettings) is notified about these messages with a RedeliverFailure message. Besides other application-specific tasks, this listener can restart the sending processor to enforce a redelivery of these messages or confirm these messages to prevent further redeliveries.

Annotations
@deprecated
Deprecated

(Since version 2.3.4) Channel will be removed, see akka.persistence.AtLeastOnceDelivery instead.

Source
Channel.scala
See also

Deliver

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  1. Channel
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Type Members

  1. type Receive = PartialFunction[Any, Unit]

    Definition Classes
    Actor

Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any
  3. final def ##(): Int

    Definition Classes
    AnyRef → Any
  4. def +(other: String): String

    Implicit information
    This member is added by an implicit conversion from Channel to StringAdd performed by method any2stringadd in scala.Predef.
    Definition Classes
    StringAdd
  5. def ->[B](y: B): (Channel, B)

    Implicit information
    This member is added by an implicit conversion from Channel to ArrowAssoc[Channel] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  6. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  7. final def ==(arg0: Any): Boolean

    Definition Classes
    Any
  8. def aroundPostRestart(reason: Throwable): Unit

    Can be overridden to intercept calls to postRestart.

    Can be overridden to intercept calls to postRestart. Calls postRestart by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
  9. def aroundPostStop(): Unit

    Can be overridden to intercept calls to postStop.

    Can be overridden to intercept calls to postStop. Calls postStop by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
  10. def aroundPreRestart(reason: Throwable, message: Option[Any]): Unit

    Can be overridden to intercept calls to preRestart.

    Can be overridden to intercept calls to preRestart. Calls preRestart by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
  11. def aroundPreStart(): Unit

    Can be overridden to intercept calls to preStart.

    Can be overridden to intercept calls to preStart. Calls preStart by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
  12. def aroundReceive(receive: actor.Actor.Receive, msg: Any): Unit

    INTERNAL API.

    INTERNAL API.

    Can be overridden to intercept calls to this actor's current behavior.

    receive

    current behavior.

    msg

    current message.

    Attributes
    protected[akka]
    Definition Classes
    Actor
  13. final def asInstanceOf[T0]: T0

    Definition Classes
    Any
  14. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  15. implicit val context: ActorContext

    Stores the context for this actor, including self, and sender.

    Stores the context for this actor, including self, and sender. It is implicit to support operations such as forward.

    WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!

    akka.actor.ActorContext is the Scala API. getContext returns a akka.actor.UntypedActorContext, which is the Java API of the actor context.

    Definition Classes
    Actor
  16. def ensuring(cond: (Channel) ⇒ Boolean, msg: ⇒ Any): Channel

    Implicit information
    This member is added by an implicit conversion from Channel to Ensuring[Channel] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  17. def ensuring(cond: (Channel) ⇒ Boolean): Channel

    Implicit information
    This member is added by an implicit conversion from Channel to Ensuring[Channel] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  18. def ensuring(cond: Boolean, msg: ⇒ Any): Channel

    Implicit information
    This member is added by an implicit conversion from Channel to Ensuring[Channel] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  19. def ensuring(cond: Boolean): Channel

    Implicit information
    This member is added by an implicit conversion from Channel to Ensuring[Channel] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  20. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  21. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  22. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  23. def formatted(fmtstr: String): String

    Implicit information
    This member is added by an implicit conversion from Channel to StringFormat performed by method any2stringfmt in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  24. final def getClass(): Class[_]

    Definition Classes
    AnyRef → Any
  25. def hashCode(): Int

    Definition Classes
    AnyRef → Any
  26. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any
  27. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  28. final def notify(): Unit

    Definition Classes
    AnyRef
  29. final def notifyAll(): Unit

    Definition Classes
    AnyRef
  30. def postRestart(reason: Throwable): Unit

    User overridable callback: By default it calls preStart().

    User overridable callback: By default it calls preStart().

    reason

    the Throwable that caused the restart to happen

    Is called right AFTER restart on the newly created Actor to allow reinitialization after an Actor crash.

    Definition Classes
    Actor
    Annotations
    @throws( classOf[Exception] )
  31. def postStop(): Unit

    User overridable callback.

    User overridable callback.

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

    Definition Classes
    Actor
    Annotations
    @throws( classOf[Exception] )
  32. def preRestart(reason: Throwable, message: Option[Any]): Unit

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

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

    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.

    Definition Classes
    Actor
    Annotations
    @throws( classOf[Exception] )
  33. def preStart(): Unit

    User overridable callback.

    User overridable callback.

    Is called when an Actor is started. Actors are automatically started asynchronously when created. Empty default implementation.

    Definition Classes
    Actor
    Annotations
    @throws( classOf[Exception] )
  34. def receive: PartialFunction[Any, Unit]

    This defines the initial actor behavior, it must return a partial function with the actor logic.

    This defines the initial actor behavior, it must return a partial function with the actor logic.

    Definition Classes
    ChannelActor
  35. implicit final val self: ActorRef

    The 'self' field holds the ActorRef for this actor.

    The 'self' field holds the ActorRef for this actor.

    Can be used to send messages to itself:

    self ! message
    

    Definition Classes
    Actor
  36. final def sender(): ActorRef

    The reference sender Actor of the last received message.

    The reference sender Actor of the last received message. Is defined if the message was sent from another Actor, else deadLetters in akka.actor.ActorSystem.

    WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!

    Definition Classes
    Actor
  37. def supervisorStrategy: SupervisorStrategy

    User overridable definition the strategy to use for supervising child actors.

    User overridable definition the strategy to use for supervising child actors.

    Definition Classes
    Actor
  38. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  39. def toString(): String

    Definition Classes
    AnyRef → Any
  40. def unhandled(message: Any): Unit

    User overridable callback.

    User overridable callback.

    Is called when a message isn't handled by the current behavior of the actor by default it fails with either a akka.actor.DeathPactException (in case of an unhandled akka.actor.Terminated message) or publishes an akka.actor.UnhandledMessage to the actor's system's akka.event.EventStream

    Definition Classes
    Actor
  41. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  42. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  43. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  44. def [B](y: B): (Channel, B)

    Implicit information
    This member is added by an implicit conversion from Channel to ArrowAssoc[Channel] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Shadowed Implicit Value Members

  1. val self: Any

    Implicit information
    This member is added by an implicit conversion from Channel to StringAdd performed by method any2stringadd in scala.Predef.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (channel: StringAdd).self
    Definition Classes
    StringAdd
  2. val self: Any

    Implicit information
    This member is added by an implicit conversion from Channel to StringFormat performed by method any2stringfmt in scala.Predef.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (channel: StringFormat).self
    Definition Classes
    StringFormat

Deprecated Value Members

  1. def x: Channel

    Implicit information
    This member is added by an implicit conversion from Channel to ArrowAssoc[Channel] performed by method any2ArrowAssoc in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (channel: ArrowAssoc[Channel]).x
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use leftOfArrow instead

  2. def x: Channel

    Implicit information
    This member is added by an implicit conversion from Channel to Ensuring[Channel] performed by method any2Ensuring in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (channel: Ensuring[Channel]).x
    Definition Classes
    Ensuring
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use resultOfEnsuring instead

Inherited from Actor

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from Channel to StringAdd

Inherited by implicit conversion any2stringfmt from Channel to StringFormat

Inherited by implicit conversion any2ArrowAssoc from Channel to ArrowAssoc[Channel]

Inherited by implicit conversion any2Ensuring from Channel to Ensuring[Channel]

Ungrouped