Akka/Scala example source code file (AsyncWriteJournal.scala)

This example Akka source code file (AsyncWriteJournal.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorref, akka, any, asyncwritejournal, boolean, collection, concurrent, desequenced, failure, future, pattern, persistence, persistentrepr, success

The AsyncWriteJournal.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 * Copyright (C) 2012-2013 Eligotech BV.
 */

package akka.persistence.journal

import scala.collection.immutable
import scala.concurrent.Future
import scala.util._

import akka.actor._
import akka.pattern.pipe
import akka.persistence._

/**
 * Abstract journal, optimized for asynchronous, non-blocking writes.
 */
trait AsyncWriteJournal extends Actor with WriteJournalBase with AsyncRecovery {
  import JournalProtocol._
  import AsyncWriteJournal._
  import context.dispatcher

  private val extension = Persistence(context.system)
  private val publish = extension.settings.internal.publishPluginCommands

  private val resequencer = context.actorOf(Props[Resequencer]())
  private var resequencerCounter = 1L

  def receive = {
    case WriteMessages(resequenceables, processor, actorInstanceId) ⇒
      val cctr = resequencerCounter
      def resequence(f: PersistentRepr ⇒ Any) = resequenceables.zipWithIndex.foreach {
        case (p: PersistentRepr, i) ⇒ resequencer ! Desequenced(f(p), cctr + i + 1, processor, p.sender)
        case (r, i)                 ⇒ resequencer ! Desequenced(LoopMessageSuccess(r.payload, actorInstanceId), cctr + i + 1, processor, r.sender)
      }
      asyncWriteMessages(preparePersistentBatch(resequenceables)) onComplete {
        case Success(_) ⇒
          resequencer ! Desequenced(WriteMessagesSuccessful, cctr, processor, self)
          resequence(WriteMessageSuccess(_, actorInstanceId))
        case Failure(e) ⇒
          resequencer ! Desequenced(WriteMessagesFailed(e), cctr, processor, self)
          resequence(WriteMessageFailure(_, e, actorInstanceId))
      }
      resequencerCounter += resequenceables.length + 1
    case r @ ReplayMessages(fromSequenceNr, toSequenceNr, max, persistenceId, processor, replayDeleted) ⇒
      // Send replayed messages and replay result to processor directly. No need
      // to resequence replayed messages relative to written and looped messages.
      asyncReplayMessages(persistenceId, fromSequenceNr, toSequenceNr, max) { p ⇒
        if (!p.deleted || replayDeleted) processor.tell(ReplayedMessage(p), p.sender)
      } map {
        case _ ⇒ ReplayMessagesSuccess
      } recover {
        case e ⇒ ReplayMessagesFailure(e)
      } pipeTo (processor) onSuccess {
        case _ if publish ⇒ context.system.eventStream.publish(r)
      }
    case ReadHighestSequenceNr(fromSequenceNr, persistenceId, processor) ⇒
      // Send read highest sequence number to processor directly. No need
      // to resequence the result relative to written and looped messages.
      asyncReadHighestSequenceNr(persistenceId, fromSequenceNr).map {
        highest ⇒ ReadHighestSequenceNrSuccess(highest)
      } recover {
        case e ⇒ ReadHighestSequenceNrFailure(e)
      } pipeTo (processor)
    case c @ WriteConfirmations(confirmationsBatch, requestor) ⇒
      asyncWriteConfirmations(confirmationsBatch) onComplete {
        case Success(_) ⇒ requestor ! WriteConfirmationsSuccess(confirmationsBatch)
        case Failure(e) ⇒ requestor ! WriteConfirmationsFailure(e)
      }
    case d @ DeleteMessages(messageIds, permanent, requestorOption) ⇒
      asyncDeleteMessages(messageIds, permanent) onComplete {
        case Success(_) ⇒
          requestorOption.foreach(_ ! DeleteMessagesSuccess(messageIds))
          if (publish) context.system.eventStream.publish(d)
        case Failure(e) ⇒
      }
    case d @ DeleteMessagesTo(persistenceId, toSequenceNr, permanent) ⇒
      asyncDeleteMessagesTo(persistenceId, toSequenceNr, permanent) onComplete {
        case Success(_) ⇒ if (publish) context.system.eventStream.publish(d)
        case Failure(e) ⇒
      }
    case LoopMessage(message, processor, actorInstanceId) ⇒
      resequencer ! Desequenced(LoopMessageSuccess(message, actorInstanceId), resequencerCounter, processor, sender)
      resequencerCounter += 1
  }

  //#journal-plugin-api
  /**
   * Plugin API: asynchronously writes a batch of persistent messages to the journal.
   * The batch write must be atomic i.e. either all persistent messages in the batch
   * are written or none.
   */
  def asyncWriteMessages(messages: immutable.Seq[PersistentRepr]): Future[Unit]

  /**
   * Plugin API: asynchronously writes a batch of delivery confirmations to the journal.
   */
  @deprecated("writeConfirmations will be removed, since Channels will be removed.", since = "2.3.4")
  def asyncWriteConfirmations(confirmations: immutable.Seq[PersistentConfirmation]): Future[Unit]

  /**
   * Plugin API: asynchronously deletes messages identified by `messageIds` from the
   * journal. If `permanent` is set to `false`, the persistent messages are marked as
   * deleted, otherwise they are permanently deleted.
   */
  @deprecated("asyncDeleteMessages will be removed.", since = "2.3.4")
  def asyncDeleteMessages(messageIds: immutable.Seq[PersistentId], permanent: Boolean): Future[Unit]

  /**
   * Plugin API: asynchronously deletes all persistent messages up to `toSequenceNr`
   * (inclusive). If `permanent` is set to `false`, the persistent messages are marked
   * as deleted, otherwise they are permanently deleted.
   */
  def asyncDeleteMessagesTo(persistenceId: String, toSequenceNr: Long, permanent: Boolean): Future[Unit]
  //#journal-plugin-api
}

/**
 * INTERNAL API.
 */
private[persistence] object AsyncWriteJournal {
  final case class Desequenced(msg: Any, snr: Long, target: ActorRef, sender: ActorRef)

  class Resequencer extends Actor {
    import scala.collection.mutable.Map

    private val delayed = Map.empty[Long, Desequenced]
    private var delivered = 0L

    def receive = {
      case d: Desequenced ⇒ resequence(d)
    }

    @scala.annotation.tailrec
    private def resequence(d: Desequenced) {
      if (d.snr == delivered + 1) {
        delivered = d.snr
        d.target tell (d.msg, d.sender)
      } else {
        delayed += (d.snr -> d)
      }
      val ro = delayed.remove(delivered + 1)
      if (ro.isDefined) resequence(ro.get)
    }
  }
}