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

This example Akka source code file (ChaosJournal.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

akka, boolean, chaosjournalmessages, collection, concurrent, forkjoin, future, journal, long, persistence, readhighestfailedexception, seq, string, testexception, unit, writefailedexception

The ChaosJournal.scala Akka example source code

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

package akka.persistence.journal.chaos

import scala.collection.immutable
import scala.concurrent.Future
import scala.concurrent.forkjoin.ThreadLocalRandom

import akka.persistence._
import akka.persistence.journal.SyncWriteJournal
import akka.persistence.journal.inmem.InmemMessages

class WriteFailedException(ps: Seq[PersistentRepr])
  extends TestException(s"write failed for payloads = [${ps.map(_.payload)}]")

class ConfirmFailedException(cs: Seq[PersistentConfirmation])
  extends TestException(s"write failed for confirmations = [${cs.map(c ⇒ s"${c.persistenceId}-${c.sequenceNr}-${c.channelId}")}]")

class ReplayFailedException(ps: Seq[PersistentRepr])
  extends TestException(s"recovery failed after replaying payloads = [${ps.map(_.payload)}]")

class ReadHighestFailedException
  extends TestException(s"recovery failed when reading highest sequence number")

class DeleteFailedException(messageIds: immutable.Seq[PersistentId])
  extends TestException(s"delete failed for message ids = [${messageIds}]")

/**
 * Keep [[ChaosJournal]] state in an external singleton so that it survives journal restarts.
 * The journal itself uses a dedicated dispatcher, so there won't be any visibility issues.
 */
private object ChaosJournalMessages extends InmemMessages

class ChaosJournal extends SyncWriteJournal {
  import ChaosJournalMessages.{ delete ⇒ del, _ }

  val config = context.system.settings.config.getConfig("akka.persistence.journal.chaos")
  val writeFailureRate = config.getDouble("write-failure-rate")
  val confirmFailureRate = config.getDouble("confirm-failure-rate")
  val deleteFailureRate = config.getDouble("delete-failure-rate")
  val replayFailureRate = config.getDouble("replay-failure-rate")
  val readHighestFailureRate = config.getDouble("read-highest-failure-rate")

  def random = ThreadLocalRandom.current

  def writeMessages(messages: immutable.Seq[PersistentRepr]): Unit =
    if (shouldFail(writeFailureRate)) throw new WriteFailedException(messages)
    else messages.foreach(add)

  def writeConfirmations(confirmations: immutable.Seq[PersistentConfirmation]): Unit =
    if (shouldFail(confirmFailureRate)) throw new ConfirmFailedException(confirmations)
    else confirmations.foreach(cnf ⇒ update(cnf.persistenceId, cnf.sequenceNr)(p ⇒ p.update(confirms = cnf.channelId +: p.confirms)))

  def deleteMessages(messageIds: immutable.Seq[PersistentId], permanent: Boolean): Unit =
    if (shouldFail(deleteFailureRate)) throw new DeleteFailedException(messageIds)
    else if (permanent) messageIds.foreach(mid ⇒ update(mid.persistenceId, mid.sequenceNr)(_.update(deleted = true)))
    else messageIds.foreach(mid ⇒ del(mid.persistenceId, mid.sequenceNr))

  def deleteMessagesTo(persistenceId: String, toSequenceNr: Long, permanent: Boolean): Unit =
    (1L to toSequenceNr).map(PersistentIdImpl(persistenceId, _))

  def asyncReplayMessages(persistenceId: String, fromSequenceNr: Long, toSequenceNr: Long, max: Long)(replayCallback: (PersistentRepr) ⇒ Unit): Future[Unit] =
    if (shouldFail(replayFailureRate)) {
      val rm = read(persistenceId, fromSequenceNr, toSequenceNr, max)
      val sm = rm.take(random.nextInt(rm.length + 1))
      sm.foreach(replayCallback)
      Future.failed(new ReplayFailedException(sm))
    } else {
      read(persistenceId, fromSequenceNr, toSequenceNr, max).foreach(replayCallback)
      Future.successful(())
    }

  def asyncReadHighestSequenceNr(persistenceId: String, fromSequenceNr: Long): Future[Long] =
    if (shouldFail(readHighestFailureRate)) Future.failed(new ReadHighestFailedException)
    else Future.successful(highestSequenceNr(persistenceId))

  def shouldFail(rate: Double): Boolean =
    random.nextDouble() < rate
}