asynchorswim / fusion

State management and flexible persistence for Akka

Version Matrix

Fusion Build Status

Fusion provides state management and flexible persistence for Scala/Akka.



Add the following to your build.sbt file:

libraryDependencies += "net.asynchorswim" %% "fusion" % "1.1.3"


Add the following to ytour build.gradle file within the dependencies section:

compile 'net.asynchorswim:fusion_2,12:1.1.3'


The first step in using fusion is to model your domain in terms of one or more Entity. An entity defines state and behavior and will map to either a single Akka actor or a collection of actors.

For example, the following defines an entity that can be used to count the occurance of words in a sentence:

final case class WordCounter(count: Int) extends Entity[WordCounter] {
  override def receive(implicit ctx: Context) = {
    case CountWord(_) => applying(CountIncremented)
    case QueryCount(_) => reply(couhnt); NoOp

  override def applyEvent = {
    case CountIncremented => copy(count = count + 1)

object WordCounter extends EntityCompanion[WordCounter] {
  val empty = WordCounter(0)

  final case class CountWord(word: String) extends Command with ShardingId { def id = word }
  final case class QueryCount(word: String) extends ShardingId { def id = word }

  case object CountIncremented extends Event

This enntity definition can then be used to create an Aggregate Root of word counters as follows:

implicit val timeProvider = SystemTimeProvider
implicit val system = ActorSystem()
implicit val timeout = Timeout(1 second)


val words = system.actorOf(AggregateRoot.props[WordCounter](TransientEntity))

"The rain in Spain falls mainly in the plain"
  .split(" ")
  .map(w => WordCounter.CountWord(w.toUpperCase))
  .foreach(c => words ! c)

val c = words ? WordCounter.QueryCount("IN") // Returns Future[Int] that completes with "2"

Persistence Mechanisms

  • TransientEntity
  • CommandSourcedEntity
  • EventSourcedEntity
  • PersistedEntity