I want to persist events in Akka only when there is a failure in the actor.
I am trying the following code to achieve persistence.
package persistence
import akka.actor._import akka.persistence._
case class Cmd(data: String)case class Evt(data: String)
case class ExampleState(events: List[String] = Nil) {
def updated(evt: Evt): ExampleState = copy(evt.data :: events)
def size: Int = events.length
override def toString: String = events.reverse.toString}
class ExamplePersistentActor extends PersistentActor {
var list = new java.util.ArrayList[String]
override def postStop (): Unit = {
println("inside postStop")
println(list.size())
import scala.collection.JavaConversions._
for( data <- list) {
persist(Evt(s"${data}-${numEvents}")) { event ⇒
println("persisting")
updateState(event)
context.system.eventStream.publish(event)
if (lastSequenceNr % snapShotInterval == 0 && lastSequenceNr != 0)
saveSnapshot(state)
}
}
}
override def persistenceId = "sample-id-1"
var state = ExampleState()
def updateState(event: Evt): Unit =
state = state.updated(event)
def numEvents =
state.size
val receiveRecover: Receive = {
case evt: Evt ⇒ updateState(evt)
case SnapshotOffer(_, snapshot: ExampleState) ⇒ state = snapshot
}
val snapShotInterval = 1000
val receiveCommand: Receive = {
case 'test =>
println("test")
case Cmd(data) ⇒
println(data)
list.add(data)
case "print" ⇒ println(state)
}}//#persistent-actor-example
object PersistentActorExample extends App {
val system = ActorSystem("example")
val persistentActor = system.actorOf(Props[ExamplePersistentActor],
"persistentActor-4-scala")
persistentActor ! 'test
persistentActor ! Cmd("foo")
persistentActor ! Cmd("baz")
persistentActor ! Cmd("bar")
persistentActor ! Cmd("buzz")
persistentActor ! "print"
Thread.sleep(10000)
persistentActor ! PoisonPill
system.terminate()}
Can anyone help me in the above code? Is this code is the best approach to
achieve what I want or Do I have to look for some other way?
One more approach I can think of is to add a shutdown hook but I don't know
whether I will be able to use akka persistence in shutdown hook
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