gistfile1.scala

// doesn't work
  val receiveReplica: Receive = withPersistence { (sender, key, id) => sender ! SnapshotAck(key, id) } {
    var expectedSeq = 0
    {
      case Get(key, id) =>
        sender ! GetResult(key, kv.get(key), id)
      case OperationTimeout(seq) =>
        persisting.get(seq).foreach {
          case PersistingValue(_, timer, _, _) =>
            timer.cancel()
            persisting -= seq
        }
      case msg@Snapshot(key, _, seq) if seq < expectedSeq =>
        sender ! SnapshotAck(key, seq)
      case msg@Snapshot(key, valueOption, seq) if seq == expectedSeq =>
        persist(key, valueOption, seq, Set.empty[ActorRef])
        setOperationTimeout(seq)

        expectedSeq += 1
        if (valueOption.isDefined)
          kv = kv.updated(key, valueOption.get)
        else
          kv -= key
    }
  }
  
// works
  val receiveReplica: Receive = withPersistence { (sender, key, id) => sender ! SnapshotAck(key, id) } {
    var expectedSeq = 0

    {
      case Get(key, id) =>
        sender ! GetResult(key, kv.get(key), id)
      case OperationTimeout(seq) =>
        persisting.get(seq).foreach {
          case PersistingValue(_, timer, _, _) =>
            timer.cancel()
            persisting -= seq
        }
      case msg@Snapshot(key, _, seq) if seq < expectedSeq =>
        sender ! SnapshotAck(key, seq)
      case msg@Snapshot(key, valueOption, seq) if seq == expectedSeq =>
        persist(key, valueOption, seq, Set.empty[ActorRef])
        setOperationTimeout(seq)

        expectedSeq += 1
        if (valueOption.isDefined)
          kv = kv.updated(key, valueOption.get)
        else
          kv -= key
    }
  }