Akka consolidate concurrent database requests

Question

I want to be able to make concurrent requests to multiple data repositories and consolidate the results. I am trying to understand if my approach is at all valid or if ther

Answer 1

Following the reading of Effective Akka by Jamie Allen, I am going to attempt to apply his "Cameo" pattern suggestion.

Slideshare: http://www.slideshare.net/shinolajla/effective-akka-scalaio

Github: https://github.com/jamie-allen/effective_akka

I think what I created will work, but doesn't sound like the best approach based on Jamie's comments in his talks. I will update / edit back to this post what I have implemented (or try to).

Summary Actor (Cameo Actor):

object SummaryResponseHandler {
  case object DbRetrievalTimeout

  def props(mongoDb: ActorRef, redisDb: ActorRef, originalSender: ActorRef): Props = {
    Props(new SummaryResponseHandler(mongoDb, redisDb, originalSender))
  }
}

class SummaryResponseHandler(mongoDb: ActorRef, redisDb: ActorRef,
                             originalSender: ActorRef) extends Actor with ActorLogging {

  import SummaryResponseHandler._
  var mongoSummary, redisSummary: Option[String] = None
  def receive = LoggingReceive {
    case MongoSummary(summary) =>
      log.debug(s"Received mongo summary: $summary")
      mongoSummary = summary
      collectSummaries
    case RedisSummary(summary) =>
      log.debug(s"Received redis summary: $summary")
      redisSummary = summary
      collectSummaries
    case DbRetrievalTimeout =>
      log.debug("Timeout occurred")
      sendResponseAndShutdown(DbRetrievalTimeout)
  }

  def collectSummaries = (mongoSummary, redisSummary) match {
    case (Some(m), Some(r)) =>
      log.debug(s"Values received for both databases")
      timeoutMessager.cancel
      sendResponseAndShutdown(DataSetSummary(mongoSummary, redisSummary))
    case _ =>
  }

  def sendResponseAndShutdown(response: Any) = {
    originalSender ! response
    log.debug("Stopping context capturing actor")
    context.stop(self)
  }

  import context.dispatcher
  val timeoutMessager = context.system.scheduler.scheduleOnce(
    250 milliseconds, self, DbRetrievalTimeout)
}

class SummaryRetriever(mongoDb: ActorRef, redisDb: ActorRef) extends Actor with ActorLogging {
  def receive = {
    case GetSummary(dataSet) =>
      log.debug("received dataSet")
      val originalSender = sender
      val handler = context.actorOf(SummaryResponseHandler.props(mongoDb,redisDb, originalSender), "cameo-message-handler")
      mongoDb.tell(GetSummary(dataSet), handler)
      redisDb.tell(GetSummary(dataSet), handler)
    case _ => log.debug(s"Unknown result $GetSummary(datset)")
  }

}

Common:

case class GetSummary(dataSet: String)
case class DataSetSummary(
   mongo: Option[String],
   redis: Option[String]
)

case class MongoSummary(
    summary: Option[String]
                         )

case class RedisSummary(
   summary: Option[String]
                         )

trait MongoProxy extends Actor with ActorLogging
trait RedisProxy extends Actor with ActorLogging

Mock Stubs:

class MongoProxyStub extends RedisProxy {
  val summaryData = Map[String, String](
    "dataset1" -> "MongoData1",
    "dataset2" -> "MongoData2")

  def receive = LoggingReceive {
    case GetSummary(dataSet: String) =>
      log.debug(s"Received GetSummary for ID: $dataSet")
      summaryData.get(dataSet) match {
        case Some(data) => sender ! MongoSummary(Some(data))
        case None => sender ! MongoSummary(Some(""))
      }
  }
}

class RedisProxyStub extends MongoProxy{
  val summaryData = Map[String, String](
    "dataset1" -> "RedisData1",
    "dataset2" -> "RedisData2")

  def receive = LoggingReceive {
    case GetSummary(dataSet: String) =>
      log.debug(s"Received GetSummary for ID: $dataSet")
      summaryData.get(dataSet) match {
        case Some(data) => sender ! RedisSummary(Some(data))
        case None => sender ! RedisSummary(Some(""))
      }
  }
}

Boot (You should use test, but was just wanting to run from boot):

object Boot extends App{

  val system = ActorSystem("DbSystem")

  val redisProxy = system.actorOf(Props[RedisProxyStub], "cameo-success-mongo")
  val mongoProxy = system.actorOf(Props[MongoProxyStub], "cameo-success-redis")
  val summaryRetrieverActor = system.actorOf(Props(new SummaryRetriever(redisProxy, mongoProxy)), "cameo-retriever1")

  implicit val timeout = Timeout(5 seconds)
  val future = summaryRetrieverActor ? GetSummary("dataset1")
  val result = Await.result(future, timeout.duration).asInstanceOf[DataSetSummary]
  println(Some(result.mongo).x)
  println(result.redis)

  system.shutdown()

}

Application Config:

akka.loglevel = "DEBUG"
akka.event-handlers = ["akka.event.slf4j.Slf4jEventHandler"]
akka.actor.debug.autoreceive = on
akka.actor.debug.lifecycle = on
akka.actor.debug.receive = on
akka.actor.debug.event-stream = on