akka- how to ensure all responses of dynamic number of actors are returned to parent actor? - scala

Question

I need to create variable number of actors each time my program starts and then must ensure all responses are return after a period of time. This
link gives a good idea for fixed number of actors but what about dynamic number?
This is my code that creates actor and passes messages to them:
ruleList = ...
val childActorList: Iterable[ActorRef] = ruleList.map(ruleItem =>
context.actorOf(DbActor.props(ruleItem.parameter1, ruleItem.parameter2)))
implicit val timeout = Timeout(10.second)
childActorList.foreach(childActor =>
childActor ? (tempTableName, lastDate)
)
Updated-1
According to #Raman Mishra guides , I updated my code as bellow, this is the code in parent actor:
override val supervisorStrategy: SupervisorStrategy = {
OneForOneStrategy(maxNrOfRetries = 10, withinTimeRange = 10 seconds) {
case exp: SQLException => //Resume;
throw exp
case exp:AskTimeoutException => throw exp
case other: Exception => throw other
}
}
override def receive: Receive = {
case Start(tempTableName, lastDate) => {
implicit val timeout = Timeout(10.second)
ruleList.foreach { ruleItem =>
val childActor = context.actorOf(DbActor.props(ruleItem._1, query = ruleItem._2))
ask(childActor, (tempTableName, lastDate)).mapTo[Seq[Int]]
onComplete {
lastDate)).mapTo[Seq[Int]] onComplete {
case util.Success(res) => println("done" + res + ruleItem._2)
case util.Failure(exp: AskTimeoutException) => println("Failed query:" + ruleItem._2); throw exp
case other => println(other)
}
}
And in child actor:
case (brokerTableName, lastDate) => {
Logger("Started query by actor" + self.path.name + ':' +
val repo = new Db()
val res = repo.getAggResult(query = (brokerTableName, lastDate))
val resWrapper = res match {
case elem: Future[Any] => elem
case elem:Any => Future(elem)
}
resWrapper pipeTo self
}
case res:List[Map[Any, Any]] => {
// here final result is send to parent actor
repo.insertAggresults(res, aggTableName) pipeTo context.parent
}
Now, whenever I run main app, first, parent actor starts and create child actors and send messages to them using ask method. Child actors do their tasks but the problem here is child actors response never returns back to parent actor and in every run of app, AskTimeoutException occurs. I doubt if the use of onComplete method is correct or not. Any help will be appreciated.
"Updated-2"
I found out the problem is in using context.parent instead of sender(). Also, when I pipe to sender, first part of my result, and the sender ask for second part, the problem is resolved but I don't know what happens here, why Can't I pipe to self and return the final result to parent?
This is the last code:
In parent actor:
override def receive: Receive = {
case Start(tempTableName, lastDate) => {
println("started: called by remote actor")
implicit val timeout = Timeout(5 second)
ruleList.foreach { ruleItem =>
val childActor = context.actorOf(DbActor.props(ruleItem._1, query = ruleItem._2))
ask(childActor, Broker(tempTableName, lastDate)) onComplete {
// (childActor ? Broker(tempTableName, lastDate)).mapTo[Seq[Int]] onComplete {
case util.Success(res: List[Map[Any, Any]]) => (childActor ? res) onComplete {
case util.Success(res: Seq[Any]) => println("Successfull- Num,ber of documents:" + res.length + " " + ruleItem._2)
case util.Failure(exp: AskTimeoutException) => println("Failed for writing - query:" + ruleItem._2); throw exp
}
case util.Failure(exp: AskTimeoutException) => println("Failed for reading - query :" + ruleItem._2); throw exp
case other => println(other)
}
}
}
}
In child actor:
case (brokerTableName, lastDate) => {
Logger("Started query by actor" + self.path.name + ':' +
val repo = new Db()
val res = repo.getAggResult(query = (brokerTableName, lastDate))
val resWrapper = res match {
case elem: Future[Any] => elem
case elem:Any => Future(elem)
}
resWrapper pipeTo sender()
}
case res:List[Map[Any, Any]] => {
// here final result is send to parent actor
repo.insertAggresults(res, aggTableName) pipeTo sender()
}

Answer 1

The reason that replying to sender() works where replying to context.parent does not is that ask creates an temporary actor to handle the response. You need to reply to this temporary actor: the sender (which is different from the parent).
Also it's not clear whether the getAggResult method is blocking. If so this will not help (see here).