Akka TCP Request Response need Thread.sleep - scala

Question

Good morning , I hava a problem with basic akka IO by TCP
I've a basic implemetation of Client and Server as shown on akka documentation:
Client is https://github.com/akka/akka/blob/v2.5.20/akka-docs/src/test/scala/docs/io/IODocSpec.scala#L67-L103
And Handler is [SimpleEchoHandler] (https://github.com/akka/akka/blob/v2.5.20/akka-docs/src/test/scala/docs/io/EchoServer.scala#L227-L304) but also the other act as the same way.
I've a main test method that stop on first connection to the server:
package core.september
import java.net.InetSocketAddress
import akka.actor.{Actor, ActorLogging, ActorRef, ActorSystem, Props}
import akka.util.ByteString
import com.typesafe.config.ConfigFactory
import core.september.fastchain.network.Client
/**
* #author ${user.name}
*/
object App {
class ClientHandler extends Actor with ActorLogging {
def receive = {
case toLog ⇒ {
log.debug("Client received "+ toLog.toString)
}
//Thread.sleep(200)
}
}
def main(args : Array[String]) {
val config = ConfigFactory.parseString("akka.loglevel = DEBUG")
implicit val system = ActorSystem("EchoServer", config)
var clientHand:ActorRef = system.actorOf(Props(classOf[ClientHandler]))
var address:InetSocketAddress = new InetSocketAddress("localhost",5080)
var ackServer = system.actorOf(Props(classOf[EchoManager], classOf[SimpleEchoHandler],5080), "simple")
var client:ActorRef = system.actorOf(Props(classOf[Client],address,clientHand));
//Thread.sleep(200)
client ! ByteString("echo")
//Thread.sleep(200)
client ! "close"
}
}
If I' don't comment out the two Thread.sleep after each message I can't see the output of the sent message, the output, without sleep is just:
[DEBUG] [02/07/2019 15:47:21.812] [EchoServer-akka.actor.default-dispatcher-4] [akka://EchoServer/system/IO-TCP/selectors/$a/0] Attempting connection to [localhost/127.0.0.1:5080]
[DEBUG] [02/07/2019 15:47:21.816] [EchoServer-akka.actor.default-dispatcher-4] [akka://EchoServer/system/IO-TCP/selectors/$a/0] Connection established to [localhost/127.0.0.1:5080]
[DEBUG] [02/07/2019 15:47:21.825] [EchoServer-akka.actor.default-dispatcher-3] [akka://EchoServer/user/$a] Client received Connected(localhost/127.0.0.1:5080,/127.0.0.1:54616)
I completely loose ByteString message and the "close" message.
My question is why i need to put the main thread in sleep to show also other messages.
With thread.sleep message are correctly logged:
[DEBUG] [02/07/2019 15:53:55.988] [EchoServer-akka.actor.default-dispatcher-5] [akka://EchoServer/system/IO-TCP/selectors/$a/0] Attempting connection to [localhost/127.0.0.1:5080]
[DEBUG] [02/07/2019 15:53:55.999] [EchoServer-akka.actor.default-dispatcher-5] [akka://EchoServer/system/IO-TCP/selectors/$a/0] Connection established to [localhost/127.0.0.1:5080]
[DEBUG] [02/07/2019 15:53:56.011] [EchoServer-akka.actor.default-dispatcher-5] [akka://EchoServer/user/$a] Client received Connected(localhost/127.0.0.1:5080,/127.0.0.1:54712)
[DEBUG] [02/07/2019 15:53:56.157] [EchoServer-akka.actor.default-dispatcher-2] [akka://EchoServer/user/$a] Client received ByteString(101, 99, 104, 111)
[DEBUG] [02/07/2019 15:53:56.374] [EchoServer-akka.actor.default-dispatcher-4] [akka://EchoServer/user/$a] Client received connection closed
ClientActor implementation is:
package core.september.fastchain.network
import akka.actor.{ Actor, ActorRef, Props }
import akka.io.{ IO, Tcp }
import akka.util.ByteString
import java.net.InetSocketAddress
object Client {
def props(remote: InetSocketAddress, replies: ActorRef) =
Props(classOf[Client], remote, replies)
}
class Client(remote: InetSocketAddress, listener: ActorRef) extends Actor {
import Tcp._
import context.system
import akka.io.Tcp
/*if (listener == null) {
listener = Tcp.get(context.system).manager
}*/
IO(Tcp) ! Connect(remote)
def receive = {
case CommandFailed(_: Connect) ⇒
listener ! "connect failed"
context stop self
case c # Connected(remote, local) ⇒
listener ! c
val connection = sender()
connection ! Register(self)
context become {
case data: ByteString ⇒
connection ! Write(data)
case CommandFailed(w: Write) ⇒
// O/S buffer was full
listener ! "write failed"
case Received(data) ⇒
listener ! data
case "close" ⇒
connection ! Close
case _: ConnectionClosed ⇒
listener ! "connection closed"
context stop self
}
}
}
thank you vey much.

Answer 1

You gotta wait for the actor to process your messages before exiting the app.
The easiest way is to use Akka's gracefulStop pattern:
import akka.pattern.gracefulStop
client ! ByteString("echo")
client ! "close"
Await.result(gracefulStop(client, 1 second)(system)