How to terminate the akka grpc client after calling?

Question

I have an akka grpc client, the code attempts to send a seq to remote python grpc server to get results:

package com.example.predict

import akka.actor.typed.ActorSystem
import akka.actor.typed.scaladsl.Behaviors
import akka.grpc.GrpcClientSettings
import org.apache.openwhisk.grpc.{PredictRequest, PredictServiceClient}

import scala.concurrent.ExecutionContext
import scala.util.{Failure, Success}

object PredictClient {
  def main(args: Array[String]): Unit = {
    implicit val sys: ActorSystem[_] = ActorSystem(Behaviors.empty, "PredictClient")
    implicit val ec: ExecutionContext = sys.executionContext

    val clientSettings = GrpcClientSettings.connectToServiceAt("127.0.0.1", 9999).withTls(false)
    val client = PredictServiceClient(clientSettings)
    val reply = client.predict(PredictRequest(Seq(1,2,2,3,3,4)))
    reply.onComplete{
      case Success(msg) =>
        println(s"the result is : ${msg.results}")
      case Failure(e) =>
        println(s"Error: $e")
    }
  }
}

I simply click run PredictClient in IntelliJ IDEA to run the main method, but after successfully getting the result and printing, the code kept running. Even when I added client.close() at the end of the main method still kept running and coundn't stop. How to successfully finish the main method after I getting the result? Is there something I missed?

Answer 1

The ActorSystem typically has to be manually terminated, e.g. with:

reply.onComplete {
  case _ => system.terminate()
}