How to stop gracefully the actor system for an akka-http server that must be deployed.

Question

I just created my first rest server with akka-http. The problem is that I do not know how to deploy the server in such a way that I could gracefully shutdown the actor system.

For example I found something here: https://stackoverflow.com/a/17399574/5388513 where you could use Akka's microkernel, but it is deprecated. I tried using sbt-native-package, but I do not know how to gracefully shutdown the actor system.

Thank you!

Answer 1

You can add shutdown hook:

// import scala.concurrent.duration._
//shutdown Hook
scala.sys.addShutdownHook {
  logger.info("Terminating...")
  actorSystem.terminate()
  Await.result(actorSystem.whenTerminated, 30 seconds)
  logger.info("Terminated... Bye")
}

Answer 2

You could add to your main method

Runtime.getRuntime.addShutdownHook(new Thread() {
  override def run() {
    system.shutdown()
    system.awaitTermination()
  }
})

Your app will wait until actor system will be shutt down and all postStop callbacks in your actors will be executed.

Answer 3

One solution is to add an Actor to your ActorSystem that listens for a particular signal and calls shutdown:

import akka.actor.{Actor, Props}

object ShutdownMessage

object KillSwitchActor {
  def props : Props = Props[KillSwitchActor]
}

class KillSwitchActor extends Actor {
  def receive = {
    case ShutdownMessage => context.system.shutdown()
    case _ => {}
  }
}//end class KillSwitchActor

Then you simply setup your KillSwitchActor:

import akka.actor.ActorSystem

val actorSystem : ActorSystem = ActorSystem("testKillSwitch")

val killRef = actorSystem actorOf KillSwitchActor.props

//"Say hello to my little friend!" - Tony Montana 
if(someTerminatingCondition) { killRef ! ShutdownMessage }