How to terminate Akka actor system from a main method? - scala

Question

I've this application using Akka Streams and ReactiveMongo. There are no user defined actors. The application is launched from a main method.
Problem is the JVM continues to run forever after the main method has completed. This is what I'm doing now:
val g = (file: String) => RunnableGraph.fromGraph(GraphDSL.create(Sink.ignore) {
implicit builder =>
sink =>
import GraphDSL.Implicits._
// Source
val A: Outlet[(String, String)] = builder.add(Source.fromIterator(() => parseMovies(file).iterator)).out
// Flow
val B: FlowShape[(String, String), Either[String, Movie]] = builder.add(findMovie)
// Flow
val C: FlowShape[Either[String, Movie], Option[String]] = builder.add(persistMovie)
A ~> B ~> C ~> sink.in
ClosedShape
})
def main(args: Array[String]): Unit = {
require(args.size >= 1, "Path to file is required.")
g(args(0)).run
.onComplete(_ => Await.result(system.terminate(), 5.seconds))
}
I've read this thread, and this, none of which work. system.shutdown is deprecated and I don't have any explicit actors to watch for. I can call system.exit but that's hardly graceful.
From the logs, it appears that Akka is trying to shut down but then I see a bunch of Mongo messages.
2017-01-13 11:35:57.320 [DEBUG] a.e.EventStream.$anonfun$applyOrElse$4 - shutting down: StandardOutLogger started
2017-01-13 11:36:05.397 [DEBUG] r.c.a.MongoDBSystem.debug - [Supervisor-1/Connection-2] ConnectAll Job running... Status: {{NodeSet None Node[localhost:27017: Primary (10/10 available connections), latency=6], auth=Set() }}
2017-01-13 11:36:05.420 [DEBUG] r.c.a.MongoDBSystem.debug - [Supervisor-1/Connection-2] RefreshAll Job running... Status: {{NodeSet None Node[localhost:27017: Primary (10/10 available connections), latency=6], auth=Set() }}
// more of MongoDBSystem.debug messages
Why won't it.just.die?

Answer 1

I think you want to add a shutdown hook or call actorSystem.registerOnTermination(driver.close()):
def main(args: Array[String]): Unit = {
import akka.actor.CoordinatedShutdown
require(args.size >= 1, "Path to file is required.")
CoordinatedShutdown(system).addTask(CooordinatedShutdown.PhaseBeforeActorSystemTerminate, "shutdownMongoDriver") { () => driver.close(5.seconds); Future.successful(Done) }
g(args(0)).run.onComplete(_ => CoordinatedShutdown(system).run())
}