Coordinated Shutdown inconsistently ignored when automatic JVM hook set to be true

Akka Libraries
1

Hi there,

I have akka.coordinated-shutdown.run-by-jvm-shutdown-hook set true (it’s default).
Akka Streams version 2.5.22.

For the following code:

    CoordinatedShutdown(system).addTask(CoordinatedShutdown.PhaseBeforeServiceUnbind, "graceful-kill")(() => {
      killSwitch.shutdown()
      Future(done())
    })

    CoordinatedShutdown(system).addTask(CoordinatedShutdown.PhaseBeforeActorSystemTerminate, "wait-streams-finished")(() => {
      streams.foreach(Await.ready(_, 1.minutes))
      Future(done())
    })

    system.registerOnTermination(db.close())

    sys.addShutdownHook {
      logger.info("Terminating Actor system...")
      Await.result(system.whenTerminated, Duration.Inf)
      logger.info("Actor system terminated")
    }

sometimes the app terminates with both graceful-kill and wait-streams-finished phases executed, and sometimes with only graceful-kill, sometimes with neither. despite the hook system.registerOnTermination(db.close()) is always executed and awaited.

What am I doing wrong?

Thank you very much.

3

I’d recommend to not use Await there. The list of futures can be turned into a single Future that that can be returned from the task. Future.sequence

sys.addShutdownHook adds a jvm shutdown hook. CoordinatedShutdown adds another. Order of execution of such hooks are not deterministic. Not sure what the purpose of your hook would be?

4

hey Patrik,

sys.addShutdownHook should prevent JVM from turning off unless actor system is terminated.

system.whenTerminated returns Future[Terminated], looks like no need for Future.sequence as Terminated is not an heir of Seq.

5

but that is already handled by the jvm hook added by CoordinatedShutdown

Future.sequence was instead of the streams.foreach Await