Greetings, I have a node with a number of top level actors and cluster
shards that I want to shut down gracefully. I have added the redacted code
before for the startup and shutdown via a SystemManagerActor but I am
staring at it wondering if there is a better way. A number of questions
occur.
1. Should I have this SystemManagerActor hold onto the refs of the actors
it starts and when shutting down send the refs Poison pills, or restart
them if the system is not shutting down?
2. If I go with option 1, is there any way that I can make the Cluster
Shard actors children of the SystemManagerActor? I could easily start the
other actors as children of the manager. What I am not sure about is the
cluster singleton and the cluster shards. It seems to me there is no way I
know to create them as children of other actors.
3. If question 2 is impossible, is it at all appropriate for the actor to
watch actors that aren't its children?
4. Any other suggestions?
Thanks in advance
package actors.system;
public class SystemManagerActor extends UntypedActor {
private static final Logger.ALogger log =
Logger.of(SystemManagerActor.class); // play framework logger
private static ActorSystem system = MyApp.getActorSystem();
private static Cluster cluster = Cluster.get(system);
private final CompletableFuture<Void> future;
// -- Shard regions for cluster sharded actors.
private final List<ActorRef> shardRegions = Stream.of(
ShardedActorA.shardRegion(),
ShardedActorB.shardRegion()
).collect(toList());
// -- Actors that are not sharded.
private final List<ActorSelection> actors = Stream.of(
SimpleActorA.actorSelection(),
SimpleActorB.actorSelection(),
SingletonActor.actorSelection()
).collect(toList());
public SystemManagerActor(final CompletableFuture<Void> future) {
this.future = future;
log.info("Shutting down MyApp ActorSystem actors");
// wait 5 seconds for load balancer.
context().system().scheduler().scheduleOnce(Duration.create(5,
SECONDS), self(),
SignalMessages.BEGIN_SHUTDOWN, context().dispatcher(), self());
}
@Override
public void onReceive(final Object message) throws Throwable {
if (message instanceof SignalMessages &&
SignalMessages.BEGIN_SHUTDOWN.equals(message)) {
shardRegions.forEach(ref -> {
context().watch(ref);
ref.tell(ShardRegion.gracefulShutdownInstance(), getSelf());
});
} else if (message instanceof Terminated && !shardRegions.isEmpty()) {
shardRegions.remove(((Terminated) message).getActor());
if (!shardRegions.isEmpty()) return;
actors.forEach(actorSelection ->
actorSelection.tell(PoisonPill.getInstance(), getSelf()));
log.info("Actors Shut down.");
cluster.subscribe(getSelf(), ClusterEvent.initialStateAsSnapshot(),
ClusterEvent.MemberRemoved.class);
cluster.leave(cluster.selfAddress());
} else if (message instanceof ClusterEvent.MemberRemoved) {
// wait 10 seconds for graceful stop.
context().system().scheduler().scheduleOnce(Duration.create(10,
SECONDS), self(),
SignalMessages.STOP_ACTOR_SYSTEM, context().dispatcher(),
self());
} else if (message instanceof SignalMessages &&
SignalMessages.STOP_ACTOR_SYSTEM.equals(message)) {
system.terminate();
future.complete(null);
} else {
unhandled(message);
}
}
public static CompletableFuture<Void> onStop() {
final CompletableFuture<Void> future = new CompletableFuture<>();
MyApp.getActorSystem().actorOf(Props.create(SystemManagerActor.class,
future));
return future;
}
public static void onStart() {
system.actorOf(SimpleActorA.props(), SimpleActorA.ACTOR_NAME);
system.actorOf(SimpleActorB.props(), SimpleActorB.ACTOR_NAME);
SingletonActor.register();
ShardedActorA.startShardRegion();
ShardedActorB.startShardRegion();
}
private enum SignalMessages {
BEGIN_SHUTDOWN, STOP_ACTOR_SYSTEM;
}
}
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