Guava: Does awaitRunning() method guarantee that runOneIteration() is called before returning?

Question

I need to start a service which extends the service AbstractScheduledService in Guava. I want to start the service in such a way that runOneIteration() method is executed as soon as the service is started by running it's start method.

I don't want to use startAsync() method as that would return asynchronously.

If I use awaitRunning(), the documentation specifies that it will only return after the service reaches RUNNING state. But does that guarantee that runOneIteration() is called before returning? If not, is there any way I can guarantee that runOneIteration() is called at least once before returning from starting the service.

Here is one approach:

1. If I Override the startUp() method and call runOneIteration() in it, is this going to work?

   @Override
   public void startUp() {
   runOneIteration();
   }
   

Answer 1

Here is a dirty hack I used to solve this issue.

public void start() {
  runOneIteration();
  startAsync();
}

@Override
protected Scheduler scheduler() {
    return Scheduler.newFixedRateSchedule(0, 10, TimeUnit.SECONDS);
}

I call the start() method on this service.

serviceName.start();

This ensures that runOneIteration is executed once when serviceName.start() is called.