private Scheduler() {}
  }

  /* use AbstractService for state management */
  private final AbstractService delegate = new ServiceDelegate();

  @WeakOuter
  private final class ServiceDelegate extends AbstractService {

    // A handle to the running task so that we can stop it when a shutdown has been requested.

    private Scheduler() {}
  }

  /* use AbstractService for state management */
  private final AbstractService delegate = new ServiceDelegate();

  @WeakOuter
  private final class ServiceDelegate extends AbstractService {

    // A handle to the running task so that we can stop it when a shutdown has been requested.