presto-main/src/main/java/io/prestosql/execution/scheduler/ScaledWriterScheduler.java/ScaledWriterScheduler/schedule
class ScaledWriterScheduler:    @Override
    public ScheduleResult schedule()
    {
        List<RemoteTask> writers = scheduleTasks(getNewTaskCount());

        future.set(null);
        future = SettableFuture.create();
        executor.schedule(() -> future.set(null), 200, MILLISECONDS);

        return new ScheduleResult(done.get(), writers, future, WRITER_SCALING, 0);
    }