code: public static void reset() {
          ScheduledExecutor ex = INSTANCE.executor.getAndSet(null);
          if (ex != null && ex.getThreadPool() != null) {
              ex.getThreadPool().shutdownNow();
          }
      }
docs: Clears all listeners.
  <p>
  NOTE: This will result in race conditions if {@link #addTimerListener(com.netflix.hystrix.util.HystrixTimer.TimerListener)} is being concurrently called.
  </p>