public synchronized void cancelAllScheduledActions() {
    if (!isShuttingDown) {
      futureHandles.keySet().forEach(this::tryCancelScheduledAction);
      futureHandles.clear();
    }
  }
Stops the scheduler. After this invocation no further schedule calls will be accepted
and all pending enqueued tasks will be cancelled.
samza-core/src/main/java/org/apache/samza/zk/ScheduleAfterDebounceTime.java