code: private synchronized void queueValid() throws InterruptedException {
          if(this.queue.isEmpty() && !this.faildQueue.isEmpty()){
              for (Task task : this.faildQueue) {
                  this.push(task, false);
              }
              this.faildQueue.clear();
          }
          if (this.queue.isEmpty()) {
              logger.info(Thread.currentThread().getName() + " queue is empty");
          }
      }
docs: 如果 queue 为空
  如果 task retry 次数小于系统设置的 DEFAULT_TASK_RESTY
  把失败任务重新添加到队列中