code: protected void checkLeak() {
          if (CommonUtils.isNotEmpty(urlConnectionMap)) {
              if (LOGGER.isWarnEnabled()) {
                  LOGGER.warn("Bolt client transport maybe leak. {}", urlConnectionMap);
              }
              urlConnectionMap.clear();
          }
          if (CommonUtils.isNotEmpty(connectionRefCounter)) {
              if (LOGGER.isWarnEnabled()) {
                  LOGGER.warn("Bolt client transport maybe leak. {}", connectionRefCounter);
              }
              connectionRefCounter.clear();
          }
      }
docs: 检查是否有没回收