code: public static void apply(TracingGetter tracingGetter) {
          String groupId = Optional.ofNullable(tracingGetter.get(TracingConstants.HEADER_KEY_GROUP_ID)).orElse("");
          String appList = Optional.ofNullable(tracingGetter.get(TracingConstants.HEADER_KEY_APP_MAP)).orElse("");
          TracingContext.init(Maps.newHashMap(TracingConstants.GROUP_ID, groupId, TracingConstants.APP_MAP,
                  StringUtils.isEmpty(appList) ? appList : new String(Base64Utils.decodeFromString(appList), StandardCharsets.UTF_8)));
          if (TracingContext.tracing().hasGroup()) {
              log.debug("tracing apply group:{}, app map:{}", groupId, appList);
          }
      }
docs: 获取传输的Tracing信息
  
  @param tracingGetter Tracing信息获取器