code: protected void handleStatsResetIfNeeded(StatusData<NginxMetrics> status) {
          StatValue previousHandled = getStatValue(NginxMetrics.HANDLED);
          Long currentHandled = Long.class.cast(status.get(NginxMetrics.HANDLED));
          if (previousHandled != null && currentHandled != null && previousHandled.getValueAsLong() > currentHandled) {
              for (NginxMetrics metric : getAvailableMetrics()) {
                  if (metric.getType() == StatValueTypes.DIFFLONG) {
                      StatValue stat = getStatValue(metric);
                      if (stat != null)
                          stat.reset();
                  }
              }
          }
      }
docs: Check HANDLED metric and if its value is lower than the stored one -
  monitored Nginx server was restarted. In this case all DIFFLONG statValues
  need resetting.
  
  @param status latest status data.