apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/PortalSettings.java/PortalSettings/handleEnvDown
class PortalSettings:    private void handleEnvDown(Env env) {
      int failedTimes = healthCheckFailedCounter.get(env);
      healthCheckFailedCounter.put(env, ++failedTimes);

      if (!envStatusMark.get(env)) {
        logger.error("Env is down. env: {}, failed times: {}, meta server address: {}", env, failedTimes,
                portalMetaDomainService.getDomain(env));
      } else {
        if (failedTimes >= ENV_DOWN_THRESHOLD) {
          envStatusMark.put(env, false);
          logger.error("Env is down because health check failed for {} times, "
                       + "which equals to down threshold. env: {}, meta server address: {}", ENV_DOWN_THRESHOLD, env,
                  portalMetaDomainService.getDomain(env));
        } else {
          logger.error(
              "Env health check failed for {} times which less than down threshold. down threshold:{}, env: {}, meta server address: {}",
              failedTimes, ENV_DOWN_THRESHOLD, env, portalMetaDomainService.getDomain(env));
        }
      }

    }