apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/PortalSettings.java/HealthCheckTask/run
class HealthCheckTask:    public void run() {

      for (Env env : allEnvs) {
        try {
          if (isUp(env)) {
            //revive
            if (!envStatusMark.get(env)) {
              envStatusMark.put(env, true);
              healthCheckFailedCounter.put(env, 0);
              logger.info("Env revived because env health check success. env: {}", env);
            }
          } else {
            logger.error("Env health check failed, maybe because of admin server down. env: {}, meta server address: {}", env,
                    portalMetaDomainService.getDomain(env));
            handleEnvDown(env);
          }

        } catch (Exception e) {
          logger.error("Env health check failed, maybe because of meta server down "
                       + "or configure wrong meta server address. env: {}, meta server address: {}", env,
                  portalMetaDomainService.getDomain(env), e);
          handleEnvDown(env);
        }
      }

    }