apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/util/InstanceConfigAuditUtil.java/InstanceConfigAuditUtil/doAudit
class InstanceConfigAuditUtil:  void doAudit(InstanceConfigAuditModel auditModel) {
    String instanceCacheKey = assembleInstanceKey(auditModel.getAppId(), auditModel
        .getClusterName(), auditModel.getIp(), auditModel.getDataCenter());
    Long instanceId = instanceCache.getIfPresent(instanceCacheKey);
    if (instanceId == null) {
      instanceId = prepareInstanceId(auditModel);
      instanceCache.put(instanceCacheKey, instanceId);
    }

    //load instance config release key from cache, and check if release key is the same
    String instanceConfigCacheKey = assembleInstanceConfigKey(instanceId, auditModel
        .getConfigAppId(), auditModel.getConfigNamespace());
    String cacheReleaseKey = instanceConfigReleaseKeyCache.getIfPresent(instanceConfigCacheKey);

    //if release key is the same, then skip audit
    if (cacheReleaseKey != null && Objects.equals(cacheReleaseKey, auditModel.getReleaseKey())) {
      return;
    }

    instanceConfigReleaseKeyCache.put(instanceConfigCacheKey, auditModel.getReleaseKey());

    //if release key is not the same or cannot find in cache, then do audit
    InstanceConfig instanceConfig = instanceService.findInstanceConfig(instanceId, auditModel
        .getConfigAppId(), auditModel.getConfigNamespace());

    if (instanceConfig != null) {
      if (!Objects.equals(instanceConfig.getReleaseKey(), auditModel.getReleaseKey())) {
        instanceConfig.setConfigClusterName(auditModel.getConfigClusterName());
        instanceConfig.setReleaseKey(auditModel.getReleaseKey());
        instanceConfig.setReleaseDeliveryTime(auditModel.getOfferTime());
      } else if (offerTimeAndLastModifiedTimeCloseEnough(auditModel.getOfferTime(),
          instanceConfig.getDataChangeLastModifiedTime())) {
        //when releaseKey is the same, optimize to reduce writes if the record was updated not long ago
        return;
      }
      //we need to update no matter the release key is the same or not, to ensure the
      //last modified time is updated each day
      instanceConfig.setDataChangeLastModifiedTime(auditModel.getOfferTime());
      instanceService.updateInstanceConfig(instanceConfig);
      return;
    }

    instanceConfig = new InstanceConfig();
    instanceConfig.setInstanceId(instanceId);
    instanceConfig.setConfigAppId(auditModel.getConfigAppId());
    instanceConfig.setConfigClusterName(auditModel.getConfigClusterName());
    instanceConfig.setConfigNamespaceName(auditModel.getConfigNamespace());
    instanceConfig.setReleaseKey(auditModel.getReleaseKey());
    instanceConfig.setReleaseDeliveryTime(auditModel.getOfferTime());
    instanceConfig.setDataChangeCreatedTime(auditModel.getOfferTime());

    try {
      instanceService.createInstanceConfig(instanceConfig);
    } catch (DataIntegrityViolationException ex) {
      //concurrent insertion, safe to ignore
    }
  }