docs: private void registerCachedServiceInstance(ProvidedServiceInstance instance, ServiceInstanceHealth registryHealth) {
          try {
              write.lock();
              ServiceInstanceId id = new ServiceInstanceId(instance.getServiceName(),
                      instance.getProviderId());
              CachedProviderServiceInstance cachedInstance = getCacheServiceInstances().get(id);
  
              if(cachedInstance == null){
                  cachedInstance = new CachedProviderServiceInstance(
                      instance);
                  getCacheServiceInstances().put(id, cachedInstance);
  
              }
              if(LOGGER.isDebugEnabled()){
                  LOGGER.debug("add cached ProvidedServiceInstance: {}.", cachedInstance.toString());
              }
              cachedInstance.setServiceInstanceHealth(registryHealth);
          } finally {
              write.unlock();
          }
      }