@Override
  public void onDataNodeConfigChange(List<DataNodeConfig> configs) {
    for (DataNodeConfig currNodeConfig : configs) {
      String instanceName = currNodeConfig.getInstanceName();
      if (instanceName.equals(localInstanceName)) {
        dataNodeLatch.countDown();
        break;
      }
    }
  }
This method is called when the dataNodeConfigs changes in cluster map.
@param configs the list of {@link DataNodeConfig} that changed.
ambry-server/src/main/java/com/github/ambry/server/AmbryServerClusterMapChangeListenerImpl.java