@Override
  public void close() throws IOException {
    super.close();

    if (factory != null) {
      factory.close();
    }
  }
  @Override
  public void init(Map<String, Object> pluginConfig) {
    super.init(pluginConfig);

    String httpClientBuilderFactory =
        (String)
            Objects.requireNonNull(
                pluginConfig.get(HTTPCLIENT_BUILDER_FACTORY),
                "Please specify clientBuilderFactory to be used for Solr internal communication.");
    factory =
        this.coreContainer
            .getResourceLoader()
            .newInstance(httpClientBuilderFactory, HttpClientBuilderFactory.class);
  }