}

    /**
     * Set the value of clustername, used in parameter comment. <br>
     * Even if empty string, treated as empty plainly. So "IF pmb != null" is false if empty.
     * @param clustername The parameter value of clustername. (NotNull)
     */
    public void setClustername(String clustername) {
        registerVariable("clustername", clustername);
    }

    /**

        clusterName = response.getClusterName();
        clusterStatus = response.getStatus().toString();
        final Set<String> fieldSet = ComponentUtil.getFessConfig().getApiPingEsFieldSet();
        try (OutputStream out = SearchEngineUtil.getXContentBuilderOutputStream((builder, params) -> {
            builder.startObject();
            if (fieldSet.contains(CLUSTER_NAME)) {

    // Helper method to create mock ClusterHealthResponse
    private ClusterHealthResponse createMockHealthResponse(String clusterName, ClusterHealthStatus status) {
        return new ClusterHealthResponse() {
            @Override
            public String getClusterName() {
                return clusterName;
            }

            @Override
            public ClusterHealthStatus getStatus() {

            final ClusterHealthResponse response =
                    esClient.admin().cluster().prepareHealth().execute().actionGet(fessConfig.getIndexHealthTimeout());
            engineObj.clusterName = response.getClusterName();
            engineObj.numberOfNodes = response.getNumberOfNodes();
            engineObj.numberOfDataNodes = response.getNumberOfDataNodes();

        T build(R response, H hit);
    }

    /**
     * Sets the name of the search engine cluster.
     *
     * @param clusterName the cluster name
     */
    public void setClusterName(final String clusterName) {
        this.clusterName = clusterName;
    }

    /**
     * Gets information about the search engine.
     *
     * @return the engine information

    * to ensure backword and forward compat:
    * - SingleStack -v4 (pre v1.16) => BackendPool name == clusterName
    * - SingleStack -v6 => BackendPool name == clusterName (all cluster bootstrap uses this name)
    * DualStack:
    * => IPv4 BackendPool name == clusterName
    * => IPv6 BackendPool name == <clusterName>-IPv6
    * This result into:
    * - clusters moving from IPv4 to duakstack will require no changes

- AWS cloud provider supports auto-discovering subnets without any `kubernetes.io/cluster/<clusterName>` tags. It also supports additional service annotation `service.beta.kubernetes.io/aws-load-balancer-subnets` to manually configure the subnets. ([#97431](https://github.com/kubernetes/kubernetes/pull/97431), [@kishorj](https://github.com/kishorj))...

### Feature

    }

    public void test_fieldSetConfiguration() {
        // Test that field set configuration is properly handled
        Set<String> fieldSet = new HashSet<>();
        fieldSet.add("cluster_name");
        fieldSet.add("status");

        FessConfig mockConfig = new FessConfig.SimpleImpl() {
            private static final long serialVersionUID = 1L;

            @Override

                    .setThreads(threads)
                    .setTimeout(timeout)
                    .setType(type)
                    .execute()
                    .actionGet(timeout);
            append(buf, "cluster_name", () -> response.getClusterName().value()).append(',');
            final String hotThreads = response.getNodesMap().entrySet().stream().map(e -> {
                final StringBuilder tempBuf = new StringBuilder();