1.RestClient

/**
 * Client that connects to an Elasticsearch cluster through HTTP.
 * <p>
 * Must be created using {@link RestClientBuilder}, which allows to set all the different options or just rely on defaults.
 * The hosts that are part of the cluster need to be provided at creation time, but can also be replaced later
 * by calling {
 
@link #setNodes(Collection)}.
 * <p>
 * The method {@link #performRequest(Request)} allows to send a request to the cluster. When
 * sending a request, a host gets selected out of the provided ones in a round-robin fashion. Failing hosts are marked dead and
 * retried after a certain amount of time (minimum 1 minute, maximum 30 minutes), depending on how many times they previously
 * failed (the more failures, the later they will be retried). In case of failures all of the alive nodes (or dead nodes that
 * deserve a retry) are retried until one responds or none of them does, in which case an {
 
@link IOException} will be thrown.
 * <p>
 * Requests can be either synchronous or asynchronous. The asynchronous variants all end with {@code Async}.
 * <p>
 * Requests can be traced by enabling trace logging for "tracer". The trace logger outputs requests and responses in curl format.
 
 
*/

2.RestHighLevelClient

/**
 * High level REST client that wraps an instance of the low level {@link RestClient} and allows to build requests and read responses.
 * The {@link RestClient} instance is internally built based on the provided {@link RestClientBuilder} and it gets closed automatically
 * when closing the {@link RestHighLevelClient} instance that wraps it.
 * In case an already existing instance of a low-level REST client needs to be provided, this class can be subclassed and the
 * {@link #RestHighLevelClient(RestClient, CheckedConsumer, List)}  constructor can be used.
 * This class can also be sub-classed to expose additional client methods that make use of endpoints added to Elasticsearch through
 * plugins, or to add support for custom response sections, again added to Elasticsearch through plugins.
 */

2.1 IndicesClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Indices API.
 * <p>
 * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/indices.html">Indices API on elastic.co</a>
 */

2.2 ClusterClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Cluster API.
 * <p>
 * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/cluster.html">Cluster API on elastic.co</a>
 */

2.3 IngestClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Ingest API.
 * <p>
 * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/ingest.html">Ingest API on elastic.co</a>
 */

2.4 SnapshotClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Snapshot API.
 * <p>
 * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-snapshots.html">Snapshot API on elastic.co</a>
 */

2.5 TasksClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Tasks API.
 * <p>
 * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/tasks.html">Task Management API on elastic.co</a>
 */

2.6 XPackClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for
 * accessing the Elastic Licensed X-Pack APIs that are shipped with the
 * default distribution of Elasticsearch. All of these APIs will 404 if run
 * against the OSS distribution of Elasticsearch.
 * <p>
 * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/xpack-api.html">
 * X-Pack APIs on elastic.co</a> for more information.
 */

2.7 WatcherClient

   /**
     * Start the watch service
     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-start.html">
     * the docs</a> for more.
     * @param request the request
     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
     * @return the response
     * @throws IOException in case there is a problem sending the request or parsing back the response
     */

2.8 GraphClient

    /**
     * Executes an exploration request using the Graph API.
     *
     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/graph-explore-api.html">Graph API
     * on elastic.co</a>.
     */

2.9 LicenseClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for
 * accessing the Elastic License-related methods
 * <p>
 * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/licensing-apis.html">
 * X-Pack Licensing APIs on elastic.co</a> for more information.
 */

2.10 MigrationClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for
 * accessing the Elastic License-related methods
 * <p>
 * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/migration-api.html">
 * X-Pack Migration APIs on elastic.co</a> for more information.
 */

2.11 MachineLearningClient

/**
 * Machine Learning API client wrapper for the {@link RestHighLevelClient}
 * <p>
 * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/ml-apis.html">
 * X-Pack Machine Learning APIs </a> for additional information.
 */

2.12 SecurityClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Security APIs.
 * <p>
 * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api.html">Security APIs on elastic.co</a>
 */

2.13 RollupClient

/**
 * A wrapper for the {@link RestHighLevelClient} that provides methods for
 * accessing the Elastic Rollup-related methods
 * <p>
 * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/rollup-apis.html">
 * X-Pack Rollup APIs on elastic.co</a> for more information.
 */

3.TransportClient

/**
 * The transport client allows to create a client that is not part of the cluster, but simply connects to one
 * or more nodes directly by adding their respective addresses using
 * {@link #addTransportAddress(org.elasticsearch.common.transport.TransportAddress)}.
 * <p>
 * The transport client important modules used is the {@link org.elasticsearch.common.network.NetworkModule} which is
 * started in client mode (only connects, no bind).
 *
 * @deprecated {@link TransportClient} is deprecated in favour of the High Level REST client and will
 * be removed in Elasticsearch 8.0.
 */