[FEATURE] Reactive version of the clients

settings.gradle.kts

@@ -30,6 +30,7 @@ dependencyResolutionManagement {
       library("boot-test", "org.springframework.boot", "spring-boot-test").versionRef("spring-boot")
       library("boot-test-autoconfigure", "org.springframework.boot", "spring-boot-test-autoconfigure").versionRef("spring-boot")
       library("boot-testcontainers", "org.springframework.boot", "spring-boot-testcontainers").versionRef("spring-boot")
+      library("projectreactor", "io.projectreactor:reactor-test:3.7.5")
       plugin("spring-boot", "org.springframework.boot").versionRef("spring-boot")
     }
 

spring-data-opensearch/build.gradle.kts

@@ -38,6 +38,7 @@ dependencies {
   compileOnly(springLibs.web)
   compileOnly(opensearchLibs.java.client)
 
+  testImplementation(springLibs.projectreactor)
   testImplementation(opensearchLibs.java.client)
   testImplementation("jakarta.enterprise:jakarta.enterprise.cdi-api:3.0.0")
   testImplementation("org.slf4j:log4j-over-slf4j:2.0.17")

spring-data-opensearch/src/main/java/org/opensearch/data/client/osc/OpenSearchClients.java

@@ -62,6 +62,7 @@
 @SuppressWarnings("unused")
 public final class OpenSearchClients {
     public static final String IMPERATIVE_CLIENT = "imperative";
+    public static final String REACTIVE_CLIENT = "reactive";
 
     /**
      * Name of whose value can be used to correlate log messages for this request.
@@ -282,6 +283,93 @@ public static OpenSearchTransport getOpenSearchTransport(RestClient restClient,
     }
     // endregion
 
+    // region reactive client
+    /**
+     * Creates a new {@link ReactiveOpenSearchClient}
+     *
+     * @param clientConfiguration configuration options, must not be {@literal null}.
+     * @return the {@link ReactiveOpenSearchClient}
+     */
+    public static ReactiveOpenSearchClient createReactive(ClientConfiguration clientConfiguration) {
+
+        Assert.notNull(clientConfiguration, "clientConfiguration must not be null");
+
+        return createReactive(getRestClient(clientConfiguration), null, DEFAULT_JSONP_MAPPER);
+    }
+
+    /**
+     * Creates a new {@link ReactiveOpenSearchClient}
+     *
+     * @param clientConfiguration configuration options, must not be {@literal null}.
+     * @param transportOptions options to be added to each request.
+     * @return the {@link ReactiveOpenSearchClient}
+     */
+    public static ReactiveOpenSearchClient createReactive(ClientConfiguration clientConfiguration,
+            @Nullable TransportOptions transportOptions) {
+
+        Assert.notNull(clientConfiguration, "ClientConfiguration must not be null!");
+
+        return createReactive(getRestClient(clientConfiguration), transportOptions, DEFAULT_JSONP_MAPPER);
+    }
+
+    /**
+     * Creates a new {@link ReactiveOpenSearchClient}
+     *
+     * @param clientConfiguration configuration options, must not be {@literal null}.
+     * @param transportOptions options to be added to each request.
+     * @param jsonpMapper the JsonpMapper to use
+     * @return the {@link ReactiveOpenSearchClient}
+     */
+    public static ReactiveOpenSearchClient createReactive(ClientConfiguration clientConfiguration,
+            @Nullable TransportOptions transportOptions, JsonpMapper jsonpMapper) {
+
+        Assert.notNull(clientConfiguration, "ClientConfiguration must not be null!");
+        Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
+
+        return createReactive(getRestClient(clientConfiguration), transportOptions, jsonpMapper);
+    }
+
+    /**
+     * Creates a new {@link ReactiveOpenSearchClient}.
+     *
+     * @param restClient the underlying {@link RestClient}
+     * @return the {@link ReactiveOpenSearchClient}
+     */
+    public static ReactiveOpenSearchClient createReactive(RestClient restClient) {
+        return createReactive(restClient, null, DEFAULT_JSONP_MAPPER);
+    }
+
+    /**
+     * Creates a new {@link ReactiveOpenSearchClient}.
+     *
+     * @param restClient the underlying {@link RestClient}
+     * @param transportOptions options to be added to each request.
+     * @return the {@link ReactiveOpenSearchClient}
+     */
+    public static ReactiveOpenSearchClient createReactive(RestClient restClient,
+            @Nullable TransportOptions transportOptions, JsonpMapper jsonpMapper) {
+
+        Assert.notNull(restClient, "restClient must not be null");
+
+        var transport = getOpenSearchTransport(restClient, REACTIVE_CLIENT, transportOptions, jsonpMapper);
+        return createReactive(transport);
+    }
+
+    /**
+     * Creates a new {@link ReactiveOpenSearchClient} that uses the given {@link OpenSearchTransport}.
+     *
+     * @param transport the transport to use
+     * @return the {@link ReactiveOpenSearchClient}
+     */
+    public static ReactiveOpenSearchClient createReactive(OpenSearchTransport transport) {
+
+        Assert.notNull(transport, "transport must not be null");
+
+        return new ReactiveOpenSearchClient(transport);
+    }
+    // endregion
+
+
     private static List<String> formattedHosts(List<InetSocketAddress> hosts, boolean useSsl) {
         return hosts.stream().map(it -> (useSsl ? "https" : "http") + "://" + it.getHostString() + ':' + it.getPort())
                 .collect(Collectors.toList());

spring-data-opensearch/src/main/java/org/opensearch/data/client/osc/ReactiveChildTemplate.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.data.client.osc;
+
+import org.opensearch.client.ApiClient;
+import org.opensearch.client.json.JsonpMapper;
+import org.opensearch.client.transport.Transport;
+import org.reactivestreams.Publisher;
+import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
+import org.springframework.util.Assert;
+import reactor.core.publisher.Flux;
+
+/**
+ * base class for a reactive template that uses on of the {@link ReactiveOpenSearchClient}'s child clients.
+ */
+public class ReactiveChildTemplate<T extends Transport, CLIENT extends ApiClient<T, CLIENT>> {
+    protected final CLIENT client;
+    protected final ElasticsearchConverter elasticsearchConverter;
+    protected final RequestConverter requestConverter;
+    protected final ResponseConverter responseConverter;
+    protected final OpenSearchExceptionTranslator exceptionTranslator;
+
+    public ReactiveChildTemplate(CLIENT client, ElasticsearchConverter elasticsearchConverter) {
+        this.client = client;
+        this.elasticsearchConverter = elasticsearchConverter;
+        JsonpMapper jsonpMapper = client._transport().jsonpMapper();
+        requestConverter = new RequestConverter(elasticsearchConverter, jsonpMapper);
+        responseConverter = new ResponseConverter(jsonpMapper);
+        exceptionTranslator = new OpenSearchExceptionTranslator(jsonpMapper);
+    }
+
+    /**
+     * Callback interface to be used with {@link #execute(ClientCallback)} for operating directly on the client.
+     */
+    @FunctionalInterface
+    public interface ClientCallback<CLIENT, RESULT extends Publisher<?>> {
+        RESULT doWithClient(CLIENT client);
+    }
+
+    /**
+     * Execute a callback with the client and provide exception translation.
+     *
+     * @param callback the callback to execute, must not be {@literal null}
+     * @param <RESULT> the type returned from the callback
+     * @return the callback result
+     */
+    public <RESULT> Publisher<RESULT> execute(ClientCallback<CLIENT, Publisher<RESULT>> callback) {
+
+        Assert.notNull(callback, "callback must not be null");
+
+        return Flux.defer(() -> callback.doWithClient(client)).onErrorMap(exceptionTranslator::translateException);
+    }
+
+}

spring-data-opensearch/src/main/java/org/opensearch/data/client/osc/ReactiveClusterTemplate.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.data.client.osc;
+
+import org.opensearch.client.opensearch.cluster.HealthRequest;
+import org.opensearch.client.opensearch.cluster.HealthResponse;
+import org.opensearch.client.transport.OpenSearchTransport;
+import org.springframework.data.elasticsearch.core.cluster.ClusterHealth;
+import org.springframework.data.elasticsearch.core.cluster.ReactiveClusterOperations;
+import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
+import reactor.core.publisher.Mono;
+
+/**
+ * Reactive cluster template
+ */
+public class ReactiveClusterTemplate
+        extends ReactiveChildTemplate<OpenSearchTransport, ReactiveOpenSearchClusterClient>
+        implements ReactiveClusterOperations {
+
+    public ReactiveClusterTemplate(ReactiveOpenSearchClusterClient client,
+            ElasticsearchConverter elasticsearchConverter) {
+        super(client, elasticsearchConverter);
+    }
+
+    @Override
+    public Mono<ClusterHealth> health() {
+
+        HealthRequest healthRequest = requestConverter.clusterHealthRequest();
+        Mono<HealthResponse> healthResponse = Mono.from(execute(client -> client.health(healthRequest)));
+        return healthResponse.map(responseConverter::clusterHealth);
+    }
+
+}