Documentation about compatibility headers.

Original Pull Request #2093
Closes #2088

Author: sothawo

src/main/asciidoc/reference/elasticsearch-clients.adoc

@@ -151,6 +151,29 @@ Default is 5 sec.
 IMPORTANT: Adding a Header supplier as shown in above example allows to inject headers that may change over the time, like authentication JWT tokens.
 If this is used in the reactive setup, the supplier function *must not* block!
 
+=== Elasticsearch 7 compatibility headers
+
+When using Spring Data Elasticsearch 4 - which uses the Elasticsearch 7 client libraries - and accessing an Elasticsearch cluster that is running on version 8, it is necessary to set the compatibility headers
+https://www.elastic.co/guide/en/elasticsearch/reference/8.0/rest-api-compatibility.html[see Elasticserach documentation].
+This should be done using a header supplier like shown above:
+
+====
+[source,java]
+----
+ClientConfigurationBuilder configurationBuilder = new ClientConfigurationBuilder();
+    configurationBuilder //
+		// ...
+		.withHeaders(() -> {
+			HttpHeaders defaultCompatibilityHeaders = new HttpHeaders();
+			defaultCompatibilityHeaders.add("Accept",
+                          "application/vnd.elasticsearch+json;compatible-with=7");
+			defaultCompatibilityHeaders.add("Content-Type",
+                          "application/vnd.elasticsearch+json;compatible-with=7");
+			return defaultCompatibilityHeaders;
+		});
+----
+====
+
 [[elasticsearch.clients.logging]]
 == Client Logging
 

src/test/java/org/springframework/data/elasticsearch/client/RestClientsTest.java

@@ -32,8 +32,10 @@
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 
+import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.client.RequestOptions;
 import org.elasticsearch.client.RestHighLevelClient;
+import org.elasticsearch.xcontent.XContentType;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -66,10 +68,6 @@ void shouldUseConfiguredProxy(ClientUnderTestFactory clientUnderTestFactory, Hov
 		wireMockServer(server -> {
 
 			// wiremock is the dummy server, hoverfly the proxy
-			WireMock.configureFor(server.port());
-			stubForElasticsearchVersionCheck();
-			stubFor(head(urlEqualTo("/")).willReturn(aResponse() //
-					.withHeader("Content-Type", "application/json; charset=UTF-8")));
 
 			String serviceHost = "localhost:" + server.port();
 			String proxyHost = "localhost:" + hoverfly.getHoverflyConfig().getProxyPort();
@@ -95,12 +93,6 @@ void shouldUseConfiguredProxy(ClientUnderTestFactory clientUnderTestFactory, Hov
 	void shouldConfigureClientAndSetAllRequiredHeaders(ClientUnderTestFactory clientUnderTestFactory) {
 		wireMockServer(server -> {
 
-			WireMock.configureFor(server.port());
-
-			stubForElasticsearchVersionCheck();
-			stubFor(head(urlEqualTo("/")).willReturn(aResponse() //
-					.withHeader("Content-Type", "application/json; charset=UTF-8")));
-
 			HttpHeaders defaultHeaders = new HttpHeaders();
 			defaultHeaders.addAll("def1", Arrays.asList("def1-1", "def1-2"));
 			defaultHeaders.add("def2", "def2-1");
@@ -156,6 +148,63 @@ void shouldConfigureClientAndSetAllRequiredHeaders(ClientUnderTestFactory client
 		});
 	}
 
+	@ParameterizedTest // #2088
+	@MethodSource("clientUnderTestFactorySource")
+	@DisplayName("should set compatibility headers")
+	void shouldSetCompatibilityHeaders(ClientUnderTestFactory clientUnderTestFactory) {
+
+		wireMockServer(server -> {
+
+			stubFor(put(urlMatching("^/index/_doc/42(\\?.*)$?")) //
+					.willReturn(jsonResponse("{\n" + //
+			"  \"_id\": \"42\",\n" + //
+			"  \"_index\": \"test\",\n" + //
+			"  \"_primary_term\": 1,\n" + //
+			"  \"_seq_no\": 0,\n" + //
+			"  \"_shards\": {\n" + //
+			"    \"failed\": 0,\n" + //
+			"    \"successful\": 1,\n" + //
+			"    \"total\": 2\n" + //
+			"  },\n" + //
+			"  \"_type\": \"_doc\",\n" + //
+			"  \"_version\": 1,\n" + //
+			"  \"result\": \"created\"\n" + //
+			"}\n" //
+			, 201) //
+					.withHeader("Content-Type", "application/vnd.elasticsearch+json;compatible-with=7") //
+					.withHeader("X-Elastic-Product", "Elasticsearch")));
+
+			ClientConfigurationBuilder configurationBuilder = new ClientConfigurationBuilder();
+			configurationBuilder //
+					.connectedTo("localhost:" + server.port()) //
+					.withHeaders(() -> {
+						HttpHeaders defaultCompatibilityHeaders = new HttpHeaders();
+						defaultCompatibilityHeaders.add("Accept", "application/vnd.elasticsearch+json;compatible-with=7");
+						defaultCompatibilityHeaders.add("Content-Type", "application/vnd.elasticsearch+json;compatible-with=7");
+						return defaultCompatibilityHeaders;
+					});
+
+			ClientConfiguration clientConfiguration = configurationBuilder.build();
+			ClientUnderTest clientUnderTest = clientUnderTestFactory.create(clientConfiguration);
+
+			class Foo {
+				public String id;
+
+				Foo(String id) {
+					this.id = id;
+				}
+			}
+			;
+
+			clientUnderTest.save(new Foo("42"));
+
+			verify(putRequestedFor(urlMatching("^/index/_doc/42(\\?.*)$?")) //
+					.withHeader("Accept", new EqualToPattern("application/vnd.elasticsearch+json;compatible-with=7")) //
+					.withHeader("Content-Type", new EqualToPattern("application/vnd.elasticsearch+json;compatible-with=7")) //
+			);
+		});
+	}
+
 	private StubMapping stubForElasticsearchVersionCheck() {
 		return stubFor(get(urlEqualTo("/")) //
 				.willReturn(okJson("{\n" + //
@@ -179,6 +228,12 @@ private StubMapping stubForElasticsearchVersionCheck() {
 								.withHeader("X-Elastic-Product", "Elasticsearch")));
 	}
 
+	private StubMapping stubForHead() {
+		return stubFor(head(urlEqualTo("/")) //
+				.willReturn(ok() //
+						.withHeader("X-Elastic-Product", "Elasticsearch")));
+	}
+
 	/**
 	 * Consumer extension that catches checked exceptions and wraps them in a RuntimeException.
 	 */
@@ -198,6 +253,8 @@ default void accept(WireMockServer wiremockConsumer) {
 
 	/**
 	 * starts a Wiremock server and calls consumer with the server as argument. Stops the server after consumer execution.
+	 * Before the consumer ids called the {@link #stubForHead()} and {@link #stubForElasticsearchVersionCheck()} are
+	 * registered.
 	 *
 	 * @param consumer the consumer
 	 */
@@ -208,6 +265,10 @@ private void wireMockServer(WiremockConsumer consumer) {
 		// test/resources/mappings
 		try {
 			wireMockServer.start();
+			WireMock.configureFor(wireMockServer.port());
+			stubForHead();
+			stubForElasticsearchVersionCheck();
+
 			consumer.accept(wireMockServer);
 		} finally {
 			wireMockServer.shutdown();
@@ -224,6 +285,8 @@ interface ClientUnderTest {
 		 * @return true if successful
 		 */
 		boolean ping() throws Exception;
+
+		<T> void save(T entity) throws IOException;
 	}
 
 	/**
@@ -253,7 +316,20 @@ protected String getDisplayName() {
 		@Override
 		ClientUnderTest create(ClientConfiguration clientConfiguration) {
 			RestHighLevelClient client = RestClients.create(clientConfiguration).rest();
-			return () -> client.ping(RequestOptions.DEFAULT);
+			return new ClientUnderTest() {
+				@Override
+				public boolean ping() throws Exception {
+					return client.ping(RequestOptions.DEFAULT);
+				}
+
+				@Override
+				public <T> void save(T entity) throws IOException {
+					IndexRequest indexRequest = new IndexRequest("index");
+					indexRequest.id("42");
+					indexRequest.source(entity, XContentType.JSON);
+					client.index(indexRequest, RequestOptions.DEFAULT);
+				}
+			};
 		}
 
 	}
@@ -271,7 +347,20 @@ protected String getDisplayName() {
 		@Override
 		ClientUnderTest create(ClientConfiguration clientConfiguration) {
 			ReactiveElasticsearchClient client = ReactiveRestClients.create(clientConfiguration);
-			return () -> client.ping().block();
+			return new ClientUnderTest() {
+				@Override
+				public boolean ping() throws Exception {
+					return client.ping().block();
+				}
+
+				@Override
+				public <T> void save(T entity) throws IOException {
+					IndexRequest indexRequest = new IndexRequest("index");
+					indexRequest.id("42");
+					indexRequest.source("{}", XContentType.JSON);
+					client.index(indexRequest).block();
+				}
+			};
 		}
 	}