Bring back Elasticsearch RestClient auto-configuration

Prior to this commit, Spring Boot would only auto-configure
the `RestHighLevelClient` and `RestClientBuilder` if the `RestHighLevelClient`
was present. This was done in 1d73d4e.

This commit brings back the exposing of the `RestClient` bean in
Spring Boot when exposing the `RestHighLevelClient` or
when the `RestHighLevelClient` is not present.
It allows for using the Spring Boot auto configuration and its customizers
of the `RestClientBuilder` in a similar way as it is done for the `RestTeamplateBuilder`
and the `WebClient.Builder`.
Now the presence of the `org.elasticsearch.client:elasticsearch-rest-high-level-client` is optional.
This opens the door for potentially adding support to the new
[Elasticsearch Java Client](https://github.com/elastic/elasticsearch-java) that is based on the same `RestClient`

It also adapts the health contributor to only depend on the low level RestClient.

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/elasticsearch/ElasticSearchRestHealthContributorAutoConfiguration.java

@@ -16,43 +16,31 @@
 
 package org.springframework.boot.actuate.autoconfigure.elasticsearch;
 
-import java.util.Map;
-
 import org.elasticsearch.client.RestClient;
-import org.elasticsearch.client.RestHighLevelClient;
 
-import org.springframework.boot.actuate.autoconfigure.health.CompositeHealthContributorConfiguration;
+import org.springframework.boot.actuate.autoconfigure.elasticsearch.ElasticSearchRestHealthContributorConfigurations.RestClientHealthContributorConfiguration;
 import org.springframework.boot.actuate.autoconfigure.health.ConditionalOnEnabledHealthIndicator;
-import org.springframework.boot.actuate.elasticsearch.ElasticsearchRestHealthIndicator;
-import org.springframework.boot.actuate.health.HealthContributor;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientAutoConfiguration;
-import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 
 /**
- * {@link EnableAutoConfiguration Auto-configuration} for
- * {@link ElasticsearchRestHealthIndicator} using the {@link RestClient}.
+ * {@link EnableAutoConfiguration Auto-configuration} for Elasticsearch health indicator
+ * using REST clients.
  *
  * @author Artsiom Yudovin
  * @since 2.1.1
  */
+@SuppressWarnings("deprecation")
 @Configuration(proxyBeanMethods = false)
-@ConditionalOnClass(RestHighLevelClient.class)
-@ConditionalOnBean(RestHighLevelClient.class)
+@ConditionalOnClass(RestClient.class)
 @ConditionalOnEnabledHealthIndicator("elasticsearch")
 @AutoConfigureAfter(ElasticsearchRestClientAutoConfiguration.class)
-public class ElasticSearchRestHealthContributorAutoConfiguration
-		extends CompositeHealthContributorConfiguration<ElasticsearchRestHealthIndicator, RestHighLevelClient> {
-
-	@Bean
-	@ConditionalOnMissingBean(name = { "elasticsearchHealthIndicator", "elasticsearchHealthContributor" })
-	public HealthContributor elasticsearchHealthContributor(Map<String, RestHighLevelClient> clients) {
-		return createContributor(clients);
-	}
+@Import({ ElasticSearchRestHealthContributorConfigurations.RestHighLevelClientHealthContributorConfiguration.class,
+		RestClientHealthContributorConfiguration.class })
+public class ElasticSearchRestHealthContributorAutoConfiguration {
 
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/elasticsearch/ElasticSearchRestHealthContributorConfigurations.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.elasticsearch;
+
+import java.util.Map;
+
+import org.elasticsearch.client.RestClient;
+import org.elasticsearch.client.RestHighLevelClient;
+
+import org.springframework.boot.actuate.autoconfigure.health.CompositeHealthContributorConfiguration;
+import org.springframework.boot.actuate.elasticsearch.ElasticsearchRestClientHealthIndicator;
+import org.springframework.boot.actuate.health.HealthContributor;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * Elasticsearch rest client health contributor configurations.
+ *
+ * @author Filip Hrisafov
+ */
+class ElasticSearchRestHealthContributorConfigurations {
+
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(RestHighLevelClient.class)
+	@ConditionalOnBean(RestHighLevelClient.class)
+	@Deprecated
+	static class RestHighLevelClientHealthContributorConfiguration extends
+			CompositeHealthContributorConfiguration<org.springframework.boot.actuate.elasticsearch.ElasticsearchRestHealthIndicator, RestHighLevelClient> {
+
+		@Bean
+		@ConditionalOnMissingBean(name = { "elasticsearchHealthIndicator", "elasticsearchHealthContributor" })
+		HealthContributor elasticsearchHealthContributor(Map<String, RestHighLevelClient> clients) {
+			return createContributor(clients);
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnBean(RestClient.class)
+	@ConditionalOnMissingBean(RestHighLevelClient.class)
+	static class RestClientHealthContributorConfiguration
+			extends CompositeHealthContributorConfiguration<ElasticsearchRestClientHealthIndicator, RestClient> {
+
+		@Bean
+		@ConditionalOnMissingBean(name = { "elasticsearchHealthIndicator", "elasticsearchHealthContributor" })
+		HealthContributor elasticsearchHealthContributor(Map<String, RestClient> clients) {
+			return createContributor(clients);
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/elasticsearch/ElasticsearchRestHealthContributorAutoConfigurationTests.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.elasticsearch;
+
+import org.elasticsearch.client.RestClient;
+import org.elasticsearch.client.RestClientBuilder;
+import org.elasticsearch.client.RestHighLevelClient;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.actuate.autoconfigure.health.HealthContributorAutoConfiguration;
+import org.springframework.boot.actuate.elasticsearch.ElasticsearchRestClientHealthIndicator;
+import org.springframework.boot.actuate.elasticsearch.ElasticsearchRestHealthIndicator;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientAutoConfiguration;
+import org.springframework.boot.test.context.FilteredClassLoader;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ElasticsearchRestClientAutoConfiguration}.
+ *
+ * @author Filip Hrisafov
+ */
+class ElasticsearchRestHealthContributorAutoConfigurationTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(ElasticsearchRestClientAutoConfiguration.class,
+					ElasticSearchRestHealthContributorAutoConfiguration.class,
+					HealthContributorAutoConfiguration.class));
+
+	@Test
+	@SuppressWarnings("deprecation")
+	void runShouldCreateIndicator() {
+		this.contextRunner.run((context) -> assertThat(context).hasSingleBean(ElasticsearchRestHealthIndicator.class)
+				.hasBean("elasticsearchHealthContributor"));
+	}
+
+	@Test
+	void runWithoutRestHighLevelClientAndWithoutRestClientShouldNotCreateIndicator() {
+		this.contextRunner.withClassLoader(new FilteredClassLoader(RestHighLevelClient.class, RestClient.class))
+				.run((context) -> assertThat(context).doesNotHaveBean(ElasticsearchRestClientHealthIndicator.class)
+						.doesNotHaveBean("elasticsearchHealthContributor"));
+	}
+
+	@Test
+	@SuppressWarnings("deprecation")
+	void runWithoutRestHighLevelClientAndWithRestClientShouldCreateIndicator() {
+		this.contextRunner.withUserConfiguration(CustomRestClientConfiguration.class)
+				.run((context) -> assertThat(context).hasSingleBean(ElasticsearchRestClientHealthIndicator.class)
+						.doesNotHaveBean(ElasticsearchRestHealthIndicator.class)
+						.hasBean("elasticsearchHealthContributor"));
+	}
+
+	@Test
+	@SuppressWarnings("deprecation")
+	void runWithRestHighLevelClientAndWithRestClientShouldCreateIndicator() {
+		this.contextRunner.withUserConfiguration(CustomRestHighClientConfiguration.class)
+				.run((context) -> assertThat(context).hasSingleBean(ElasticsearchRestClientHealthIndicator.class)
+						.hasBean("elasticsearchHealthContributor"));
+	}
+
+	@Test
+	void runWhenDisabledShouldNotCreateIndicator() {
+		this.contextRunner.withPropertyValues("management.health.elasticsearch.enabled:false")
+				.run((context) -> assertThat(context).doesNotHaveBean(ElasticsearchRestClientHealthIndicator.class)
+						.doesNotHaveBean("elasticsearchHealthContributor"));
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class CustomRestClientConfiguration {
+
+		@Bean
+		RestClient customRestClient(RestClientBuilder builder) {
+			return builder.build();
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class CustomRestHighClientConfiguration {
+
+		@Bean
+		RestHighLevelClient customRestHighClient(RestClientBuilder builder) {
+			return new RestHighLevelClient(builder);
+		}
+
+		@Bean
+		RestClient customClient(RestHighLevelClient restHighLevelClient) {
+			return restHighLevelClient.getLowLevelClient();
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/elasticsearch/ElasticsearchRestClientHealthIndicator.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.elasticsearch;
+
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+
+import org.apache.http.HttpStatus;
+import org.apache.http.StatusLine;
+import org.elasticsearch.client.Request;
+import org.elasticsearch.client.Response;
+import org.elasticsearch.client.RestClient;
+
+import org.springframework.boot.actuate.health.AbstractHealthIndicator;
+import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.HealthIndicator;
+import org.springframework.boot.json.JsonParser;
+import org.springframework.boot.json.JsonParserFactory;
+import org.springframework.util.StreamUtils;
+
+/**
+ * {@link HealthIndicator} for an Elasticsearch cluster using a {@link RestClient}.
+ *
+ * @author Artsiom Yudovin
+ * @author Brian Clozel
+ * @author Filip Hrisafov
+ * @since 2.7
+ */
+public class ElasticsearchRestClientHealthIndicator extends AbstractHealthIndicator {
+
+	private static final String RED_STATUS = "red";
+
+	private final RestClient client;
+
+	private final JsonParser jsonParser;
+
+	public ElasticsearchRestClientHealthIndicator(RestClient client) {
+		super("Elasticsearch health check failed");
+		this.client = client;
+		this.jsonParser = JsonParserFactory.getJsonParser();
+	}
+
+	@Override
+	protected void doHealthCheck(Health.Builder builder) throws Exception {
+		Response response = this.client.performRequest(new Request("GET", "/_cluster/health/"));
+		StatusLine statusLine = response.getStatusLine();
+		if (statusLine.getStatusCode() != HttpStatus.SC_OK) {
+			builder.down();
+			builder.withDetail("statusCode", statusLine.getStatusCode());
+			builder.withDetail("reasonPhrase", statusLine.getReasonPhrase());
+			return;
+		}
+		try (InputStream inputStream = response.getEntity().getContent()) {
+			doHealthCheck(builder, StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8));
+		}
+	}
+
+	private void doHealthCheck(Health.Builder builder, String json) {
+		Map<String, Object> response = this.jsonParser.parseMap(json);
+		String status = (String) response.get("status");
+		if (RED_STATUS.equals(status)) {
+			builder.outOfService();
+		}
+		else {
+			builder.up();
+		}
+		builder.withDetails(response);
+	}
+
+}