Auto-configure Observation support for RestTemplate

Prior to this commit, Spring Boot would auto-configure a customizer that
instruments `RestTemplate` through a `RestTemplateBuilder`. This would
install a request interceptor that instrumented client exchanges for
producing metrics.

As of spring-projects/spring-framework#28341, the instrumentation is
done at the `RestTemplate` level directly using the `Observation` API.
The `Tag` (now `KeyValue`) extraction, observation name and
instrumentation behavior now lives in the Spring Framework project.

This commit updates the auto-configuration to switch from Boot-specific
Metrics instrumentation to a generic Observation instrumentation.
As a migration path, some configuration properties are deprecated in
favor of the new `management.observations.*` namespace.

Closes gh-32484

spring-boot-project/spring-boot-actuator-autoconfigure/build.gradle

@@ -147,6 +147,7 @@ dependencies {
 
 	testImplementation(project(":spring-boot-project:spring-boot-test"))
 	testImplementation(project(":spring-boot-project:spring-boot-tools:spring-boot-test-support"))
+	testImplementation("io.micrometer:micrometer-observation-test")
 	testImplementation("io.projectreactor:reactor-test")
 	testImplementation("io.r2dbc:r2dbc-h2")
 	testImplementation("com.squareup.okhttp3:mockwebserver")

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsProperties.java

@@ -25,6 +25,7 @@
 import java.util.Map;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.DeprecatedConfigurationProperty;
 import org.springframework.boot.context.properties.NestedConfigurationProperty;
 
 /**
@@ -158,6 +159,7 @@ public AutoTimeProperties getAutotime() {
 					return this.autotime;
 				}
 
+				@DeprecatedConfigurationProperty(replacement = "management.observations.http.client.requests.name")
 				public String getMetricName() {
 					return this.metricName;
 				}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/web/client/ClientHttpObservationConventionAdapter.java

@@ -0,0 +1,71 @@
+/*
+ * 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.metrics.web.client;
+
+import io.micrometer.common.KeyValues;
+import io.micrometer.core.instrument.Tag;
+import io.micrometer.observation.Observation;
+
+import org.springframework.boot.actuate.metrics.web.client.RestTemplateExchangeTagsProvider;
+import org.springframework.http.client.observation.ClientHttpObservationContext;
+import org.springframework.http.client.observation.ClientHttpObservationConvention;
+
+/**
+ * Adapter class that applies {@link RestTemplateExchangeTagsProvider} tags as a
+ * {@link ClientHttpObservationConvention}.
+ *
+ * @author Brian Clozel
+ */
+@SuppressWarnings("deprecation")
+class ClientHttpObservationConventionAdapter implements ClientHttpObservationConvention {
+
+	private final String metricName;
+
+	private final RestTemplateExchangeTagsProvider tagsProvider;
+
+	ClientHttpObservationConventionAdapter(String metricName, RestTemplateExchangeTagsProvider tagsProvider) {
+		this.metricName = metricName;
+		this.tagsProvider = tagsProvider;
+	}
+
+	@Override
+	public boolean supportsContext(Observation.Context context) {
+		return context instanceof ClientHttpObservationContext;
+	}
+
+	@Override
+	public KeyValues getLowCardinalityKeyValues(ClientHttpObservationContext context) {
+		KeyValues keyValues = KeyValues.empty();
+		Iterable<Tag> tags = this.tagsProvider.getTags(context.getUriTemplate(), context.getCarrier(),
+				context.getResponse());
+		for (Tag tag : tags) {
+			keyValues = keyValues.and(tag.getKey(), tag.getValue());
+		}
+		return keyValues;
+	}
+
+	@Override
+	public KeyValues getHighCardinalityKeyValues(ClientHttpObservationContext context) {
+		return KeyValues.empty();
+	}
+
+	@Override
+	public String getName() {
+		return this.metricName;
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/web/client/HttpClientMetricsAutoConfiguration.java

@@ -20,15 +20,15 @@
 import io.micrometer.core.instrument.config.MeterFilter;
 
 import org.springframework.boot.actuate.autoconfigure.metrics.CompositeMeterRegistryAutoConfiguration;
-import org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.MetricsProperties;
 import org.springframework.boot.actuate.autoconfigure.metrics.OnlyOnceLoggingDenyMeterFilter;
-import org.springframework.boot.actuate.autoconfigure.metrics.export.simple.SimpleMetricsExportAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 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.web.client.RestTemplateAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Import;
 import org.springframework.core.annotation.Order;
@@ -42,11 +42,11 @@
  * @author Raheela Aslam
  * @since 2.1.0
  */
-@AutoConfiguration(after = { MetricsAutoConfiguration.class, CompositeMeterRegistryAutoConfiguration.class,
-		SimpleMetricsExportAutoConfiguration.class, RestTemplateAutoConfiguration.class })
+@AutoConfiguration(after = { ObservationAutoConfiguration.class, CompositeMeterRegistryAutoConfiguration.class,
+		RestTemplateAutoConfiguration.class, WebClientAutoConfiguration.class })
 @ConditionalOnClass(MeterRegistry.class)
 @ConditionalOnBean(MeterRegistry.class)
-@Import({ RestTemplateMetricsConfiguration.class, WebClientMetricsConfiguration.class })
+@Import({ RestTemplateObservationConfiguration.class, WebClientMetricsConfiguration.class })
 public class HttpClientMetricsAutoConfiguration {
 
 	@Bean

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/web/client/RestTemplateObservationConfiguration.java

@@ -0,0 +1,61 @@
+/*
+ * 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.metrics.web.client;
+
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationRegistry;
+
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.boot.actuate.autoconfigure.metrics.MetricsProperties;
+import org.springframework.boot.actuate.autoconfigure.observation.ObservationProperties;
+import org.springframework.boot.actuate.metrics.web.client.ObservationRestTemplateCustomizer;
+import org.springframework.boot.actuate.metrics.web.client.RestTemplateExchangeTagsProvider;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.web.client.RestTemplateBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.client.observation.ClientHttpObservationConvention;
+import org.springframework.http.client.observation.DefaultClientHttpObservationConvention;
+import org.springframework.web.client.RestTemplate;
+
+/**
+ * Configure the instrumentation of {@link RestTemplate}.
+ *
+ * @author Brian Clozel
+ */
+@Configuration(proxyBeanMethods = false)
+@ConditionalOnClass({ RestTemplate.class, Observation.class })
+@ConditionalOnBean({ RestTemplateBuilder.class, ObservationRegistry.class })
+@SuppressWarnings("deprecation")
+class RestTemplateObservationConfiguration {
+
+	@Bean
+	ObservationRestTemplateCustomizer metricsRestTemplateCustomizer(ObservationRegistry observationRegistry,
+			ObservationProperties observationProperties, MetricsProperties metricsProperties,
+			ObjectProvider<RestTemplateExchangeTagsProvider> optionalTagsProvider) {
+		String metricName = metricsProperties.getWeb().getClient().getRequest().getMetricName();
+		String observationName = observationProperties.getHttp().getClient().getRequests().getName();
+		String name = (observationName != null) ? observationName : metricName;
+		RestTemplateExchangeTagsProvider tagsProvider = optionalTagsProvider.getIfAvailable();
+		ClientHttpObservationConvention observationConvention = (tagsProvider != null)
+				? new ClientHttpObservationConventionAdapter(name, tagsProvider)
+				: new DefaultClientHttpObservationConvention(name);
+		return new ObservationRestTemplateCustomizer(observationRegistry, observationConvention);
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/ObservationAutoConfiguration.java

@@ -33,17 +33,20 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for the Micrometer Observation API.
  *
  * @author Moritz Halbritter
+ * @author Brian Clozel
  * @since 3.0.0
  */
 @AutoConfiguration(after = CompositeMeterRegistryAutoConfiguration.class)
 @ConditionalOnClass(ObservationRegistry.class)
+@EnableConfigurationProperties(ObservationProperties.class)
 public class ObservationAutoConfiguration {
 
 	@Bean

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/ObservationProperties.java

@@ -0,0 +1,75 @@
+/*
+ * 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.observation;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ * {@link ConfigurationProperties @ConfigurationProperties} for configuring Micrometer
+ * observations.
+ *
+ * @author Brian Clozel
+ * @since 3.0.0
+ */
+@ConfigurationProperties("management.observations")
+public class ObservationProperties {
+
+	private final Http http = new Http();
+
+	public Http getHttp() {
+		return this.http;
+	}
+
+	public static class Http {
+
+		private final Client client = new Client();
+
+		public Client getClient() {
+			return this.client;
+		}
+
+		public static class Client {
+
+			private final ClientRequests requests = new ClientRequests();
+
+			public ClientRequests getRequests() {
+				return this.requests;
+			}
+
+			public static class ClientRequests {
+
+				/**
+				 * Name of the observation for client requests. If empty, will use the
+				 * default "http.client.requests".
+				 */
+				private String name;
+
+				public String getName() {
+					return this.name;
+				}
+
+				public void setName(String name) {
+					this.name = name;
+				}
+
+			}
+
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/test/MetricsIntegrationTests.java

@@ -44,6 +44,7 @@
 import org.springframework.boot.actuate.autoconfigure.metrics.web.client.HttpClientMetricsAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.web.reactive.WebFluxMetricsAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.web.servlet.WebMvcMetricsAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
 import org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter;
 import org.springframework.boot.autoconfigure.ImportAutoConfiguration;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
@@ -135,12 +136,12 @@ void metricsFilterRegisteredForAsyncDispatches() {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	@ImportAutoConfiguration({ MetricsAutoConfiguration.class, JvmMetricsAutoConfiguration.class,
-			LogbackMetricsAutoConfiguration.class, SystemMetricsAutoConfiguration.class,
-			RabbitMetricsAutoConfiguration.class, CacheMetricsAutoConfiguration.class,
-			DataSourcePoolMetricsAutoConfiguration.class, HibernateMetricsAutoConfiguration.class,
-			HttpClientMetricsAutoConfiguration.class, WebFluxMetricsAutoConfiguration.class,
-			WebMvcMetricsAutoConfiguration.class, JacksonAutoConfiguration.class,
+	@ImportAutoConfiguration({ MetricsAutoConfiguration.class, ObservationAutoConfiguration.class,
+			JvmMetricsAutoConfiguration.class, LogbackMetricsAutoConfiguration.class,
+			SystemMetricsAutoConfiguration.class, RabbitMetricsAutoConfiguration.class,
+			CacheMetricsAutoConfiguration.class, DataSourcePoolMetricsAutoConfiguration.class,
+			HibernateMetricsAutoConfiguration.class, HttpClientMetricsAutoConfiguration.class,
+			WebFluxMetricsAutoConfiguration.class, WebMvcMetricsAutoConfiguration.class, JacksonAutoConfiguration.class,
 			HttpMessageConvertersAutoConfiguration.class, RestTemplateAutoConfiguration.class,
 			WebMvcAutoConfiguration.class, DispatcherServletAutoConfiguration.class,
 			ServletWebServerFactoryAutoConfiguration.class })