Write TraceResponse HTTP observability header

Prior to this commit, we added support for the "X-Trace-Id" HTTP
response header in spring-projectsgh-40857. This wrote the traceId information for MVC
applications, if the `management.observations.http.server.requests.write-trace-header`
was set.

After receiving feedback from the community, we are revisiting this
feature with the following changes:

* the header is now "traceresponse" and implements the W3C draft
  standard, see https://w3c.github.io/trace-context/#trace-context-http-response-headers-format
* the property is now
  "management.observations.http.server.requests.write-traceresponse"
* both MVC and WebFlux are now supported

Closes spring-projectsgh-44431

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

@@ -128,9 +128,9 @@ public static class ServerRequests {
 				private String name = "http.server.requests";
 
 				/**
-				 * Whether to write the "X-Trace-Id" HTTP response header.
+				 * Whether to write the "traceresponse" HTTP response header.
 				 */
-				private boolean writeTraceHeader = false;
+				private boolean writeTraceresponse = false;
 
 				public String getName() {
 					return this.name;
@@ -140,12 +140,12 @@ public void setName(String name) {
 					this.name = name;
 				}
 
-				public boolean isWriteTraceHeader() {
-					return this.writeTraceHeader;
+				public boolean isWriteTraceresponse() {
+					return this.writeTraceresponse;
 				}
 
-				public void setWriteTraceHeader(boolean writeTraceHeader) {
-					this.writeTraceHeader = writeTraceHeader;
+				public void setWriteTraceresponse(boolean writeTraceresponse) {
+					this.writeTraceresponse = writeTraceresponse;
 				}
 
 			}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/web/reactive/WebFluxObservationAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -20,20 +20,24 @@
 import io.micrometer.core.instrument.config.MeterFilter;
 import io.micrometer.observation.Observation;
 import io.micrometer.observation.ObservationRegistry;
+import io.micrometer.tracing.Tracer;
 
 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.actuate.autoconfigure.observation.ObservationProperties;
+import org.springframework.boot.actuate.web.tracing.reactive.TraceResponseObservationWebFilter;
 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.ConditionalOnBooleanProperty;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
+import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.http.server.reactive.observation.DefaultServerRequestObservationConvention;
 import org.springframework.http.server.reactive.observation.ServerRequestObservationConvention;
@@ -61,6 +65,15 @@ public class WebFluxObservationAutoConfiguration {
 		this.observationProperties = observationProperties;
 	}
 
+	@Bean
+	@ConditionalOnBooleanProperty("management.observations.http.server.requests.write-traceresponse")
+	@ConditionalOnBean(Tracer.class)
+	@ConditionalOnMissingBean
+	@Order(Ordered.HIGHEST_PRECEDENCE + 1)
+	public TraceResponseObservationWebFilter traceResponseObservationWebFilter() {
+		return new TraceResponseObservationWebFilter();
+	}
+
 	@Bean
 	@Order(0)
 	MeterFilter metricsHttpServerUriTagFilter(MetricsProperties metricsProperties) {

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/web/servlet/ObservationFilterConfigurations.java

@@ -22,6 +22,7 @@
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.actuate.autoconfigure.observation.ObservationProperties;
+import org.springframework.boot.actuate.web.tracing.servlet.TraceResponseHeaderObservationFilter;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBooleanProperty;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
@@ -54,16 +55,18 @@ static <T extends ServerHttpObservationFilter> FilterRegistrationBean<T> filterR
 	static class TracingHeaderObservation {
 
 		@Bean
-		@ConditionalOnBooleanProperty("management.observations.http.server.requests.write-trace-header")
+		@ConditionalOnBooleanProperty("management.observations.http.server.requests.write-traceresponse")
 		@ConditionalOnBean(Tracer.class)
-		@ConditionalOnMissingFilterBean({ ServerHttpObservationFilter.class, TraceHeaderObservationFilter.class })
-		FilterRegistrationBean<TraceHeaderObservationFilter> webMvcObservationFilter(ObservationRegistry registry,
-				Tracer tracer, ObjectProvider<ServerRequestObservationConvention> customConvention,
+		@ConditionalOnMissingFilterBean({ ServerHttpObservationFilter.class,
+				TraceResponseHeaderObservationFilter.class })
+		FilterRegistrationBean<TraceResponseHeaderObservationFilter> webMvcObservationFilter(
+				ObservationRegistry registry, ObjectProvider<ServerRequestObservationConvention> customConvention,
 				ObservationProperties observationProperties) {
 			String name = observationProperties.getHttp().getServer().getRequests().getName();
 			ServerRequestObservationConvention convention = customConvention
 				.getIfAvailable(() -> new DefaultServerRequestObservationConvention(name));
-			TraceHeaderObservationFilter filter = new TraceHeaderObservationFilter(tracer, registry, convention);
+			TraceResponseHeaderObservationFilter filter = new TraceResponseHeaderObservationFilter(registry,
+					convention);
 			return filterRegistration(filter);
 		}
 
@@ -73,7 +76,8 @@ FilterRegistrationBean<TraceHeaderObservationFilter> webMvcObservationFilter(Obs
 	static class DefaultObservation {
 
 		@Bean
-		@ConditionalOnMissingFilterBean({ ServerHttpObservationFilter.class, TraceHeaderObservationFilter.class })
+		@ConditionalOnMissingFilterBean({ ServerHttpObservationFilter.class,
+				TraceResponseHeaderObservationFilter.class })
 		FilterRegistrationBean<ServerHttpObservationFilter> webMvcObservationFilter(ObservationRegistry registry,
 				ObjectProvider<ServerRequestObservationConvention> customConvention,
 				ObservationProperties observationProperties) {

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/observation/web/reactive/WebFluxObservationAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -20,13 +20,16 @@
 import java.time.temporal.ChronoUnit;
 
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.tracing.Tracer;
+import io.micrometer.tracing.test.simple.SimpleTracer;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
 import org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.test.MetricsRun;
 import org.springframework.boot.actuate.autoconfigure.metrics.web.TestController;
 import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
+import org.springframework.boot.actuate.web.tracing.reactive.TraceResponseObservationWebFilter;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration;
 import org.springframework.boot.test.context.assertj.AssertableReactiveWebApplicationContext;
@@ -117,6 +120,25 @@ void shouldBackOffOnCustomServerRequestObservationConvention() {
 			});
 	}
 
+	@Test
+	void shouldNotConfigureTraceResponseObservationWebFilterByDefault() {
+		this.contextRunner
+			.run((context) -> assertThat(context).doesNotHaveBean(TraceResponseObservationWebFilter.class));
+	}
+
+	@Test
+	void shouldNotConfigureTraceResponseObservationWebFilterIfTracerMissing() {
+		this.contextRunner.withPropertyValues("management.observations.http.server.requests.write-traceresponse=true")
+			.run((context) -> assertThat(context).doesNotHaveBean(TraceResponseObservationWebFilter.class));
+	}
+
+	@Test
+	void shouldConfigureTraceResponseObservationWebFilter() {
+		this.contextRunner.withPropertyValues("management.observations.http.server.requests.write-traceresponse=true")
+			.withBean(Tracer.class, SimpleTracer::new)
+			.run((context) -> assertThat(context).hasSingleBean(TraceResponseObservationWebFilter.class));
+	}
+
 	private MeterRegistry getInitializedMeterRegistry(AssertableReactiveWebApplicationContext context) {
 		return getInitializedMeterRegistry(context, "http.server.requests");
 	}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/observation/web/servlet/WebMvcObservationAutoConfigurationTests.java

@@ -20,7 +20,6 @@
 
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.observation.tck.TestObservationRegistry;
-import io.micrometer.tracing.Tracer;
 import jakarta.servlet.DispatcherType;
 import jakarta.servlet.Filter;
 import org.junit.jupiter.api.Test;
@@ -31,6 +30,7 @@
 import org.springframework.boot.actuate.autoconfigure.metrics.web.TestController;
 import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.tracing.NoopTracerAutoConfiguration;
+import org.springframework.boot.actuate.web.tracing.servlet.TraceResponseHeaderObservationFilter;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration;
 import org.springframework.boot.test.context.assertj.AssertableWebApplicationContext;
@@ -78,7 +78,7 @@ void definesFilterWhenRegistryIsPresent() {
 			assertThat(context).hasSingleBean(FilterRegistrationBean.class);
 			assertThat(context.getBean(FilterRegistrationBean.class).getFilter())
 				.isInstanceOf(ServerHttpObservationFilter.class)
-				.isNotInstanceOf(TraceHeaderObservationFilter.class);
+				.isNotInstanceOf(TraceResponseHeaderObservationFilter.class);
 		});
 	}
 
@@ -132,18 +132,18 @@ void filterRegistrationDoesNotBackOffWithOtherFilter() {
 	@Test
 	void usesTracingFilterWhenTracingIsPresentAndEnabled() {
 		this.contextRunner.withConfiguration(AutoConfigurations.of(NoopTracerAutoConfiguration.class))
-			.withPropertyValues("management.observations.http.server.requests.write-trace-header=true")
+			.withPropertyValues("management.observations.http.server.requests.write-traceresponse=true")
 			.run((context) -> {
 				assertThat(context).hasSingleBean(FilterRegistrationBean.class);
 				assertThat(context.getBean(FilterRegistrationBean.class).getFilter())
-					.isInstanceOf(TraceHeaderObservationFilter.class);
+					.isInstanceOf(TraceResponseHeaderObservationFilter.class);
 			});
 	}
 
 	@Test
 	void tracingFilterRegistrationHasExpectedDispatcherTypesAndOrder() {
 		this.contextRunner.withConfiguration(AutoConfigurations.of(NoopTracerAutoConfiguration.class))
-			.withPropertyValues("management.observations.http.server.requests.write-trace-header=true")
+			.withPropertyValues("management.observations.http.server.requests.write-traceresponse=true")
 			.run((context) -> {
 				FilterRegistrationBean<?> registration = context.getBean(FilterRegistrationBean.class);
 				assertThat(registration).hasFieldOrPropertyWithValue("dispatcherTypes",
@@ -155,7 +155,7 @@ void tracingFilterRegistrationHasExpectedDispatcherTypesAndOrder() {
 	@Test
 	void filterRegistrationBacksOffWithAnotherTraceHeaderObservationFilterRegistration() {
 		this.contextRunner.withConfiguration(AutoConfigurations.of(NoopTracerAutoConfiguration.class))
-			.withPropertyValues("management.observations.http.server.requests.write-trace-header=true")
+			.withPropertyValues("management.observations.http.server.requests.write-traceresponse=true")
 			.withUserConfiguration(TestTraceHeaderObservationFilterRegistrationConfiguration.class)
 			.run((context) -> {
 				assertThat(context).hasSingleBean(FilterRegistrationBean.class);
@@ -167,10 +167,10 @@ void filterRegistrationBacksOffWithAnotherTraceHeaderObservationFilterRegistrati
 	@Test
 	void filterRegistrationBacksOffWithAnotherTraceHeaderObservationFilter() {
 		this.contextRunner.withConfiguration(AutoConfigurations.of(NoopTracerAutoConfiguration.class))
-			.withPropertyValues("management.observations.http.server.requests.write-trace-header=true")
+			.withPropertyValues("management.observations.http.server.requests.write-traceresponse=true")
 			.withUserConfiguration(TestTraceHeaderObservationFilterConfiguration.class)
 			.run((context) -> assertThat(context).doesNotHaveBean(FilterRegistrationBean.class)
-				.hasSingleBean(TraceHeaderObservationFilter.class));
+				.hasSingleBean(TraceResponseHeaderObservationFilter.class));
 	}
 
 	@Test
@@ -254,7 +254,7 @@ static class TestTraceHeaderObservationFilterRegistrationConfiguration {
 
 		@Bean
 		@SuppressWarnings("unchecked")
-		FilterRegistrationBean<TraceHeaderObservationFilter> testTraceHeaderObservationFilter() {
+		FilterRegistrationBean<TraceResponseHeaderObservationFilter> testTraceHeaderObservationFilter() {
 			return mock(FilterRegistrationBean.class);
 		}
 
@@ -264,8 +264,8 @@ FilterRegistrationBean<TraceHeaderObservationFilter> testTraceHeaderObservationF
 	static class TestTraceHeaderObservationFilterConfiguration {
 
 		@Bean
-		TraceHeaderObservationFilter testTraceHeaderObservationFilter() {
-			return new TraceHeaderObservationFilter(Tracer.NOOP, TestObservationRegistry.create());
+		TraceResponseHeaderObservationFilter testTraceHeaderObservationFilter() {
+			return new TraceResponseHeaderObservationFilter(TestObservationRegistry.create());
 		}
 
 	}

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

@@ -97,6 +97,7 @@ dependencies {
 	testImplementation("org.assertj:assertj-core")
 	testImplementation("com.jayway.jsonpath:json-path")
 	testImplementation("io.micrometer:micrometer-observation-test")
+	testImplementation("io.micrometer:micrometer-tracing-test")
 	testImplementation("io.projectreactor:reactor-test")
 	testImplementation("io.r2dbc:r2dbc-h2")
 	testImplementation("net.minidev:json-smart")