Configure GraphQL web propagation for tracing

As of spring-projects/spring-graphql#547, Spring GraphQL introduced a
`PropagationWebGraphQlInterceptor` that propagates the incoming tracing
information in HTTP request headers into the GraphQL context.

This commit auto-configures the propagation interceptor if the
application exposes a GraphQL HTTP endpoint and if it is configured for
Tracing support.

Fixes gh-33542

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

@@ -19,6 +19,7 @@ package org.springframework.boot.actuate.autoconfigure.observation.graphql;
 import graphql.GraphQL;
 import io.micrometer.observation.Observation;
 import io.micrometer.observation.ObservationRegistry;
+import io.micrometer.tracing.propagation.Propagator;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
@@ -28,10 +29,15 @@ 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;
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
 import org.springframework.graphql.execution.GraphQlSource;
 import org.springframework.graphql.observation.DataFetcherObservationConvention;
 import org.springframework.graphql.observation.ExecutionRequestObservationConvention;
 import org.springframework.graphql.observation.GraphQlObservationInstrumentation;
+import org.springframework.graphql.observation.PropagationWebGraphQlInterceptor;
+import org.springframework.graphql.server.WebGraphQlHandler;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for instrumentation of Spring
@@ -55,4 +61,19 @@ public class GraphQlObservationAutoConfiguration {
 				dataFetcherConvention.getIfAvailable());
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(Propagator.class)
+	@ConditionalOnBean(WebGraphQlHandler.class)
+	static class TracingObservationConfiguration {
+
+		@Bean
+		@ConditionalOnBean(Propagator.class)
+		@ConditionalOnMissingBean
+		@Order(Ordered.HIGHEST_PRECEDENCE + 1)
+		public PropagationWebGraphQlInterceptor propagationWebGraphQlInterceptor(Propagator propagator) {
+			return new PropagationWebGraphQlInterceptor(propagator);
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/observation/graphql/GraphQlObservationAutoConfigurationTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.actuate.autoconfigure.observation.graphql;
 
 import io.micrometer.observation.ObservationRegistry;
 import io.micrometer.observation.tck.TestObservationRegistry;
+import io.micrometer.tracing.propagation.Propagator;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
@@ -27,8 +28,11 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.graphql.observation.DefaultDataFetcherObservationConvention;
 import org.springframework.graphql.observation.DefaultExecutionRequestObservationConvention;
 import org.springframework.graphql.observation.GraphQlObservationInstrumentation;
+import org.springframework.graphql.observation.PropagationWebGraphQlInterceptor;
+import org.springframework.graphql.server.WebGraphQlHandler;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
 
 /**
  * Tests for {@link GraphQlObservationAutoConfiguration}.
@@ -72,6 +76,24 @@ class GraphQlObservationAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void propagationInterceptorNotContributedWhenPropagatorIsMissing() {
+		this.contextRunner.withUserConfiguration(WebGraphQlConfiguration.class)
+				.run((context) -> assertThat(context).doesNotHaveBean(PropagationWebGraphQlInterceptor.class));
+	}
+
+	@Test
+	void propagationInterceptorNotContributedWhenNotWebApplication() {
+		this.contextRunner.withUserConfiguration(TracingConfiguration.class)
+				.run((context) -> assertThat(context).doesNotHaveBean(PropagationWebGraphQlInterceptor.class));
+	}
+
+	@Test
+	void propagationInterceptorContributed() {
+		this.contextRunner.withUserConfiguration(WebGraphQlConfiguration.class, TracingConfiguration.class)
+				.run((context) -> assertThat(context).hasSingleBean(PropagationWebGraphQlInterceptor.class));
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class InstrumentationConfiguration {
 
@@ -105,4 +127,22 @@ class GraphQlObservationAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class WebGraphQlConfiguration {
+
+		@Bean
+		WebGraphQlHandler webGraphQlHandler() {
+			return mock(WebGraphQlHandler.class);
+		}
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class TracingConfiguration {
+
+		@Bean
+		Propagator propagator() {
+			return mock(Propagator.class);
+		}
+	}
+
 }