Use TracingAwareMeterObservationHandler if tracing is configured

See gh-32399

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

@@ -20,19 +20,21 @@ import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.observation.DefaultMeterObservationHandler;
 import io.micrometer.core.instrument.observation.MeterObservationHandler;
 import io.micrometer.observation.GlobalObservationConvention;
+import io.micrometer.observation.Observation;
 import io.micrometer.observation.ObservationHandler;
 import io.micrometer.observation.ObservationPredicate;
 import io.micrometer.observation.ObservationRegistry;
-import io.micrometer.tracing.handler.TracingObservationHandler;
+import io.micrometer.tracing.Tracer;
+import io.micrometer.tracing.handler.TracingAwareMeterObservationHandler;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.actuate.autoconfigure.metrics.CompositeMeterRegistryAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.tracing.MicrometerTracingAutoConfiguration;
 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.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;
@@ -42,9 +44,10 @@ import org.springframework.context.annotation.Configuration;
  *
  * @author Moritz Halbritter
  * @author Brian Clozel
+ * @author Jonatan Ivanov
  * @since 3.0.0
  */
-@AutoConfiguration(after = CompositeMeterRegistryAutoConfiguration.class)
+@AutoConfiguration(after = { CompositeMeterRegistryAutoConfiguration.class, MicrometerTracingAutoConfiguration.class })
 @ConditionalOnClass(ObservationRegistry.class)
 @EnableConfigurationProperties(ObservationProperties.class)
 public class ObservationAutoConfiguration {
@@ -67,21 +70,16 @@ public class ObservationAutoConfiguration {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	@ConditionalOnBean(MeterRegistry.class)
-	static class MetricsConfiguration {
+	@ConditionalOnMissingBean(type = "io.micrometer.tracing.Tracer")
+	static class OnlyMetricsConfiguration {
 
 		@Bean
 		@ConditionalOnMissingBean(MeterObservationHandler.class)
+		@ConditionalOnBean(MeterRegistry.class)
 		DefaultMeterObservationHandler defaultMeterObservationHandler(MeterRegistry meterRegistry) {
 			return new DefaultMeterObservationHandler(meterRegistry);
 		}
 
-	}
-
-	@Configuration(proxyBeanMethods = false)
-	@ConditionalOnMissingClass("io.micrometer.tracing.handler.TracingObservationHandler")
-	static class OnlyMetricsConfiguration {
-
 		@Bean
 		OnlyMetricsObservationHandlerGrouping onlyMetricsObservationHandlerGrouping() {
 			return new OnlyMetricsObservationHandlerGrouping();
@@ -90,8 +88,16 @@ public class ObservationAutoConfiguration {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	@ConditionalOnClass(TracingObservationHandler.class)
-	static class TracingConfiguration {
+	@ConditionalOnBean(Tracer.class)
+	static class MetricsWithTracingConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean(MeterObservationHandler.class)
+		@ConditionalOnBean(MeterRegistry.class)
+		TracingAwareMeterObservationHandler<Observation.Context> tracingAwareMeterObservationHandler(
+				MeterRegistry meterRegistry, Tracer tracer) {
+			return new TracingAwareMeterObservationHandler<>(new DefaultMeterObservationHandler(meterRegistry), tracer);
+		}
 
 		@Bean
 		TracingObservationHandlerGrouping tracingObservationHandlerGrouping() {

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

@@ -34,6 +34,7 @@ import io.micrometer.observation.ObservationHandler.FirstMatchingCompositeObserv
 import io.micrometer.observation.ObservationPredicate;
 import io.micrometer.observation.ObservationRegistry;
 import io.micrometer.tracing.Tracer;
+import io.micrometer.tracing.handler.TracingAwareMeterObservationHandler;
 import io.micrometer.tracing.handler.TracingObservationHandler;
 import org.junit.jupiter.api.Test;
 import org.mockito.Answers;
@@ -55,6 +56,7 @@ import static org.mockito.Mockito.mock;
  * Tests for {@link ObservationAutoConfiguration}.
  *
  * @author Moritz Halbritter
+ * @author Jonatan Ivanov
  */
 class ObservationAutoConfigurationTests {
 
@@ -65,6 +67,16 @@ class ObservationAutoConfigurationTests {
 	private final ApplicationContextRunner tracingContextRunner = new ApplicationContextRunner()
 			.with(MetricsRun.simple()).withConfiguration(AutoConfigurations.of(ObservationAutoConfiguration.class));
 
+	@Test
+	void beansShouldNotBeSuppliedWhenMicrometerObservationIsNotOnClassPath() {
+		this.tracingContextRunner.withClassLoader(new FilteredClassLoader("io.micrometer.observation"))
+				.run((context) -> {
+					assertThat(context).hasSingleBean(MeterRegistry.class);
+					assertThat(context).doesNotHaveBean(ObservationRegistry.class);
+					assertThat(context).doesNotHaveBean(MeterObservationHandler.class);
+				});
+	}
+
 	@Test
 	void autoConfiguresDefaultMeterObservationHandler() {
 		this.contextRunner.run((context) -> {
@@ -75,9 +87,17 @@ class ObservationAutoConfigurationTests {
 			// Observation leads to a timer
 			MeterRegistry meterRegistry = context.getBean(MeterRegistry.class);
 			assertThat(meterRegistry.get("test-observation").timer().count()).isEqualTo(1);
+			assertThat(context).hasSingleBean(DefaultMeterObservationHandler.class);
+			assertThat(context.getBeansOfType(ObservationHandler.class)).hasSize(1);
 		});
 	}
 
+	@Test
+	void allowsDefaultMeterObservationHandlerToBeDisabled() {
+		this.contextRunner.withClassLoader(new FilteredClassLoader(MeterRegistry.class))
+				.run((context) -> assertThat(context).doesNotHaveBean(ObservationHandler.class));
+	}
+
 	@Test
 	void autoConfiguresObservationPredicates() {
 		this.contextRunner.withUserConfiguration(ObservationPredicates.class).run((context) -> {
@@ -119,6 +139,8 @@ class ObservationAutoConfigurationTests {
 			assertThat(handlers.get(1)).isInstanceOf(CustomMeterObservationHandler.class);
 			assertThat(((CustomMeterObservationHandler) handlers.get(1)).getName())
 					.isEqualTo("customMeterObservationHandler1");
+			assertThat(context).doesNotHaveBean(DefaultMeterObservationHandler.class);
+			assertThat(context).doesNotHaveBean(TracingAwareMeterObservationHandler.class);
 		});
 	}
 
@@ -132,6 +154,23 @@ class ObservationAutoConfigurationTests {
 					Observation.start("test-observation", () -> customContext, observationRegistry).stop();
 					assertThat(handlers).hasSize(1);
 					assertThat(handlers.get(0)).isInstanceOf(ObservationHandlerWithCustomContext.class);
+					assertThat(context).hasSingleBean(DefaultMeterObservationHandler.class);
+					assertThat(context).doesNotHaveBean(TracingAwareMeterObservationHandler.class);
+				});
+	}
+
+	@Test
+	void autoConfiguresTracingAwareMeterObservationHandler() {
+		this.tracingContextRunner.withUserConfiguration(CustomTracingObservationHandlers.class).run((context) -> {
+			ObservationRegistry observationRegistry = context.getBean(ObservationRegistry.class);
+			List<ObservationHandler<?>> handlers = context.getBean(CalledHandlers.class).getCalledHandlers();
+			// Intentionally not stopped since that will trigger additional logic in
+			// TracingAwareMeterObservationHandler that we don't test here
+			Observation.start("test-observation", observationRegistry);
+			assertThat(handlers).hasSize(1);
+			assertThat(handlers.get(0)).isInstanceOf(CustomTracingObservationHandler.class);
+			assertThat(context).hasSingleBean(TracingAwareMeterObservationHandler.class);
+			assertThat(context.getBeansOfType(ObservationHandler.class)).hasSize(2);
 		});
 	}
 
@@ -156,6 +195,8 @@ class ObservationAutoConfigurationTests {
 			assertThat(handlers.get(2)).isInstanceOf(CustomMeterObservationHandler.class);
 			assertThat(((CustomMeterObservationHandler) handlers.get(2)).getName())
 					.isEqualTo("customMeterObservationHandler1");
+			assertThat(context).doesNotHaveBean(TracingAwareMeterObservationHandler.class);
+			assertThat(context).doesNotHaveBean(DefaultMeterObservationHandler.class);
 		});
 	}
 
@@ -236,6 +277,22 @@ class ObservationAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@Import(CalledHandlersConfiguration.class)
+	static class CustomTracingObservationHandlers {
+
+		@Bean
+		CustomTracingObservationHandler customTracingHandler1(CalledHandlers calledHandlers) {
+			return new CustomTracingObservationHandler("customTracingHandler1", calledHandlers);
+		}
+
+		@Bean
+		Tracer tracer() {
+			return mock(Tracer.class); // simulating tracer configuration
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@Import(CalledHandlersConfiguration.class)
 	static class ObservationHandlersTracing {
@@ -282,6 +339,11 @@ class ObservationAutoConfigurationTests {
 			return new CustomMeterObservationHandler("customMeterObservationHandler1", calledHandlers);
 		}
 
+		@Bean
+		Tracer tracer() {
+			return mock(Tracer.class); // simulating tracer configuration
+		}
+
 	}
 
 	private static class CustomTracingObservationHandler implements TracingObservationHandler<Context> {