Allow DefaultMeterObservationHandler to be replaced by user's bean

Closes gh-32462

Co-authored-by: Jonatan Ivanov <jonatan.ivanov@gmail.com>

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

@@ -1,43 +0,0 @@
-/*
- * 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 io.micrometer.core.instrument.MeterRegistry;
-import io.micrometer.core.instrument.observation.DefaultMeterObservationHandler;
-import io.micrometer.observation.ObservationRegistry;
-
-/**
- * Registers the {@link DefaultMeterObservationHandler} with an
- * {@link ObservationRegistry}.
- *
- * @author Moritz Halbritter
- */
-class DefaultMeterObservationHandlerObservationRegistryCustomizer
-		implements ObservationRegistryCustomizer<ObservationRegistry> {
-
-	private final MeterRegistry meterRegistry;
-
-	DefaultMeterObservationHandlerObservationRegistryCustomizer(MeterRegistry meterRegistry) {
-		this.meterRegistry = meterRegistry;
-	}
-
-	@Override
-	public void customize(ObservationRegistry registry) {
-		registry.observationConfig().observationHandler(new DefaultMeterObservationHandler(this.meterRegistry));
-	}
-
-}

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

@@ -17,6 +17,8 @@
 package org.springframework.boot.actuate.autoconfigure.observation;
 
 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.ObservationHandler;
 import io.micrometer.observation.ObservationPredicate;
@@ -66,9 +68,9 @@ public class ObservationAutoConfiguration {
 	static class MetricsConfiguration {
 
 		@Bean
-		DefaultMeterObservationHandlerObservationRegistryCustomizer enableDefaultMeterObservationHandler(
-				MeterRegistry meterRegistry) {
-			return new DefaultMeterObservationHandlerObservationRegistryCustomizer(meterRegistry);
+		@ConditionalOnMissingBean(MeterObservationHandler.class)
+		DefaultMeterObservationHandler defaultMeterObservationHandler(MeterRegistry meterRegistry) {
+			return new DefaultMeterObservationHandler(meterRegistry);
 		}
 
 	}

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

@@ -1,45 +0,0 @@
-/*
- * 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 io.micrometer.core.instrument.MeterRegistry;
-import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
-import io.micrometer.observation.Observation;
-import io.micrometer.observation.ObservationRegistry;
-import org.junit.jupiter.api.Test;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-/**
- * Tests for {@link DefaultMeterObservationHandlerObservationRegistryCustomizer}.
- *
- * @author Moritz Halbritter
- */
-class DefaultMeterObservationHandlerObservationRegistryCustomizerTests {
-
-	@Test
-	void customizeInstallsDefaultMeterObservationHandler() {
-		MeterRegistry meterRegistry = new SimpleMeterRegistry();
-		DefaultMeterObservationHandlerObservationRegistryCustomizer sut = new DefaultMeterObservationHandlerObservationRegistryCustomizer(
-				meterRegistry);
-		ObservationRegistry observationRegistry = ObservationRegistry.create();
-		sut.customize(observationRegistry);
-		Observation.start("test-1", observationRegistry).stop();
-		assertThat(meterRegistry.find("test-1").timer().count()).isEqualTo(1);
-	}
-
-}

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

@@ -22,6 +22,7 @@ import java.util.List;
 import io.micrometer.common.KeyValue;
 import io.micrometer.common.KeyValues;
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.observation.DefaultMeterObservationHandler;
 import io.micrometer.core.instrument.observation.MeterObservationHandler;
 import io.micrometer.core.instrument.search.MeterNotFoundException;
 import io.micrometer.observation.GlobalObservationConvention;
@@ -67,6 +68,7 @@ class ObservationAutoConfigurationTests {
 	@Test
 	void autoConfiguresDefaultMeterObservationHandler() {
 		this.contextRunner.run((context) -> {
+			assertThat(context).hasSingleBean(DefaultMeterObservationHandler.class);
 			ObservationRegistry observationRegistry = context.getBean(ObservationRegistry.class);
 			Observation.start("test-observation", observationRegistry).stop();
 			// When a DefaultMeterObservationHandler is registered, every stopped
@@ -76,13 +78,6 @@ class ObservationAutoConfigurationTests {
 		});
 	}
 
-	@Test
-	void allowsDefaultMeterObservationHandlerToBeDisabled() {
-		this.contextRunner.withClassLoader(new FilteredClassLoader(MeterRegistry.class))
-				.run((context) -> assertThat(context)
-						.doesNotHaveBean(DefaultMeterObservationHandlerObservationRegistryCustomizer.class));
-	}
-
 	@Test
 	void autoConfiguresObservationPredicates() {
 		this.contextRunner.withUserConfiguration(ObservationPredicates.class).run((context) -> {
@@ -109,11 +104,12 @@ class ObservationAutoConfigurationTests {
 	}
 
 	@Test
-	void autoConfiguresObservationHandler() {
+	void autoConfiguresObservationHandlers() {
 		this.contextRunner.withUserConfiguration(ObservationHandlers.class).run((context) -> {
 			ObservationRegistry observationRegistry = context.getBean(ObservationRegistry.class);
 			List<ObservationHandler<?>> handlers = context.getBean(CalledHandlers.class).getCalledHandlers();
 			Observation.start("test-observation", observationRegistry);
+			assertThat(context).doesNotHaveBean(DefaultMeterObservationHandler.class);
 			assertThat(handlers).hasSize(2);
 			// Regular handlers are registered first
 			assertThat(handlers.get(0)).isInstanceOf(CustomObservationHandler.class);