Polish "Break cycles between Zipkin senders and HTTP client observation"

See gh-32528

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinConfigurations.java

@@ -16,8 +16,6 @@
 
 package org.springframework.boot.actuate.autoconfigure.tracing.zipkin;
 
-import java.util.List;
-
 import io.opentelemetry.exporter.zipkin.ZipkinSpanExporter;
 import zipkin2.Span;
 import zipkin2.codec.BytesEncoder;
@@ -27,6 +25,7 @@
 import zipkin2.reporter.brave.ZipkinSpanHandler;
 import zipkin2.reporter.urlconnection.URLConnectionSender;
 
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
@@ -76,10 +75,10 @@ static class RestTemplateSenderConfiguration {
 		@Bean
 		@ConditionalOnMissingBean(Sender.class)
 		ZipkinRestTemplateSender restTemplateSender(ZipkinProperties properties,
-				List<ZipkinRestTemplateBuilderCustomizer> customizers) {
+				ObjectProvider<ZipkinRestTemplateBuilderCustomizer> customizers) {
 			RestTemplateBuilder restTemplateBuilder = new RestTemplateBuilder()
 					.setConnectTimeout(properties.getConnectTimeout()).setReadTimeout(properties.getReadTimeout());
-			customizers.forEach((c) -> c.customize(restTemplateBuilder));
+			customizers.orderedStream().forEach((c) -> c.customize(restTemplateBuilder));
 			return new ZipkinRestTemplateSender(properties.getEndpoint(), restTemplateBuilder.build());
 		}
 
@@ -93,9 +92,9 @@ static class WebClientSenderConfiguration {
 		@Bean
 		@ConditionalOnMissingBean(Sender.class)
 		ZipkinWebClientSender webClientSender(ZipkinProperties properties,
-				List<ZipkinWebClientBuilderCustomizer> customizers) {
+				ObjectProvider<ZipkinWebClientBuilderCustomizer> customizers) {
 			WebClient.Builder builder = WebClient.builder();
-			customizers.forEach((c) -> c.customize(builder));
+			customizers.orderedStream().forEach((c) -> c.customize(builder));
 			return new ZipkinWebClientSender(properties.getEndpoint(), builder.build());
 		}
 

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinRestTemplateBuilderCustomizer.java

@@ -0,0 +1,37 @@
+/*
+ * 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.tracing.zipkin;
+
+import org.springframework.boot.web.client.RestTemplateBuilder;
+
+/**
+ * Callback interface that can be implemented by beans wishing to customize the
+ * {@link RestTemplateBuilder} used to send spans to Zipkin.
+ *
+ * @author Marcin Grzejszczak
+ * @since 3.0.0
+ */
+@FunctionalInterface
+public interface ZipkinRestTemplateBuilderCustomizer {
+
+	/**
+	 * Customize the rest template builder.
+	 * @param restTemplateBuilder the {@code RestTemplateBuilder} to customize
+	 */
+	void customize(RestTemplateBuilder restTemplateBuilder);
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinWebClientBuilderCustomizer.java

@@ -0,0 +1,38 @@
+/*
+ * 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.tracing.zipkin;
+
+import org.springframework.web.reactive.function.client.WebClient;
+import org.springframework.web.reactive.function.client.WebClient.Builder;
+
+/**
+ * Callback interface that can be implemented by beans wishing to customize the
+ * {@link Builder} used to send spans to Zipkin.
+ *
+ * @author Marcin Grzejszczak
+ * @since 3.0.0
+ */
+@FunctionalInterface
+public interface ZipkinWebClientBuilderCustomizer {
+
+	/**
+	 * Customize the web client builder.
+	 * @param webClientBuilder the {@code WebClient.Builder} to customize
+	 */
+	void customize(WebClient.Builder webClientBuilder);
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinAutoConfigurationIntegrationTests.java

@@ -0,0 +1,72 @@
+/*
+ * 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.tracing.zipkin;
+
+import org.junit.jupiter.api.Test;
+import zipkin2.reporter.urlconnection.URLConnectionSender;
+
+import org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.metrics.export.simple.SimpleMetricsExportAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.metrics.web.client.HttpClientMetricsAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.tracing.BraveAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.tracing.MicrometerTracingAutoConfiguration;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration;
+import org.springframework.boot.test.context.FilteredClassLoader;
+import org.springframework.boot.test.context.assertj.ApplicationContextAssertProvider;
+import org.springframework.boot.test.context.runner.AbstractApplicationContextRunner;
+import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
+import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
+import org.springframework.context.ConfigurableApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link ZipkinAutoConfiguration} and other related
+ * auto-configurations.
+ *
+ * @author Andy Wilkinson
+ */
+class ZipkinAutoConfigurationIntegrationTests {
+
+	@Test
+	void zipkinsUseOfRestTemplateDoesNotCauseACycle() {
+		configure(new WebApplicationContextRunner())
+				.withConfiguration(AutoConfigurations.of(RestTemplateAutoConfiguration.class))
+				.run((context) -> assertThat(context).hasNotFailed());
+	}
+
+	@Test
+	void zipkinsUseOfWebClientDoesNotCauseACycle() {
+		configure(new ReactiveWebApplicationContextRunner())
+				.withConfiguration(AutoConfigurations.of(WebClientAutoConfiguration.class))
+				.run((context) -> assertThat(context).hasNotFailed());
+	}
+
+	<SELF extends AbstractApplicationContextRunner<SELF, C, A>, C extends ConfigurableApplicationContext, A extends ApplicationContextAssertProvider<C>> AbstractApplicationContextRunner<SELF, C, A> configure(
+			AbstractApplicationContextRunner<SELF, ?, ?> runner) {
+		return runner
+				.withConfiguration(AutoConfigurations.of(MicrometerTracingAutoConfiguration.class,
+						ObservationAutoConfiguration.class, BraveAutoConfiguration.class, ZipkinAutoConfiguration.class,
+						HttpClientMetricsAutoConfiguration.class, MetricsAutoConfiguration.class,
+						SimpleMetricsExportAutoConfiguration.class))
+				.withClassLoader(new FilteredClassLoader(URLConnectionSender.class));
+	}
+
+}