Prevent propagation for local fields when using W3C propagation

Closes gh-37109

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

@@ -37,7 +37,9 @@ import brave.handler.SpanHandler;
 import brave.propagation.CurrentTraceContext;
 import brave.propagation.CurrentTraceContext.ScopeDecorator;
 import brave.propagation.CurrentTraceContextCustomizer;
+import brave.propagation.Propagation;
 import brave.propagation.Propagation.Factory;
+import brave.propagation.Propagation.KeyFactory;
 import brave.propagation.ThreadLocalCurrentTraceContext;
 import brave.sampler.Sampler;
 import io.micrometer.tracing.brave.bridge.BraveBaggageManager;
@@ -168,7 +170,7 @@ public class BraveAutoConfiguration {
 		@Bean
 		@ConditionalOnMissingBean
 		Factory propagationFactory(TracingProperties properties) {
-			return CompositePropagationFactory.create(properties.getPropagation(), null);
+			return CompositePropagationFactory.create(properties.getPropagation());
 		}
 
 	}
@@ -187,13 +189,31 @@ public class BraveAutoConfiguration {
 		@ConditionalOnMissingBean
 		BaggagePropagation.FactoryBuilder propagationFactoryBuilder(
 				ObjectProvider<BaggagePropagationCustomizer> baggagePropagationCustomizers) {
-			CompositePropagationFactory factory = CompositePropagationFactory
-				.create(this.tracingProperties.getPropagation(), BRAVE_BAGGAGE_MANAGER);
-			FactoryBuilder builder = BaggagePropagation.newFactoryBuilder(factory);
-			baggagePropagationCustomizers.orderedStream().forEach((customizer) -> customizer.customize(builder));
+			// There's a chicken-and-egg problem here: to create a builder, we need a
+			// factory. But the CompositePropagationFactory needs data from the builder.
+			// We create a throw-away builder with a throw-away factory, and then copy the
+			// config to the real builder
+			FactoryBuilder throwAwayBuilder = BaggagePropagation.newFactoryBuilder(createThrowAwayFactory());
+			baggagePropagationCustomizers.orderedStream()
+				.forEach((customizer) -> customizer.customize(throwAwayBuilder));
+			CompositePropagationFactory propagationFactory = CompositePropagationFactory.create(
+					this.tracingProperties.getPropagation(), BRAVE_BAGGAGE_MANAGER,
+					LocalBaggageFields.extractFrom(throwAwayBuilder));
+			FactoryBuilder builder = BaggagePropagation.newFactoryBuilder(propagationFactory);
+			throwAwayBuilder.configs().forEach(builder::add);
 			return builder;
 		}
 
+		@SuppressWarnings("deprecation")
+		private Factory createThrowAwayFactory() {
+			return new Factory() {
+				@Override
+				public <K> Propagation<K> create(KeyFactory<K> keyFactory) {
+					return null;
+				}
+			};
+		}
+
 		@Bean
 		@Order(0)
 		BaggagePropagationCustomizer remoteFieldsBaggagePropagationCustomizer() {

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

@@ -17,7 +17,6 @@
 package org.springframework.boot.actuate.autoconfigure.tracing;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -85,15 +84,27 @@ class CompositePropagationFactory extends Propagation.Factory {
 			.orElse(context);
 	}
 
+	/**
+	 * Creates a new {@link CompositePropagationFactory}, which uses the given
+	 * {@code injectionTypes} for injection and {@code extractionTypes} for extraction.
+	 * @param properties the propagation properties
+	 * @return the {@link CompositePropagationFactory}
+	 */
+	static CompositePropagationFactory create(TracingProperties.Propagation properties) {
+		return create(properties, null, null);
+	}
+
 	/**
 	 * Creates a new {@link CompositePropagationFactory}, which uses the given
 	 * {@code injectionTypes} for injection and {@code extractionTypes} for extraction.
 	 * @param properties the propagation properties
 	 * @param baggageManager the baggage manager to use, or {@code null}
+	 * @param localFields the local fields, or {@code null}
 	 * @return the {@link CompositePropagationFactory}
 	 */
-	static CompositePropagationFactory create(TracingProperties.Propagation properties, BaggageManager baggageManager) {
-		PropagationFactoryMapper mapper = new PropagationFactoryMapper(baggageManager);
+	static CompositePropagationFactory create(TracingProperties.Propagation properties, BaggageManager baggageManager,
+			LocalBaggageFields localFields) {
+		PropagationFactoryMapper mapper = new PropagationFactoryMapper(baggageManager, localFields);
 		List<Factory> injectors = properties.getEffectiveProducedTypes().stream().map(mapper::map).toList();
 		List<Factory> extractors = properties.getEffectiveConsumedTypes().stream().map(mapper::map).toList();
 		return new CompositePropagationFactory(injectors, extractors);
@@ -107,8 +118,11 @@ class CompositePropagationFactory extends Propagation.Factory {
 
 		private final BaggageManager baggageManager;
 
-		PropagationFactoryMapper(BaggageManager baggageManager) {
+		private final LocalBaggageFields localFields;
+
+		PropagationFactoryMapper(BaggageManager baggageManager, LocalBaggageFields localFields) {
 			this.baggageManager = baggageManager;
+			this.localFields = (localFields != null) ? localFields : LocalBaggageFields.empty();
 		}
 
 		Propagation.Factory map(PropagationType type) {
@@ -140,8 +154,10 @@ class CompositePropagationFactory extends Propagation.Factory {
 		 * @return the W3C propagation factory
 		 */
 		private Propagation.Factory w3c() {
-			return (this.baggageManager != null) ? new W3CPropagation(this.baggageManager, Collections.emptyList())
-					: new W3CPropagation();
+			if (this.baggageManager == null) {
+				return new W3CPropagation();
+			}
+			return new W3CPropagation(this.baggageManager, this.localFields.asList());
 		}
 
 	}

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

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012-2023 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;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import brave.baggage.BaggagePropagation;
+import brave.baggage.BaggagePropagationConfig;
+import brave.baggage.BaggagePropagationConfig.SingleBaggageField;
+
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+
+/**
+ * Local baggage fields.
+ *
+ * @author Moritz Halbritter
+ */
+class LocalBaggageFields {
+
+	private final List<String> fields;
+
+	LocalBaggageFields(List<String> fields) {
+		Assert.notNull(fields, "fields must not be null");
+		this.fields = fields;
+	}
+
+	/**
+	 * Returns the local fields as a list.
+	 * @return the list
+	 */
+	List<String> asList() {
+		return Collections.unmodifiableList(this.fields);
+	}
+
+	/**
+	 * Extracts the local fields from the given propagation factory builder.
+	 * @param builder the propagation factory builder to extract the local fields from
+	 * @return the local fields
+	 */
+	static LocalBaggageFields extractFrom(BaggagePropagation.FactoryBuilder builder) {
+		List<String> localFields = new ArrayList<>();
+		for (BaggagePropagationConfig config : builder.configs()) {
+			if (config instanceof SingleBaggageField field) {
+				if (CollectionUtils.isEmpty(field.keyNames())) {
+					localFields.add(field.field().name());
+				}
+			}
+		}
+		return new LocalBaggageFields(localFields);
+	}
+
+	/**
+	 * Creates empty local fields.
+	 * @return the empty local fields
+	 */
+	static LocalBaggageFields empty() {
+		return new LocalBaggageFields(Collections.emptyList());
+	}
+
+}

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

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2012-2023 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;
+
+import brave.baggage.BaggageField;
+import brave.baggage.BaggagePropagation;
+import brave.baggage.BaggagePropagation.FactoryBuilder;
+import brave.baggage.BaggagePropagationConfig;
+import brave.propagation.Propagation;
+import brave.propagation.Propagation.Factory;
+import brave.propagation.Propagation.KeyFactory;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link LocalBaggageFields}.
+ *
+ * @author Moritz Halbritter
+ */
+class LocalBaggageFieldsTests {
+
+	@Test
+	void extractFromBuilder() {
+		FactoryBuilder builder = createBuilder();
+		builder.add(BaggagePropagationConfig.SingleBaggageField.remote(BaggageField.create("remote-field-1")));
+		builder.add(BaggagePropagationConfig.SingleBaggageField.remote(BaggageField.create("remote-field-2")));
+		builder.add(BaggagePropagationConfig.SingleBaggageField.local(BaggageField.create("local-field-1")));
+		builder.add(BaggagePropagationConfig.SingleBaggageField.local(BaggageField.create("local-field-2")));
+		LocalBaggageFields fields = LocalBaggageFields.extractFrom(builder);
+		assertThat(fields.asList()).containsExactlyInAnyOrder("local-field-1", "local-field-2");
+	}
+
+	@Test
+	void empty() {
+		assertThat(LocalBaggageFields.empty().asList()).isEmpty();
+	}
+
+	@SuppressWarnings("deprecation")
+	private static FactoryBuilder createBuilder() {
+		return BaggagePropagation.newFactoryBuilder(new Factory() {
+			@Override
+			public <K> Propagation<K> create(KeyFactory<K> keyFactory) {
+				return null;
+			}
+		});
+	}
+
+}