Add OTLP span exporter builder customizers

This commit adds customizers for both OtlpHttpSpanExporterBuilder
and OtlpGrpcSpanExporterBuilder.

See gh-44900

Signed-off-by: Dmytro Nosan <dimanosan@gmail.com>

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2025 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.otlp;
+
+import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporterBuilder;
+
+/**
+ * Callback interface that can be implemented by beans wishing to customize the
+ * {@link OtlpGrpcSpanExporterBuilder} whilst retaining default auto-configuration.
+ *
+ * @author Dmytro Nosan
+ * @since 3.5.0
+ */
+@FunctionalInterface
+public interface OtlpGrpcSpanExporterBuilderCustomizer {
+
+	/**
+	 * Customize the {@link OtlpGrpcSpanExporterBuilder}.
+	 * @param builder the builder to customize
+	 */
+	void customize(OtlpGrpcSpanExporterBuilder builder);
+
+}

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2025 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.otlp;
+
+import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporterBuilder;
+
+/**
+ * Callback interface that can be implemented by beans wishing to customize the
+ * {@link OtlpHttpSpanExporterBuilder} whilst retaining default auto-configuration.
+ *
+ * @author Dmytro Nosan
+ * @since 3.5.0
+ */
+@FunctionalInterface
+public interface OtlpHttpSpanExporterBuilderCustomizer {
+
+	/**
+	 * Customize the {@link OtlpHttpSpanExporterBuilder}.
+	 * @param builder the builder to customize
+	 */
+	void customize(OtlpHttpSpanExporterBuilder builder);
+
+}

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

@@ -83,7 +83,8 @@ class OtlpTracingConfigurations {
 		@Bean
 		@ConditionalOnProperty(name = "management.otlp.tracing.transport", havingValue = "http", matchIfMissing = true)
 		OtlpHttpSpanExporter otlpHttpSpanExporter(OtlpTracingProperties properties,
-				OtlpTracingConnectionDetails connectionDetails, ObjectProvider<MeterProvider> meterProvider) {
+				OtlpTracingConnectionDetails connectionDetails, ObjectProvider<MeterProvider> meterProvider,
+				ObjectProvider<OtlpHttpSpanExporterBuilderCustomizer> customizers) {
 			OtlpHttpSpanExporterBuilder builder = OtlpHttpSpanExporter.builder()
 				.setEndpoint(connectionDetails.getUrl(Transport.HTTP))
 				.setTimeout(properties.getTimeout())
@@ -91,13 +92,15 @@ class OtlpTracingConfigurations {
 				.setCompression(properties.getCompression().name().toLowerCase(Locale.ROOT));
 			properties.getHeaders().forEach(builder::addHeader);
 			meterProvider.ifAvailable(builder::setMeterProvider);
+			customizers.orderedStream().forEach((customizer) -> customizer.customize(builder));
 			return builder.build();
 		}
 
 		@Bean
 		@ConditionalOnProperty(name = "management.otlp.tracing.transport", havingValue = "grpc")
 		OtlpGrpcSpanExporter otlpGrpcSpanExporter(OtlpTracingProperties properties,
-				OtlpTracingConnectionDetails connectionDetails, ObjectProvider<MeterProvider> meterProvider) {
+				OtlpTracingConnectionDetails connectionDetails, ObjectProvider<MeterProvider> meterProvider,
+				ObjectProvider<OtlpGrpcSpanExporterBuilderCustomizer> customizers) {
 			OtlpGrpcSpanExporterBuilder builder = OtlpGrpcSpanExporter.builder()
 				.setEndpoint(connectionDetails.getUrl(Transport.GRPC))
 				.setTimeout(properties.getTimeout())
@@ -105,6 +108,7 @@ class OtlpTracingConfigurations {
 				.setCompression(properties.getCompression().name().toLowerCase(Locale.ROOT));
 			properties.getHeaders().forEach(builder::addHeader);
 			meterProvider.ifAvailable(builder::setMeterProvider);
+			customizers.orderedStream().forEach((customizer) -> customizer.customize(builder));
 			return builder.build();
 		}
 

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

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.tracing.otlp;
 
+import java.time.Duration;
 import java.util.List;
 import java.util.function.Supplier;
 
@@ -230,6 +231,45 @@ class OtlpTracingAutoConfigurationTests {
 			});
 	}
 
+	@Test
+	void shouldCustomizeHttpTransportWithOtlpHttpSpanExporterBuilderCustomizer() {
+		Duration connectTimeout = Duration.ofMinutes(20);
+		Duration timeout = Duration.ofMinutes(10);
+		this.contextRunner
+			.withBean("httpCustomizer1", OtlpHttpSpanExporterBuilderCustomizer.class,
+					() -> (builder) -> builder.setConnectTimeout(connectTimeout))
+			.withBean("httpCustomizer2", OtlpHttpSpanExporterBuilderCustomizer.class,
+					() -> (builder) -> builder.setTimeout(timeout))
+			.withPropertyValues("management.otlp.tracing.endpoint=http://localhost:4317/v1/traces")
+			.run((context) -> {
+				assertThat(context).hasSingleBean(OtlpHttpSpanExporter.class).hasSingleBean(SpanExporter.class);
+				OtlpHttpSpanExporter exporter = context.getBean(OtlpHttpSpanExporter.class);
+				assertThat(exporter).extracting("delegate.httpSender.client")
+					.hasFieldOrPropertyWithValue("connectTimeoutMillis", (int) connectTimeout.toMillis())
+					.hasFieldOrPropertyWithValue("callTimeoutMillis", (int) timeout.toMillis());
+			});
+	}
+
+	@Test
+	void shouldCustomizeGrpcTransportWhenEnabledWithOtlpGrpcSpanExporterBuilderCustomizer() {
+		Duration timeout = Duration.ofMinutes(10);
+		Duration connectTimeout = Duration.ofMinutes(20);
+		this.contextRunner
+			.withBean("grpcCustomizer1", OtlpGrpcSpanExporterBuilderCustomizer.class,
+					() -> (builder) -> builder.setConnectTimeout(connectTimeout))
+			.withBean("grpcCustomizer2", OtlpGrpcSpanExporterBuilderCustomizer.class,
+					() -> (builder) -> builder.setTimeout(timeout))
+			.withPropertyValues("management.otlp.tracing.endpoint=http://localhost:4317/v1/traces",
+					"management.otlp.tracing.transport=grpc")
+			.run((context) -> {
+				assertThat(context).hasSingleBean(OtlpGrpcSpanExporter.class).hasSingleBean(SpanExporter.class);
+				OtlpGrpcSpanExporter exporter = context.getBean(OtlpGrpcSpanExporter.class);
+				assertThat(exporter).extracting("delegate.grpcSender.client")
+					.hasFieldOrPropertyWithValue("connectTimeoutMillis", (int) connectTimeout.toMillis())
+					.hasFieldOrPropertyWithValue("callTimeoutMillis", (int) timeout.toMillis());
+			});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	private static final class MeterProviderConfiguration {
 

spring-boot-project/spring-boot-docs/src/docs/antora/modules/reference/pages/actuator/tracing.adoc

@@ -150,6 +150,8 @@ Tracing with OpenTelemetry and reporting using OTLP requires the following depen
 
 Use the `management.otlp.tracing.*` configuration properties to configure reporting using OTLP.
 
+NOTE: If you need to apply advanced customizations to OTLP span exporters, consider registering javadoc:org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpHttpSpanExporterBuilderCustomizer[] or javadoc:org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpGrpcSpanExporterBuilderCustomizer[] beans. These will be invoked **before** the creation of the `OtlpHttpSpanExporter` or `OtlpGrpcSpanExporter`. The customizers take precedence over anything applied by the auto-configuration.
+
 
 
 [[actuator.micrometer-tracing.tracer-implementations.brave-zipkin]]