Add missing OTel Span attributes

OTel semantic conventions mandate certain resource attributes to present
on exported spans. This commits make sure that the attribute we add are
merged with the defaults, rather than replacing them.

See gh-36155

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

@@ -97,9 +97,10 @@ public class OpenTelemetryAutoConfiguration {
 	SdkTracerProvider otelSdkTracerProvider(Environment environment, ObjectProvider<SpanProcessor> spanProcessors,
 			Sampler sampler) {
 		String applicationName = environment.getProperty("spring.application.name", DEFAULT_APPLICATION_NAME);
+		Resource springResource = Resource.create(Attributes.of(ResourceAttributes.SERVICE_NAME, applicationName));
 		SdkTracerProviderBuilder builder = SdkTracerProvider.builder()
 			.setSampler(sampler)
-			.setResource(Resource.create(Attributes.of(ResourceAttributes.SERVICE_NAME, applicationName)));
+			.setResource(Resource.getDefault().merge(springResource));
 		spanProcessors.orderedStream().forEach(builder::addSpanProcessor);
 		return builder.build();
 	}

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

@@ -16,8 +16,14 @@
 
 package org.springframework.boot.actuate.autoconfigure.tracing;
 
+import java.time.Duration;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 import java.util.stream.Stream;
 
 import io.micrometer.tracing.SpanCustomizer;
@@ -30,18 +36,26 @@ import io.micrometer.tracing.otel.bridge.Slf4JBaggageEventListener;
 import io.micrometer.tracing.otel.bridge.Slf4JEventListener;
 import io.micrometer.tracing.otel.propagation.BaggageTextMapPropagator;
 import io.opentelemetry.api.OpenTelemetry;
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.api.trace.Tracer;
 import io.opentelemetry.api.trace.propagation.W3CTraceContextPropagator;
 import io.opentelemetry.context.propagation.ContextPropagators;
 import io.opentelemetry.context.propagation.TextMapPropagator;
 import io.opentelemetry.extension.trace.propagation.B3Propagator;
+import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.trace.SdkTracerProvider;
 import io.opentelemetry.sdk.trace.SpanProcessor;
+import io.opentelemetry.sdk.trace.data.SpanData;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
 import io.opentelemetry.sdk.trace.samplers.Sampler;
+import io.opentelemetry.semconv.resource.attributes.ResourceAttributes;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 
+import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
@@ -143,6 +157,26 @@ class OpenTelemetryAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void shouldSetupDefaultResourceAttributes() {
+		this.contextRunner
+			.withConfiguration(
+					AutoConfigurations.of(ObservationAutoConfiguration.class, MicrometerTracingAutoConfiguration.class))
+			.withUserConfiguration(InMemoryRecordingSpanExporterConfiguration.class)
+			.withPropertyValues("management.tracing.sampling.probability=1.0")
+			.run((context) -> {
+				context.getBean(io.micrometer.tracing.Tracer.class).nextSpan().name("test").end();
+				InMemoryRecordingSpanExporter exporter = context.getBean(InMemoryRecordingSpanExporter.class);
+				exporter.await(Duration.ofSeconds(10));
+				SpanData spanData = exporter.getExportedSpans().get(0);
+				Map<AttributeKey<?>, Object> expectedAttributes = Resource.getDefault()
+					.merge(Resource.create(Attributes.of(ResourceAttributes.SERVICE_NAME, "application")))
+					.getAttributes()
+					.asMap();
+				assertThat(spanData.getResource().getAttributes().asMap()).isEqualTo(expectedAttributes);
+			});
+	}
+
 	@Test
 	void shouldAllowMultipleSpanProcessors() {
 		this.contextRunner.withUserConfiguration(CustomConfiguration.class).run((context) -> {
@@ -297,4 +331,50 @@ class OpenTelemetryAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	private static class InMemoryRecordingSpanExporterConfiguration {
+
+		@Bean
+		InMemoryRecordingSpanExporter spanExporter() {
+			return new InMemoryRecordingSpanExporter();
+		}
+
+	}
+
+	private static class InMemoryRecordingSpanExporter implements SpanExporter {
+
+		private final List<SpanData> exportedSpans = new ArrayList<>();
+
+		private final CountDownLatch latch = new CountDownLatch(1);
+
+		@Override
+		public CompletableResultCode export(Collection<SpanData> spans) {
+			this.exportedSpans.addAll(spans);
+			this.latch.countDown();
+			return CompletableResultCode.ofSuccess();
+		}
+
+		@Override
+		public CompletableResultCode flush() {
+			return CompletableResultCode.ofSuccess();
+		}
+
+		@Override
+		public CompletableResultCode shutdown() {
+			this.exportedSpans.clear();
+			return CompletableResultCode.ofSuccess();
+		}
+
+		List<SpanData> getExportedSpans() {
+			return this.exportedSpans;
+		}
+
+		void await(Duration timeout) throws InterruptedException, TimeoutException {
+			if (!this.latch.await(timeout.toMillis(), TimeUnit.MILLISECONDS)) {
+				throw new TimeoutException("Waiting for exporting spans timed out (%s)".formatted(timeout));
+			}
+		}
+
+	}
+
 }