Add auto-configuration for OTLP gRPC format when using tracing

See gh-41213

spring-boot-project/spring-boot-actuator-autoconfigure/build.gradle

@@ -161,6 +161,7 @@ dependencies {
 	testImplementation("org.awaitility:awaitility")
 	testImplementation("org.cache2k:cache2k-api")
 	testImplementation("org.eclipse.jetty.ee10:jetty-ee10-webapp")
+	testImplementation("org.eclipse.jetty.http2:jetty-http2-server")
 	testImplementation("org.glassfish.jersey.ext:jersey-spring6")
 	testImplementation("org.glassfish.jersey.media:jersey-media-json-jackson")
 	testImplementation("org.hamcrest:hamcrest")

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

@@ -36,8 +36,10 @@ import org.springframework.context.annotation.Import;
  * the future, see: <a href=
  * "https://github.com/open-telemetry/opentelemetry-java/issues/3651">opentelemetry-java#3651</a>.
  * Because this class configures components from the OTel SDK, it can't support HTTP/JSON.
- * To keep things simple, we only auto-configure HTTP/protobuf. If you want to use gRPC,
- * define an {@link OtlpGrpcSpanExporter} and this auto-configuration will back off.
+ * By default, we auto-configure HTTP/protobuf. If you want to use gRPC, you need to set
+ * {@code management.otlp.tracing.transport=grpc}. If you define a
+ * {@link OtlpHttpSpanExporter} or {@link OtlpGrpcSpanExporter}, this auto-configuration
+ * will back off.
  *
  * @author Jonatan Ivanov
  * @author Moritz Halbritter

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

@@ -44,6 +44,11 @@ public class OtlpProperties {
 	 */
 	private Duration timeout = Duration.ofSeconds(10);
 
+	/**
+	 * Transport used to send the spans. Defaults to HTTP.
+	 */
+	private Transport transport = Transport.HTTP;
+
 	/**
 	 * Method used to compress the payload.
 	 */
@@ -70,6 +75,14 @@ public class OtlpProperties {
 		this.timeout = timeout;
 	}
 
+	public Transport getTransport() {
+		return this.transport;
+	}
+
+	public void setTransport(Transport transport) {
+		this.transport = transport;
+	}
+
 	public Compression getCompression() {
 		return this.compression;
 	}
@@ -86,6 +99,20 @@ public class OtlpProperties {
 		this.headers = headers;
 	}
 
+	enum Transport {
+
+		/**
+		 * HTTP exporter.
+		 */
+		HTTP,
+
+		/**
+		 * gRPC exporter.
+		 */
+		GRPC
+
+	}
+
 	enum Compression {
 
 		/**

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

@@ -20,6 +20,8 @@ import java.util.Map.Entry;
 
 import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
 import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporterBuilder;
+import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter;
+import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporterBuilder;
 
 import org.springframework.boot.actuate.autoconfigure.tracing.ConditionalOnEnabledTracing;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
@@ -69,10 +71,11 @@ class OtlpTracingConfigurations {
 	static class Exporters {
 
 		@Bean
-		@ConditionalOnMissingBean(value = OtlpHttpSpanExporter.class,
-				type = "io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter")
+		@ConditionalOnMissingBean({ OtlpGrpcSpanExporter.class, OtlpHttpSpanExporter.class })
 		@ConditionalOnBean(OtlpTracingConnectionDetails.class)
 		@ConditionalOnEnabledTracing("otlp")
+		@ConditionalOnProperty(prefix = "management.otlp.tracing", name = "transport", havingValue = "http",
+				matchIfMissing = true)
 		OtlpHttpSpanExporter otlpHttpSpanExporter(OtlpProperties properties,
 				OtlpTracingConnectionDetails connectionDetails) {
 			OtlpHttpSpanExporterBuilder builder = OtlpHttpSpanExporter.builder()
@@ -85,6 +88,23 @@ class OtlpTracingConfigurations {
 			return builder.build();
 		}
 
+		@Bean
+		@ConditionalOnMissingBean({ OtlpGrpcSpanExporter.class, OtlpHttpSpanExporter.class })
+		@ConditionalOnBean(OtlpTracingConnectionDetails.class)
+		@ConditionalOnEnabledTracing("otlp")
+		@ConditionalOnProperty(prefix = "management.otlp.tracing", name = "transport", havingValue = "grpc")
+		OtlpGrpcSpanExporter otlpGrpcSpanExporter(OtlpProperties properties,
+				OtlpTracingConnectionDetails connectionDetails) {
+			OtlpGrpcSpanExporterBuilder builder = OtlpGrpcSpanExporter.builder()
+				.setEndpoint(connectionDetails.getUrl())
+				.setTimeout(properties.getTimeout())
+				.setCompression(properties.getCompression().name().toLowerCase());
+			for (Entry<String, String> header : properties.getHeaders().entrySet()) {
+				builder.addHeader(header.getKey(), header.getValue());
+			}
+			return builder.build();
+		}
+
 	}
 
 }

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

@@ -17,11 +17,15 @@
 package org.springframework.boot.actuate.autoconfigure.tracing.otlp;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 
 import io.micrometer.tracing.Tracer;
 import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
+import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter;
 import io.opentelemetry.sdk.common.CompletableResultCode;
 import io.opentelemetry.sdk.trace.export.SpanExporter;
 import okhttp3.mockwebserver.MockResponse;
@@ -29,6 +33,16 @@ import okhttp3.mockwebserver.MockWebServer;
 import okhttp3.mockwebserver.RecordedRequest;
 import okio.Buffer;
 import okio.GzipSource;
+import org.eclipse.jetty.http.HttpFields;
+import org.eclipse.jetty.http2.server.HTTP2CServerConnectionFactory;
+import org.eclipse.jetty.io.Content;
+import org.eclipse.jetty.server.Handler;
+import org.eclipse.jetty.server.HttpConfiguration;
+import org.eclipse.jetty.server.Request;
+import org.eclipse.jetty.server.Response;
+import org.eclipse.jetty.server.Server;
+import org.eclipse.jetty.server.ServerConnector;
+import org.eclipse.jetty.util.Callback;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -36,8 +50,10 @@ import org.junit.jupiter.api.Test;
 import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.opentelemetry.OpenTelemetryAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.tracing.MicrometerTracingAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpAutoConfigurationIntegrationTests.MockGrpcServer.RecordedGrpcRequest;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.util.StreamUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -57,16 +73,28 @@ class OtlpAutoConfigurationIntegrationTests {
 
 	private final MockWebServer mockWebServer = new MockWebServer();
 
+	private final MockGrpcServer mockGrpcServer = new MockGrpcServer();
+
 	@BeforeEach
-	void setUp() throws IOException {
+	void startMockWebServer() throws IOException {
 		this.mockWebServer.start();
 	}
 
+	@BeforeEach
+	void startMockGrpcServer() throws Exception {
+		this.mockGrpcServer.start();
+	}
+
 	@AfterEach
-	void tearDown() throws IOException {
+	void stopMockWebServer() throws IOException {
 		this.mockWebServer.close();
 	}
 
+	@AfterEach
+	void stopMockGrpcServer() throws Exception {
+		this.mockGrpcServer.stop();
+	}
+
 	@Test
 	void httpSpanExporterShouldUseProtobufAndNoCompressionByDefault() {
 		this.mockWebServer.enqueue(new MockResponse());
@@ -113,4 +141,88 @@ class OtlpAutoConfigurationIntegrationTests {
 			});
 	}
 
+	@Test
+	void grpcSpanExporter() {
+		this.contextRunner
+			.withPropertyValues(
+					"management.otlp.tracing.endpoint=http://localhost:%d".formatted(this.mockGrpcServer.getPort()),
+					"management.otlp.tracing.headers.custom=42", "management.otlp.tracing.transport=grpc")
+			.run((context) -> {
+				context.getBean(Tracer.class).nextSpan().name("test").end();
+				assertThat(context.getBean(OtlpGrpcSpanExporter.class).flush())
+					.isSameAs(CompletableResultCode.ofSuccess());
+				RecordedGrpcRequest request = this.mockGrpcServer.takeRequest(10, TimeUnit.SECONDS);
+				assertThat(request).isNotNull();
+				assertThat(request.headers().get("Content-Type")).isEqualTo("application/grpc");
+				assertThat(request.headers().get("custom")).isEqualTo("42");
+				assertThat(request.body()).contains("org.springframework.boot");
+			});
+	}
+
+	static class MockGrpcServer {
+
+		private final Server server = createServer();
+
+		private final BlockingQueue<RecordedGrpcRequest> recordedRequests = new LinkedBlockingQueue<>();
+
+		void start() throws Exception {
+			this.server.start();
+		}
+
+		void stop() throws Exception {
+			this.server.stop();
+		}
+
+		int getPort() {
+			return this.server.getURI().getPort();
+		}
+
+		RecordedGrpcRequest takeRequest(int timeout, TimeUnit unit) throws InterruptedException {
+			return this.recordedRequests.poll(timeout, unit);
+		}
+
+		void recordRequest(RecordedGrpcRequest request) {
+			this.recordedRequests.add(request);
+		}
+
+		private Server createServer() {
+			Server server = new Server();
+			server.addConnector(createConnector(server));
+			server.setHandler(new GrpcHandler());
+
+			return server;
+		}
+
+		private ServerConnector createConnector(Server server) {
+			ServerConnector connector = new ServerConnector(server,
+					new HTTP2CServerConnectionFactory(new HttpConfiguration()));
+			connector.setPort(0);
+
+			return connector;
+		}
+
+		class GrpcHandler extends Handler.Abstract {
+
+			@Override
+			public boolean handle(Request request, Response response, Callback callback) throws Exception {
+				try (InputStream in = Content.Source.asInputStream(request)) {
+					recordRequest(new RecordedGrpcRequest(request.getHeaders(),
+							StreamUtils.copyToString(in, StandardCharsets.UTF_8)));
+				}
+
+				response.getHeaders().add("Content-Type", "application/grpc");
+				response.getHeaders().add("Grpc-Status", "0");
+
+				callback.succeeded();
+
+				return true;
+			}
+
+		}
+
+		record RecordedGrpcRequest(HttpFields headers, String body) {
+		}
+
+	}
+
 }

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

@@ -51,6 +51,12 @@ class OtlpAutoConfigurationTests {
 		this.contextRunner.run((context) -> assertThat(context).doesNotHaveBean(OtlpHttpSpanExporter.class));
 	}
 
+	@Test
+	void shouldNotSupplyBeansIfGrpcTransportIsEnabledButPropertyIsNotSet() {
+		this.contextRunner.withPropertyValues("management.otlp.tracing.transport=grpc")
+			.run((context) -> assertThat(context).doesNotHaveBean(OtlpGrpcSpanExporter.class));
+	}
+
 	@Test
 	void shouldSupplyBeans() {
 		this.contextRunner.withPropertyValues("management.otlp.tracing.endpoint=http://localhost:4318/v1/traces")
@@ -58,6 +64,15 @@ class OtlpAutoConfigurationTests {
 				.hasSingleBean(SpanExporter.class));
 	}
 
+	@Test
+	void shouldSupplyBeansIfGrpcTransportIsEnabled() {
+		this.contextRunner
+			.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));
+	}
+
 	@Test
 	void shouldNotSupplyBeansIfGlobalTracingIsDisabled() {
 		this.contextRunner.withPropertyValues("management.tracing.enabled=false")