Add auto-configuration for OTLP span exporter

With these changes an OTLP HTTP/protobuf exporter is auto-configured
if opentelemetry-exporter-otlp is on the classpath.

See gh-34508

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

@@ -70,6 +70,7 @@ dependencies {
 	optional("io.micrometer:micrometer-registry-wavefront")
 	optional("io.zipkin.reporter2:zipkin-sender-urlconnection")
 	optional("io.opentelemetry:opentelemetry-exporter-zipkin")
+	optional("io.opentelemetry:opentelemetry-exporter-otlp")
 	optional("io.projectreactor.netty:reactor-netty-http")
 	optional("io.r2dbc:r2dbc-pool")
 	optional("io.r2dbc:r2dbc-spi")

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

@@ -0,0 +1,71 @@
+/*
+ * 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.otlp;
+
+import java.util.Map.Entry;
+
+import io.micrometer.tracing.otel.bridge.OtelTracer;
+import io.opentelemetry.api.OpenTelemetry;
+import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
+import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporterBuilder;
+import io.opentelemetry.sdk.trace.SdkTracerProvider;
+
+import org.springframework.boot.actuate.autoconfigure.tracing.ConditionalOnEnabledTracing;
+import org.springframework.boot.autoconfigure.AutoConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for OTLP. Brave does not support
+ * OTLP, so we only configure it for OpenTelemetry. OTLP defines three transports that are
+ * supported: gRPC (/protobuf), HTTP/protobuf, HTTP/JSON. From these transports HTTP/JSON
+ * is not supported by the OTel Java SDK, and it seems there are no plans supporting it in
+ * 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,
+ * please disable this auto-configuration and create a bean.
+ *
+ * @author Jonatan Ivanov
+ * @since 3.1.0
+ */
+@AutoConfiguration
+@ConditionalOnEnabledTracing
+@ConditionalOnClass({ OtelTracer.class, SdkTracerProvider.class, OpenTelemetry.class, OtlpHttpSpanExporter.class })
+@EnableConfigurationProperties(OtlpProperties.class)
+public class OtlpAutoConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean
+	OtlpHttpSpanExporter otlpHttpSpanExporter(OtlpProperties properties) {
+		OtlpHttpSpanExporterBuilder builder = OtlpHttpSpanExporter.builder()
+			.setEndpoint(properties.getEndpoint())
+			.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/main/java/org/springframework/boot/actuate/autoconfigure/tracing/otlp/OtlpProperties.java

@@ -0,0 +1,103 @@
+/*
+ * 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.otlp;
+
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ * Configuration properties for {@link OtlpAutoConfiguration}.
+ *
+ * @author Jonatan Ivanov
+ * @since 3.1.0
+ */
+@ConfigurationProperties("management.otlp.tracing")
+public class OtlpProperties {
+
+	/**
+	 * URL to the OTel collector's HTTP API.
+	 */
+	private String endpoint = "http://localhost:4318/v1/traces";
+
+	/**
+	 * Call timeout for the OTel Collector to process an exported batch of data. This
+	 * timeout spans the entire call: resolving DNS, connecting, writing the request body,
+	 * server processing, and reading the response body. If the call requires redirects or
+	 * retries all must complete within one timeout period.
+	 */
+	private Duration timeout = Duration.ofSeconds(10);
+
+	/**
+	 * The method used to compress the payload.
+	 */
+	private Compression compression = Compression.NONE;
+
+	/**
+	 * Custom HTTP headers you want to pass to the collector, for example auth headers.
+	 */
+	private Map<String, String> headers = new HashMap<>();
+
+	public String getEndpoint() {
+		return this.endpoint;
+	}
+
+	public void setEndpoint(String endpoint) {
+		this.endpoint = endpoint;
+	}
+
+	public Duration getTimeout() {
+		return this.timeout;
+	}
+
+	public void setTimeout(Duration timeout) {
+		this.timeout = timeout;
+	}
+
+	public Compression getCompression() {
+		return this.compression;
+	}
+
+	public void setCompression(Compression compression) {
+		this.compression = compression;
+	}
+
+	public Map<String, String> getHeaders() {
+		return this.headers;
+	}
+
+	public void setHeaders(Map<String, String> headers) {
+		this.headers = headers;
+	}
+
+	enum Compression {
+
+		/**
+		 * Gzip compression.
+		 */
+		GZIP,
+
+		/**
+		 * No compression.
+		 */
+		NONE
+
+	}
+
+}

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

@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+
+/**
+ * Auto-configuration for tracing with OTLP.
+ */
+package org.springframework.boot.actuate.autoconfigure.tracing.otlp;

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -101,6 +101,7 @@ org.springframework.boot.actuate.autoconfigure.system.DiskSpaceHealthContributor
 org.springframework.boot.actuate.autoconfigure.tracing.BraveAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.tracing.MicrometerTracingAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.tracing.OpenTelemetryAutoConfiguration
+org.springframework.boot.actuate.autoconfigure.tracing.otlp.OtlpAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.tracing.prometheus.PrometheusExemplarsAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.tracing.wavefront.WavefrontTracingAutoConfiguration
 org.springframework.boot.actuate.autoconfigure.tracing.zipkin.ZipkinAutoConfiguration

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

@@ -0,0 +1,118 @@
+/*
+ * 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.otlp;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.TimeUnit;
+
+import io.micrometer.tracing.Tracer;
+import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
+import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+import okhttp3.mockwebserver.RecordedRequest;
+import okio.Buffer;
+import okio.GzipSource;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.tracing.MicrometerTracingAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.tracing.OpenTelemetryAutoConfiguration;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link OtlpAutoConfiguration}.
+ *
+ * @author Jonatan Ivanov
+ */
+class OtlpAutoConfigurationIntegrationTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+		.withPropertyValues("management.tracing.sampling.probability=1.0")
+		.withConfiguration(
+				AutoConfigurations.of(ObservationAutoConfiguration.class, MicrometerTracingAutoConfiguration.class,
+						OpenTelemetryAutoConfiguration.class, OtlpAutoConfiguration.class));
+
+	private MockWebServer mockWebServer;
+
+	@BeforeEach
+	void setUp() throws IOException {
+		this.mockWebServer = new MockWebServer();
+		this.mockWebServer.start();
+	}
+
+	@AfterEach
+	void tearDown() throws IOException {
+		this.mockWebServer.close();
+	}
+
+	@Test
+	void httpSpanExporterShouldUseProtoBufAndNoCompression() {
+		this.mockWebServer.enqueue(new MockResponse());
+		this.contextRunner
+			.withPropertyValues("management.otlp.tracing.endpoint=http://localhost:%d/v1/traces"
+				.formatted(this.mockWebServer.getPort()), "management.otlp.tracing.headers.custom=42")
+			.run((context) -> {
+				context.getBean(Tracer.class).nextSpan().name("test").end();
+				assertThat(context.getBean(OtlpHttpSpanExporter.class).flush())
+					.isSameAs(CompletableResultCode.ofSuccess());
+
+				RecordedRequest request = this.mockWebServer.takeRequest(10, TimeUnit.SECONDS);
+				assertThat(request).isNotNull();
+				assertThat(request.getRequestLine()).contains("/v1/traces");
+				assertThat(request.getHeader("Content-Type")).isEqualTo("application/x-protobuf");
+				assertThat(request.getHeader("custom")).isEqualTo("42");
+				assertThat(request.getBodySize()).isPositive();
+				try (Buffer body = request.getBody()) {
+					assertThat(body.readString(StandardCharsets.UTF_8)).contains("org.springframework.boot");
+				}
+			});
+	}
+
+	@Test
+	void httpSpanExporterShouldUseProtoBufAndGzip() {
+		this.mockWebServer.enqueue(new MockResponse());
+		this.contextRunner
+			.withPropertyValues("management.otlp.tracing.compression=GZIP",
+					"management.otlp.tracing.endpoint=http://localhost:%d/test".formatted(this.mockWebServer.getPort()))
+			.run((context) -> {
+				assertThat(context).hasSingleBean(OtlpHttpSpanExporter.class).hasSingleBean(SpanExporter.class);
+				context.getBean(Tracer.class).nextSpan().name("test").end();
+				assertThat(context.getBean(OtlpHttpSpanExporter.class).flush())
+					.isSameAs(CompletableResultCode.ofSuccess());
+
+				RecordedRequest request = this.mockWebServer.takeRequest(10, TimeUnit.SECONDS);
+				assertThat(request).isNotNull();
+				assertThat(request.getRequestLine()).contains("/test");
+				assertThat(request.getHeader("Content-Type")).isEqualTo("application/x-protobuf");
+				assertThat(request.getHeader("Content-Encoding")).isEqualTo("gzip");
+				assertThat(request.getBodySize()).isPositive();
+				try (Buffer unCompressed = new Buffer(); Buffer body = request.getBody()) {
+					unCompressed.writeAll(new GzipSource(body));
+					assertThat(unCompressed.readString(StandardCharsets.UTF_8)).contains("org.springframework.boot");
+				}
+			});
+	}
+
+}