Polish "Add support for OTel-specific environment variables"

See gh-44394

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/otlp/OtlpMetricsPropertiesConfigAdapter.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.export.otlp;
 
+import java.util.Collections;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -27,6 +28,7 @@
 import org.springframework.boot.actuate.autoconfigure.opentelemetry.OpenTelemetryProperties;
 import org.springframework.boot.actuate.autoconfigure.opentelemetry.OpenTelemetryResourceAttributes;
 import org.springframework.core.env.Environment;
+import org.springframework.util.StringUtils;
 
 /**
  * Adapter to convert {@link OtlpMetricsProperties} to an {@link OtlpConfig}.
@@ -80,15 +82,16 @@ public Map<String, String> resourceAttributes() {
 			.asMap();
 		attributes.computeIfAbsent("service.name", (key) -> getApplicationName());
 		attributes.computeIfAbsent("service.group", (key) -> getApplicationGroup());
-		return attributes;
+		return Collections.unmodifiableMap(attributes);
 	}
 
 	private String getApplicationName() {
 		return this.environment.getProperty("spring.application.name", DEFAULT_APPLICATION_NAME);
 	}
 
 	private String getApplicationGroup() {
-		return this.environment.getProperty("spring.application.group");
+		String applicationGroup = this.environment.getProperty("spring.application.group");
+		return (StringUtils.hasLength(applicationGroup)) ? applicationGroup : null;
 	}
 
 	@Override

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

@@ -36,6 +36,7 @@
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.core.env.Environment;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for OpenTelemetry.
@@ -88,7 +89,8 @@ private String getApplicationName(Environment environment) {
 	}
 
 	private String getApplicationGroup(Environment environment) {
-		return environment.getProperty("spring.application.group");
+		String applicationGroup = environment.getProperty("spring.application.group");
+		return (StringUtils.hasLength(applicationGroup)) ? applicationGroup : null;
 	}
 
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/opentelemetry/OpenTelemetryResourceAttributes.java

@@ -130,21 +130,21 @@ public static String decode(String value) {
 		ByteArrayOutputStream bos = new ByteArrayOutputStream(bytes.length);
 		for (int i = 0; i < bytes.length; i++) {
 			byte b = bytes[i];
-			if (b == '%') {
-				int u = decodeHex(bytes, ++i);
-				int l = decodeHex(bytes, ++i);
-				if (u >= 0 && l >= 0) {
-					bos.write((u << 4) + l);
-				}
-				else {
-					throw new IllegalArgumentException(
-							"Failed to decode percent-encoded characters at index %d in the value: '%s'"
-								.formatted(i - 2, value));
-				}
+			if (b != '%') {
+				bos.write(b);
+				continue;
+			}
+			int u = decodeHex(bytes, i + 1);
+			int l = decodeHex(bytes, i + 2);
+			if (u >= 0 && l >= 0) {
+				bos.write((u << 4) + l);
 			}
 			else {
-				bos.write(b);
+				throw new IllegalArgumentException(
+						"Failed to decode percent-encoded characters at index %d in the value: '%s'".formatted(i,
+								value));
 			}
+			i += 2;
 		}
 		return bos.toString(StandardCharsets.UTF_8);
 	}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/opentelemetry/OpenTelemetryResourceAttributesTests.java

@@ -24,6 +24,7 @@
 
 import io.opentelemetry.api.internal.PercentEscaper;
 import org.assertj.core.api.InstanceOfAssertFactories;
+import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -36,19 +37,25 @@
  */
 class OpenTelemetryResourceAttributesTests {
 
-	private static final Random random = new Random();
+	private static Random random;
 
 	private static final PercentEscaper escaper = PercentEscaper.create();
 
 	private final Map<String, String> environmentVariables = new LinkedHashMap<>();
 
 	private final Map<String, String> resourceAttributes = new LinkedHashMap<>();
 
+	@BeforeAll
+	static void beforeAll() {
+		long seed = new Random().nextLong();
+		System.out.println("Seed: " + seed);
+		random = new Random(seed);
+	}
+
 	@Test
 	void otelServiceNameShouldTakePrecedenceOverOtelResourceAttributes() {
 		this.environmentVariables.put("OTEL_RESOURCE_ATTRIBUTES", "service.name=ignored");
 		this.environmentVariables.put("OTEL_SERVICE_NAME", "otel-service");
-
 		OpenTelemetryResourceAttributes attributes = getAttributes();
 		assertThat(attributes.asMap()).hasSize(1).containsEntry("service.name", "otel-service");
 	}
@@ -57,7 +64,6 @@ void otelServiceNameShouldTakePrecedenceOverOtelResourceAttributes() {
 	void otelServiceNameWhenEmptyShouldTakePrecedenceOverOtelResourceAttributes() {
 		this.environmentVariables.put("OTEL_RESOURCE_ATTRIBUTES", "service.name=ignored");
 		this.environmentVariables.put("OTEL_SERVICE_NAME", "");
-
 		OpenTelemetryResourceAttributes attributes = getAttributes();
 		assertThat(attributes.asMap()).hasSize(1).containsEntry("service.name", "");
 	}
@@ -66,7 +72,6 @@ void otelServiceNameWhenEmptyShouldTakePrecedenceOverOtelResourceAttributes() {
 	void otelResourceAttributesShouldBeUsed() {
 		this.environmentVariables.put("OTEL_RESOURCE_ATTRIBUTES",
 				", ,,key1=value1,key2= value2, key3=value3,key4=,=value5,key6,=,key7=spring+boot,key8=ś");
-
 		OpenTelemetryResourceAttributes attributes = getAttributes();
 		assertThat(attributes.asMap()).hasSize(6)
 			.containsEntry("key1", "value1")
@@ -83,7 +88,6 @@ void resourceAttributesShouldBeMergedWithEnvironmentVariables() {
 		this.resourceAttributes.put("key2", "");
 		this.environmentVariables.put("OTEL_SERVICE_NAME", "custom-service");
 		this.environmentVariables.put("OTEL_RESOURCE_ATTRIBUTES", "key1=value1,key2=value2");
-
 		OpenTelemetryResourceAttributes attributes = getAttributes();
 		assertThat(attributes.asMap()).hasSize(4)
 			.containsEntry("service.name", "custom-service")
@@ -99,7 +103,6 @@ void resourceAttributesWithNullKeyOrValueShouldBeIgnored() {
 		this.resourceAttributes.put(null, "value");
 		this.environmentVariables.put("OTEL_SERVICE_NAME", "custom-service");
 		this.environmentVariables.put("OTEL_RESOURCE_ATTRIBUTES", "key1=value1,key2=value2");
-
 		OpenTelemetryResourceAttributes attributes = getAttributes();
 		assertThat(attributes.asMap()).hasSize(3)
 			.containsEntry("service.name", "custom-service")

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

@@ -95,15 +95,18 @@ Spring Boot's actuator module includes basic support for OpenTelemetry.
 
 It provides a bean of type javadoc:io.opentelemetry.api.OpenTelemetry[], and if there are beans of type javadoc:io.opentelemetry.sdk.trace.SdkTracerProvider[], javadoc:io.opentelemetry.context.propagation.ContextPropagators[], javadoc:io.opentelemetry.sdk.logs.SdkLoggerProvider[] or javadoc:io.opentelemetry.sdk.metrics.SdkMeterProvider[] in the application context, they automatically get registered.
 Additionally, it provides a javadoc:io.opentelemetry.sdk.resources.Resource[] bean.
-The attributes of the auto-configured javadoc:io.opentelemetry.sdk.resources.Resource[] can be configured via the configprop:management.opentelemetry.resource-attributes[] configuration property. Auto-configured attributes will be merged with attributes from the `OTEL_RESOURCE_ATTRIBUTES` and `OTEL_SERVICE_NAME` environment variables, with attributes configured through the configuration property taking precedence over those from the environment variables.
+The attributes of the auto-configured javadoc:io.opentelemetry.sdk.resources.Resource[] can be configured via the configprop:management.opentelemetry.resource-attributes[] configuration property.
+Auto-configured attributes will be merged with attributes from the `OTEL_RESOURCE_ATTRIBUTES` and `OTEL_SERVICE_NAME` environment variables, with attributes configured through the configuration property taking precedence over those from the environment variables.
 
 
 If you have defined your own javadoc:io.opentelemetry.sdk.resources.Resource[] bean, this will no longer be the case.
 
 NOTE: Spring Boot does not provide auto-configuration for OpenTelemetry metrics or logging.
 OpenTelemetry tracing is only auto-configured when used together with xref:actuator/tracing.adoc[Micrometer Tracing].
 
-NOTE: The `OTEL_RESOURCE_ATTRIBUTES` environment variable consist of a list of key-value pairs. For example: `key1=value1,key2=value2,key3=spring%20boot`. All attribute values are treated as strings, and any characters outside the baggage-octet range must be **percent-encoded**.
+NOTE: The `OTEL_RESOURCE_ATTRIBUTES` environment variable consist of a list of key-value pairs.
+For example: `key1=value1,key2=value2,key3=spring%20boot`.
+All attribute values are treated as strings, and any characters outside the baggage-octet range must be **percent-encoded**.
 
 
 The next sections will provide more details about logging, metrics and traces.