Programmatically configure auth headers

Author: psx95

build.gradle

@@ -138,6 +138,7 @@ subprojects {
 		autoServiceVersion = '1.1.1'
 		autoValueVersion = '1.10.4'
 		slf4jVersion = '2.0.9'
+		googleAuthVersion = '1.23.0'
 		googleCloudVersion = '2.27.0'
 		googleTraceVersion = '2.30.0'
 		googleCloudBom = '26.26.0'
@@ -169,6 +170,7 @@ subprojects {
 			auto_value_annotations           : "com.google.auto.value:auto-value-annotations:${autoValueVersion}",
 			auto_value                       : "com.google.auto.value:auto-value:${autoValueVersion}",
 			cloudevents_core                 : "io.cloudevents:cloudevents-core:${cloudEventsCoreVersion}",
+			google_auth                      : "com.google.auth:google-auth-library-oauth2-http:${googleAuthVersion}",
 			google_cloud_core                : "com.google.cloud:google-cloud-core:${googleCloudVersion}",
 			google_cloud_trace               : "com.google.cloud:google-cloud-trace:${googleTraceVersion}",
 			google_cloud_trace_grpc          : "com.google.api.grpc:grpc-google-cloud-trace-v2:${googleTraceVersion}",

examples/otlptrace/build.gradle

@@ -26,15 +26,15 @@ dependencies {
 	implementation(libraries.opentelemetry_api)
 	implementation(libraries.opentelemetry_sdk)
 	implementation(libraries.opentelemetry_otlp_exporter)
-	implementation(libraries.google_auth)
 	implementation(libraries.opentelemetry_sdk_autoconf)
+	implementation(libraries.google_auth)
 }
 
 // Provide headers from env variable
-// export OTEL_EXPORTER_OTLP_HEADERS="Authorization=Bearer $(gcloud auth print-access-token),X-Goog-User-Project=otel-test-starter"
 // export OTEL_EXPORTER_OTLP_ENDPOINT="http://path/to/yourendpoint:port"
 def autoconf_config = [
-	'-Dotel.resource.attributes=gcp.project_id=otel-test-starter',
+	'-Dotel.resource.attributes=gcp.project_id=your-gcp-project',
+	'-Dotel.exporter.otlp.headers=X-Goog-User-Project=your-gcp-project',
 	'-Dotel.traces.exporter=otlp',
 	'-Dotel.java.global-autoconfigure.enabled=true',
 ]

examples/otlptrace/src/main/java/com/google/cloud/opentelemetry/example/otlptrace/OTLPTraceExample.java

@@ -15,11 +15,15 @@
  */
 package com.google.cloud.opentelemetry.example.otlptrace;
 
+import com.google.auth.oauth2.GoogleCredentials;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.context.Scope;
+import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
+import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporterBuilder;
 import io.opentelemetry.sdk.OpenTelemetrySdk;
 import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk;
 import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
 import java.io.IOException;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
@@ -30,9 +34,29 @@ public class OTLPTraceExample {
 
   private static OpenTelemetrySdk openTelemetrySdk;
 
-  private static OpenTelemetrySdk setupTraceExporter() {
-    // Let the SDK configure itself using environment variables and system properties
-    return AutoConfiguredOpenTelemetrySdk.initialize().getOpenTelemetrySdk();
+  private static OpenTelemetrySdk setupTraceExporter() throws IOException {
+    GoogleCredentials credentials = GoogleCredentials.getApplicationDefault();
+
+    // Update the SDK configured using environment variables and system properties
+    AutoConfiguredOpenTelemetrySdk autoConfOTelSdk =
+        AutoConfiguredOpenTelemetrySdk.builder()
+            .addSpanExporterCustomizer(
+                (exporter, configProperties) -> addAuthorizationHeaders(exporter, credentials))
+            .build();
+    return autoConfOTelSdk.getOpenTelemetrySdk();
+  }
+
+  // Configures span exporter using configuration from
+  private static SpanExporter addAuthorizationHeaders(
+      SpanExporter exporter, GoogleCredentials credentials) {
+    if (exporter instanceof OtlpHttpSpanExporter) {
+      OtlpHttpSpanExporterBuilder builder =
+          ((OtlpHttpSpanExporter) exporter)
+              .toBuilder().addHeader("Authorization", "Bearer " + credentials.getAccessToken());
+
+      return builder.build();
+    }
+    return exporter;
   }
 
   private static void myUseCase(String description) {