feat(spanner): Update OpenTelemetry OTLP trace sample to use Google Cloud OTLP endpoint

Author: surbhigarg92

spanner/opentelemetry_traces/src/main/java/com/example/spanner/OpenTelemetryUsage.java

@@ -16,6 +16,7 @@
 
 package com.example.spanner;
 
+import com.google.auth.oauth2.GoogleCredentials;
 import com.google.cloud.opentelemetry.trace.TraceConfiguration;
 import com.google.cloud.opentelemetry.trace.TraceExporter;
 import com.google.cloud.spanner.DatabaseClient;
@@ -33,6 +34,12 @@
 import io.opentelemetry.sdk.trace.export.SpanExporter;
 import io.opentelemetry.sdk.trace.samplers.Sampler;
 
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
 /**
  * This sample demonstrates how to configure OpenTelemetry and inject via Spanner Options.
  */
@@ -46,11 +53,10 @@ public class OpenTelemetryUsage {
   static String instanceId = "my-instance";
   static String databaseId = "my-database";
 
-  // Replace these variables to use OTLP Exporter
-  static boolean useCloudTraceExporter = true; // Replace to false for OTLP
-  static String otlpEndpoint = "http://localhost:4317"; // Replace with your OTLP endpoint
+  static boolean useCloudTraceExporter = false; // Replace to true for Cloud Trace exporter
+  static String otlpEndpoint = "https://telemetry.googleapis.com"; // Replace with your OTLP endpoint
 
-  public static void main(String[] args) {
+  public static void main(String[] args) throws IOException {
 
     if (useCloudTraceExporter) {
       spanner = getSpannerWithCloudTraceExporter();
@@ -64,25 +70,42 @@ public static void main(String[] args) {
     try (ResultSet resultSet =
         dbClient
             .singleUse() // Execute a single read or query against Cloud Spanner.
-            .executeQuery(Statement.of("SELECT SingerId, AlbumId, AlbumTitle FROM Albums"))) {
+                .executeQuery(Statement.of("SELECT SingerId, AlbumId, AlbumTitle FROM Albums"))) {
       while (resultSet.next()) {
         System.out.printf(
-            "%d %d %s", resultSet.getLong(0), resultSet.getLong(1), resultSet.getString(2));
+                "%d %d %s", resultSet.getLong(0), resultSet.getLong(1), resultSet.getString(2));
       }
     }
 
     sdkTracerProvider.forceFlush();
   }
 
-  public static Spanner getSpannerWithOtlpExporter() {
+  public static Spanner getSpannerWithOtlpExporter() throws IOException {
     // [START spanner_opentelemetry_traces_otlp_usage]
     Resource resource = Resource
-        .getDefault().merge(Resource.builder().put("service.name", "My App").build());
+        .getDefault().merge(Resource.builder().put("service.name", "My App").put("gcp.project_id", projectId).build());
 
+    GoogleCredentials credentials = GoogleCredentials.getApplicationDefault()
+            .createScoped(Collections.singleton("https://www.googleapis.com/auth/trace.append"));
     OtlpGrpcSpanExporter otlpGrpcSpanExporter =
         OtlpGrpcSpanExporter
             .builder()
-            .setEndpoint(otlpEndpoint) // Replace with your OTLP endpoint
+            .setEndpoint(otlpEndpoint)
+                .setHeaders(() -> {
+                  try {
+                    credentials.refreshIfExpired();
+                    Map<String, List<String>> metadata = credentials.getRequestMetadata();
+                    Map<String, String> headers = new HashMap<>();
+                    if (metadata != null) {
+                      metadata.forEach((key, values) ->
+                              headers.put(key, String.join(",", values)));
+                    }
+                    return headers;
+                  } catch (Exception e) {
+                    // Handle error fetching credentials
+                    return Collections.emptyMap();
+                  }
+                })// Replace with your OTLP endpoint
             .build();
 
     // Using a batch span processor