Update otlpmetrics sample (#410)

* Udpate otlptrace example documentation

* Defer adding quota project header to auth library

* Add code to show token dynamic refresh

* Fix stylecheck

Author: psx95

examples/otlpmetric/README.md

@@ -11,23 +11,15 @@ Executing this command will save your application credentials to default path wh
  - Linux, macOS: `$HOME/.config/gcloud/application_default_credentials.json`
  - Windows: `%APPDATA%\gcloud\application_default_credentials.json`
 
-Next, set your endpoint with the `OTEL_EXPORTER_OTLP_ENDPOINT` environment variable:
-
-```shell
-export OTEL_EXPORTER_OTLP_ENDPOINT="http://your-endpoint:port"
-```
-
 Next, update [`build.gradle`](build.grade) to set the following:
 
 ```
 	'-Dotel.resource.attributes=gcp.project_id=<YOUR_PROJECT_ID>,
-	'-Dotel.exporter.otlp.headers=X-Goog-User-Project=<YOUR_QUOTA_PROJECT>',
 	# Optional - if you want to export using gRPC protocol
 	'-Dotel.exporter.otlp.protocol=grpc',
 ```
 
 Finally, to run the sample from the project root:
-
 ```
-cd examples/otlpmetric && gradle run
+./gradlew :examples-otlpmetric:run
 ```

examples/otlpmetric/build.gradle

@@ -29,19 +29,22 @@ dependencies {
 	implementation(libraries.opentelemetry_sdk)
 	implementation(libraries.opentelemetry_otlp_exporter)
 	implementation(libraries.opentelemetry_sdk_autoconf)
+	implementation(libraries.opentelemetry_gcp_resources)
 	implementation(libraries.google_auth)
 }
 
-// Provide headers from env variable
-// export OTEL_EXPORTER_OTLP_ENDPOINT="http://path/to/yourendpoint:port"
 def autoconf_config = [
-	'-Dotel.resource.attributes=gcp.project_id=<YOUR_PROJECT>',
-	'-Dotel.exporter.otlp.headers=X-Goog-User-Project=<YOUR_QUOTA_PROJECT>',
+	'-Dotel.exporter.otlp.endpoint=https://telemetry.googleapis.com',
+	'-Dotel.resource.attributes=gcp.project_id=<YOUR_PROJECT_ID>',
 	'-Dotel.metrics.exporter=otlp',
+	'-Dotel.logs.exporter=none',
+	'-Dotel.traces.exporter=none',
+	'-Dotel.service.name=otlpmetrics-example',
 	'-Dotel.exporter.otlp.protocol=http/protobuf',
 	'-Dotel.java.global-autoconfigure.enabled=true',
 ]
 
 application {
+	mainClassName = 'com.google.cloud.opentelemetry.example.otlpmetric.OTLPMetricExample'
 	applicationDefaultJvmArgs = autoconf_config
 }

examples/otlpmetric/src/main/java/com/google/cloud/opentelemetry/example/otlpmetric/OTLPMetricExample.java

@@ -18,14 +18,14 @@
 import com.google.auth.oauth2.GoogleCredentials;
 import io.opentelemetry.api.metrics.LongCounter;
 import io.opentelemetry.exporter.otlp.http.metrics.OtlpHttpMetricExporter;
-import io.opentelemetry.exporter.otlp.http.metrics.OtlpHttpMetricExporterBuilder;
 import io.opentelemetry.exporter.otlp.metrics.OtlpGrpcMetricExporter;
-import io.opentelemetry.exporter.otlp.metrics.OtlpGrpcMetricExporterBuilder;
 import io.opentelemetry.sdk.OpenTelemetrySdk;
 import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk;
 import io.opentelemetry.sdk.common.CompletableResultCode;
 import io.opentelemetry.sdk.metrics.export.MetricExporter;
 import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
 
@@ -49,39 +49,35 @@ private static OpenTelemetrySdk setupMetricExporter() throws IOException {
   }
 
   // Modifies the metric exporter initially auto-configured using environment variables
-  // Note: This adds static authorization headers which are set only at initialization time.
-  // This will stop working after the token expires, since the token is not refreshed.
+  // This will invoke the header supplier function to compute the headers, which takes care of the
+  // refresh.
   private static MetricExporter addAuthorizationHeaders(
       MetricExporter exporter, GoogleCredentials credentials) {
     if (exporter instanceof OtlpHttpMetricExporter) {
-      try {
-        credentials.refreshIfExpired();
-        OtlpHttpMetricExporterBuilder builder =
-            ((OtlpHttpMetricExporter) exporter)
-                .toBuilder()
-                    .addHeader(
-                        "Authorization", "Bearer " + credentials.getAccessToken().getTokenValue());
-
-        return builder.build();
-      } catch (IOException e) {
-        System.out.println("error:" + e.getMessage());
-      }
+      return ((OtlpHttpMetricExporter) exporter)
+          .toBuilder().setHeaders(() -> getRequiredHeaderMap(credentials)).build();
     } else if (exporter instanceof OtlpGrpcMetricExporter) {
-      try {
-        credentials.refreshIfExpired();
-        OtlpGrpcMetricExporterBuilder builder =
-            ((OtlpGrpcMetricExporter) exporter)
-                .toBuilder()
-                    .addHeader(
-                        "Authorization", "Bearer " + credentials.getAccessToken().getTokenValue());
-        return builder.build();
-      } catch (IOException e) {
-        throw new RuntimeException(e);
-      }
+      return ((OtlpGrpcMetricExporter) exporter)
+          .toBuilder().setHeaders(() -> getRequiredHeaderMap(credentials)).build();
     }
     return exporter;
   }
 
+  private static Map<String, String> getRequiredHeaderMap(GoogleCredentials credentials) {
+    Map<String, String> gcpHeaders = new HashMap<>();
+    try {
+      credentials.refreshIfExpired();
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+    gcpHeaders.put("Authorization", "Bearer " + credentials.getAccessToken().getTokenValue());
+    String configuredQuotaProjectId = credentials.getQuotaProjectId();
+    if (configuredQuotaProjectId != null && !configuredQuotaProjectId.isEmpty()) {
+      gcpHeaders.put("x-goog-user-project", configuredQuotaProjectId);
+    }
+    return gcpHeaders;
+  }
+
   private static void myUseCase() {
     LongCounter counter =
         openTelemetrySdk
@@ -110,7 +106,6 @@ public static void main(String[] args) throws IOException {
 
     // Application-specific logic
     myUseCase();
-    myUseCase();
 
     // Flush all buffered metrics
     CompletableResultCode completableResultCode = openTelemetrySdk.getSdkMeterProvider().shutdown();

examples/otlptrace/README.md

@@ -16,11 +16,12 @@ Next, export the `GOOGLE_CLOUD_PROJECT` environment variable:
 # Use your GCP project ID
 export GOOGLE_CLOUD_PROJECT="your-gcp-project-id"
 ```
+This environment variable also configures the [OpenTelemetry GCP Auth Extension](https://github.com/open-telemetry/opentelemetry-java-contrib/tree/main/gcp-auth-extension) that facilitates authentication to GCP.
 
 Finally, to run the sample from the project root:
 
 ```
-cd examples/otlptrace && gradle run
+./gradlew :examples-otlptrace:run
 ```
 
 Running this sample will generate and export Traces to Google Cloud.

examples/otlptrace/build.gradle

@@ -31,7 +31,6 @@ dependencies {
 	implementation(libraries.opentelemetry_gcp_resources)
 }
 
-// Provide headers from env variable
 def autoconf_config = [
 	'-Dotel.exporter.otlp.endpoint=https://telemetry.googleapis.com',
 	'-Dotel.traces.exporter=otlp',