Refresh credentials and add readme

Author: damemi

examples/otlptrace/README.md

@@ -0,0 +1,27 @@
+# OTLP Trace with Google Auth Example
+
+Run this sample to connect to an endpoint that is protected by GCP authentication.
+
+First, get GCP credentials on your machine:
+
+```shell
+gcloud auth application-default login
+```
+Executing this command will save your application credentials to default path which will depend on the type of machine -
+ - 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>',
+```
+
+Finally, run `gradle run` to run the sample.

examples/otlptrace/build.gradle

@@ -33,9 +33,10 @@ dependencies {
 // 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-gcp-project',
-	'-Dotel.exporter.otlp.headers=X-Goog-User-Project=your-gcp-project',
+	'-Dotel.resource.attributes=gcp.project_id=<YOUR_PROJECT>',
+	'-Dotel.exporter.otlp.headers=X-Goog-User-Project=<YOUR_QUOTA_PROJECT>',
 	'-Dotel.traces.exporter=otlp',
+	'-Dotel.exporter.otlp.protocol=http/protobuf',
 	'-Dotel.java.global-autoconfigure.enabled=true',
 ]
 

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

@@ -16,6 +16,7 @@
 package com.google.cloud.opentelemetry.example.otlptrace;
 
 import com.google.auth.oauth2.GoogleCredentials;
+import com.google.auth.oauth2.AccessToken;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.context.Scope;
 import io.opentelemetry.exporter.otlp.http.trace.OtlpHttpSpanExporter;
@@ -24,6 +25,7 @@
 import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk;
 import io.opentelemetry.sdk.common.CompletableResultCode;
 import io.opentelemetry.sdk.trace.export.SpanExporter;
+import java.io.*;
 import java.io.IOException;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
@@ -50,11 +52,17 @@ private static OpenTelemetrySdk setupTraceExporter() throws IOException {
   private static SpanExporter addAuthorizationHeaders(
       SpanExporter exporter, GoogleCredentials credentials) {
     if (exporter instanceof OtlpHttpSpanExporter) {
-      OtlpHttpSpanExporterBuilder builder =
-          ((OtlpHttpSpanExporter) exporter)
-              .toBuilder().addHeader("Authorization", "Bearer " + credentials.getAccessToken());
+      try {
+        credentials.refreshIfExpired();
+        OtlpHttpSpanExporterBuilder builder =
+            ((OtlpHttpSpanExporter) exporter)
+                .toBuilder().addHeader("Authorization", "Bearer " + credentials.getAccessToken().getTokenValue());
 
-      return builder.build();
+        return builder.build();
+      }
+      catch(IOException e) {
+        System.out.println("error");
+      }
     }
     return exporter;
   }