GCP Auth extension - allow users to specify quota project ID

gcp-auth-extension/README.md

@@ -36,7 +36,10 @@ Here is a list of configurable options for the extension:
 
 - `GOOGLE_CLOUD_PROJECT`: Environment variable that represents the Google Cloud Project ID to which the telemetry needs to be exported.
   - Can also be configured using `google.cloud.project` system property.
-  - If this option is not configured, the extension would infer GCP Project ID from the application default credentials. For more information on application default credentials, see [here](https://cloud.google.com/docs/authentication/application-default-credentials).
+  - This is a required option, the agent configuration will fail if this option is not set.
+- `GOOGLE_CLOUD_QUOTA_PROJECT`: Environment variable that represents the Google Cloud Quota Project ID which will be charged for the GCP API usage. To learn more about a *quota project*, see [here](https://cloud.google.com/docs/quotas/quota-project).
+  - Can also be configured using `google.cloud.quota.project` system property.
+  - If this option is not configured, the extension will use the Quota Project ID found in the Application Default Credentials (ADC), if available. For more information on application default credentials, see [here](https://cloud.google.com/docs/authentication/application-default-credentials).
 
 ## Usage
 

gcp-auth-extension/build.gradle.kts

@@ -29,6 +29,7 @@ dependencies {
   testCompileOnly("com.google.auto.service:auto-service-annotations")
   testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine")
   testImplementation("org.junit.jupiter:junit-jupiter-api")
+  testCompileOnly("org.junit.jupiter:junit-jupiter-params")
 
   testImplementation("io.opentelemetry:opentelemetry-api")
   testImplementation("io.opentelemetry:opentelemetry-exporter-otlp")
@@ -45,6 +46,9 @@ dependencies {
   testImplementation("org.springframework.boot:spring-boot-starter:2.7.18")
   testImplementation("org.springframework.boot:spring-boot-starter-test:2.7.18")
 
+  testAnnotationProcessor("com.google.auto.value:auto-value")
+  testCompileOnly("com.google.auto.value:auto-value-annotations")
+
   agent("io.opentelemetry.javaagent:opentelemetry-javaagent")
 }
 

gcp-auth-extension/src/main/java/io/opentelemetry/contrib/gcp/auth/ConfigurableOption.java

@@ -18,7 +18,18 @@ public enum ConfigurableOption {
    * Represents the Google Cloud Project ID option. Can be configured using the environment variable
    * `GOOGLE_CLOUD_PROJECT` or the system property `google.cloud.project`.
    */
-  GOOGLE_CLOUD_PROJECT("Google Cloud Project ID");
+  GOOGLE_CLOUD_PROJECT("Google Cloud Project ID"),
+
+  /**
+   * Represents the Google Cloud Quota Project ID option. Can be configured using the environment
+   * variable `GOOGLE_CLOUD_QUOTA_PROJECT` or the system property `google.cloud.quota.project`. The
+   * quota project is the project that is used for quota management and billing for the API usage.
+   *
+   * <p>The environment variable name is selected to be consistent with the <a
+   * href="https://cloud.google.com/docs/quotas/set-quota-project">official GCP client
+   * libraries</a>.
+   */
+  GOOGLE_CLOUD_QUOTA_PROJECT("Google Cloud Quota Project ID");
 
   private final String userReadableName;
   private final String environmentVariableName;

gcp-auth-extension/src/main/java/io/opentelemetry/contrib/gcp/auth/GcpAuthAutoConfigurationCustomizerProvider.java

@@ -59,15 +59,16 @@ public class GcpAuthAutoConfigurationCustomizerProvider
    */
   @Override
   public void customize(AutoConfigurationCustomizer autoConfiguration) {
+    GoogleCredentials credentials;
     try {
-      GoogleCredentials credentials = GoogleCredentials.getApplicationDefault();
-      autoConfiguration
-          .addSpanExporterCustomizer(
-              (exporter, configProperties) -> addAuthorizationHeaders(exporter, credentials))
-          .addResourceCustomizer(GcpAuthAutoConfigurationCustomizerProvider::customizeResource);
+      credentials = GoogleCredentials.getApplicationDefault();
     } catch (IOException e) {
       throw new GoogleAuthException(Reason.FAILED_ADC_RETRIEVAL, e);
     }
+    autoConfiguration
+        .addSpanExporterCustomizer(
+            (exporter, configProperties) -> addAuthorizationHeaders(exporter, credentials))
+        .addResourceCustomizer(GcpAuthAutoConfigurationCustomizerProvider::customizeResource);
   }
 
   @Override
@@ -100,24 +101,19 @@ private static Map<String, String> getRequiredHeaderMap(GoogleCredentials creden
     } catch (IOException e) {
       throw new GoogleAuthException(Reason.FAILED_ADC_REFRESH, e);
     }
-    gcpHeaders.put(QUOTA_USER_PROJECT_HEADER, credentials.getQuotaProjectId());
     gcpHeaders.put("Authorization", "Bearer " + credentials.getAccessToken().getTokenValue());
+    String configuredQuotaProjectId =
+        ConfigurableOption.GOOGLE_CLOUD_QUOTA_PROJECT.getConfiguredValueWithFallback(
+            credentials::getQuotaProjectId);
+    if (configuredQuotaProjectId != null && !configuredQuotaProjectId.isEmpty()) {
+      gcpHeaders.put(QUOTA_USER_PROJECT_HEADER, configuredQuotaProjectId);
+    }
     return gcpHeaders;
   }
 
   // Updates the current resource with the attributes required for ingesting OTLP data on GCP.
   private static Resource customizeResource(Resource resource, ConfigProperties configProperties) {
-    String gcpProjectId =
-        ConfigurableOption.GOOGLE_CLOUD_PROJECT.getConfiguredValueWithFallback(
-            () -> {
-              try {
-                GoogleCredentials googleCredentials = GoogleCredentials.getApplicationDefault();
-                return googleCredentials.getQuotaProjectId();
-              } catch (IOException e) {
-                throw new GoogleAuthException(Reason.FAILED_ADC_RETRIEVAL, e);
-              }
-            });
-
+    String gcpProjectId = ConfigurableOption.GOOGLE_CLOUD_PROJECT.getConfiguredValue();
     Resource res =
         Resource.create(
             Attributes.of(AttributeKey.stringKey(GCP_USER_PROJECT_ID_KEY), gcpProjectId));