[gcp-auth-extension]: Try resolving GCP_PROJECT with ServiceOptions if not provided

gcp-auth-extension/README.md

@@ -34,14 +34,13 @@ The extension can be configured either by environment variables or system proper
 
 Here is a list of required and optional configuration available for the extension:
 
-#### Required Config
+#### Optional Config
 
 - `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.
-  - This is a required option, the agent configuration will fail if this option is not set.
-
-#### Optional Config
+  - If neither of these options are set, the extension will attempt to use the `ServiceOptions` class from `google-cloud-core` to determine the project ID. The `ServiceOptions` has a comprehensive logic to determine the project ID, which includes checking the environment variable `GOOGLE_CLOUD_PROJECT`, the `gcloud` configuration, the local metadata server, and the `GOOGLE_APPLICATION_CREDENTIALS` file.
+  - **Important Note**: The agent configuration will fail if this option is not set or cannot be inferred.
 
 - `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 the [Quota project overview](https://cloud.google.com/docs/quotas/quota-project) page. Additional details about configuring the *quota project* can be found on the [Set the quota project](https://cloud.google.com/docs/quotas/set-quota-project) page.
 

gcp-auth-extension/build.gradle.kts

@@ -25,6 +25,7 @@ dependencies {
 
   // Only dependencies added to `implementation` configuration will be picked up by Shadow plugin
   implementation("com.google.auth:google-auth-library-oauth2-http:1.37.1")
+  implementation("com.google.cloud:google-cloud-core:2.58.1")
 
   // Test dependencies
   testCompileOnly("com.google.auto.service:auto-service-annotations")

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

@@ -7,6 +7,7 @@
 
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.auto.service.AutoService;
+import com.google.cloud.ServiceOptions;
 import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.contrib.gcp.auth.GoogleAuthException.Reason;
@@ -21,6 +22,7 @@
 import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizer;
 import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizerProvider;
 import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigurationException;
 import io.opentelemetry.sdk.metrics.export.MetricExporter;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.trace.export.SpanExporter;
@@ -109,7 +111,12 @@ public void customize(@Nonnull AutoConfigurationCustomizer autoConfiguration) {
         .addMetricExporterCustomizer(
             (metricExporter, configProperties) ->
                 customizeMetricExporter(metricExporter, credentials, configProperties))
-        .addResourceCustomizer(GcpAuthAutoConfigurationCustomizerProvider::customizeResource);
+        .addResourceCustomizer(
+            (resource, configProperties) -> {
+              String gcpProjectId = getGoogleProjectId(configProperties);
+
+              return customizeResource(resource, gcpProjectId);
+            });
   }
 
   @Override
@@ -227,12 +234,35 @@ private static Map<String, String> getRequiredHeaderMap(
   }
 
   // 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.getConfiguredValue(configProperties);
+  private static Resource customizeResource(Resource resource, String gcpProjectId) {
     Resource res =
         Resource.create(
             Attributes.of(AttributeKey.stringKey(GCP_USER_PROJECT_ID_KEY), gcpProjectId));
     return resource.merge(res);
   }
+
+  /**
+   * Retrieves the Google Cloud Project ID from the configuration properties, falling back to
+   * google-cloud-core's ServiceOptions project ID resolution if not explicitly set.
+   *
+   * @param configProperties The configuration properties containing the GCP project ID.
+   * @return The Google Cloud Project ID.
+   */
+  @Nonnull
+  static String getGoogleProjectId(ConfigProperties configProperties) {
+    String googleProjectId =
+        ConfigurableOption.GOOGLE_CLOUD_PROJECT.getConfiguredValueWithFallback(
+            configProperties, ServiceOptions::getDefaultProjectId);
+
+    if (googleProjectId == null || googleProjectId.isEmpty()) {
+      throw new ConfigurationException(
+          String.format(
+              "GCP Authentication Extension not configured properly: %s not configured. Configure it by exporting environment variable %s or system property %s",
+              ConfigurableOption.GOOGLE_CLOUD_PROJECT,
+              ConfigurableOption.GOOGLE_CLOUD_PROJECT.getEnvironmentVariable(),
+              ConfigurableOption.GOOGLE_CLOUD_PROJECT.getSystemProperty()));
+    }
+
+    return googleProjectId;
+  }
 }

gcp-auth-extension/src/test/java/io/opentelemetry/contrib/gcp/auth/GcpAuthAutoConfigurationCustomizerProviderTest.java

@@ -39,6 +39,7 @@
 import io.opentelemetry.sdk.autoconfigure.internal.SpiHelper;
 import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
 import io.opentelemetry.sdk.autoconfigure.spi.ConfigurationException;
+import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
 import io.opentelemetry.sdk.autoconfigure.spi.metrics.ConfigurableMetricExporterProvider;
 import io.opentelemetry.sdk.autoconfigure.spi.traces.ConfigurableSpanExporterProvider;
 import io.opentelemetry.sdk.common.CompletableResultCode;
@@ -538,6 +539,49 @@ public void testTargetSignalsBehavior(TargetSignalBehavior testCase) {
     }
   }
 
+  @Test
+  void testThrowsExceptionIfGoogleProjectIsNotFound() {
+    // Clear the system property to ensure it does not interfere with the test
+    System.clearProperty(ConfigurableOption.GOOGLE_CLOUD_PROJECT.getSystemProperty());
+    System.clearProperty("GOOGLE_CLOUD_PROJECT");
+
+    DefaultConfigProperties configProperties =
+        DefaultConfigProperties.create(Collections.emptyMap(), Mockito.mock(ComponentLoader.class));
+
+    assertThrows(
+        ConfigurationException.class,
+        () -> GcpAuthAutoConfigurationCustomizerProvider.getGoogleProjectId(configProperties));
+  }
+
+  @Test
+  void testResolveGoogleProjectIdFromSystemProperty() {
+    System.setProperty(
+        ConfigurableOption.GOOGLE_CLOUD_PROJECT.getSystemProperty(), DUMMY_GCP_RESOURCE_PROJECT_ID);
+
+    DefaultConfigProperties configProperties =
+        DefaultConfigProperties.create(Collections.emptyMap(), Mockito.mock(ComponentLoader.class));
+
+    assertEquals(
+        DUMMY_GCP_RESOURCE_PROJECT_ID,
+        GcpAuthAutoConfigurationCustomizerProvider.getGoogleProjectId(configProperties));
+  }
+
+  @Test
+  void testResolveGoogleProjectIdFromServiceOptions() {
+    // Clear the system property to ensure it does not interfere with the test
+    System.clearProperty(ConfigurableOption.GOOGLE_CLOUD_PROJECT.getSystemProperty());
+    // Property that the extension expects is google.cloud.project, ServiceOptions works with
+    // GOOGLE_CLOUD_PROJECT, so this will highlight the fallback to ServiceOptions
+    System.setProperty("GOOGLE_CLOUD_PROJECT", DUMMY_GCP_RESOURCE_PROJECT_ID);
+
+    DefaultConfigProperties configProperties =
+        DefaultConfigProperties.create(Collections.emptyMap(), Mockito.mock(ComponentLoader.class));
+
+    assertEquals(
+        DUMMY_GCP_RESOURCE_PROJECT_ID,
+        GcpAuthAutoConfigurationCustomizerProvider.getGoogleProjectId(configProperties));
+  }
+
   /** Test cases specifying expected behavior for GOOGLE_OTEL_AUTH_TARGET_SIGNALS */
   private static Stream<Arguments> provideTargetSignalBehaviorTestCases() {
     return Stream.of(