GcpObservabilityConfig: Fall-back to GCP environment variables (#31022)

src/cpp/ext/gcp/observability_config.cc

@@ -71,6 +71,27 @@ absl::StatusOr<std::string> GetGcpObservabilityConfigContents() {
       "not defined");
 }
 
+// Tries to get the GCP Project ID from environment variables, or returns an
+// empty string if not found.
+std::string GetProjectIdFromGcpEnvVar() {
+  // First check GCP_PROEJCT
+  absl::optional<std::string> project_id = grpc_core::GetEnv("GCP_PROJECT");
+  if (project_id.has_value() && !project_id->empty()) {
+    return project_id.value();
+  }
+  // Next, try GCLOUD_PROJECT
+  project_id = grpc_core::GetEnv("GCLOUD_PROJECT");
+  if (project_id.has_value() && !project_id->empty()) {
+    return project_id.value();
+  }
+  // Lastly, try GOOGLE_CLOUD_PROJECT
+  project_id = grpc_core::GetEnv("GOOGLE_CLOUD_PROJECT");
+  if (project_id.has_value() && !project_id->empty()) {
+    return project_id.value();
+  }
+  return "";
+}
+
 }  // namespace
 
 absl::StatusOr<GcpObservabilityConfig> GcpObservabilityConfig::ReadFromEnv() {
@@ -82,7 +103,20 @@ absl::StatusOr<GcpObservabilityConfig> GcpObservabilityConfig::ReadFromEnv() {
   if (!config_json.ok()) {
     return config_json.status();
   }
-  return grpc_core::LoadFromJson<GcpObservabilityConfig>(*config_json);
+  auto config = grpc_core::LoadFromJson<GcpObservabilityConfig>(*config_json);
+  if (!config.ok()) {
+    return config.status();
+  }
+  if (config->project_id.empty()) {
+    // Get project ID from GCP environment variables since project ID was not
+    // set it in the GCP observability config.
+    config->project_id = GetProjectIdFromGcpEnvVar();
+    if (config->project_id.empty()) {
+      // Could not find project ID from GCP environment variables either.
+      return absl::FailedPreconditionError("GCP Project ID not found.");
+    }
+  }
+  return config;
 }
 
 }  // namespace internal

test/cpp/ext/gcp/observability_config_test.cc

@@ -21,6 +21,7 @@
 
 #include <grpc/support/alloc.h>
 
+#include "src/core/lib/config/core_configuration.h"
 #include "src/core/lib/gpr/tmpfile.h"
 #include "src/core/lib/gprpp/env.h"
 #include "test/core/util/test_config.h"
@@ -93,6 +94,56 @@ TEST(GcpEnvParsingTest, ConfigFileDoesNotExist) {
   grpc_core::UnsetEnv("GRPC_OBSERVABILITY_CONFIG_FILE");
 }
 
+TEST(GcpEnvParsingTest, ProjectIdNotSet) {
+  grpc_core::SetEnv("GRPC_OBSERVABILITY_CONFIG", "{}");
+
+  auto config = GcpObservabilityConfig::ReadFromEnv();
+  EXPECT_EQ(config.status(),
+            absl::FailedPreconditionError("GCP Project ID not found."));
+
+  grpc_core::UnsetEnv("GRPC_OBSERVABILITY_CONFIG");
+  grpc_core::CoreConfiguration::Reset();
+}
+
+TEST(GcpEnvParsingTest, ProjectIdFromGcpProjectEnvVar) {
+  grpc_core::SetEnv("GRPC_OBSERVABILITY_CONFIG", "{}");
+  grpc_core::SetEnv("GCP_PROJECT", "gcp_project");
+
+  auto config = GcpObservabilityConfig::ReadFromEnv();
+  EXPECT_TRUE(config.ok());
+  EXPECT_EQ(config->project_id, "gcp_project");
+
+  grpc_core::UnsetEnv("GCP_PROJECT");
+  grpc_core::UnsetEnv("GRPC_OBSERVABILITY_CONFIG");
+  grpc_core::CoreConfiguration::Reset();
+}
+
+TEST(GcpEnvParsingTest, ProjectIdFromGcloudProjectEnvVar) {
+  grpc_core::SetEnv("GRPC_OBSERVABILITY_CONFIG", "{}");
+  grpc_core::SetEnv("GCLOUD_PROJECT", "gcloud_project");
+
+  auto config = GcpObservabilityConfig::ReadFromEnv();
+  EXPECT_TRUE(config.ok());
+  EXPECT_EQ(config->project_id, "gcloud_project");
+
+  grpc_core::UnsetEnv("GCLOUD_PROJECT");
+  grpc_core::UnsetEnv("GRPC_OBSERVABILITY_CONFIG");
+  grpc_core::CoreConfiguration::Reset();
+}
+
+TEST(GcpEnvParsingTest, ProjectIdFromGoogleCloudProjectEnvVar) {
+  grpc_core::SetEnv("GRPC_OBSERVABILITY_CONFIG", "{}");
+  grpc_core::SetEnv("GOOGLE_CLOUD_PROJECT", "google_cloud_project");
+
+  auto config = GcpObservabilityConfig::ReadFromEnv();
+  EXPECT_TRUE(config.ok());
+  EXPECT_EQ(config->project_id, "google_cloud_project");
+
+  grpc_core::UnsetEnv("GOOGLE_CLOUD_PROJECT");
+  grpc_core::UnsetEnv("GRPC_OBSERVABILITY_CONFIG");
+  grpc_core::CoreConfiguration::Reset();
+}
+
 class EnvParsingTestType {
  public:
   enum class ConfigSource {