feat(storage): inject feature tracker into client config and REST transport (#2657)

Author: v-pratap

google/cloud/storage/client.cc

@@ -16,6 +16,7 @@
 #include "google/cloud/storage/idempotency_policy.h"
 #include "google/cloud/storage/internal/base64.h"
 #include "google/cloud/storage/internal/connection_factory.h"
+#include "google/cloud/storage/internal/feature_tracker.h"
 #include "google/cloud/storage/options.h"
 #include "google/cloud/internal/curl_handle.h"
 #include "google/cloud/internal/curl_options.h"
@@ -624,8 +625,8 @@ Options DefaultOptions(Options opts) {
     rest_defaults.set<rest::CAPathOption>(o.get<internal::CAPathOption>());
   }
 
-  return google::cloud::internal::MergeOptions(std::move(o),
-                                               std::move(rest_defaults));
+  return internal::SetupFeatureTracker(google::cloud::internal::MergeOptions(
+      std::move(o), std::move(rest_defaults)));
 }
 
 Options DefaultOptionsWithCredentials(Options opts) {

google/cloud/storage/internal/async/default_options.cc

@@ -18,6 +18,7 @@
 #include "google/cloud/storage/async/resume_policy.h"
 #include "google/cloud/storage/async/retry_policy.h"
 #include "google/cloud/storage/async/writer_connection.h"
+#include "google/cloud/storage/internal/feature_tracker.h"
 #include "google/cloud/storage/internal/grpc/default_options.h"
 #include <limits>
 
@@ -77,7 +78,8 @@ Options DefaultOptionsAsync(Options opts) {
           .set<storage::EnableCrc32cValidationOption>(true)
           .set<storage::MaximumRangeSizeOption>(128 * 1024 * 1024L)
           .set<storage::EnableMultiStreamOptimizationOption>(true));
-  return Adjust(DefaultOptionsGrpc(std::move(opts)));
+  return storage::internal::SetupFeatureTracker(
+      Adjust(DefaultOptionsGrpc(std::move(opts))));
 }
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/storage/internal/rest/stub.cc

@@ -15,6 +15,9 @@
 #include "google/cloud/storage/internal/rest/stub.h"
 #include "google/cloud/storage/internal/bucket_access_control_parser.h"
 #include "google/cloud/storage/internal/bucket_metadata_parser.h"
+#include "google/cloud/storage/internal/feature_tracker.h"
+#include "google/cloud/storage/options.h"
+#include "google/cloud/storage/internal/base64.h"
 #include "google/cloud/storage/internal/bucket_requests.h"
 #include "google/cloud/storage/internal/generate_message_boundary.h"
 #include "google/cloud/storage/internal/hmac_key_metadata_parser.h"
@@ -116,6 +119,18 @@ void AddCustomHeaders(Options const& options, RestRequestBuilder& builder) {
 
 Status AddHeaders(Options const& options, RestRequestBuilder& builder) {
   AddCustomHeaders(options, builder);
+  bool const enable_reports =
+      !options.has<EnableFeatureReportsOption>() ||
+      options.get<EnableFeatureReportsOption>();
+  if (enable_reports && options.has<FeatureTrackerOption>()) {
+    auto const& tracker = options.get<FeatureTrackerOption>();
+    if (tracker) {
+      auto const val = tracker->HeaderValue();
+      if (!val.empty()) {
+        builder.AddHeader(kFeatureTrackerHeaderName, val);
+      }
+    }
+  }
   return {};
 }
 

google/cloud/storage/internal/rest/stub_test.cc

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "google/cloud/storage/internal/rest/stub.h"
+#include "google/cloud/storage/internal/feature_tracker.h"
 #include "google/cloud/storage/internal/hash_function.h"
 #include "google/cloud/storage/testing/canonical_errors.h"
 #include "google/cloud/internal/api_client_header.h"
@@ -1028,6 +1029,27 @@ TEST(RestStubTest, UploadChunkIntermediate) {
               StatusIs(PermanentError().code(), PermanentError().message()));
 }
 
+TEST(RestStubTest, FeatureTrackerHeaderAppearsInRequest) {
+  auto tracker = std::make_shared<FeatureTracker>();
+  tracker->RegisterFeature(TrackedFeature::kPCU);
+  auto options = Options{}.set<FeatureTrackerOption>(tracker);
+
+  auto mock = std::make_shared<MockRestClient>();
+  EXPECT_CALL(
+      *mock,
+      Get(An<RestContext&>(),
+          ResultOf(
+              "request includes feature tracker header",
+              [](RestRequest const& r) { return r.headers(); },
+              Contains(Pair(kFeatureTrackerHeaderName,
+                            ElementsAre(tracker->HeaderValue()))))))
+      .WillOnce(Return(PermanentError()));
+
+  auto tested = std::make_unique<RestStub>(options, mock, mock);
+  RestContext context;
+  tested->ListBuckets(context, options, ListBucketsRequest());
+}
+
 }  // namespace
 }  // namespace internal
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END