feat(bigtable): better support for PSC and VPC-SC (#8458)

Author: dbolduc

google/cloud/bigtable/data_client.cc

@@ -48,10 +48,13 @@ class DefaultDataClient : public DataClient {
                     Options options = {})
       : project_(std::move(project)),
         instance_(std::move(instance)),
+        authority_(options.has<AuthorityOption>()
+                       ? absl::make_optional(options.get<AuthorityOption>())
+                       : absl::nullopt),
         user_project_(
             options.has<UserProjectOption>()
-                ? absl::nullopt
-                : absl::make_optional(options.get<UserProjectOption>())),
+                ? absl::make_optional(options.get<UserProjectOption>())
+                : absl::nullopt),
         impl_(std::move(options)) {}
 
   std::string const& project_id() const override { return project_; };
@@ -189,12 +192,17 @@ class DefaultDataClient : public DataClient {
   }
 
   void ApplyOptions(grpc::ClientContext* context) {
-    if (!user_project_) return;
-    context->AddMetadata("x-goog-user-project", *user_project_);
+    if (authority_) {
+      context->set_authority(*authority_);
+    }
+    if (user_project_) {
+      context->AddMetadata("x-goog-user-project", *user_project_);
+    }
   }
 
   std::string project_;
   std::string instance_;
+  absl::optional<std::string> authority_;
   absl::optional<std::string> user_project_;
   internal::CommonClient<btproto::Bigtable> impl_;
 };

google/cloud/bigtable/internal/defaults.cc

@@ -164,6 +164,9 @@ Options DefaultDataOptions(Options opts) {
   if (user_project && !user_project->empty()) {
     opts.set<UserProjectOption>(*std::move(user_project));
   }
+  if (!opts.has<AuthorityOption>()) {
+    opts.set<AuthorityOption>("bigtable.googleapis.com");
+  }
   opts = DefaultOptions(std::move(opts));
   return opts.set<EndpointOption>(opts.get<DataEndpointOption>());
 }

google/cloud/bigtable/internal/defaults_test.cc

@@ -167,6 +167,15 @@ TEST(OptionsTest, DataUserProjectOption) {
   EXPECT_EQ(options.get<UserProjectOption>(), "env-project");
 }
 
+TEST(OptionsTest, DataAuthorityOption) {
+  auto options = DefaultDataOptions(Options{});
+  EXPECT_EQ(options.get<AuthorityOption>(), "bigtable.googleapis.com");
+
+  options = DefaultDataOptions(
+      Options{}.set<AuthorityOption>("custom-endpoint.googleapis.com"));
+  EXPECT_EQ(options.get<AuthorityOption>(), "custom-endpoint.googleapis.com");
+}
+
 TEST(EndpointEnvTest, EmulatorEnvOnly) {
   ScopedEnvironment emulator("BIGTABLE_EMULATOR_HOST", "emulator-host:8000");