Capture compilation flag telemetry. (#1758)

This would be useful in the future when we need to prioritize features /
compiler support, etc. It captures the compiler name and version, as
well as the `-fexceptions` settings in the user-agent string.

Also refactored the two places in Bigtable where we built a user-agent
string.

Author: coryan

google/cloud/bigtable/client_options.cc

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 
 #include "google/cloud/bigtable/client_options.h"
+#include "google/cloud/internal/build_info.h"
 #include "google/cloud/internal/getenv.h"
 #include <thread>
 
@@ -56,7 +57,7 @@ ClientOptions::ClientOptions(std::shared_ptr<grpc::ChannelCredentials> creds)
       data_endpoint_("bigtable.googleapis.com"),
       admin_endpoint_("bigtableadmin.googleapis.com"),
       instance_admin_endpoint_("bigtableadmin.googleapis.com") {
-  static std::string const user_agent_prefix = "cbt-c++/" + version_string();
+  static std::string const user_agent_prefix = UserAgentPrefix();
   channel_arguments_.SetUserAgentPrefix(user_agent_prefix);
 }
 
@@ -74,6 +75,18 @@ ClientOptions::ClientOptions() : ClientOptions(BigtableDefaultCredentials()) {
   }
 }
 
+std::string ClientOptions::UserAgentPrefix() {
+  std::string agent = "cbt-c++/" + version_string();
+#if GOOGLE_CLOUD_CPP_HAVE_EXCEPTIONS
+  agent += " ex";
+#else
+  agent += " noex";
+#endif  // GOOGLE_CLOUD_CPP_HAVE_EXCEPTIONS
+  agent += ' ';
+  agent += google::cloud::internal::compiler();
+  return agent;
+}
+
 }  // namespace BIGTABLE_CLIENT_NS
 }  // namespace bigtable
 }  // namespace cloud

google/cloud/bigtable/client_options.h

@@ -285,6 +285,9 @@ class ClientOptions {
     channel_arguments_.SetSslTargetNameOverride(name);
   }
 
+  /// Return the user agent prefix used by the library.
+  static std::string UserAgentPrefix();
+
  private:
   /// Return the current endpoint for instance admin RPCs.
   friend struct InstanceAdminTraits;

google/cloud/bigtable/client_options_test.cc

@@ -31,6 +31,8 @@ struct ClientOptionsTestTraits {
 
 namespace {
 
+using ::testing::HasSubstr;
+
 TEST(ClientOptionsTest, ClientOptionsDefaultSettings) {
   bigtable::ClientOptions client_options_object = bigtable::ClientOptions();
   EXPECT_EQ("bigtable.googleapis.com", client_options_object.data_endpoint());
@@ -300,6 +302,13 @@ TEST(ClientOptionsTest, SetSslTargetNameOverride) {
             grpc::string(test_args.args[1].key));
 }
 
+TEST(ClientOptionsTest, UserAgentPrefix) {
+  std::string const actual = bigtable::ClientOptions::UserAgentPrefix();
+
+  EXPECT_THAT(actual, HasSubstr("cbt-c++/"));
+  EXPECT_THAT(actual, ::testing::AnyOf(HasSubstr(" noex "), HasSubstr(" ex ")));
+}
+
 }  // namespace
 }  // namespace BIGTABLE_CLIENT_NS
 }  // namespace bigtable

google/cloud/bigtable/testing/embedded_server_test_fixture.cc

@@ -14,6 +14,7 @@
 
 #include "google/cloud/bigtable/testing/embedded_server_test_fixture.h"
 #include "google/cloud/bigtable/internal/grpc_error_delegate.h"
+#include "google/cloud/internal/build_info.h"
 #include <thread>
 
 namespace google {
@@ -36,8 +37,8 @@ void EmbeddedServerTestFixture::SetUp() {
   StartServer();
 
   grpc::ChannelArguments channel_arguments;
-  static std::string const prefix = "cbt-c++/" + version_string();
-  channel_arguments.SetUserAgentPrefix(prefix);
+  static std::string const user_agent_prefix = ClientOptions::UserAgentPrefix();
+  channel_arguments.SetUserAgentPrefix(user_agent_prefix);
 
   std::shared_ptr<grpc::Channel> data_channel =
       server_->InProcessChannel(channel_arguments);

google/cloud/storage/internal/curl_request_builder.cc

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "google/cloud/storage/internal/curl_request_builder.h"
+#include "google/cloud/internal/build_info.h"
 
 namespace google {
 namespace cloud {
@@ -133,6 +134,13 @@ std::string CurlRequestBuilder::UserAgentSuffix() const {
   static std::string const user_agent_suffix = [] {
     std::string agent = "gcs-c++/";
     agent += storage::version_string();
+#if GOOGLE_CLOUD_CPP_HAVE_EXCEPTIONS
+    agent += " ex";
+#else
+    agent += " noex";
+#endif  // GOOGLE_CLOUD_CPP_HAVE_EXCEPTIONS
+    agent += ' ';
+    agent += google::cloud::internal::compiler();
     agent += ' ';
     agent += curl_version();
     return agent;