Metadata tutorial

14 files changed, 1666 insertions, 0 deletions

diff --git a/examples/cpp/metadata/Makefile b/examples/cpp/metadata/Makefile
new file mode 100644
index 0000000000..46be8bfaa3
--- /dev/null
+++ b/examples/cpp/metadata/Makefile
@@ -0,0 +1,96 @@
+#
+# Copyright 2018 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+ HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
+SYSTEM ?= $(HOST_SYSTEM)
+CXX = g++
+CPPFLAGS += `pkg-config --cflags protobuf grpc`
+CXXFLAGS += -std=c++11
+ifeq ($(SYSTEM),Darwin)
+LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++ grpc`\
+           -lgrpc++_reflection\
+           -ldl
+else
+LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++ grpc`\
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed\
+           -ldl
+endif
+PROTOC = protoc
+GRPC_CPP_PLUGIN = grpc_cpp_plugin
+GRPC_CPP_PLUGIN_PATH ?= `which $(GRPC_CPP_PLUGIN)`
+ PROTOS_PATH = ../../protos
+ vpath %.proto $(PROTOS_PATH)
+ all: system-check greeter_client greeter_server
+ greeter_client: helloworld.pb.o helloworld.grpc.pb.o greeter_client.o
+	$(CXX) $^ $(LDFLAGS) -o $@
+ greeter_server: helloworld.pb.o helloworld.grpc.pb.o greeter_server.o
+	$(CXX) $^ $(LDFLAGS) -o $@
+ .PRECIOUS: %.grpc.pb.cc
+%.grpc.pb.cc: %.proto
+	$(PROTOC) -I $(PROTOS_PATH) --grpc_out=. --plugin=protoc-gen-grpc=$(GRPC_CPP_PLUGIN_PATH) $<
+ .PRECIOUS: %.pb.cc
+%.pb.cc: %.proto
+	$(PROTOC) -I $(PROTOS_PATH) --cpp_out=. $<
+ clean:
+	rm -f *.o *.pb.cc *.pb.h greeter_client greeter_server
+ # The following is to test your system and ensure a smoother experience.
+# They are by no means necessary to actually compile a grpc-enabled software.
+ PROTOC_CMD = which $(PROTOC)
+PROTOC_CHECK_CMD = $(PROTOC) --version | grep -q libprotoc.3
+PLUGIN_CHECK_CMD = which $(GRPC_CPP_PLUGIN)
+HAS_PROTOC = $(shell $(PROTOC_CMD) > /dev/null && echo true || echo false)
+ifeq ($(HAS_PROTOC),true)
+HAS_VALID_PROTOC = $(shell $(PROTOC_CHECK_CMD) 2> /dev/null && echo true || echo false)
+endif
+HAS_PLUGIN = $(shell $(PLUGIN_CHECK_CMD) > /dev/null && echo true || echo false)
+ SYSTEM_OK = false
+ifeq ($(HAS_VALID_PROTOC),true)
+ifeq ($(HAS_PLUGIN),true)
+SYSTEM_OK = true
+endif
+endif
+ system-check:
+ifneq ($(HAS_VALID_PROTOC),true)
+	@echo " DEPENDENCY ERROR"
+	@echo
+	@echo "You don't have protoc 3.0.0 installed in your path."
+	@echo "Please install Google protocol buffers 3.0.0 and its compiler."
+	@echo "You can find it here:"
+	@echo
+	@echo "   https://github.com/google/protobuf/releases/tag/v3.0.0"
+	@echo
+	@echo "Here is what I get when trying to evaluate your version of protoc:"
+	@echo
+	-$(PROTOC) --version
+	@echo
+	@echo
+endif
+ifneq ($(HAS_PLUGIN),true)
+	@echo " DEPENDENCY ERROR"
+	@echo
+	@echo "You don't have the grpc c++ protobuf plugin installed in your path."
+	@echo "Please install grpc. You can find it here:"
+	@echo
+	@echo "   https://github.com/grpc/grpc"
+	@echo
+	@echo "Here is what I get when trying to detect if you have the plugin:"
+	@echo
+	-which $(GRPC_CPP_PLUGIN)
+	@echo
+	@echo
+endif
+ifneq ($(SYSTEM_OK),true)
+	@false
+endif
diff --git a/examples/cpp/metadata/README.md b/examples/cpp/metadata/README.md
new file mode 100644
index 0000000000..7b33074ba1
--- /dev/null
+++ b/examples/cpp/metadata/README.md
@@ -0,0 +1,69 @@
+# Metadata Example
+
+## Overview
+
+This example shows you how to add custom headers on the client and server and 
+how to access them.
+
+Custom metadata must follow the "Custom-Metadata" format listed in 
+https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md, with the 
+exception of binary headers, which don't have to be base64 encoded.
+
+### Get the tutorial source code
+ The example code for this and our other examples lives in the `examples` directory. Clone this repository to your local machine by running the following command:
+ ```sh
+$ git clone -b $(curl -L https://grpc.io/release) https://github.com/grpc/grpc
+```
+ Change your current directory to examples/cpp/metadata
+ ```sh
+$ cd examples/cpp/metadata
+```
+
+### Generating gRPC code
+ To generate the client and server side interfaces:
+ ```sh
+$ make helloworld.grpc.pb.cc helloworld.pb.cc
+```
+Which internally invokes the proto-compiler as:
+ ```sh
+$ protoc -I ../../protos/ --grpc_out=. --plugin=protoc-gen-grpc=grpc_cpp_plugin ../../protos/helloworld.proto
+$ protoc -I ../../protos/ --cpp_out=. ../../protos/helloworld.proto
+```
+### Try it!
+Build client and server:
+
+```sh
+$ make
+```
+
+Run the server, which will listen on port 50051:
+
+```sh
+$ ./greeter_server
+```
+
+Run the client (in a different terminal):
+
+```sh
+$ ./greeter_client
+```
+
+If things go smoothly, you will see in the client terminal:
+
+"Client received initial metadata from server: initial metadata value"
+"Client received trailing metadata from server: trailing metadata value"
+"Client received message: Hello World"
+
+
+And in the server terminal:
+
+"Header key: custom-bin , value: 
"
+"Header key: custom-header , value: Custom Value"
+"Header key: user-agent , value: grpc-c++/1.16.0-dev grpc-c/6.0.0-dev (linux; chttp2; gao)"
+
+Note that the value for custom-bin doesn't print nicely because it's a binary 
+value. You can indicate a binary value through appending "-bin" to the header key.
+
+We did not add the user-agent metadata as a custom header. This shows how 
+the gRPC framework adds some headers under the hood that may show up in the 
+metadata map.
diff --git a/examples/cpp/metadata/greeter_client b/examples/cpp/metadata/greeter_client
new file mode 100755
index 0000000000..929a51c3a5
--- /dev/null
+++ b/examples/cpp/metadata/greeter_client
diff --git a/examples/cpp/metadata/greeter_client.cc b/examples/cpp/metadata/greeter_client.cc
new file mode 100644
index 0000000000..8049438993
--- /dev/null
+++ b/examples/cpp/metadata/greeter_client.cc
@@ -0,0 +1,95 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <iostream>
+#include <memory>
+#include <string>
+
+#include <grpcpp/grpcpp.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/protos/helloworld.grpc.pb.h"
+#else
+#include "helloworld.grpc.pb.h"
+#endif
+
+using grpc::Channel;
+using grpc::ClientContext;
+using grpc::Status;
+using helloworld::HelloRequest;
+using helloworld::HelloReply;
+using helloworld::Greeter;
+
+class CustomHeaderClient {
+ public:
+  CustomHeaderClient(std::shared_ptr<Channel> channel)
+      : stub_(Greeter::NewStub(channel)) {}
+
+  // Assembles the client's payload, sends it and presents the response back
+  // from the server.
+  std::string SayHello(const std::string& user) {
+    // Data we are sending to the server.
+    HelloRequest request;
+    request.set_name(user);
+
+    // Container for the data we expect from the server.
+    HelloReply reply;
+
+    // Context for the client. It could be used to convey extra information to
+    // the server and/or tweak certain RPC behaviors.
+    ClientContext context;
+
+    // Setting custom metadata to be sent to the server
+    context.AddMetadata("custom-header", "Custom Value");
+
+    // Setting custom binary metadata 
+    char bytes[8] = {'\0', '\1', '\2', '\3',
+                     '\4', '\5', '\6', '\7'};
+    context.AddMetadata("custom-bin", grpc::string(bytes, 8));
+
+    // The actual RPC.
+    Status status = stub_->SayHello(&context, request, &reply);
+
+    // Act upon its status.
+    if (status.ok()) {
+      std::cout << "Client received initial metadata from server: " << context.GetServerInitialMetadata().find("custom-server-metadata")->second << std::endl;
+      std::cout << "Client received trailing metadata from server: " << context.GetServerTrailingMetadata().find("custom-trailing-metadata")->second << std::endl;
+      return reply.message();
+    } else {
+      std::cout << status.error_code() << ": " << status.error_message()
+                << std::endl;
+      return "RPC failed";
+    }
+  }
+
+ private:
+  std::unique_ptr<Greeter::Stub> stub_;
+};
+
+int main(int argc, char** argv) {
+  // Instantiate the client. It requires a channel, out of which the actual RPCs
+  // are created. This channel models a connection to an endpoint (in this case,
+  // localhost at port 50051). We indicate that the channel isn't authenticated
+  // (use of InsecureChannelCredentials()).
+  CustomHeaderClient greeter(grpc::CreateChannel(
+      "localhost:50051", grpc::InsecureChannelCredentials()));
+  std::string user("world");
+  std::string reply = greeter.SayHello(user);
+  std::cout << "Client received message: " << reply << std::endl;
+  return 0;
+}
diff --git a/examples/cpp/metadata/greeter_client.o b/examples/cpp/metadata/greeter_client.o
new file mode 100644
index 0000000000..483cb0741c
--- /dev/null
+++ b/examples/cpp/metadata/greeter_client.o
diff --git a/examples/cpp/metadata/greeter_server b/examples/cpp/metadata/greeter_server
new file mode 100755
index 0000000000..6b03f51475
--- /dev/null
+++ b/examples/cpp/metadata/greeter_server
diff --git a/examples/cpp/metadata/greeter_server.cc b/examples/cpp/metadata/greeter_server.cc
new file mode 100644
index 0000000000..db2fecbcaf
--- /dev/null
+++ b/examples/cpp/metadata/greeter_server.cc
@@ -0,0 +1,82 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <iostream>
+#include <memory>
+#include <string>
+
+#include <grpcpp/grpcpp.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/protos/helloworld.grpc.pb.h"
+#else
+#include "helloworld.grpc.pb.h"
+#endif
+
+using grpc::Server;
+using grpc::ServerBuilder;
+using grpc::ServerContext;
+using grpc::Status;
+using helloworld::HelloRequest;
+using helloworld::HelloReply;
+using helloworld::Greeter;
+
+// Logic and data behind the server's behavior.
+class GreeterServiceImpl final : public Greeter::Service {
+  Status SayHello(ServerContext* context, const HelloRequest* request,
+                  HelloReply* reply) override {
+    std::string prefix("Hello ");
+
+    // Get the client's initial metadata
+    std::cout << "Client metadata: " << std::endl;
+    const std::multimap<grpc::string_ref, grpc::string_ref> metadata = context->client_metadata();
+    for (auto iter = metadata.begin(); iter != metadata.end(); ++iter) {
+      std::cout << "Header key: " << iter->first << " , value: " << iter->second << std::endl;
+    }
+
+    context->AddInitialMetadata("custom-server-metadata", "initial metadata value");
+    context->AddTrailingMetadata("custom-trailing-metadata", "trailing metadata value");
+    reply->set_message(prefix + request->name());
+    return Status::OK;
+  }
+};
+
+void RunServer() {
+  std::string server_address("0.0.0.0:50051");
+  GreeterServiceImpl service;
+
+  ServerBuilder builder;
+  // Listen on the given address without any authentication mechanism.
+  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
+  // Register "service" as the instance through which we'll communicate with
+  // clients. In this case it corresponds to an *synchronous* service.
+  builder.RegisterService(&service);
+  // Finally assemble the server.
+  std::unique_ptr<Server> server(builder.BuildAndStart());
+  std::cout << "Server listening on " << server_address << std::endl;
+
+  // Wait for the server to shutdown. Note that some other thread must be
+  // responsible for shutting down the server for this call to ever return.
+  server->Wait();
+}
+
+int main(int argc, char** argv) {
+  RunServer();
+
+  return 0;
+}
diff --git a/examples/cpp/metadata/greeter_server.o b/examples/cpp/metadata/greeter_server.o
new file mode 100644
index 0000000000..dc197b2d14
--- /dev/null
+++ b/examples/cpp/metadata/greeter_server.o
diff --git a/examples/cpp/metadata/helloworld.grpc.pb.cc b/examples/cpp/metadata/helloworld.grpc.pb.cc
new file mode 100644
index 0000000000..4255687148
--- /dev/null
+++ b/examples/cpp/metadata/helloworld.grpc.pb.cc
@@ -0,0 +1,70 @@
+// Generated by the gRPC C++ plugin.
+// If you make any local change, they will be lost.
+// source: helloworld.proto
+
+#include "helloworld.pb.h"
+#include "helloworld.grpc.pb.h"
+
+#include <functional>
+#include <grpcpp/impl/codegen/async_stream.h>
+#include <grpcpp/impl/codegen/async_unary_call.h>
+#include <grpcpp/impl/codegen/channel_interface.h>
+#include <grpcpp/impl/codegen/client_unary_call.h>
+#include <grpcpp/impl/codegen/client_callback.h>
+#include <grpcpp/impl/codegen/method_handler_impl.h>
+#include <grpcpp/impl/codegen/rpc_service_method.h>
+#include <grpcpp/impl/codegen/service_type.h>
+#include <grpcpp/impl/codegen/sync_stream.h>
+namespace helloworld {
+
+static const char* Greeter_method_names[] = {
+  "/helloworld.Greeter/SayHello",
+};
+
+std::unique_ptr< Greeter::Stub> Greeter::NewStub(const std::shared_ptr< ::grpc::ChannelInterface>& channel, const ::grpc::StubOptions& options) {
+  (void)options;
+  std::unique_ptr< Greeter::Stub> stub(new Greeter::Stub(channel));
+  return stub;
+}
+
+Greeter::Stub::Stub(const std::shared_ptr< ::grpc::ChannelInterface>& channel)
+  : channel_(channel), rpcmethod_SayHello_(Greeter_method_names[0], ::grpc::internal::RpcMethod::NORMAL_RPC, channel)
+  {}
+
+::grpc::Status Greeter::Stub::SayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::helloworld::HelloReply* response) {
+  return ::grpc::internal::BlockingUnaryCall(channel_.get(), rpcmethod_SayHello_, context, request, response);
+}
+
+void Greeter::Stub::experimental_async::SayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response, std::function<void(::grpc::Status)> f) {
+  return ::grpc::internal::CallbackUnaryCall(stub_->channel_.get(), stub_->rpcmethod_SayHello_, context, request, response, std::move(f));
+}
+
+::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>* Greeter::Stub::AsyncSayHelloRaw(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) {
+  return ::grpc::internal::ClientAsyncResponseReaderFactory< ::helloworld::HelloReply>::Create(channel_.get(), cq, rpcmethod_SayHello_, context, request, true);
+}
+
+::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>* Greeter::Stub::PrepareAsyncSayHelloRaw(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) {
+  return ::grpc::internal::ClientAsyncResponseReaderFactory< ::helloworld::HelloReply>::Create(channel_.get(), cq, rpcmethod_SayHello_, context, request, false);
+}
+
+Greeter::Service::Service() {
+  AddMethod(new ::grpc::internal::RpcServiceMethod(
+      Greeter_method_names[0],
+      ::grpc::internal::RpcMethod::NORMAL_RPC,
+      new ::grpc::internal::RpcMethodHandler< Greeter::Service, ::helloworld::HelloRequest, ::helloworld::HelloReply>(
+          std::mem_fn(&Greeter::Service::SayHello), this)));
+}
+
+Greeter::Service::~Service() {
+}
+
+::grpc::Status Greeter::Service::SayHello(::grpc::ServerContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response) {
+  (void) context;
+  (void) request;
+  (void) response;
+  return ::grpc::Status(::grpc::StatusCode::UNIMPLEMENTED, "");
+}
+
+
+}  // namespace helloworld
+
diff --git a/examples/cpp/metadata/helloworld.grpc.pb.h b/examples/cpp/metadata/helloworld.grpc.pb.h
new file mode 100644
index 0000000000..73cc75e0a6
--- /dev/null
+++ b/examples/cpp/metadata/helloworld.grpc.pb.h
@@ -0,0 +1,197 @@
+// Generated by the gRPC C++ plugin.
+// If you make any local change, they will be lost.
+// source: helloworld.proto
+// Original file comments:
+// Copyright 2015 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#ifndef GRPC_helloworld_2eproto__INCLUDED
+#define GRPC_helloworld_2eproto__INCLUDED
+
+#include "helloworld.pb.h"
+
+#include <functional>
+#include <grpcpp/impl/codegen/async_generic_service.h>
+#include <grpcpp/impl/codegen/async_stream.h>
+#include <grpcpp/impl/codegen/async_unary_call.h>
+#include <grpcpp/impl/codegen/method_handler_impl.h>
+#include <grpcpp/impl/codegen/proto_utils.h>
+#include <grpcpp/impl/codegen/rpc_method.h>
+#include <grpcpp/impl/codegen/service_type.h>
+#include <grpcpp/impl/codegen/status.h>
+#include <grpcpp/impl/codegen/stub_options.h>
+#include <grpcpp/impl/codegen/sync_stream.h>
+
+namespace grpc {
+class CompletionQueue;
+class Channel;
+class ServerCompletionQueue;
+class ServerContext;
+}  // namespace grpc
+
+namespace helloworld {
+
+// The greeting service definition.
+class Greeter final {
+ public:
+  static constexpr char const* service_full_name() {
+    return "helloworld.Greeter";
+  }
+  class StubInterface {
+   public:
+    virtual ~StubInterface() {}
+    // Sends a greeting
+    virtual ::grpc::Status SayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::helloworld::HelloReply* response) = 0;
+    std::unique_ptr< ::grpc::ClientAsyncResponseReaderInterface< ::helloworld::HelloReply>> AsyncSayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) {
+      return std::unique_ptr< ::grpc::ClientAsyncResponseReaderInterface< ::helloworld::HelloReply>>(AsyncSayHelloRaw(context, request, cq));
+    }
+    std::unique_ptr< ::grpc::ClientAsyncResponseReaderInterface< ::helloworld::HelloReply>> PrepareAsyncSayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) {
+      return std::unique_ptr< ::grpc::ClientAsyncResponseReaderInterface< ::helloworld::HelloReply>>(PrepareAsyncSayHelloRaw(context, request, cq));
+    }
+    class experimental_async_interface {
+     public:
+      virtual ~experimental_async_interface() {}
+      // Sends a greeting
+      virtual void SayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response, std::function<void(::grpc::Status)>) = 0;
+    };
+    virtual class experimental_async_interface* experimental_async() { return nullptr; }
+  private:
+    virtual ::grpc::ClientAsyncResponseReaderInterface< ::helloworld::HelloReply>* AsyncSayHelloRaw(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) = 0;
+    virtual ::grpc::ClientAsyncResponseReaderInterface< ::helloworld::HelloReply>* PrepareAsyncSayHelloRaw(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) = 0;
+  };
+  class Stub final : public StubInterface {
+   public:
+    Stub(const std::shared_ptr< ::grpc::ChannelInterface>& channel);
+    ::grpc::Status SayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::helloworld::HelloReply* response) override;
+    std::unique_ptr< ::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>> AsyncSayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) {
+      return std::unique_ptr< ::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>>(AsyncSayHelloRaw(context, request, cq));
+    }
+    std::unique_ptr< ::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>> PrepareAsyncSayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) {
+      return std::unique_ptr< ::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>>(PrepareAsyncSayHelloRaw(context, request, cq));
+    }
+    class experimental_async final :
+      public StubInterface::experimental_async_interface {
+     public:
+      void SayHello(::grpc::ClientContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response, std::function<void(::grpc::Status)>) override;
+     private:
+      friend class Stub;
+      explicit experimental_async(Stub* stub): stub_(stub) { }
+      Stub* stub() { return stub_; }
+      Stub* stub_;
+    };
+    class experimental_async_interface* experimental_async() override { return &async_stub_; }
+
+   private:
+    std::shared_ptr< ::grpc::ChannelInterface> channel_;
+    class experimental_async async_stub_{this};
+    ::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>* AsyncSayHelloRaw(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) override;
+    ::grpc::ClientAsyncResponseReader< ::helloworld::HelloReply>* PrepareAsyncSayHelloRaw(::grpc::ClientContext* context, const ::helloworld::HelloRequest& request, ::grpc::CompletionQueue* cq) override;
+    const ::grpc::internal::RpcMethod rpcmethod_SayHello_;
+  };
+  static std::unique_ptr<Stub> NewStub(const std::shared_ptr< ::grpc::ChannelInterface>& channel, const ::grpc::StubOptions& options = ::grpc::StubOptions());
+
+  class Service : public ::grpc::Service {
+   public:
+    Service();
+    virtual ~Service();
+    // Sends a greeting
+    virtual ::grpc::Status SayHello(::grpc::ServerContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response);
+  };
+  template <class BaseClass>
+  class WithAsyncMethod_SayHello : public BaseClass {
+   private:
+    void BaseClassMustBeDerivedFromService(const Service *service) {}
+   public:
+    WithAsyncMethod_SayHello() {
+      ::grpc::Service::MarkMethodAsync(0);
+    }
+    ~WithAsyncMethod_SayHello() override {
+      BaseClassMustBeDerivedFromService(this);
+    }
+    // disable synchronous version of this method
+    ::grpc::Status SayHello(::grpc::ServerContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response) override {
+      abort();
+      return ::grpc::Status(::grpc::StatusCode::UNIMPLEMENTED, "");
+    }
+    void RequestSayHello(::grpc::ServerContext* context, ::helloworld::HelloRequest* request, ::grpc::ServerAsyncResponseWriter< ::helloworld::HelloReply>* response, ::grpc::CompletionQueue* new_call_cq, ::grpc::ServerCompletionQueue* notification_cq, void *tag) {
+      ::grpc::Service::RequestAsyncUnary(0, context, request, response, new_call_cq, notification_cq, tag);
+    }
+  };
+  typedef WithAsyncMethod_SayHello<Service > AsyncService;
+  template <class BaseClass>
+  class WithGenericMethod_SayHello : public BaseClass {
+   private:
+    void BaseClassMustBeDerivedFromService(const Service *service) {}
+   public:
+    WithGenericMethod_SayHello() {
+      ::grpc::Service::MarkMethodGeneric(0);
+    }
+    ~WithGenericMethod_SayHello() override {
+      BaseClassMustBeDerivedFromService(this);
+    }
+    // disable synchronous version of this method
+    ::grpc::Status SayHello(::grpc::ServerContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response) override {
+      abort();
+      return ::grpc::Status(::grpc::StatusCode::UNIMPLEMENTED, "");
+    }
+  };
+  template <class BaseClass>
+  class WithRawMethod_SayHello : public BaseClass {
+   private:
+    void BaseClassMustBeDerivedFromService(const Service *service) {}
+   public:
+    WithRawMethod_SayHello() {
+      ::grpc::Service::MarkMethodRaw(0);
+    }
+    ~WithRawMethod_SayHello() override {
+      BaseClassMustBeDerivedFromService(this);
+    }
+    // disable synchronous version of this method
+    ::grpc::Status SayHello(::grpc::ServerContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response) override {
+      abort();
+      return ::grpc::Status(::grpc::StatusCode::UNIMPLEMENTED, "");
+    }
+    void RequestSayHello(::grpc::ServerContext* context, ::grpc::ByteBuffer* request, ::grpc::ServerAsyncResponseWriter< ::grpc::ByteBuffer>* response, ::grpc::CompletionQueue* new_call_cq, ::grpc::ServerCompletionQueue* notification_cq, void *tag) {
+      ::grpc::Service::RequestAsyncUnary(0, context, request, response, new_call_cq, notification_cq, tag);
+    }
+  };
+  template <class BaseClass>
+  class WithStreamedUnaryMethod_SayHello : public BaseClass {
+   private:
+    void BaseClassMustBeDerivedFromService(const Service *service) {}
+   public:
+    WithStreamedUnaryMethod_SayHello() {
+      ::grpc::Service::MarkMethodStreamed(0,
+        new ::grpc::internal::StreamedUnaryHandler< ::helloworld::HelloRequest, ::helloworld::HelloReply>(std::bind(&WithStreamedUnaryMethod_SayHello<BaseClass>::StreamedSayHello, this, std::placeholders::_1, std::placeholders::_2)));
+    }
+    ~WithStreamedUnaryMethod_SayHello() override {
+      BaseClassMustBeDerivedFromService(this);
+    }
+    // disable regular version of this method
+    ::grpc::Status SayHello(::grpc::ServerContext* context, const ::helloworld::HelloRequest* request, ::helloworld::HelloReply* response) override {
+      abort();
+      return ::grpc::Status(::grpc::StatusCode::UNIMPLEMENTED, "");
+    }
+    // replace default version of method with streamed unary
+    virtual ::grpc::Status StreamedSayHello(::grpc::ServerContext* context, ::grpc::ServerUnaryStreamer< ::helloworld::HelloRequest,::helloworld::HelloReply>* server_unary_streamer) = 0;
+  };
+  typedef WithStreamedUnaryMethod_SayHello<Service > StreamedUnaryService;
+  typedef Service SplitStreamedService;
+  typedef WithStreamedUnaryMethod_SayHello<Service > StreamedService;
+};
+
+}  // namespace helloworld
+
+
+#endif  // GRPC_helloworld_2eproto__INCLUDED
diff --git a/examples/cpp/metadata/helloworld.grpc.pb.o b/examples/cpp/metadata/helloworld.grpc.pb.o
new file mode 100644
index 0000000000..234283660c
--- /dev/null
+++ b/examples/cpp/metadata/helloworld.grpc.pb.o
diff --git a/examples/cpp/metadata/helloworld.pb.cc b/examples/cpp/metadata/helloworld.pb.cc
new file mode 100644
index 0000000000..cfbc8d3194
--- /dev/null
+++ b/examples/cpp/metadata/helloworld.pb.cc
@@ -0,0 +1,638 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: helloworld.proto
+
+#include "helloworld.pb.h"
+
+#include <algorithm>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/port.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/wire_format_lite_inl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/generated_message_reflection.h>
+#include <google/protobuf/reflection_ops.h>
+#include <google/protobuf/wire_format.h>
+// This is a temporary google only hack
+#ifdef GOOGLE_PROTOBUF_ENFORCE_UNIQUENESS
+#include "third_party/protobuf/version.h"
+#endif
+// @@protoc_insertion_point(includes)
+
+namespace helloworld {
+class HelloRequestDefaultTypeInternal {
+ public:
+  ::google::protobuf::internal::ExplicitlyConstructed<HelloRequest>
+      _instance;
+} _HelloRequest_default_instance_;
+class HelloReplyDefaultTypeInternal {
+ public:
+  ::google::protobuf::internal::ExplicitlyConstructed<HelloReply>
+      _instance;
+} _HelloReply_default_instance_;
+}  // namespace helloworld
+namespace protobuf_helloworld_2eproto {
+static void InitDefaultsHelloRequest() {
+  GOOGLE_PROTOBUF_VERIFY_VERSION;
+
+  {
+    void* ptr = &::helloworld::_HelloRequest_default_instance_;
+    new (ptr) ::helloworld::HelloRequest();
+    ::google::protobuf::internal::OnShutdownDestroyMessage(ptr);
+  }
+  ::helloworld::HelloRequest::InitAsDefaultInstance();
+}
+
+::google::protobuf::internal::SCCInfo<0> scc_info_HelloRequest =
+    {{ATOMIC_VAR_INIT(::google::protobuf::internal::SCCInfoBase::kUninitialized), 0, InitDefaultsHelloRequest}, {}};
+
+static void InitDefaultsHelloReply() {
+  GOOGLE_PROTOBUF_VERIFY_VERSION;
+
+  {
+    void* ptr = &::helloworld::_HelloReply_default_instance_;
+    new (ptr) ::helloworld::HelloReply();
+    ::google::protobuf::internal::OnShutdownDestroyMessage(ptr);
+  }
+  ::helloworld::HelloReply::InitAsDefaultInstance();
+}
+
+::google::protobuf::internal::SCCInfo<0> scc_info_HelloReply =
+    {{ATOMIC_VAR_INIT(::google::protobuf::internal::SCCInfoBase::kUninitialized), 0, InitDefaultsHelloReply}, {}};
+
+void InitDefaults() {
+  ::google::protobuf::internal::InitSCC(&scc_info_HelloRequest.base);
+  ::google::protobuf::internal::InitSCC(&scc_info_HelloReply.base);
+}
+
+::google::protobuf::Metadata file_level_metadata[2];
+
+const ::google::protobuf::uint32 TableStruct::offsets[] GOOGLE_PROTOBUF_ATTRIBUTE_SECTION_VARIABLE(protodesc_cold) = {
+  ~0u,  // no _has_bits_
+  GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(::helloworld::HelloRequest, _internal_metadata_),
+  ~0u,  // no _extensions_
+  ~0u,  // no _oneof_case_
+  ~0u,  // no _weak_field_map_
+  GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(::helloworld::HelloRequest, name_),
+  ~0u,  // no _has_bits_
+  GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(::helloworld::HelloReply, _internal_metadata_),
+  ~0u,  // no _extensions_
+  ~0u,  // no _oneof_case_
+  ~0u,  // no _weak_field_map_
+  GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(::helloworld::HelloReply, message_),
+};
+static const ::google::protobuf::internal::MigrationSchema schemas[] GOOGLE_PROTOBUF_ATTRIBUTE_SECTION_VARIABLE(protodesc_cold) = {
+  { 0, -1, sizeof(::helloworld::HelloRequest)},
+  { 6, -1, sizeof(::helloworld::HelloReply)},
+};
+
+static ::google::protobuf::Message const * const file_default_instances[] = {
+  reinterpret_cast<const ::google::protobuf::Message*>(&::helloworld::_HelloRequest_default_instance_),
+  reinterpret_cast<const ::google::protobuf::Message*>(&::helloworld::_HelloReply_default_instance_),
+};
+
+void protobuf_AssignDescriptors() {
+  AddDescriptors();
+  AssignDescriptors(
+      "helloworld.proto", schemas, file_default_instances, TableStruct::offsets,
+      file_level_metadata, NULL, NULL);
+}
+
+void protobuf_AssignDescriptorsOnce() {
+  static ::google::protobuf::internal::once_flag once;
+  ::google::protobuf::internal::call_once(once, protobuf_AssignDescriptors);
+}
+
+void protobuf_RegisterTypes(const ::std::string&) GOOGLE_PROTOBUF_ATTRIBUTE_COLD;
+void protobuf_RegisterTypes(const ::std::string&) {
+  protobuf_AssignDescriptorsOnce();
+  ::google::protobuf::internal::RegisterAllTypes(file_level_metadata, 2);
+}
+
+void AddDescriptorsImpl() {
+  InitDefaults();
+  static const char descriptor[] GOOGLE_PROTOBUF_ATTRIBUTE_SECTION_VARIABLE(protodesc_cold) = {
+      "\n\020helloworld.proto\022\nhelloworld\"\034\n\014HelloR"
+      "equest\022\014\n\004name\030\001 \001(\t\"\035\n\nHelloReply\022\017\n\007me"
+      "ssage\030\001 \001(\t2I\n\007Greeter\022>\n\010SayHello\022\030.hel"
+      "loworld.HelloRequest\032\026.helloworld.HelloR"
+      "eply\"\000B6\n\033io.grpc.examples.helloworldB\017H"
+      "elloWorldProtoP\001\242\002\003HLWb\006proto3"
+  };
+  ::google::protobuf::DescriptorPool::InternalAddGeneratedFile(
+      descriptor, 230);
+  ::google::protobuf::MessageFactory::InternalRegisterGeneratedFile(
+    "helloworld.proto", &protobuf_RegisterTypes);
+}
+
+void AddDescriptors() {
+  static ::google::protobuf::internal::once_flag once;
+  ::google::protobuf::internal::call_once(once, AddDescriptorsImpl);
+}
+// Force AddDescriptors() to be called at dynamic initialization time.
+struct StaticDescriptorInitializer {
+  StaticDescriptorInitializer() {
+    AddDescriptors();
+  }
+} static_descriptor_initializer;
+}  // namespace protobuf_helloworld_2eproto
+namespace helloworld {
+
+// ===================================================================
+
+void HelloRequest::InitAsDefaultInstance() {
+}
+#if !defined(_MSC_VER) || _MSC_VER >= 1900
+const int HelloRequest::kNameFieldNumber;
+#endif  // !defined(_MSC_VER) || _MSC_VER >= 1900
+
+HelloRequest::HelloRequest()
+  : ::google::protobuf::Message(), _internal_metadata_(NULL) {
+  ::google::protobuf::internal::InitSCC(
+      &protobuf_helloworld_2eproto::scc_info_HelloRequest.base);
+  SharedCtor();
+  // @@protoc_insertion_point(constructor:helloworld.HelloRequest)
+}
+HelloRequest::HelloRequest(const HelloRequest& from)
+  : ::google::protobuf::Message(),
+      _internal_metadata_(NULL) {
+  _internal_metadata_.MergeFrom(from._internal_metadata_);
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  if (from.name().size() > 0) {
+    name_.AssignWithDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), from.name_);
+  }
+  // @@protoc_insertion_point(copy_constructor:helloworld.HelloRequest)
+}
+
+void HelloRequest::SharedCtor() {
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+
+HelloRequest::~HelloRequest() {
+  // @@protoc_insertion_point(destructor:helloworld.HelloRequest)
+  SharedDtor();
+}
+
+void HelloRequest::SharedDtor() {
+  name_.DestroyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+
+void HelloRequest::SetCachedSize(int size) const {
+  _cached_size_.Set(size);
+}
+const ::google::protobuf::Descriptor* HelloRequest::descriptor() {
+  ::protobuf_helloworld_2eproto::protobuf_AssignDescriptorsOnce();
+  return ::protobuf_helloworld_2eproto::file_level_metadata[kIndexInFileMessages].descriptor;
+}
+
+const HelloRequest& HelloRequest::default_instance() {
+  ::google::protobuf::internal::InitSCC(&protobuf_helloworld_2eproto::scc_info_HelloRequest.base);
+  return *internal_default_instance();
+}
+
+
+void HelloRequest::Clear() {
+// @@protoc_insertion_point(message_clear_start:helloworld.HelloRequest)
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  // Prevent compiler warnings about cached_has_bits being unused
+  (void) cached_has_bits;
+
+  name_.ClearToEmptyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  _internal_metadata_.Clear();
+}
+
+bool HelloRequest::MergePartialFromCodedStream(
+    ::google::protobuf::io::CodedInputStream* input) {
+#define DO_(EXPRESSION) if (!GOOGLE_PREDICT_TRUE(EXPRESSION)) goto failure
+  ::google::protobuf::uint32 tag;
+  // @@protoc_insertion_point(parse_start:helloworld.HelloRequest)
+  for (;;) {
+    ::std::pair<::google::protobuf::uint32, bool> p = input->ReadTagWithCutoffNoLastTag(127u);
+    tag = p.first;
+    if (!p.second) goto handle_unusual;
+    switch (::google::protobuf::internal::WireFormatLite::GetTagFieldNumber(tag)) {
+      // string name = 1;
+      case 1: {
+        if (static_cast< ::google::protobuf::uint8>(tag) ==
+            static_cast< ::google::protobuf::uint8>(10u /* 10 & 0xFF */)) {
+          DO_(::google::protobuf::internal::WireFormatLite::ReadString(
+                input, this->mutable_name()));
+          DO_(::google::protobuf::internal::WireFormatLite::VerifyUtf8String(
+            this->name().data(), static_cast<int>(this->name().length()),
+            ::google::protobuf::internal::WireFormatLite::PARSE,
+            "helloworld.HelloRequest.name"));
+        } else {
+          goto handle_unusual;
+        }
+        break;
+      }
+
+      default: {
+      handle_unusual:
+        if (tag == 0) {
+          goto success;
+        }
+        DO_(::google::protobuf::internal::WireFormat::SkipField(
+              input, tag, _internal_metadata_.mutable_unknown_fields()));
+        break;
+      }
+    }
+  }
+success:
+  // @@protoc_insertion_point(parse_success:helloworld.HelloRequest)
+  return true;
+failure:
+  // @@protoc_insertion_point(parse_failure:helloworld.HelloRequest)
+  return false;
+#undef DO_
+}
+
+void HelloRequest::SerializeWithCachedSizes(
+    ::google::protobuf::io::CodedOutputStream* output) const {
+  // @@protoc_insertion_point(serialize_start:helloworld.HelloRequest)
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  (void) cached_has_bits;
+
+  // string name = 1;
+  if (this->name().size() > 0) {
+    ::google::protobuf::internal::WireFormatLite::VerifyUtf8String(
+      this->name().data(), static_cast<int>(this->name().length()),
+      ::google::protobuf::internal::WireFormatLite::SERIALIZE,
+      "helloworld.HelloRequest.name");
+    ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
+      1, this->name(), output);
+  }
+
+  if ((_internal_metadata_.have_unknown_fields() &&  ::google::protobuf::internal::GetProto3PreserveUnknownsDefault())) {
+    ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
+        (::google::protobuf::internal::GetProto3PreserveUnknownsDefault()   ? _internal_metadata_.unknown_fields()   : _internal_metadata_.default_instance()), output);
+  }
+  // @@protoc_insertion_point(serialize_end:helloworld.HelloRequest)
+}
+
+::google::protobuf::uint8* HelloRequest::InternalSerializeWithCachedSizesToArray(
+    bool deterministic, ::google::protobuf::uint8* target) const {
+  (void)deterministic; // Unused
+  // @@protoc_insertion_point(serialize_to_array_start:helloworld.HelloRequest)
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  (void) cached_has_bits;
+
+  // string name = 1;
+  if (this->name().size() > 0) {
+    ::google::protobuf::internal::WireFormatLite::VerifyUtf8String(
+      this->name().data(), static_cast<int>(this->name().length()),
+      ::google::protobuf::internal::WireFormatLite::SERIALIZE,
+      "helloworld.HelloRequest.name");
+    target =
+      ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
+        1, this->name(), target);
+  }
+
+  if ((_internal_metadata_.have_unknown_fields() &&  ::google::protobuf::internal::GetProto3PreserveUnknownsDefault())) {
+    target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
+        (::google::protobuf::internal::GetProto3PreserveUnknownsDefault()   ? _internal_metadata_.unknown_fields()   : _internal_metadata_.default_instance()), target);
+  }
+  // @@protoc_insertion_point(serialize_to_array_end:helloworld.HelloRequest)
+  return target;
+}
+
+size_t HelloRequest::ByteSizeLong() const {
+// @@protoc_insertion_point(message_byte_size_start:helloworld.HelloRequest)
+  size_t total_size = 0;
+
+  if ((_internal_metadata_.have_unknown_fields() &&  ::google::protobuf::internal::GetProto3PreserveUnknownsDefault())) {
+    total_size +=
+      ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
+        (::google::protobuf::internal::GetProto3PreserveUnknownsDefault()   ? _internal_metadata_.unknown_fields()   : _internal_metadata_.default_instance()));
+  }
+  // string name = 1;
+  if (this->name().size() > 0) {
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->name());
+  }
+
+  int cached_size = ::google::protobuf::internal::ToCachedSize(total_size);
+  SetCachedSize(cached_size);
+  return total_size;
+}
+
+void HelloRequest::MergeFrom(const ::google::protobuf::Message& from) {
+// @@protoc_insertion_point(generalized_merge_from_start:helloworld.HelloRequest)
+  GOOGLE_DCHECK_NE(&from, this);
+  const HelloRequest* source =
+      ::google::protobuf::internal::DynamicCastToGenerated<const HelloRequest>(
+          &from);
+  if (source == NULL) {
+  // @@protoc_insertion_point(generalized_merge_from_cast_fail:helloworld.HelloRequest)
+    ::google::protobuf::internal::ReflectionOps::Merge(from, this);
+  } else {
+  // @@protoc_insertion_point(generalized_merge_from_cast_success:helloworld.HelloRequest)
+    MergeFrom(*source);
+  }
+}
+
+void HelloRequest::MergeFrom(const HelloRequest& from) {
+// @@protoc_insertion_point(class_specific_merge_from_start:helloworld.HelloRequest)
+  GOOGLE_DCHECK_NE(&from, this);
+  _internal_metadata_.MergeFrom(from._internal_metadata_);
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  (void) cached_has_bits;
+
+  if (from.name().size() > 0) {
+
+    name_.AssignWithDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), from.name_);
+  }
+}
+
+void HelloRequest::CopyFrom(const ::google::protobuf::Message& from) {
+// @@protoc_insertion_point(generalized_copy_from_start:helloworld.HelloRequest)
+  if (&from == this) return;
+  Clear();
+  MergeFrom(from);
+}
+
+void HelloRequest::CopyFrom(const HelloRequest& from) {
+// @@protoc_insertion_point(class_specific_copy_from_start:helloworld.HelloRequest)
+  if (&from == this) return;
+  Clear();
+  MergeFrom(from);
+}
+
+bool HelloRequest::IsInitialized() const {
+  return true;
+}
+
+void HelloRequest::Swap(HelloRequest* other) {
+  if (other == this) return;
+  InternalSwap(other);
+}
+void HelloRequest::InternalSwap(HelloRequest* other) {
+  using std::swap;
+  name_.Swap(&other->name_, &::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+    GetArenaNoVirtual());
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+}
+
+::google::protobuf::Metadata HelloRequest::GetMetadata() const {
+  protobuf_helloworld_2eproto::protobuf_AssignDescriptorsOnce();
+  return ::protobuf_helloworld_2eproto::file_level_metadata[kIndexInFileMessages];
+}
+
+
+// ===================================================================
+
+void HelloReply::InitAsDefaultInstance() {
+}
+#if !defined(_MSC_VER) || _MSC_VER >= 1900
+const int HelloReply::kMessageFieldNumber;
+#endif  // !defined(_MSC_VER) || _MSC_VER >= 1900
+
+HelloReply::HelloReply()
+  : ::google::protobuf::Message(), _internal_metadata_(NULL) {
+  ::google::protobuf::internal::InitSCC(
+      &protobuf_helloworld_2eproto::scc_info_HelloReply.base);
+  SharedCtor();
+  // @@protoc_insertion_point(constructor:helloworld.HelloReply)
+}
+HelloReply::HelloReply(const HelloReply& from)
+  : ::google::protobuf::Message(),
+      _internal_metadata_(NULL) {
+  _internal_metadata_.MergeFrom(from._internal_metadata_);
+  message_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  if (from.message().size() > 0) {
+    message_.AssignWithDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), from.message_);
+  }
+  // @@protoc_insertion_point(copy_constructor:helloworld.HelloReply)
+}
+
+void HelloReply::SharedCtor() {
+  message_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+
+HelloReply::~HelloReply() {
+  // @@protoc_insertion_point(destructor:helloworld.HelloReply)
+  SharedDtor();
+}
+
+void HelloReply::SharedDtor() {
+  message_.DestroyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+
+void HelloReply::SetCachedSize(int size) const {
+  _cached_size_.Set(size);
+}
+const ::google::protobuf::Descriptor* HelloReply::descriptor() {
+  ::protobuf_helloworld_2eproto::protobuf_AssignDescriptorsOnce();
+  return ::protobuf_helloworld_2eproto::file_level_metadata[kIndexInFileMessages].descriptor;
+}
+
+const HelloReply& HelloReply::default_instance() {
+  ::google::protobuf::internal::InitSCC(&protobuf_helloworld_2eproto::scc_info_HelloReply.base);
+  return *internal_default_instance();
+}
+
+
+void HelloReply::Clear() {
+// @@protoc_insertion_point(message_clear_start:helloworld.HelloReply)
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  // Prevent compiler warnings about cached_has_bits being unused
+  (void) cached_has_bits;
+
+  message_.ClearToEmptyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  _internal_metadata_.Clear();
+}
+
+bool HelloReply::MergePartialFromCodedStream(
+    ::google::protobuf::io::CodedInputStream* input) {
+#define DO_(EXPRESSION) if (!GOOGLE_PREDICT_TRUE(EXPRESSION)) goto failure
+  ::google::protobuf::uint32 tag;
+  // @@protoc_insertion_point(parse_start:helloworld.HelloReply)
+  for (;;) {
+    ::std::pair<::google::protobuf::uint32, bool> p = input->ReadTagWithCutoffNoLastTag(127u);
+    tag = p.first;
+    if (!p.second) goto handle_unusual;
+    switch (::google::protobuf::internal::WireFormatLite::GetTagFieldNumber(tag)) {
+      // string message = 1;
+      case 1: {
+        if (static_cast< ::google::protobuf::uint8>(tag) ==
+            static_cast< ::google::protobuf::uint8>(10u /* 10 & 0xFF */)) {
+          DO_(::google::protobuf::internal::WireFormatLite::ReadString(
+                input, this->mutable_message()));
+          DO_(::google::protobuf::internal::WireFormatLite::VerifyUtf8String(
+            this->message().data(), static_cast<int>(this->message().length()),
+            ::google::protobuf::internal::WireFormatLite::PARSE,
+            "helloworld.HelloReply.message"));
+        } else {
+          goto handle_unusual;
+        }
+        break;
+      }
+
+      default: {
+      handle_unusual:
+        if (tag == 0) {
+          goto success;
+        }
+        DO_(::google::protobuf::internal::WireFormat::SkipField(
+              input, tag, _internal_metadata_.mutable_unknown_fields()));
+        break;
+      }
+    }
+  }
+success:
+  // @@protoc_insertion_point(parse_success:helloworld.HelloReply)
+  return true;
+failure:
+  // @@protoc_insertion_point(parse_failure:helloworld.HelloReply)
+  return false;
+#undef DO_
+}
+
+void HelloReply::SerializeWithCachedSizes(
+    ::google::protobuf::io::CodedOutputStream* output) const {
+  // @@protoc_insertion_point(serialize_start:helloworld.HelloReply)
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  (void) cached_has_bits;
+
+  // string message = 1;
+  if (this->message().size() > 0) {
+    ::google::protobuf::internal::WireFormatLite::VerifyUtf8String(
+      this->message().data(), static_cast<int>(this->message().length()),
+      ::google::protobuf::internal::WireFormatLite::SERIALIZE,
+      "helloworld.HelloReply.message");
+    ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
+      1, this->message(), output);
+  }
+
+  if ((_internal_metadata_.have_unknown_fields() &&  ::google::protobuf::internal::GetProto3PreserveUnknownsDefault())) {
+    ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
+        (::google::protobuf::internal::GetProto3PreserveUnknownsDefault()   ? _internal_metadata_.unknown_fields()   : _internal_metadata_.default_instance()), output);
+  }
+  // @@protoc_insertion_point(serialize_end:helloworld.HelloReply)
+}
+
+::google::protobuf::uint8* HelloReply::InternalSerializeWithCachedSizesToArray(
+    bool deterministic, ::google::protobuf::uint8* target) const {
+  (void)deterministic; // Unused
+  // @@protoc_insertion_point(serialize_to_array_start:helloworld.HelloReply)
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  (void) cached_has_bits;
+
+  // string message = 1;
+  if (this->message().size() > 0) {
+    ::google::protobuf::internal::WireFormatLite::VerifyUtf8String(
+      this->message().data(), static_cast<int>(this->message().length()),
+      ::google::protobuf::internal::WireFormatLite::SERIALIZE,
+      "helloworld.HelloReply.message");
+    target =
+      ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
+        1, this->message(), target);
+  }
+
+  if ((_internal_metadata_.have_unknown_fields() &&  ::google::protobuf::internal::GetProto3PreserveUnknownsDefault())) {
+    target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
+        (::google::protobuf::internal::GetProto3PreserveUnknownsDefault()   ? _internal_metadata_.unknown_fields()   : _internal_metadata_.default_instance()), target);
+  }
+  // @@protoc_insertion_point(serialize_to_array_end:helloworld.HelloReply)
+  return target;
+}
+
+size_t HelloReply::ByteSizeLong() const {
+// @@protoc_insertion_point(message_byte_size_start:helloworld.HelloReply)
+  size_t total_size = 0;
+
+  if ((_internal_metadata_.have_unknown_fields() &&  ::google::protobuf::internal::GetProto3PreserveUnknownsDefault())) {
+    total_size +=
+      ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
+        (::google::protobuf::internal::GetProto3PreserveUnknownsDefault()   ? _internal_metadata_.unknown_fields()   : _internal_metadata_.default_instance()));
+  }
+  // string message = 1;
+  if (this->message().size() > 0) {
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->message());
+  }
+
+  int cached_size = ::google::protobuf::internal::ToCachedSize(total_size);
+  SetCachedSize(cached_size);
+  return total_size;
+}
+
+void HelloReply::MergeFrom(const ::google::protobuf::Message& from) {
+// @@protoc_insertion_point(generalized_merge_from_start:helloworld.HelloReply)
+  GOOGLE_DCHECK_NE(&from, this);
+  const HelloReply* source =
+      ::google::protobuf::internal::DynamicCastToGenerated<const HelloReply>(
+          &from);
+  if (source == NULL) {
+  // @@protoc_insertion_point(generalized_merge_from_cast_fail:helloworld.HelloReply)
+    ::google::protobuf::internal::ReflectionOps::Merge(from, this);
+  } else {
+  // @@protoc_insertion_point(generalized_merge_from_cast_success:helloworld.HelloReply)
+    MergeFrom(*source);
+  }
+}
+
+void HelloReply::MergeFrom(const HelloReply& from) {
+// @@protoc_insertion_point(class_specific_merge_from_start:helloworld.HelloReply)
+  GOOGLE_DCHECK_NE(&from, this);
+  _internal_metadata_.MergeFrom(from._internal_metadata_);
+  ::google::protobuf::uint32 cached_has_bits = 0;
+  (void) cached_has_bits;
+
+  if (from.message().size() > 0) {
+
+    message_.AssignWithDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), from.message_);
+  }
+}
+
+void HelloReply::CopyFrom(const ::google::protobuf::Message& from) {
+// @@protoc_insertion_point(generalized_copy_from_start:helloworld.HelloReply)
+  if (&from == this) return;
+  Clear();
+  MergeFrom(from);
+}
+
+void HelloReply::CopyFrom(const HelloReply& from) {
+// @@protoc_insertion_point(class_specific_copy_from_start:helloworld.HelloReply)
+  if (&from == this) return;
+  Clear();
+  MergeFrom(from);
+}
+
+bool HelloReply::IsInitialized() const {
+  return true;
+}
+
+void HelloReply::Swap(HelloReply* other) {
+  if (other == this) return;
+  InternalSwap(other);
+}
+void HelloReply::InternalSwap(HelloReply* other) {
+  using std::swap;
+  message_.Swap(&other->message_, &::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+    GetArenaNoVirtual());
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+}
+
+::google::protobuf::Metadata HelloReply::GetMetadata() const {
+  protobuf_helloworld_2eproto::protobuf_AssignDescriptorsOnce();
+  return ::protobuf_helloworld_2eproto::file_level_metadata[kIndexInFileMessages];
+}
+
+
+// @@protoc_insertion_point(namespace_scope)
+}  // namespace helloworld
+namespace google {
+namespace protobuf {
+template<> GOOGLE_PROTOBUF_ATTRIBUTE_NOINLINE ::helloworld::HelloRequest* Arena::CreateMaybeMessage< ::helloworld::HelloRequest >(Arena* arena) {
+  return Arena::CreateInternal< ::helloworld::HelloRequest >(arena);
+}
+template<> GOOGLE_PROTOBUF_ATTRIBUTE_NOINLINE ::helloworld::HelloReply* Arena::CreateMaybeMessage< ::helloworld::HelloReply >(Arena* arena) {
+  return Arena::CreateInternal< ::helloworld::HelloReply >(arena);
+}
+}  // namespace protobuf
+}  // namespace google
+
+// @@protoc_insertion_point(global_scope)
diff --git a/examples/cpp/metadata/helloworld.pb.h b/examples/cpp/metadata/helloworld.pb.h
new file mode 100644
index 0000000000..57f6817e31
--- /dev/null
+++ b/examples/cpp/metadata/helloworld.pb.h
@@ -0,0 +1,419 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: helloworld.proto
+
+#ifndef PROTOBUF_INCLUDED_helloworld_2eproto
+#define PROTOBUF_INCLUDED_helloworld_2eproto
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+#if GOOGLE_PROTOBUF_VERSION < 3006001
+#error This file was generated by a newer version of protoc which is
+#error incompatible with your Protocol Buffer headers.  Please update
+#error your headers.
+#endif
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#error This file was generated by an older version of protoc which is
+#error incompatible with your Protocol Buffer headers.  Please
+#error regenerate this file with a newer version of protoc.
+#endif
+
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/arena.h>
+#include <google/protobuf/arenastring.h>
+#include <google/protobuf/generated_message_table_driven.h>
+#include <google/protobuf/generated_message_util.h>
+#include <google/protobuf/inlined_string_field.h>
+#include <google/protobuf/metadata.h>
+#include <google/protobuf/message.h>
+#include <google/protobuf/repeated_field.h>  // IWYU pragma: export
+#include <google/protobuf/extension_set.h>  // IWYU pragma: export
+#include <google/protobuf/unknown_field_set.h>
+// @@protoc_insertion_point(includes)
+#define PROTOBUF_INTERNAL_EXPORT_protobuf_helloworld_2eproto 
+
+namespace protobuf_helloworld_2eproto {
+// Internal implementation detail -- do not use these members.
+struct TableStruct {
+  static const ::google::protobuf::internal::ParseTableField entries[];
+  static const ::google::protobuf::internal::AuxillaryParseTableField aux[];
+  static const ::google::protobuf::internal::ParseTable schema[2];
+  static const ::google::protobuf::internal::FieldMetadata field_metadata[];
+  static const ::google::protobuf::internal::SerializationTable serialization_table[];
+  static const ::google::protobuf::uint32 offsets[];
+};
+void AddDescriptors();
+}  // namespace protobuf_helloworld_2eproto
+namespace helloworld {
+class HelloReply;
+class HelloReplyDefaultTypeInternal;
+extern HelloReplyDefaultTypeInternal _HelloReply_default_instance_;
+class HelloRequest;
+class HelloRequestDefaultTypeInternal;
+extern HelloRequestDefaultTypeInternal _HelloRequest_default_instance_;
+}  // namespace helloworld
+namespace google {
+namespace protobuf {
+template<> ::helloworld::HelloReply* Arena::CreateMaybeMessage<::helloworld::HelloReply>(Arena*);
+template<> ::helloworld::HelloRequest* Arena::CreateMaybeMessage<::helloworld::HelloRequest>(Arena*);
+}  // namespace protobuf
+}  // namespace google
+namespace helloworld {
+
+// ===================================================================
+
+class HelloRequest : public ::google::protobuf::Message /* @@protoc_insertion_point(class_definition:helloworld.HelloRequest) */ {
+ public:
+  HelloRequest();
+  virtual ~HelloRequest();
+
+  HelloRequest(const HelloRequest& from);
+
+  inline HelloRequest& operator=(const HelloRequest& from) {
+    CopyFrom(from);
+    return *this;
+  }
+  #if LANG_CXX11
+  HelloRequest(HelloRequest&& from) noexcept
+    : HelloRequest() {
+    *this = ::std::move(from);
+  }
+
+  inline HelloRequest& operator=(HelloRequest&& from) noexcept {
+    if (GetArenaNoVirtual() == from.GetArenaNoVirtual()) {
+      if (this != &from) InternalSwap(&from);
+    } else {
+      CopyFrom(from);
+    }
+    return *this;
+  }
+  #endif
+  static const ::google::protobuf::Descriptor* descriptor();
+  static const HelloRequest& default_instance();
+
+  static void InitAsDefaultInstance();  // FOR INTERNAL USE ONLY
+  static inline const HelloRequest* internal_default_instance() {
+    return reinterpret_cast<const HelloRequest*>(
+               &_HelloRequest_default_instance_);
+  }
+  static constexpr int kIndexInFileMessages =
+    0;
+
+  void Swap(HelloRequest* other);
+  friend void swap(HelloRequest& a, HelloRequest& b) {
+    a.Swap(&b);
+  }
+
+  // implements Message ----------------------------------------------
+
+  inline HelloRequest* New() const final {
+    return CreateMaybeMessage<HelloRequest>(NULL);
+  }
+
+  HelloRequest* New(::google::protobuf::Arena* arena) const final {
+    return CreateMaybeMessage<HelloRequest>(arena);
+  }
+  void CopyFrom(const ::google::protobuf::Message& from) final;
+  void MergeFrom(const ::google::protobuf::Message& from) final;
+  void CopyFrom(const HelloRequest& from);
+  void MergeFrom(const HelloRequest& from);
+  void Clear() final;
+  bool IsInitialized() const final;
+
+  size_t ByteSizeLong() const final;
+  bool MergePartialFromCodedStream(
+      ::google::protobuf::io::CodedInputStream* input) final;
+  void SerializeWithCachedSizes(
+      ::google::protobuf::io::CodedOutputStream* output) const final;
+  ::google::protobuf::uint8* InternalSerializeWithCachedSizesToArray(
+      bool deterministic, ::google::protobuf::uint8* target) const final;
+  int GetCachedSize() const final { return _cached_size_.Get(); }
+
+  private:
+  void SharedCtor();
+  void SharedDtor();
+  void SetCachedSize(int size) const final;
+  void InternalSwap(HelloRequest* other);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return NULL;
+  }
+  inline void* MaybeArenaPtr() const {
+    return NULL;
+  }
+  public:
+
+  ::google::protobuf::Metadata GetMetadata() const final;
+
+  // nested types ----------------------------------------------------
+
+  // accessors -------------------------------------------------------
+
+  // string name = 1;
+  void clear_name();
+  static const int kNameFieldNumber = 1;
+  const ::std::string& name() const;
+  void set_name(const ::std::string& value);
+  #if LANG_CXX11
+  void set_name(::std::string&& value);
+  #endif
+  void set_name(const char* value);
+  void set_name(const char* value, size_t size);
+  ::std::string* mutable_name();
+  ::std::string* release_name();
+  void set_allocated_name(::std::string* name);
+
+  // @@protoc_insertion_point(class_scope:helloworld.HelloRequest)
+ private:
+
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
+  mutable ::google::protobuf::internal::CachedSize _cached_size_;
+  friend struct ::protobuf_helloworld_2eproto::TableStruct;
+};
+// -------------------------------------------------------------------
+
+class HelloReply : public ::google::protobuf::Message /* @@protoc_insertion_point(class_definition:helloworld.HelloReply) */ {
+ public:
+  HelloReply();
+  virtual ~HelloReply();
+
+  HelloReply(const HelloReply& from);
+
+  inline HelloReply& operator=(const HelloReply& from) {
+    CopyFrom(from);
+    return *this;
+  }
+  #if LANG_CXX11
+  HelloReply(HelloReply&& from) noexcept
+    : HelloReply() {
+    *this = ::std::move(from);
+  }
+
+  inline HelloReply& operator=(HelloReply&& from) noexcept {
+    if (GetArenaNoVirtual() == from.GetArenaNoVirtual()) {
+      if (this != &from) InternalSwap(&from);
+    } else {
+      CopyFrom(from);
+    }
+    return *this;
+  }
+  #endif
+  static const ::google::protobuf::Descriptor* descriptor();
+  static const HelloReply& default_instance();
+
+  static void InitAsDefaultInstance();  // FOR INTERNAL USE ONLY
+  static inline const HelloReply* internal_default_instance() {
+    return reinterpret_cast<const HelloReply*>(
+               &_HelloReply_default_instance_);
+  }
+  static constexpr int kIndexInFileMessages =
+    1;
+
+  void Swap(HelloReply* other);
+  friend void swap(HelloReply& a, HelloReply& b) {
+    a.Swap(&b);
+  }
+
+  // implements Message ----------------------------------------------
+
+  inline HelloReply* New() const final {
+    return CreateMaybeMessage<HelloReply>(NULL);
+  }
+
+  HelloReply* New(::google::protobuf::Arena* arena) const final {
+    return CreateMaybeMessage<HelloReply>(arena);
+  }
+  void CopyFrom(const ::google::protobuf::Message& from) final;
+  void MergeFrom(const ::google::protobuf::Message& from) final;
+  void CopyFrom(const HelloReply& from);
+  void MergeFrom(const HelloReply& from);
+  void Clear() final;
+  bool IsInitialized() const final;
+
+  size_t ByteSizeLong() const final;
+  bool MergePartialFromCodedStream(
+      ::google::protobuf::io::CodedInputStream* input) final;
+  void SerializeWithCachedSizes(
+      ::google::protobuf::io::CodedOutputStream* output) const final;
+  ::google::protobuf::uint8* InternalSerializeWithCachedSizesToArray(
+      bool deterministic, ::google::protobuf::uint8* target) const final;
+  int GetCachedSize() const final { return _cached_size_.Get(); }
+
+  private:
+  void SharedCtor();
+  void SharedDtor();
+  void SetCachedSize(int size) const final;
+  void InternalSwap(HelloReply* other);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return NULL;
+  }
+  inline void* MaybeArenaPtr() const {
+    return NULL;
+  }
+  public:
+
+  ::google::protobuf::Metadata GetMetadata() const final;
+
+  // nested types ----------------------------------------------------
+
+  // accessors -------------------------------------------------------
+
+  // string message = 1;
+  void clear_message();
+  static const int kMessageFieldNumber = 1;
+  const ::std::string& message() const;
+  void set_message(const ::std::string& value);
+  #if LANG_CXX11
+  void set_message(::std::string&& value);
+  #endif
+  void set_message(const char* value);
+  void set_message(const char* value, size_t size);
+  ::std::string* mutable_message();
+  ::std::string* release_message();
+  void set_allocated_message(::std::string* message);
+
+  // @@protoc_insertion_point(class_scope:helloworld.HelloReply)
+ private:
+
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  ::google::protobuf::internal::ArenaStringPtr message_;
+  mutable ::google::protobuf::internal::CachedSize _cached_size_;
+  friend struct ::protobuf_helloworld_2eproto::TableStruct;
+};
+// ===================================================================
+
+
+// ===================================================================
+
+#ifdef __GNUC__
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif  // __GNUC__
+// HelloRequest
+
+// string name = 1;
+inline void HelloRequest::clear_name() {
+  name_.ClearToEmptyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline const ::std::string& HelloRequest::name() const {
+  // @@protoc_insertion_point(field_get:helloworld.HelloRequest.name)
+  return name_.GetNoArena();
+}
+inline void HelloRequest::set_name(const ::std::string& value) {
+  
+  name_.SetNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value);
+  // @@protoc_insertion_point(field_set:helloworld.HelloRequest.name)
+}
+#if LANG_CXX11
+inline void HelloRequest::set_name(::std::string&& value) {
+  
+  name_.SetNoArena(
+    &::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::move(value));
+  // @@protoc_insertion_point(field_set_rvalue:helloworld.HelloRequest.name)
+}
+#endif
+inline void HelloRequest::set_name(const char* value) {
+  GOOGLE_DCHECK(value != NULL);
+  
+  name_.SetNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value));
+  // @@protoc_insertion_point(field_set_char:helloworld.HelloRequest.name)
+}
+inline void HelloRequest::set_name(const char* value, size_t size) {
+  
+  name_.SetNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      ::std::string(reinterpret_cast<const char*>(value), size));
+  // @@protoc_insertion_point(field_set_pointer:helloworld.HelloRequest.name)
+}
+inline ::std::string* HelloRequest::mutable_name() {
+  
+  // @@protoc_insertion_point(field_mutable:helloworld.HelloRequest.name)
+  return name_.MutableNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline ::std::string* HelloRequest::release_name() {
+  // @@protoc_insertion_point(field_release:helloworld.HelloRequest.name)
+  
+  return name_.ReleaseNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline void HelloRequest::set_allocated_name(::std::string* name) {
+  if (name != NULL) {
+    
+  } else {
+    
+  }
+  name_.SetAllocatedNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name);
+  // @@protoc_insertion_point(field_set_allocated:helloworld.HelloRequest.name)
+}
+
+// -------------------------------------------------------------------
+
+// HelloReply
+
+// string message = 1;
+inline void HelloReply::clear_message() {
+  message_.ClearToEmptyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline const ::std::string& HelloReply::message() const {
+  // @@protoc_insertion_point(field_get:helloworld.HelloReply.message)
+  return message_.GetNoArena();
+}
+inline void HelloReply::set_message(const ::std::string& value) {
+  
+  message_.SetNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value);
+  // @@protoc_insertion_point(field_set:helloworld.HelloReply.message)
+}
+#if LANG_CXX11
+inline void HelloReply::set_message(::std::string&& value) {
+  
+  message_.SetNoArena(
+    &::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::move(value));
+  // @@protoc_insertion_point(field_set_rvalue:helloworld.HelloReply.message)
+}
+#endif
+inline void HelloReply::set_message(const char* value) {
+  GOOGLE_DCHECK(value != NULL);
+  
+  message_.SetNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value));
+  // @@protoc_insertion_point(field_set_char:helloworld.HelloReply.message)
+}
+inline void HelloReply::set_message(const char* value, size_t size) {
+  
+  message_.SetNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      ::std::string(reinterpret_cast<const char*>(value), size));
+  // @@protoc_insertion_point(field_set_pointer:helloworld.HelloReply.message)
+}
+inline ::std::string* HelloReply::mutable_message() {
+  
+  // @@protoc_insertion_point(field_mutable:helloworld.HelloReply.message)
+  return message_.MutableNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline ::std::string* HelloReply::release_message() {
+  // @@protoc_insertion_point(field_release:helloworld.HelloReply.message)
+  
+  return message_.ReleaseNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline void HelloReply::set_allocated_message(::std::string* message) {
+  if (message != NULL) {
+    
+  } else {
+    
+  }
+  message_.SetAllocatedNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), message);
+  // @@protoc_insertion_point(field_set_allocated:helloworld.HelloReply.message)
+}
+
+#ifdef __GNUC__
+  #pragma GCC diagnostic pop
+#endif  // __GNUC__
+// -------------------------------------------------------------------
+
+
+// @@protoc_insertion_point(namespace_scope)
+
+}  // namespace helloworld
+
+// @@protoc_insertion_point(global_scope)
+
+#endif  // PROTOBUF_INCLUDED_helloworld_2eproto
diff --git a/examples/cpp/metadata/helloworld.pb.o b/examples/cpp/metadata/helloworld.pb.o
new file mode 100644
index 0000000000..85671e8aaa
--- /dev/null
+++ b/examples/cpp/metadata/helloworld.pb.o