google protobuf compiler doesn't generate class for service tag?

Question

I'm trying to use protobuf to generate a service using RpcChannel and RpcController. I referred to language guide of google protobuf and:

I've got sample proto file like this:

syntax = "proto2";

message SearchRequest
{
    required string Request = 1;
}

message SearchResponse
{
    required string Response = 2;
}

service SearchService {
    rpc Search (SearchRequest) returns (SearchResponse);
}

Then I compiled it with:

protoc --cpp_out=./ examples.proto

I got .h and .cc files. But when I search the generated code, I only found classes for "Request" and "Response", but not a class for "SearchService":

examples.pb.h:class SearchRequest;
examples.pb.h:class SearchResponse;
examples.pb.h:class SearchRequest : public ::google::protobuf::Message {
examples.pb.h:  // @@protoc_insertion_point(class_scope:SearchRequest)
examples.pb.h:class SearchResponse : public ::google::protobuf::Message {
examples.pb.h:  // @@protoc_insertion_point(class_scope:SearchResponse)

The language guide web-page provided an example(https://developers.google.com/protocol-buffers/docs/proto#services) which requires to use class of "SearchService": but in the generated code, there's no search service. The guide didn't provide a complete sample of RpcChannel/RpcController usages.

So how can I fix the example to make it work? I searched google but didn't find any good cpp example that gives a complete sample of how RpcChannel/RpcController could work. Any hints or links?

Thanks!

Answer 1

protobuf does not offer RPC implementation by itself; you should use plugin interface to create your own, or use grpc.

For example, grpc uses grpc_cpp_plugin plugin for it.

$ protoc -I ../../protos --grpc_out=. --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` ../../protos/route_guide.proto

https://github.com/grpc/grpc/blob/master/examples/cpp/cpptutorial.md