How to get method name in gRPC C++ interceptor?

Documentation suggests that one of the most common applications of gRPC interceptors is logging. However, I cannot figure out how I can access the name of the method being called in grpcpp.

Is this a missing feature (grpc::experimental and all), or I am missing something?

GitHub issue #17520 seems to be addressing my point exactly, and it was closed with the following reply:

What you want can be achieved with the interception API.

Please refer https://github.com/grpc/grpc/blob/master/include/grpcpp/impl/codegen/interceptor.h for documentation

I couldn't find anything in <grpcpp/support/interceptor.h>, nor in the version of grpcpp/impl/codegen/interceptor.h at the time of maintainer's response.

Solution

You do need to use experimental features to get the RPC name inside an interceptor. Here is how I managed to print the method name when the RPC is called :

#include <grpcpp/support/interceptor.h>
#include <grpcpp/support/server_interceptor.h>

#include <string>


class LoggingInterceptor final : public grpc::experimental::Interceptor {
public:
    explicit LoggingInterceptor(grpc::experimental::ServerRpcInfo *info) {
        const std::string method = info->method();

        if (method == "unknown") {
            std::cout << "Unimplemented Rpc called" << std::endl;
            return;
        }

        std::cout << "Rpc called : " << method << std::endl;
    }

    void Intercept(grpc::experimental::InterceptorBatchMethods *methods) override {
        methods->Proceed();
    }
};

class LoggingInterceptorFactory final : public grpc::experimental::ServerInterceptorFactoryInterface {
public:
    grpc::experimental::Interceptor *CreateServerInterceptor(grpc::experimental::ServerRpcInfo *info) override {
        return new LoggingInterceptor(info);
    }
};

And when creating your ServerBuilder :

std::vector<std::unique_ptr<grpc::experimental::ServerInterceptorFactoryInterface>> creators;
creators.push_back(std::make_unique<LoggingInterceptorFactory>());
builder.experimental().SetInterceptorCreators(std::move(creators));