Forward metadata with message

Hi!

I am looking for a way to forward meta-data along with the message it belong. The goal is to get the 'User-Id' in a worker behind a load balancer which own the secure socket.

Here is a simple example, you can see the metadata disappear after being forwarded. I am not sure: is this metadata 'vanishment' a bug or a feature? Is there any workaround?

#include "zmqpp/zmqpp.hpp"
#include "zmqpp/curve.hpp"

int main()
{
    zmqpp::curve::keypair client_keypair = zmqpp::curve::generate_keypair();
    zmqpp::curve::keypair server_keypair = zmqpp::curve::generate_keypair();

    std::cout << "Client Public Key :" << client_keypair.public_key << std::endl;
    std::cout << "Server Public Key :" << server_keypair.public_key << std::endl;

    zmqpp::context context;

    zmqpp::auth authenticator(context);
    authenticator.set_verbose(false);
    authenticator.configure_curve(client_keypair.public_key);

    zmqpp::socket curve_rep(context, zmqpp::socket_type::rep);
    curve_rep.set(zmqpp::socket_option::curve_server, true);
    curve_rep.set(zmqpp::socket_option::curve_secret_key, server_keypair.secret_key);
    curve_rep.bind("tcp://127.0.0.1:4242");

    zmqpp::socket curve_req(context, zmqpp::socket_type::req);
    curve_req.set(zmqpp::socket_option::curve_server_key, server_keypair.public_key);
    curve_req.set(zmqpp::socket_option::curve_public_key, client_keypair.public_key);
    curve_req.set(zmqpp::socket_option::curve_secret_key, client_keypair.secret_key);
    curve_req.connect("tcp://127.0.0.1:4242");

    zmqpp::socket internal_rep(context, zmqpp::socket_type::rep);
    internal_rep.bind("inproc://clear");

    zmqpp::socket internal_req(context, zmqpp::socket_type::req);
    internal_req.connect("inproc://clear");

    {
        zmqpp::message msg;
        msg << "Hello";
        curve_req.send(msg);
    }

    {
        zmqpp::message msg;
        curve_rep.receive(msg);

        // read User-Id
        std::string user_id;
        std::cout << "- Before forward: ";
        if (msg.get_property("User-Id", user_id))
            std::cout << user_id << std::endl;
        else
            std::cout << "No user id" << std::endl;

        // Forward message
        internal_req.send(msg);
    }

    {
        zmqpp::message msg;
        internal_rep.receive(msg);

        // read User-Id
        std::string user_id;
        std::cout << "- After forward: ";
        if (msg.get_property("User-Id", user_id))
            std::cout << user_id << std::endl;
        else
            std::cout << "No user id" << std::endl;

        std::string content;
        msg >> content;

        std::cout << "- Message: " << content << std::endl;
    }

    {
        zmqpp::message msg;
        msg << "world !";
        internal_rep.send(msg);
    }

    {
        zmqpp::message msg;
        internal_req.receive(msg);
        // Forward message
        curve_rep.send(msg);
    }

    {
        zmqpp::message msg;
        curve_req.receive(msg);
        std::cout << "- Message: " << msg.get<std::string>(0) << std::endl;
    }

    return 0;
}

Output:

Client Public Key :}-}3(fH/r!I/9*tJX0bN/TT]Y2Qd#{IqszYzBX.g
Server Public Key :!@kpBlDrmW@e3jW)q6FumkKGjv@7lU?y9mD(QWd8
auth: Starting ZAP Authentication Server
- Before forward: }-}3(fH/r!I/9*tJX0bN/TT]Y2Qd#{IqszYzBX.g
- After forward: No user id
- Message: Hello
- Message: world !
auth: Shutdown ZAP Authentication Server

zeromq / zmqpp

Forward metadata with message #150