Method set_index

example/selective_echo_c++/server.cpp:46–49

    EchoServiceImpl() : _index(0) {}
    virtual ~EchoServiceImpl() {}
    void set_index(size_t index, int64_t sleep_us) { 
        _index = index; 
        _sleep_us = sleep_us;
    }
    virtual void Echo(google::protobuf::RpcController* cntl_base,
                      const example::EchoRequest* request,
                      example::EchoResponse* response,