Ooo, so my setup should be like this? How this setup reflect API? Because some API calls requires server_id. I just provide webserver X ID? As I understand master server would be like communication centrale between all servers, nothing more.
Yes, you always have a master server that controls the whole multiserver system. As I mentioned, the master server can provide services and it often does on smaller systems, but it can also be standalone, which has benefits when it comes to maintenance and scalability on larger setups. You always connect to the API on master server only. You have server_id parameter in the function calls, as you would not be able to tell the system which server something shall be created on otherwise.