I have this requirement. I want to use nginx as the reverse proxy, which listen on address A and forward the request to the backend server with address B. However, if B is down, I want the request to be sent to address C. The question is, address B is https and address C is http. But for the argument of proxy_pass module, I can only write one prefix (either "http" or "https").

upstream backend {
server <addr B ip>:<addr B port>;
server <addr C ip>:<addr C port> backup;
}

location / {
proxy_pass http://backend; #here, only one prefix is allowed
}

So how to config to meet my requirements? Or here I shouldn't use upstream but other approach?

Thanks.