Re: [Loadbalancing] error 404 but backend work fine

2018/02/17 12:46:28 [debug] 15406#15406: *219 http upstream request: "/?"
[...]
2018/02/17 12:46:28 [debug] 15406#15406: *219 http proxy status 404 "404 Not Found"
Your upstream does not like /?

2018/02/17 12:46:28 [debug] 15406#15406: *219 http proxy header: "Server: Microsoft-HTTPAPI/2.0"
This only shows it's not a nginx thing returning 404.