http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_next_upstream
http://ohmycat.me/2017/06/12/nginx-uri-change.html
http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_next_upstream
http://ohmycat.me/2017/06/12/nginx-uri-change.html