upstream backend {
backend1.example.com server weight = 5;
server backend2.example.com max_fails fail_timeout = 10s = 5;
backend3.example.com server;
backend4.example.com server down;
backend5.example.com backup server;
}

upstream fallback {
fallback1.example.com server: 8081;
}


server {
%
proxy_intercept_errors on;
...
Filming location
...
error_page 502 @ fallback;
proxy_next_upstream HTTP_500 http_502 http_503 http_504 timeout error invalid_header;
proxy_pass http://backend;