Nginx redirect reverse proxy 404 - nginx

Question

I have the following Nginx server block:
server {
listen 80;
listen [::]:80;
server_name example.com;
root /usr/share/nginx/html;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_pass http://localhost/page-1/;
}
}
I would like that when the user gets a 404 error on example.com, the proxy_pass should change to direct to http://localhost/example-404/.
However, this server block and the one for http://localhost both have the same root so alternatively it could just point to /example-404/ internally, I'm not sure which is easier to do. Either way, I want the address in the browser's address bar to stay the same.
The reason I want this is that there will be a different 404 page if accessing the server from http://localhost directly. I would really appreciate anyone's thoughts on this!

Answer 1

You can use different vhosts to give different results depending on how the user is accessing the server. I'd imagine something like this might work:
server {
listen 80;
server_name example.com;
root /usr/share/nginx/html;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_intercept_errors on;
error_page 404 = #errors;
proxy_pass http://localhost/page-1/;
}
location #errors {
root /usr/share/nginx/errors/example.com.404.html;
}
}
server {
listen 80;
server_name localhost;
root /usr/share/nginx/html;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_intercept_errors on;
error_page 404 = #errors;
proxy_pass http://localhost/page-1/;
}
location #errors {
root /usr/share/nginx/errors/localhost.404.html;
}
}