Can NGINX change the response code after a proxy_pass? - amazon-web-services

Question

So I have an internal API server namespaced under /api/, and I want to pass all other requests to an Amazon S3 static site using proxy_pass. This all works fine, it's just since Amazon is serving a single page app, I want to always return the same HTML file. They way I did this with the S3 server, was to set the index and error page as the same file. It all looks fine on the surface, but for all other requests besides /, the S3 instance returns a 404. Can I use NGINX to change this to a 200 before returning it to the client?
server {
listen 80;
server_name example.com;
location /api/ {
# serve internal app
}
location / {
proxy_pass http://example.amazonaws.com/;
# ALWAYS RETURN A 200
}
}

Answer 1

You should be able to use the error_page and proxy_intercept_errors directives to achieve this. Something like this should do the trick.
location / {
proxy_pass http://example.amazonaws.com/;
proxy_intercept_errors on;
error_page 404 =302 /your_html_file
}
error_page
proxy_intercept_errors

Answer 2

You can internally rewrite all URLs to the document you want served. This avoids the error handling cycle and problematic redirects.
It would be something like (untested):
location / {
proxy_pass http://example.amazonaws.com/;
rewrite ^.* /index.html
}
Note that you will want to only use full or root-relative URLs in your doc, because you don't know if the docs is served from a subdirectory.
You'd also be wise to have JS code validate the URL and optionally redirect to one you consider valid. Otherwise 3rd party sites could link to offensive URLs and get them in search indexes!