NGINX, proxy_pass and SPA routing in HTML5 mode - html

Question

I have NGINX set up as a reverse proxy for a virtual network of docker containers running itself as a container. One of these containers serves an Angular 4 based SPA with client-side routing in HTML5 mode.
The application is mapped to location / on NGINX, so that http://server/ brings you to the SPA home screen.
server {
listen 80;
...
location / {
proxy_pass http://spa-server/;
}
location /other/ {
proxy_pass http://other/;
}
...
}
The Angular router changes the URL to http://server/home or other routes when navigating within the SPA.
However, when I try to access these URLs directly, a 404 is returned. This error originates from the spa-server, because it obviously does not have any content for these routes.
The examples I found for configuring NGINX to support this scenario always assume that the SPA's static content is served directly from NGINX and thus try_files is a viable option.
How is it possible to forward any unknown URLs to the SPA so that it can handle them itself?

Answer 1

The solution that works for me is to add the directives proxy_intercept_errors and error_page to the location / in NGINX:
server {
listen 80;
...
location / {
proxy_pass http://spa-server/;
proxy_intercept_errors on;
error_page 404 = /index.html;
}
location /other/ {
proxy_pass http://other/;
}
...
}
Now, NGINX will return the /index.html i.e. the SPA from the spa-server whenever an unknown URL is requested. Still, the URL is available to Angular and the router will immediately resolve it within the SPA.
Of course, now the SPA is responsible for handling "real" 404s. Fortunately, this is not a problem and a good practice within the SPA anyway.
UPDATE: Thanks to #dan