nginx - Serve file conditionally without redirection - nginx

Question

I'm currently building a multi-domain cms in rails. Since this content is the same until the next change I'd like to do caching via static files.
The public directory with some cached pages of foo.com and baz.com (/ and /asdf in both cases):
public/
assets/
cms.css
sites/
foo.com/
assets/
screen-some-hash.min.css
index.html
asdf/
index.html
baz.com/
assets/
screen-some-hash.min.css
index.html
asdf/
index.html
What I want to do is the following:
redirect www to non-www (works)
If the requests contains a subdomain (cms, admin, whatever):
If the path contains /assets serve the file in public/assets and set the expire stuff to 30d or so. No problem here since /assets = public/assets and public/ is the passenger root.
Everything else: handle it via rails, no special caching or anything required.
For all other requests (meaning no subdomain):
If the path contains /assets serve the file in public/sites/$host$request_uri and set the expire stuff to 30d or so. Everything else: check for public/sites/$host$request_uri or fall back to the rails app.
I have never worked with nginx conditionals other than the www/non-www redirects and don't really know what I have to do for the conditions mentioned above. If at all possible, I don't want to use redirects for the cached stuff (ie redirection to /sites/foo.com/asdf), instead I'd like to have nginx serve this file directly when going to http://foo.com/asdf.
Further: I don't want to hardcode the hostnames as I'd like to handle an unknown amount of domains. I also don't want to use more than a single rails application for this.

Answer 1

Got something that works, not 100% but good enough for now.
server {
listen 80;
server_name *IP*;
if ($host ~* www\.(.*)) {
set $host_without_www $1;
rewrite ^(.*)$ http://$host_without_www$1 permanent;
}
location ~ ^/(assets)/ {
try_files /sites/$host$uri $uri #passenger;
root /home/cms/app/current/public;
gzip_static on;
expires max;
add_header Cache-Control public;
}
location / {
try_files /sites/$host$uri/index.html /sites/$host$uri $uri #passenger;
root /home/cms/app/current/public;
}
location #passenger {
access_log /home/cms/app/shared/log/access.log;
error_log /home/cms/app/shared/log/error.log;
root /home/cms/app/current/public;
passenger_enabled on;
}
}

Answer 2

For subdomains, this should do the trick:
server {
server_name ~^(?<subdomain>.+)\.example\.com$;
access_log /var/log/nginx/$subdomain/access.log;
location /assets {
expires max;
}
location / {
proxy_pass http://your_rails_app;
}
}
Not really sure about the proxy_pass setting as my only experience with Ruby apps is Gitlab, which I'm running this way. I hope this helps at least a little.
server {
server_name example.com;
location /assets {
root /public/sites/$hostname/$request_uri;
expires max;
}
}
You'll have to add your own settings and play with it a little as I don't have a chance to actually test it now. But it should show you the way.