What should my Nginx rewrite rules be for Rails with Passenger for page caching in a subdirectory?

[Ian Terrell]

I'm using Nginx 0.7.64, Passenger 2.2.9, Rails 2.3.5. I have my page
caching directory set to /public/cache, and I'd like to be able to
serve cached pages when requested over HTTP, but always hit the Rails
app when requested over HTTPS.

The bulk of my config looks like this:

server {
  listen 80;
  server_name website.com www.website.com;
  proxy_set_header X-Forwarded-Proto http;
  root /home/deploy/website/current/public;
  passenger_enabled on;

  if (-f $document_root/cache/$request_filename.html) {
    rewrite (.*) $document_root/cache/$1.html break;
  }
}

server {
  listen       443;
  server_name website.com www.website.com;
  root /home/deploy/website/current/public;
  passenger_enabled on;
  proxy_set_header X-Forwarded-Proto https;

  ssl                  on;
  ssl_certificate      /home/deploy/website/shared/ssl/
www.website.com.combined.crt;
  ssl_certificate_key  /home/deploy/website/shared/ssl/
www.website.com.key;
}

I anticipate that when I request website.com/about, I should be
served /public/cache/about.html, but instead I hit the Rails server
(tailing the log shows it).

Thinking I might have an inappropriate slash (and not seeing
$document_root in most examples), I've also tried all of the following
variations, none of which work:

if (-f cache$request_filename.html) {
  rewrite (.*) cache$1.html break;
}

if (-f /cache$request_filename.html) {
  rewrite (.*) /cache$1.html break;
}

if (-f cache/$request_filename.html) {
  rewrite (.*) cache/$1.html break;
}

if (-f /cache/$request_filename.html) {
  rewrite (.*) /cache/$1.html break;
}

I've also thrown the root, passenger_enabled, and rewrite rules into a
separate location / block, but that also does not work. I've also
reordered the statements so that passenger_enabled would come at the
end. I've also tried using $uri. Clearly I'm misunderstanding
something!

This is a little bit simplified, since I also have an XML api that is
cached in places (presumably the rewrite rule will be the same except
for the .html parts), as well as I'll need to serve public/cache/
index.html when the root of website.com is requested. I just want to
get any single piece of it working. :)

The conditional

if (-f $document_root/cache$request_uri.html)

does seem to work! However, what I would think would be the rewrite
does not work! Trying

if (-f $document_root/cache$request_uri.html) {
  rewrite (.*) /cache$1.html break;
  break;
}

Rewrites the URL as /cache/cache/about.html.html and sends it to
Rails, which promptly barfs. It looks doubled, yes! But if I rewrite
to just /cache$1 it sends /cache/cache/about to Rails, and $1.html
sends /about.html.html to Rails, and just $1 sends simply /about which
goes to Rails and does not hit the cache. Obviously this is not
correct behavior Is Nginx rewriting it and then Passenger is rewriting
it, too?

Any help is appreciated!