How to create a reverse proxy to host specified in url

I always wrestle with a problem for hours before giving up and posting a question - only to solve my own problem minutes after posting ...

For those interested, the solution is not to use ProxyPassReverse, but rather to use the Header directive - it' let's you mess with outbound headers. In this case, I can capture the Location response header and run a regex on it to fix the URL's protocol:

ProxyPreserveHost       on
RewriteEngine           on
RewriteRule ^/app$ /app/ [PT]
ProxyPass /app ajp://localhost:8009/app
Header edit Location ^http(\:\/\/proxy.*)$ https$1

Voila!

If apache complains, it might be that mod_headers is not yet enabled: a2enmod headers

Any redirect to localhost doesn't make sense from a remote system (e.g. client's Web browser). So the rewrite flags permanent (301) or redirect (302) are not usable in your case.

Please try following setup using a transparent rewrite rule:

location  /foo {
  rewrite /foo/(.*) /$1  break;
  proxy_pass         http://localhost:3200;
  proxy_redirect     off;
  proxy_set_header   Host $host;
}

Use curl -i to test your rewrites. A very subtle change to the rule can cause nginx to perform a redirect.