Reverse proxy from HTTPS to HTTP from an unknown source location

[speedfirst]

normally, your backend server should do the redirect in a relative URL,
unless you really want to redirect to another host. That's something
like 

   sendRedirct("/redirectTo/anotherPath");

In this way, the backend server will send redirect URL with the HOST
header specified in the request. In your case, it should be:

   Location: http://mybackendserver:8080/redirectTo/anotherPath

If you don't use "proxy_add_header Host xxxx", nginx will the argument
specified in "proxy_pass" as the Host to the backend. And in this case,
the config:

   proxy_redirect default;

Or
   proxy_redirect http://mybackendserver:8080/      /;

will automatically handle everything.

If you insist to let the backend server do the FULL URL redirection, you
have to manually specify all possible proxy_redirect like this:

   proxy_redirect <FULL URL 1> /;
   proxy_redirect <FULL URL 2> /;
   ...

By the way, the first argument of "proxy_redirect" doesn't support var.
If you specify a var, nginx doesn't recognize it, and doesn't report an
error too. It just considers it as literal.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,212823,212827#msg-212827