Re: [Erlyaws-list] Questions about running not-as-root and proxying

[Brian C. <B.C...@po...>]

On Wed, Nov 26, 2008 at 02:40:02PM -0500, Bob Calco wrote:
> OK, proxying almost works. I am missing only one piece of the puzzle,  
> which is how to preserve the host name.
>
> <server www.example.com>
> 	port = 80
> 	listen = 1.2.3.4  # actual IP not shown
> 	rhost = localhost:3000
> 	revproxy = / localhost:3000
> </server>
>
> All is well until I use a URI off the root for example  
> www.example.com/admin
>
> It automatically "redirects" me to localhost:3000/admin (or whatever my 
> Rails routes.rb file tells mongrel to route it to). This works on the 
> machine in question but not on a remote machine.

Do you mean you get back a HTTP redirect to localhost:3000/admin? Or that
the page contains links to http://localhost:3000/? Neither should happen.
Try a manual HTTP session using telnet from the remote host:

  telnet 1.2.3.4 80
  GET /admin HTTP/1.0
  Host: www.example.com
  <blank line>

What do you see?

> How do I get Yaws to preserve the host name? Note in apache that is the 
> function of the ProxyPreserveHost directive.

I run Rails (2.1.2 and 1.2.3) behind Apache, and I don't use
ProxyPreserveHost. As far as I can tell, all the URL links generated by
Rails are relative (/foo/bar), and if you want to generate absolute links
you have to supply :only_path=>false, :host=>"somestring" (or put these in
default_url_options)

If you want to run a single Rails app which serves multiple virtual hosts,
then you should be able to inspect the X_FORWARDED_HOST request header,
which a well-behaved proxy should add. But that's a very unusual situation.

Here are the headers that Apache (2.0) adds:

        /* Add X-Forwarded-For: so that the upstream has a chance to
         * determine, where the original request came from.
         */
        apr_table_mergen(r->headers_in, "X-Forwarded-For",
                         r->connection->remote_ip);

        /* Add X-Forwarded-Host: so that upstream knows what the
         * original request hostname was.
         */
        if ((buf = apr_table_get(r->headers_in, "Host"))) {
            apr_table_mergen(r->headers_in, "X-Forwarded-Host", buf);
        }

        /* Add X-Forwarded-Server: so that upstream knows what the
         * name of this proxy server is (if there are more than one)
         * XXX: This duplicates Via: - do we strictly need it?
         */
        apr_table_mergen(r->headers_in, "X-Forwarded-Server",
                         r->server->server_hostname);

I don't know if Yaws adds those headers when proxying, but if not, it
probably should.

Regards,

Brian.