Reverse proxy and rewrite

[jims]

nginx 1.2.7 on CentOS 6.3.  Reverse-proxy with two upstream servers.  One
server should be default, the other should only be used when called from a
link on a specific web server.

I have the reverse proxy working fine for the default upstream, but not
quite right on the second, site-specific upstream.  Ignoring that I am also
rewriting for http to force https (yeah, I know, it's discouraged to go
encrypted between the nginx proxy and its upstreams, but it's a corporate
security thing) I am using a two server block configuration, one server name
for the default and another for the site-specific server.  The site-specific
server will link to the default server URL but should rewrite to the
site-specific upstream's proxy's URL.

It seems to work - not sure if it gets stuck in the proxy or on the upstream
for the site-specific setup -, but it was suggested that a single server,
selecting between upstream servers, would be preferable.  I would like to
know how that would be configured - just a quick overview or link to a
documentation page would help a lot.  

If I can throw together a quick test of a single-server-block reverse-proxy
config with multiple upstreams which are selected based on calling server, I
could test to see if it's my multi-server-block setup or a problem on the
upstream.

Thanks!

Jim.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,236487,236487#msg-236487