Change Host header in nginx reverse proxy

Question

I am running nginx as reverse proxy for the site example.com to loadbalance a ruby application running in backend server. I have the following proxy_set_header field in nginx which will pass host headers to backend ruby. This is required by ruby app to identify the subdomain names.

location / {     proxy_pass http://rubyapp.com;     proxy_set_header Host $http_host; } 

Now I want to create an alias beta.example.com, but the host header passed to backend should still be www.example.com otherwise the ruby application will reject the requests. So I want something similar to below inside location directive.

if ($http_host = "beta.example.com") {     proxy_pass http://rubyapp.com;     proxy_set_header Host www.example.com; } 

What is the best way to do this?

Answer 1

You cannot use proxy_pass in if block, so I suggest to do something like this before setting proxy header:

set $my_host $http_host; if ($http_host = "beta.example.com") {   set $my_host "www.example.com"; } 

And now you can just use proxy_pass and proxy_set_header without if block:

location / {   proxy_pass http://rubyapp.com;   proxy_set_header Host $my_host; }