Handling redirects among upstream servers

[Maxim Dounin]

Hello!

On Fri, Nov 07, 2014 at 05:11:44AM -0500, zappa wrote:

> Hello,
> 
> I'm trying to configure Nginx to access a cluster of application servers
> using a simple proxy with multiple application servers in the upstream. The
> application servers use a REST api for object storage and retrieval, and use
> 301 redirects among the nodes of the cluster for load balancing. A client
> can connect to server A, then get a redirect to server B, where the request
> will be handled.
> 
> This fails when nginx is used as a proxy in this case:
> 
> - the client connects through the proxy and gets connected to server A
> 
> - A returns a 301 with one of the other servers in the Location header
> 
> - Nginx rewrites the location header, so information about which node the
> client is supposed to connect to is lost
> 
> Does Nginx offer a solution for this? Can nginx handle the 301 itself
> without the client ever knowing the redirect happend? Would it be possible
> to store the redirect into a client cookie which is read during the next
> request and forces nginx to connect to a particular upstream server?

In no particular order:

- You can avoid changes to the Location header, or control them as 
  needed.  The flexibility provied by the proxy_redirect directive 
  should be enough to preserve information needed.  See 
  http://nginx.org/r/proxy_redirect for details.

- You can instruct nginx to forward requests to another node 
  by itself, using the X-Accel-Redirect header.  This may be a 
  good solution if you are willing to rewrite application servers to 
  use features provided by nginx.

- Redirections can be intercepted using the error_page and 
  proxy_intercept_errors directives (I wouldn't recommend this 
  though).

-- 
Maxim Dounin
http://nginx.org/