Fwd: How can i have multiple nginx plus servers route to the same app servers with sticky sessions on?

[Maxim Dounin]

Hello!

On Thu, Jun 18, 2015 at 10:13:18AM -0700, Matt wrote:

> I have multiple nginx instances behind an AWS elastic load balancer. In the
> nginx config files, I am using ip_hash to force sticky sessions when
> connecting upstream. Is there a way to sync the route tables between the
> multiple nginx servers, so that no matter which nginx server handles the
> request, the traffic is sent to the same backend application server.
> 
> When I first set this scenario up, I had no problems. But after heavy
> testing with multiple clients from different parts of the world, I was able
> to verify that the multiple nginx servers were not choosing the same
> backend application servers to route to.

First of all, as you use AWS, make sure all nginx instances 
properly see client addresses (and not addresses of Amazon ELB).  
If nginx sees ELB addresses instead, you have to configure the 
realip module appropriately, see 
http://nginx.org/en/docs/http/ngx_http_realip_module.html.

An additional problem which may hurt your case is upstream server 
errors.  See this message for a detailed explanation:

http://mailman.nginx.org/pipermail/nginx/2015-May/047590.html

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