I'd expect the ip_hash directive to work as usual http://wiki.nginx.org/HttpUpstreamModule#ip_hash http://wiki.nginx.org/HttpUpstreamModule#ip_hash although it'

I'd expect the ip_hash directive to work as usual http://wiki.nginx.org/HttpUpstreamModule#ip_hash http://wiki.nginx.org/HttpUpstreamModule#ip_hash although it's not exactly sticky sessions. There's a separate module for that https://github.com/michaelneale/nginx-sticky-module https://github.com/michaelneale/nginx-sticky-module