# Nginx + Thin cluster of 3. Which Thin took the request? **URL:** \ **Category:** NGINX\ **Created:** [February 10, 2010, 11:38am UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234 "2010-02-10T11:38:37Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 10, 2010, 11:38am UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/1 "2010-02-10T11:38:37Z")
Hi, I just managed to setup a front end web server with Nginx and then a cluster of 3 Thin servers behind it who serve instances of the same app. At least the app responds properly through Nginx. After making a request, how can I find out which app actually processed the request? The only log I see growing is the development.log I have thin.300x.log files but don’t increase in size when requests are made… Thanks ---
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 11, 2010, 12:18pm UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/2 "2010-02-11T12:18:47Z")
Anyone? I’m trying to get some logs using the http\_upstream\_ prefix but no luck yet… Cheers. ---
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 11, 2010, 12:32pm UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/3 "2010-02-11T12:32:49Z")
On Thu, Feb 11, 2010 at 12:18 PM, comopasta Gr [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Anyone? > I’m trying to get some logs using the http\_upstream\_ prefix but no luck > yet… Can you add a response header from within your app? something like X-I-Am-Pid with the pid of the serving process? or even just monitoring with top sorted by cpu usage (if 3 thins are active, it’s all 3, otherwise it’s not balancing! ---
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 11, 2010, 12:43pm UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/4 "2010-02-11T12:43:56Z")
Hello! On Thu, Feb 11, 2010 at 12:18:47PM +0100, comopasta Gr wrote: > Anyone? > I’m trying to get some logs using the http\_upstream\_ prefix but no luck > yet… Well, probably you have no headers named Upstream-\* got from client. If you instead need headers you got from upstream - use $upstream\_http\_… instead. Maxim D. ---
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 17, 2010, 11:37am UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/5 "2010-02-17T11:37:03Z")
Hi again, Thanks for the hints. I was trying to use $upstream\_http\_… but that didn’t print out anything. This is all in development environment so no big loads or anything. Just testing the setup. I actually managed to verify that the cluster is operative. By checking with Process.pid that I get responses from the three pids that belong to each server of the cluster. But I would guess that Nginx should know to which app server is forwarding the request (?) I a more friendly way… Cheers. ---
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 17, 2010, 12:03pm UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/6 "2010-02-17T12:03:17Z")
On Wed, Feb 17, 2010 at 11:37:03AM +0100, comopasta Gr wrote: > each server of the cluster. > > But I would guess that Nginx should know to which app server is > forwarding the request (?) I a more friendly way… Try to log $upstream\_addr. – Igor S. > **[Igor Sysoev](http://sysoev.ru/en/)** ---
**Author:** ![comopasta](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/59ef9b/32.png) [@comopasta](https://www.ruby-forum.com/u/comopasta)\ **Post date:** [February 17, 2010, 1:32pm UTC](https://www.ruby-forum.com/t/nginx-thin-cluster-of-3-which-thin-took-the-request/183234/7 "2010-02-17T13:32:30Z")
Thanks Igor! I am pathetic at reading documentation 😛 [http://wiki.nginx.org/NginxHttpUpstreamModule#.24upstream\_addr](http://wiki.nginx.org/NginxHttpUpstreamModule#.24upstream_addr) Yes $upstream\_addr prints out the address of the server that handled the request! Thanks!