nginx proxy_pass proxy_set_header of proxy host

Question

Using NGINX as a reverse proxy, I want to tag which load balancer/proxy the request can in on, and pass that to the end app servers...

For example, we have 2 ingress connections, using round-robin DNS to 3 load balancers,

so, connection one has 3 pubic IP's and connection two has 3 IP's. each pair points to a load balancer and they're using proxy pass upstream to send traffic to the 10 web/app servers.

I want to tag which of the 3 LB's the request comes in on, I'd love to tag it based on the connection too, if you know how.

 upstream web_cluster { random; # web server ip addresses x 10 } location / { proxy_pass http://web_cluser; proxy_set_header Proxy $proxy_server_host_name; // here proxy_set_header Route $proxy_server_public_ip; // here proxy_pass_request_headers on; } 

The servers are all deployed via Ansible scripts, so I wouldn't be able to hard-code server names into the proxy_set_header options.

Thanks

Answer 1

To tag all this we could change your configuration file to use the map directive to map the remote IP address to the corresponding load balancer name, and the $proxy_host variable to set the Proxy-Host header.

upstream web_cluster { server 10.0.0.1; server 10.0.0.2; server 10.0.0.3; # add more servers here as needed } map $remote_addr $proxy_host { 192.168.1.1 "lb1"; 192.168.1.2 "lb2"; 192.168.1.3 "lb3"; # add more mappings here as needed } server { listen 80; server_name example.com; location / { proxy_pass http://web_cluster; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Proxy-Host $proxy_host; } }