Example NGINX configuration to perform A/B deployments

nginx.conf

user  nginx;
worker_processes  auto;
error_log  /var/log/nginx/error.log info;
pid        /var/run/nginx.pid;
events { worker_connections  1024; }
http {
        default_type  text/html;
        log_format  main  '$remote_addr -> $request     $status $body_bytes_sent bytes -> $upstream_addr';
        access_log  /var/log/nginx/access.log  main;

        upstream a {
                zone a 64k;
                server 127.0.0.1:3001;
        }

        upstream b {
                zone b 64k;
                server 127.0.0.1:4001;
        }

        split_clients "${arg_token}" $dynamic {
                95%     a;
                *       b;
        }

        server {
                listen 3001;
                location / {
                        return 200 "Served from site A! \n\n";
                }
        }

        server {
                listen 4001;
                location / {
                        return 200 "Served from site B!! <<<<-------------------------- \n\n";
                }
        }

        server {
                status_zone website;
                listen 80;
                location / {
                        proxy_set_header Host $host;
                        proxy_pass http://$dynamic$uri$is_args$args;
                }

                location @healthcheck-a {
                        proxy_pass http://a;
                        proxy_connect_timeout 1s;
                        proxy_read_timeout 1s;
                        health_check uri=/ interval=1s match=health_check;
                }
                location @healthcheck-b {
                        proxy_pass http://b;
                        proxy_connect_timeout 1s;
                        proxy_read_timeout 1s;
                        health_check uri=/ interval=1s match=health_check;
                }

        }
        match health_check {
                status 200;
        }

        server {
                listen 8080;
                status_zone status-page;
                root /usr/share/nginx/html;
                location = /status.html { }
                location = /status-old.html { }
                location = / {
                        return 301 /status.html;
                }
                location /status {
                        status;
                        status_format json;
                        access_log off;
                }
                location /upstream_conf {
                        upstream_conf;
                }
        }
}