nginx.conf

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    #include /etc/nginx/conf.d/*.conf;

    upstream version_a {
        server 10.253.254.73:80;
    }

    upstream version_b {
        server 10.253.254.71:80;
    }

    split_clients "app${remote_addr}${http_user_agent}${date_gmt}" $appversion {
        50% version_a;
        *   version_b;
    }

    map $cookie_split_test_version $upstream_group {
        default $appversion;
        "version_a" "version_a";
        "version_b" "version_b";

    }

    map $cookie_split_test_version $ck_content {
       default "split_test_version=$upstream_group;Path=/;Max-Age=518400;";
       "version_a" "";
       "version_b" "";
    }

    server {
        listen 80;

        client_max_body_size 64M;

        # You may add specific rules and folders that have to use the version segmentation.
        # You can also uso just / to apply to all directories.
        
        #location /example.com/ {

            # Sets Cookie header with the content that might be empty or cookie code,
            # version and Max-Age

            #add_header Set-Cookie $ck_content;
            #proxy_set_header Host $host;


            # If you use more than just $cookie_split_test_version to decide which version
            # the user should see, you may add them here. However keep in mind this article: If Is Evil
            # https://www.nginx.com/resources/wiki/start/topics/depth/ifisevil/
            # if ($upstream_group = "version_a") {
            #     proxy_pass http://10.253.254.71:80;
            #     break;
            # }
            # if ($upstream_group = "version_b") {
            #     proxy_pass http://10.253.254.73:80;
            #     break;
            # }

            #proxy_pass http://$appversion;
        #}
        
        location / {
            # Sets Cookie header with the content that might be empty or cookie code,
            # version and Max-Age
            add_header Set-Cookie $ck_content;
            proxy_set_header Host $host;

            # $upstream_group is defined by the existance of its own value in cookie or
            # by the probabilistic definition of $appversion.
            proxy_pass http://$upstream_group;
            break;
        }
    }
}