Nginx split_clients not dividing traffic

Question

I have the following nginx.config file:

events {}

http {
    # ...
    # application version 1a 
    upstream version_1a {
        server localhost:8090;
    }

    # application version 1b
    upstream version_1b {
        server localhost:8091;
    }

    split_clients "${arg_token}" $appversion {
        50%     version_1a;
        50% version_1b;
    }

    server {
        # ...
        listen 7080;
        location / {
            proxy_set_header Host $host;
            proxy_pass http://$appversion;
        }
    }
}

I have two nodejs servers listening on port 8090 and 8091 and I am hitting the URL http://localhost:7080, my expectation here is the Nginx will randomly split the traffic to version_1a and version_1b upstream, but, all the traffic is going to version_1a. Any insight into why this might be happening?

(I want to have this configuration for the canary traffic)

Answer 1

Validate the variable you are using to split the traffic is set correctly, and the variable's value should be uniformly distributed else the traffic will not be split evenly.

Answer 2

I have the same problem with the following configuration:

upstream exercim {
    server host.docker.internal:8081;
}

upstream nutshell {
    server host.docker.internal:8082;
}

split_clients "${remote_addr}" $backend {
    50% exercim;
    *   nutshell;
}

server {
    listen       80 default_server;
    listen  [::]:80;
    server_name  localhost;

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

    location /exercim/ {
        proxy_pass  http://$backend;
    }

    location / {
        root   /usr/share/nginx/html;
        index  index.html index.htm;
    }
}

$remote_addr contains an IP address.

Still the traffic is not split.