Optional Extension: Weighted Load Balancing with Nginx

1. Goal

In this extension you will:

Weights are useful when:

Edit:

sudo nano /etc/nginx/sites-available/loadbalance.local

Find your upstream block and adjust it as follows (ensure ip_hash is NOT used here):

upstream backend_pool {
    server 127.0.0.1:8001 weight=3;
    server 127.0.0.1:8002 weight=1;
}

Explanation:

Save, test, and reload:

sudo nginx -t
sudo systemctl reload nginx

Run multiple requests:

for i in {1..20}; do curl http://loadbalance.local/; echo; done

Count how many times you see each backend:

You should see backend 1 significantly more often than backend 2.

For a more precise count, you can use:

for i in {1..50}; do curl -s http://loadbalance.local/; echo; done | sort | uniq -c

This will group and count occurrences.

Experiment by changing the weights:

upstream backend_pool {
    server 127.0.0.1:8001 weight=5;
    server 127.0.0.1:8002 weight=1;
}

Or:

upstream backend_pool {
    server 127.0.0.1:8001 weight=1;
    server 127.0.0.1:8002 weight=3;
}

Each time:

In your protocol, describe:

The weight values you tried
The approximate ratio of responses you observed
How weights could be used in real deployments, e.g.:
- Slowly shifting traffic to a new version
- Sending most traffic to a more powerful server
- “Canary testing” a new backend for a small percentage of users