Weighted round-robin in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Weighted Round-Robin in NGINX

What does the weight parameter do in an NGINX upstream block using weighted round-robin?

A It defines the timeout duration for requests to a server.

B It sets the maximum number of simultaneous connections allowed to a server.

C It assigns a relative load share to each server, so servers with higher weights receive more requests.

D It specifies the priority order in which servers are tried sequentially.

💡 Hint

Think about how NGINX balances traffic among servers with different capacities.

The weight parameter in NGINX's upstream configuration assigns a relative share of requests to each server. Servers with higher weights get more requests, allowing load balancing based on server capacity.

❓ Configuration

intermediate

Identify the Correct Weighted Round-Robin Configuration

Which NGINX upstream configuration correctly implements weighted round-robin with server1 receiving twice the traffic of server2?

A

upstream backend {
    server server1.example.com weight=2;
    server server2.example.com weight=1;
}

B

upstream backend {
    server server1.example.com weight=1;
    server server2.example.com weight=2;
}

C

upstream backend {
    server server1.example.com max_fails=2;
    server server2.example.com max_fails=1;
}

D

upstream backend {
    server server1.example.com;
    server server2.example.com;
}

💡 Hint

Look for the weight values assigned to each server.

Option A assigns weight=2 to server1 and weight=1 to server2, making server1 receive twice the requests compared to server2.

💻 Command Output

advanced

Output of NGINX Weighted Round-Robin Load Distribution

Given this upstream configuration:

upstream backend {
    server 10.0.0.1 weight=3;
    server 10.0.0.2 weight=1;
}

After 8 requests, how many requests will each server have received?

A 10.0.0.1: 3 requests, 10.0.0.2: 5 requests

B 10.0.0.1: 6 requests, 10.0.0.2: 2 requests

C 10.0.0.1: 4 requests, 10.0.0.2: 4 requests

D 10.0.0.1: 8 requests, 10.0.0.2: 0 requests

💡 Hint

Calculate requests proportional to weights: 3 parts vs 1 part.

The total weight is 4 (3+1). For 8 requests, server 10.0.0.1 gets (3/4)*8=6 requests, and 10.0.0.2 gets (1/4)*8=2 requests.

❓ Troubleshoot

advanced

Troubleshooting Weighted Round-Robin Misconfiguration

An NGINX server block uses weighted round-robin, but traffic is not distributed according to weights. Which misconfiguration is most likely causing this?

A All servers have the same weight value or no weight specified.

B The <code>max_fails</code> parameter is set too high.

C The <code>keepalive</code> directive is missing.

D The <code>proxy_pass</code> directive is outside the server block.

💡 Hint

Check if weights differ between servers.

If all servers have the same weight or no weight, NGINX treats them equally, so weighted distribution does not occur.

✅ Best Practice

expert

Best Practice for Weighted Round-Robin with Dynamic Server Health

In a weighted round-robin setup, what is the best practice to ensure traffic is not sent to unhealthy servers while maintaining weight distribution?

A Set all server weights to zero when a server is unhealthy.

B Manually remove unhealthy servers from the upstream block and reload NGINX configuration.

C Disable weighted round-robin and use simple round-robin instead.

D Use <code>max_fails</code> and <code>fail_timeout</code> to mark servers as down and exclude them from load balancing temporarily.

💡 Hint

Consider automatic health checks and failover mechanisms.

Using max_fails and fail_timeout allows NGINX to automatically mark servers as down when they fail, preventing traffic from being sent to them while preserving weighted distribution among healthy servers.