Canary deployments in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Canary deployment traffic split with NGINX

Given this NGINX configuration snippet for canary deployment, what percentage of traffic is routed to the canary backend?

Nginx

upstream backend {
    server backend-v1.example.com weight=1;
    server backend-v2.example.com weight=1;
}

server {
    listen 80;
    location / {
        proxy_pass http://backend;
    }
}

A 10%

B 25%

C 50%

D 0%

💡 Hint

Weights in upstream servers determine traffic distribution proportionally.

The upstream block has two servers: backend-v1 with weight 1 and backend-v2 with weight 1. Traffic is split evenly 50% each.

❓ Configuration

intermediate

Configure NGINX for 10% canary traffic

Which NGINX upstream configuration correctly routes 10% of traffic to the canary backend and 90% to the stable backend?

A

upstream backend {
    server stable.example.com weight=9;
    server canary.example.com weight=1;
}

B

upstream backend {
    server stable.example.com weight=10;
    server canary.example.com weight=1;
}

C

upstream backend {
    server stable.example.com;
    server canary.example.com weight=0.1;
}

D

upstream backend {
    server stable.example.com weight=1;
    server canary.example.com weight=9;
}

💡 Hint

Weights are relative and must be integers.

Weights define relative traffic. Weight 9 + 1 means 90% to stable, 10% to canary.

❓ Troubleshoot

advanced

Why is canary traffic not reaching the canary backend?

You configured NGINX with a canary backend using weights, but all traffic goes to the stable backend. What is the most likely cause?

A The canary backend server is down or unreachable.

B The stable backend has a lower weight than the canary backend.

C NGINX does not support weighted upstreams.

D The proxy_pass directive is missing in the location block.

💡 Hint

Check backend server health and connectivity.

If the canary backend is down, NGINX routes all traffic to the healthy stable backend regardless of weights.

🔀 Workflow

advanced

Steps to implement a canary deployment with NGINX

What is the correct order of steps to perform a canary deployment using NGINX?

A 2,3,1,4

B 2,1,3,4

C 1,3,2,4

D 1,2,3,4

💡 Hint

Think about deploying first, then routing traffic, then monitoring, then scaling.

First deploy canary, then route traffic, monitor results, and finally increase traffic or promote.

✅ Best Practice

expert

Best practice for canary deployment rollback with NGINX

If the canary deployment shows errors, what is the safest way to rollback using NGINX configuration?

A Stop the canary backend server without changing NGINX configuration.

B Remove the canary backend from the upstream block and reload NGINX.

C Set the canary backend weight to zero and reload NGINX.

D Increase the stable backend weight and reload NGINX.

💡 Hint

Rollback means no traffic should go to canary backend.

Removing the canary backend from upstream ensures no traffic is routed there. Setting weight to zero is invalid in NGINX.

Practice

1. What is the main purpose of a canary deployment in NGINX?

easy

A. To gradually route traffic between old and new application versions

B. To block all traffic during deployment

C. To increase server CPU usage intentionally

D. To disable logging temporarily

Solution

1. Step 1: Understand canary deployment concept

   Canary deployment means sending some traffic to a new version while most traffic still goes to the old version.

2. Step 2: Identify NGINX role in canary deployment

   NGINX controls traffic split using weights in upstream blocks to route requests gradually.

3. Final Answer:

   To gradually route traffic between old and new application versions -> Option A

4. Quick Check:

   Canary deployment = gradual traffic routing [OK]

Hint: Canary means gradual traffic shift, not blocking or disabling [OK]

Common Mistakes:

• Thinking canary blocks all traffic
• Confusing canary with load increase
• Assuming canary disables logging

2. Which NGINX configuration snippet correctly sets a 90% traffic weight to the old version and 10% to the new version?

easy

A. upstream backend { server old.example.com weight=90; server new.example.com weight=10; }

B. upstream backend { server old.example.com weight=10; server new.example.com weight=90; }

C. upstream backend { server old.example.com; server new.example.com; }

D. upstream backend { server old.example.com weight=100; server new.example.com weight=0; }

Solution

1. Step 1: Understand weight meaning in NGINX upstream

   Weight controls traffic share; higher weight means more traffic.

2. Step 2: Match weights to desired traffic split

   Old version should get 90%, new version 10%, so old weight=90, new weight=10.

3. Final Answer:

   upstream backend { server old.example.com weight=90; server new.example.com weight=10; } -> Option A

4. Quick Check:

   Weight 90 old, 10 new = 90% old traffic [OK]

Hint: Higher weight means more traffic; assign accordingly [OK]

Common Mistakes:

• Swapping weights between old and new servers
• Omitting weights defaults to equal traffic
• Setting weight=0 disables server completely

3. Given this NGINX upstream configuration:

upstream backend {
  server old.example.com weight=80;
  server new.example.com weight=20;
}

What percentage of traffic will be routed to new.example.com?

medium

A. 80%

B. 20%

C. 50%

D. 100%

Solution

1. Step 1: Calculate total weight

   Total weight = 80 (old) + 20 (new) = 100.

2. Step 2: Calculate new server traffic percentage

   New server traffic = (20 / 100) * 100% = 20%.

3. Final Answer:

   20% -> Option B

4. Quick Check:

   New server weight 20 of 100 total = 20% traffic [OK]

Hint: Traffic % = server weight / total weight * 100 [OK]

Common Mistakes:

• Confusing weight with percentage directly
• Adding weights incorrectly
• Assuming equal traffic without weights

4. You wrote this NGINX upstream block for canary deployment:

upstream backend {
  server old.example.com weight=70
  server new.example.com weight=30;
}

But NGINX fails to start. What is the error?

medium

A. Cannot use weight in upstream block

B. Weight values must be equal

C. Missing semicolon after first server directive

D. Server names must be IP addresses

Solution

1. Step 1: Check syntax of upstream block

   Each server directive must end with a semicolon in NGINX config.

2. Step 2: Identify missing semicolon

   First server line lacks semicolon after weight=70, causing syntax error.

3. Final Answer:

   Missing semicolon after first server directive -> Option C

4. Quick Check:

   Semicolons required after each directive [OK]

Hint: Check semicolons after each server line [OK]

Common Mistakes:

• Ignoring missing semicolon errors
• Thinking weights must be equal
• Assuming server names must be IPs

5. You want to deploy a new version with 5% traffic initially, then increase to 50% after testing. Which NGINX configuration approach supports this canary deployment best?

hard

A. Use limit_conn to limit new server connections

B. Use proxy_pass without weights to split traffic

C. Set weight=0 for new server until ready

D. Manually update weight values in upstream block and reload NGINX

Solution

1. Step 1: Understand canary traffic control in NGINX

   NGINX uses weights in upstream blocks to control traffic percentage per server.

2. Step 2: Adjust weights gradually and reload NGINX

   Manually changing weights from 5 to 50 and reloading NGINX safely shifts traffic as needed.

3. Final Answer:

   Manually update weight values in upstream block and reload NGINX -> Option D

4. Quick Check:

   Weight changes + reload = traffic control [OK]

Hint: Change weights and reload to shift traffic gradually [OK]

Common Mistakes:

• Using proxy_pass without weights for traffic split
• Setting weight=0 disables server, not gradual traffic
• Using limit_conn limits connections, not traffic percentage