Canary deployment in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a canary deployment?

A canary deployment is a way to release a new version of software to a small group of users first. This helps check if the new version works well before giving it to everyone.

beginner

Why use canary deployments in microservices?

Canary deployments reduce risk by testing new changes on a small part of the system. If problems happen, only a few users are affected, making it easier to fix.

intermediate

How does traffic routing work in canary deployments?

Traffic routing sends a small percentage of user requests to the new version while the rest go to the old version. This split helps monitor the new version's performance safely.

intermediate

What metrics should be monitored during a canary deployment?

Important metrics include error rates, response times, system load, and user experience feedback. Monitoring these helps decide if the new version is stable.

intermediate

What is the difference between canary deployment and blue-green deployment?

Canary deployment releases new software to a small group gradually, while blue-green deployment switches all users from old to new version at once using two separate environments.

What is the main goal of a canary deployment?

A Test new software on a small user group before full release

B Deploy software to all users at the same time

C Keep two versions running without traffic splitting

D Rollback software without monitoring

Canary deployment tests new software on a small group first to reduce risk.

In canary deployment, how is user traffic typically handled?

A Traffic is split between old and new versions

B All traffic goes to the new version immediately

C Traffic is stopped during deployment

D Traffic is routed randomly without control

Traffic is split so only some users use the new version while others use the old.

Which metric is NOT commonly monitored during canary deployment?

A Response times

B Number of developers

C User feedback

D Error rates

Number of developers is unrelated to deployment health.

What happens if the canary deployment shows problems?

A The old version is deleted immediately

B The new version is released to all users

C The new version is rolled back

D No action is taken

If issues appear, the new version is rolled back to protect users.

Which deployment strategy switches all users at once between two environments?

A Canary deployment

B A/B testing

C Rolling deployment

D Blue-green deployment

Blue-green deployment switches all users at once between two environments.

Explain how canary deployment helps reduce risk during software releases.

Think about how testing on few users first can protect the whole system.

Describe the key differences between canary deployment and blue-green deployment.

Focus on how users experience the new version in each strategy.

Practice

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

easy

A. To permanently run two versions side by side

B. To deploy all users to a new version at once

C. To release a new version to a small group of users first to reduce risk

D. To test the new version only in a development environment

Solution

1. Step 1: Understand the goal of canary deployment

   Canary deployment aims to reduce risk by releasing new software versions to a small subset of users first.

2. Step 2: Compare options with this goal

   To release a new version to a small group of users first to reduce risk matches this goal exactly, while others describe different deployment strategies.

3. Final Answer:

   To release a new version to a small group of users first to reduce risk -> Option C

4. Quick Check:

   Canary deployment = gradual rollout [OK]

Hint: Canary means small test group first, not all users [OK]

Common Mistakes:

• Confusing canary with blue-green deployment
• Thinking canary deploys to all users at once
• Assuming canary is only for testing environments

2. Which of the following is the correct way to control traffic during a canary deployment?

easy

A. Send 100% of traffic to the new version immediately

B. Route a small percentage of traffic to the new version and the rest to the old

C. Stop all traffic during deployment

D. Send traffic randomly without control

Solution

1. Step 1: Understand traffic control in canary deployment

   Traffic is gradually shifted to the new version to monitor its behavior safely.

2. Step 2: Identify the correct traffic routing method

   Route a small percentage of traffic to the new version and the rest to the old describes routing a small percentage to the new version while keeping most on the old version, which is correct.

3. Final Answer:

   Route a small percentage of traffic to the new version and the rest to the old -> Option B

4. Quick Check:

   Traffic control = gradual routing [OK]

Hint: Gradually shift traffic, never 100% at once [OK]

Common Mistakes:

• Sending all traffic immediately to new version
• Stopping traffic completely during deployment
• Ignoring traffic routing control

3. Consider this simplified code snippet for traffic routing in a canary deployment:

def route_request(user_id):
    if user_id % 10 == 0:
        return "new_version"
    else:
        return "old_version"

print(route_request(20))
print(route_request(23))

What will be the output?

medium

A. "new_version" followed by "old_version"

B. "new_version" followed by "new_version"

C. "old_version" followed by "old_version"

D. "old_version" followed by "new_version"

Solution

1. Step 1: Evaluate route_request(20)

   20 % 10 equals 0, so it returns "new_version".

2. Step 2: Evaluate route_request(23)

   23 % 10 equals 3, not 0, so it returns "old_version".

3. Final Answer:

   "new_version" followed by "old_version" -> Option A

4. Quick Check:

   Modulo 10 == 0 routes to new version [OK]

Hint: Check modulo condition carefully for routing [OK]

Common Mistakes:

• Misunderstanding modulo operator
• Assuming all users go to new version
• Mixing output order

4. A team implemented a canary deployment but noticed that 100% of users are routed to the new version immediately. What is the most likely cause?

medium

A. Traffic routing logic sends all traffic to new version without percentage control

B. Monitoring tools are not enabled

C. Rollback was triggered accidentally

D. Old version servers are down

Solution

1. Step 1: Analyze the symptom

   All users routed to new version immediately means no gradual traffic control.

2. Step 2: Identify the cause

   Traffic routing logic sends all traffic to new version without percentage control explains that routing logic lacks percentage control, causing full traffic shift.

3. Final Answer:

   Traffic routing logic sends all traffic to new version without percentage control -> Option A

4. Quick Check:

   Immediate full traffic = missing gradual routing [OK]

Hint: Check traffic routing code for percentage control [OK]

Common Mistakes:

• Blaming monitoring tools for routing issues
• Assuming rollback causes full traffic shift
• Ignoring server status impact

5. You want to design a canary deployment system that automatically rolls back if error rates exceed 5% during rollout. Which combination of components is essential?

hard

A. Load balancer, static routing, manual rollback process

B. Manual deployment script, user feedback form, database backup

C. Continuous integration server, code linter, version control

D. Traffic router, monitoring system, automated rollback controller

Solution

1. Step 1: Identify components for traffic control and monitoring

   A traffic router directs user requests between old and new versions; monitoring system tracks error rates.

2. Step 2: Include automated rollback for quick response

   An automated rollback controller triggers rollback if error thresholds are exceeded.

3. Final Answer:

   Traffic router, monitoring system, automated rollback controller -> Option D

4. Quick Check:

   Canary needs routing + monitoring + rollback [OK]

Hint: Combine routing, monitoring, and rollback for safe canary [OK]

Common Mistakes:

• Ignoring automation in rollback
• Confusing deployment tools with monitoring
• Missing traffic routing component