Rolling update strategy in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Rolling Update Basics

What is the main advantage of using a rolling update strategy in Kubernetes deployments?

A It updates pods one at a time, ensuring service availability during updates.

B It pauses the deployment until manual approval is given for each pod.

C It updates all pods simultaneously, minimizing downtime.

D It deletes all old pods before creating new ones to save resources.

💡 Hint

Think about how service availability is maintained during updates.

Rolling updates replace pods gradually, one by one, so the application stays available without downtime.

💻 Command Output

intermediate

Interpreting Rolling Update Status

What is the output of the following command if a rolling update is in progress and 2 out of 5 pods have been updated?

Kubernetes

kubectl rollout status deployment/myapp

A Waiting for rollout to finish: 3 old replicas are pending termination...

B Waiting for rollout to finish: 2 out of 5 new replicas are available...

C Error from server (NotFound): deployments.apps "myapp" not found

D deployment "myapp" successfully rolled out

💡 Hint

Look for messages indicating partial progress in rollout.

The command shows how many new pods are available during the rolling update process.

❓ Configuration

advanced

Configuring Max Surge and Max Unavailable

Given this deployment snippet, what is the maximum number of pods that can be unavailable during the rolling update?

strategy:
  type: RollingUpdate
  rollingUpdate:
    maxSurge: 2
    maxUnavailable: 1

A 1 pod can be unavailable at once

B 2 pods can be unavailable at once

C No pods can be unavailable during update

D 3 pods can be unavailable at once

💡 Hint

Check the value of maxUnavailable in the configuration.

The maxUnavailable field controls how many pods can be down during the update. Here it is set to 1.

❓ Troubleshoot

advanced

Troubleshooting a Stuck Rolling Update

You started a rolling update but it is stuck and not progressing. Which of the following is the most likely cause?

A The old pods are terminating too quickly, causing downtime.

B The deployment has <code>maxSurge</code> set to 0, allowing no extra pods.

C The new pods are failing readiness probes, so they are not marked ready.

D The deployment strategy is set to Recreate instead of RollingUpdate.

💡 Hint

Consider what prevents new pods from becoming available during update.

If readiness probes fail, new pods won't be ready, so the update waits indefinitely.

🔀 Workflow

expert

Rolling Update Workflow Steps

Arrange the steps of a Kubernetes rolling update in the correct order.

A 1,3,2,4

B 3,1,2,4

C 2,1,3,4

D 1,2,3,4

💡 Hint

Think about how new pods are created and verified before old pods are removed.

The rolling update first creates new pods (up to maxSurge), waits for readiness, then removes old pods (up to maxUnavailable), repeating until done.

Practice

1. What is the main purpose of a rolling update in Kubernetes?

easy

A. To update an application without downtime by gradually replacing pods

B. To delete all pods and recreate them at once

C. To backup the current state of the application

D. To scale the application to zero replicas

Solution

1. Step 1: Understand rolling update concept

   A rolling update replaces pods one by one to avoid downtime.

2. Step 2: Compare options with concept

   Only To update an application without downtime by gradually replacing pods describes gradual replacement without downtime.

3. Final Answer:

   To update an application without downtime by gradually replacing pods -> Option A

4. Quick Check:

   Rolling update = gradual pod replacement [OK]

Hint: Rolling update means update pods one by one without downtime [OK]

Common Mistakes:

• Thinking rolling update deletes all pods at once
• Confusing rolling update with backup
• Assuming rolling update scales pods to zero

2. Which kubectl command starts a rolling update by changing the image of a deployment?

easy

A. kubectl set image deployment/myapp myapp-container=myimage:v2

B. kubectl rollout undo deployment/myapp

C. kubectl scale deployment/myapp --replicas=0

D. kubectl get pods --watch

Solution

1. Step 1: Identify command to update image

   The command to update a deployment's image is 'kubectl set image'.

2. Step 2: Match command with options

   kubectl set image deployment/myapp myapp-container=myimage:v2 uses 'kubectl set image' correctly to start rolling update.

3. Final Answer:

   kubectl set image deployment/myapp myapp-container=myimage:v2 -> Option A

4. Quick Check:

   Change image = kubectl set image [OK]

Hint: Use kubectl set image to start rolling update [OK]

Common Mistakes:

• Using rollout undo to start update
• Scaling replicas to zero instead of updating image
• Using get pods to update image

3. After running kubectl set image deployment/myapp myapp-container=myimage:v2, what does kubectl rollout status deployment/myapp show?

medium

A. The configuration details of the deployment

B. The current rollout progress of the deployment update

C. The logs of the deployment pods

D. The list of pods in the deployment

Solution

1. Step 1: Understand purpose of rollout status

   The command 'kubectl rollout status' shows progress of deployment updates.

2. Step 2: Compare options with command purpose

   The current rollout progress of the deployment update correctly describes rollout progress; others describe different commands.

3. Final Answer:

   The current rollout progress of the deployment update -> Option B

4. Quick Check:

   Rollout status = update progress [OK]

Hint: Rollout status shows update progress, not pod list or logs [OK]

Common Mistakes:

• Confusing rollout status with pod listing
• Expecting logs from rollout status
• Thinking rollout status shows config details

4. You ran kubectl set image deployment/myapp myapp-container=myimage:v2 but the new pods crash. Which command helps you revert to the previous version?

medium

A. kubectl scale deployment/myapp --replicas=0

B. kubectl delete deployment myapp

C. kubectl rollout undo deployment/myapp

D. kubectl get pods --all-namespaces

Solution

1. Step 1: Identify command to revert deployment

   'kubectl rollout undo' reverts deployment to previous version.

2. Step 2: Match command with options

   kubectl rollout undo deployment/myapp correctly reverts the deployment; others do not revert updates.

3. Final Answer:

   kubectl rollout undo deployment/myapp -> Option C

4. Quick Check:

   Undo rollout = kubectl rollout undo [OK]

Hint: Use rollout undo to revert bad updates quickly [OK]

Common Mistakes:

• Deleting deployment instead of undoing
• Scaling replicas to zero instead of reverting
• Using get pods which only lists pods

5. You want to update your deployment with zero downtime and ensure at least 2 pods are always available during the update. Which rolling update settings in the deployment spec help achieve this?

hard

A. Set 'maxUnavailable' to 1 and 'maxSurge' to 1 in 'rollingUpdate' strategy

B. Set 'maxUnavailable' to 2 and 'maxSurge' to 0 in 'rollingUpdate' strategy

C. Set 'maxUnavailable' to 3 and 'maxSurge' to 3 in 'rollingUpdate' strategy

D. Set 'maxUnavailable' to 0 and 'maxSurge' to 2 in 'rollingUpdate' strategy

Solution

1. Step 1: Understand maxUnavailable and maxSurge

   'maxUnavailable' controls how many pods can be down; 'maxSurge' controls extra pods created during update.

2. Step 2: Ensure at least 2 pods always available

   Setting 'maxUnavailable' to 0 means no pods go down; 'maxSurge' 2 allows 2 extra pods to be created for smooth update.

3. Final Answer:

   Set 'maxUnavailable' to 0 and 'maxSurge' to 2 in 'rollingUpdate' strategy -> Option D

4. Quick Check:

   Zero unavailable + surge 2 = no downtime, 2 pods always up [OK]

Hint: maxUnavailable 0 means no pod down; maxSurge adds extra pods [OK]

Common Mistakes:

• Setting maxUnavailable > 0 causes downtime
• Setting maxSurge to 0 prevents extra pods during update
• Choosing high maxUnavailable and maxSurge causing instability