Blue-green deployments in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new deployment named 'green' in Kubernetes.

Kubernetes

kubectl create deployment [1] --image=nginx:latest

Drag options to blanks, or click blank then click option'

Ared

Bgreen

Cblue

Dyellow

Attempts:

3 left

💡 Hint

Common Mistakes

Using the old deployment name 'blue' instead of 'green'.

The new deployment for the green environment should be named 'green' to distinguish it from the blue environment.

2fill in blank

medium

Complete the code to switch the service to point to the green deployment.

Kubernetes

kubectl patch service my-service -p '{"spec": {"selector": {"app": "[1]"}}}'

Drag options to blanks, or click blank then click option'

Agreen

Bblue

Cred

Dyellow

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the selector as 'blue' so traffic does not switch.

To switch traffic to the green deployment, update the service selector to 'green'.

3fill in blank

hard

Fix the error in the command to delete the old blue deployment.

Kubernetes

kubectl delete deployment [1]

Drag options to blanks, or click blank then click option'

Agreen

Byellow

Cblue

Dred

Attempts:

3 left

💡 Hint

Common Mistakes

Deleting the 'green' deployment instead of 'blue'.

To remove the old environment, delete the 'blue' deployment after switching traffic.

4fill in blank

hard

Fill both blanks to create a service that routes traffic to the blue deployment.

Kubernetes

kubectl expose deployment [1] --port=[2] --target-port=80

Drag options to blanks, or click blank then click option'

Ablue

Bgreen

C8080

D80

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong deployment name or port number.

The service should expose the 'blue' deployment on port 80 to route traffic correctly.

5fill in blank

hard

Fill all three blanks to create a deployment with label 'app=green' and image 'nginx:stable'.

Kubernetes

kubectl create deployment [1] --image=[2] --dry-run=client -o yaml | kubectl set [3] app=[1] -f - --local -o yaml

Drag options to blanks, or click blank then click option'

Agreen

Bnginx:stable

Clabel

Dblue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong deployment name or image, or wrong kubectl command for labeling.

Create the 'green' deployment with the stable nginx image and add the label 'app=green' using 'kubectl set label'.

Practice

1. What is the main purpose of a blue-green deployment in Kubernetes?

easy

A. To update applications without downtime by switching traffic between two versions

B. To create multiple replicas of a pod for load balancing

C. To automatically scale pods based on CPU usage

D. To backup data from one cluster to another

Solution

1. Step 1: Understand blue-green deployment concept

   Blue-green deployment runs two versions of an app side by side to avoid downtime.

2. Step 2: Identify the main goal

   The main goal is to switch user traffic smoothly from the old version (blue) to the new version (green).

3. Final Answer:

   To update applications without downtime by switching traffic between two versions -> Option A

4. Quick Check:

   Blue-green deployment = zero downtime updates [OK]

Hint: Blue-green means two versions, switch traffic smoothly [OK]

Common Mistakes:

• Confusing blue-green with scaling pods
• Thinking it is for backups
• Mixing it with auto-scaling

2. Which Kubernetes resource is typically used to switch traffic between blue and green deployments?

easy

A. ConfigMap

B. PersistentVolume

C. Service

D. Ingress Controller

Solution

1. Step 1: Identify traffic routing resource

   In Kubernetes, a Service routes traffic to pods based on labels.

2. Step 2: Understand blue-green switching

   Switching traffic between blue and green versions is done by changing the Service selector to point to the desired pods.

3. Final Answer:

   Service -> Option C

4. Quick Check:

   Service routes traffic in blue-green deployments [OK]

Hint: Service controls traffic routing between versions [OK]

Common Mistakes:

• Choosing ConfigMap which stores config data
• Selecting PersistentVolume which manages storage
• Picking Ingress Controller which manages external access

3. Given the following Kubernetes Service selector for blue deployment:

selector:
  app: myapp
  version: blue

What happens if you change the selector to version: green?

medium

A. Traffic will be split evenly between blue and green pods

B. Traffic will be routed to pods labeled with version green

C. Traffic will stop because selector is invalid

D. Pods with version blue will receive traffic

Solution

1. Step 1: Understand Service selector role

   The Service selector chooses pods matching the labels to send traffic to.

2. Step 2: Effect of changing selector

   Changing selector to version: green directs traffic only to pods labeled green, ignoring blue pods.

3. Final Answer:

   Traffic will be routed to pods labeled with version green -> Option B

4. Quick Check:

   Selector change = traffic to matching pods [OK]

Hint: Service selector controls which pods get traffic [OK]

Common Mistakes:

• Assuming traffic splits automatically
• Thinking selector change breaks traffic
• Believing old pods still get traffic

4. You deployed a green version but users still see the blue version. What is the most likely cause?

medium

A. The Service selector was not updated to point to green pods

B. The green pods failed to start due to image pull error

C. The Deployment was deleted accidentally

D. The cluster is out of CPU resources

Solution

1. Step 1: Check traffic routing setup

   If users still see blue, traffic is likely still routed to blue pods.

2. Step 2: Identify cause of routing

   This happens if the Service selector was not updated to green pods after deploying green version.

3. Final Answer:

   The Service selector was not updated to point to green pods -> Option A

4. Quick Check:

   Service selector update needed to switch traffic [OK]

Hint: Update Service selector to switch traffic [OK]

Common Mistakes:

• Assuming pods failed without checking
• Thinking Deployment deletion causes this
• Blaming cluster resource issues first

5. You want to perform a blue-green deployment with zero downtime. You have:

• Blue pods running version 1
• Green pods running version 2

Which sequence of steps ensures a safe switch?

hard

A. Update Deployment to green version, wait for rollout, then update Service selector

B. Delete blue pods first, then update Service selector to green pods

C. Scale down blue pods to zero, then create green pods and update Service selector

D. Update Service selector to green pods, then delete blue pods after confirming green is healthy

Solution

1. Step 1: Switch traffic safely

   First, update the Service selector to point to green pods so new traffic goes to version 2.

2. Step 2: Confirm green pods are healthy

   Check green pods are running well before removing blue pods to avoid downtime.

3. Step 3: Remove old version

   After confirmation, delete blue pods to free resources.

4. Final Answer:

   Update Service selector to green pods, then delete blue pods after confirming green is healthy -> Option D

5. Quick Check:

   Switch traffic first, confirm health, then remove old [OK]

Hint: Switch traffic first, confirm green healthy, then remove blue [OK]

Common Mistakes:

• Deleting blue pods before switching traffic
• Not confirming green pods health
• Updating Deployment without switching Service selector