Recreate update strategy in Kubernetes - Mini Project: Build & Apply

Recreate Update Strategy in Kubernetes

📖 Scenario: You are managing a web application running on Kubernetes. You want to update the application pods so that the old pods are completely terminated before new pods start. This is important to avoid conflicts during the update.

🎯 Goal: Create a Kubernetes Deployment manifest that uses the Recreate update strategy, which terminates all old pods before creating new ones.

📋 What You'll Learn

Create a Deployment named webapp in the default namespace

Use the image nginx:1.21 for the pods

Set the update strategy to Recreate

Set the number of replicas to 2

Expose the pods on container port 80

💡 Why This Matters

🌍 Real World

Using the Recreate update strategy is useful when your application cannot run multiple versions simultaneously or when you want to avoid conflicts during updates.

💼 Career

Understanding update strategies in Kubernetes is essential for DevOps engineers to manage application deployments safely and reliably.

1

Create the basic Deployment manifest

Create a Kubernetes Deployment manifest named webapp with 2 replicas using the image nginx:1.21. Set the container port to 80. Do not add the update strategy yet.

Kubernetes

# Write the Deployment manifest YAML here
# Your code here

Hint

Start by defining apiVersion, kind, metadata, and spec. Use replicas: 2 and set the container image to nginx:1.21. Don't add the update strategy yet.

2

Add the Recreate update strategy

Add the strategy field under spec and set its type to Recreate in the Deployment manifest.

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
  namespace: default
spec:
  replicas: 2
  # Add strategy with type Recreate below
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: nginx
        image: nginx:1.21
        ports:
        - containerPort: 80

Hint

Under spec, add strategy: and set type: Recreate to specify the update strategy.

3

Apply the Deployment manifest

Use the kubectl apply -f deployment.yaml command to create the Deployment in the cluster. Assume the manifest is saved as deployment.yaml.

Kubernetes

# Run the command to apply the deployment manifest
# Your code here

Hint

Use kubectl apply -f deployment.yaml to create or update the Deployment from the YAML file.

4

Verify the update strategy

Run the command kubectl get deployment webapp -o jsonpath='{.spec.strategy.type}' to display the update strategy type of the webapp Deployment.

Kubernetes

# Run the command to check the update strategy
# Your code here

Hint

This command extracts the update strategy type from the Deployment's spec. It should print Recreate.

Practice

1. What does the Recreate update strategy do in Kubernetes?

easy

A. Deletes old pods before creating new ones, causing downtime

B. Creates new pods first, then deletes old pods to avoid downtime

C. Updates pods one by one without deleting any

D. Scales pods up and down simultaneously during update

Solution

1. Step 1: Understand the Recreate strategy behavior

   The Recreate strategy deletes all old pods before starting new pods, which causes downtime.

2. Step 2: Compare with other strategies

   Other strategies like RollingUpdate create new pods before deleting old ones to avoid downtime, unlike Recreate.

3. Final Answer:

   Deletes old pods before creating new ones, causing downtime -> Option A

4. Quick Check:

   Recreate = delete old pods first [OK]

Hint: Recreate means delete old pods first, then create new [OK]

Common Mistakes:

• Confusing Recreate with RollingUpdate
• Thinking Recreate avoids downtime
• Assuming pods update one by one

2. Which YAML snippet correctly sets the update strategy to Recreate in a Deployment?

easy

A. strategy:\n type: RollingUpdate

B. strategy:\n type: Recreate

C. updateStrategy:\n type: Recreate

D. deploymentStrategy:\n type: Recreate

Solution

1. Step 1: Identify correct field name for update strategy

   The correct field under Deployment spec is strategy with a nested type.

2. Step 2: Check correct value for Recreate

   The value must be exactly Recreate to set that strategy.

3. Final Answer:

   strategy:\n type: Recreate -> Option B

4. Quick Check:

   strategy.type = Recreate [OK]

Hint: Use 'strategy.type: Recreate' exactly in Deployment spec [OK]

Common Mistakes:

• Using wrong field names like updateStrategy or deploymentStrategy
• Setting type to RollingUpdate instead of Recreate
• Incorrect indentation or YAML syntax

3. Given this Deployment with strategy.type: Recreate, what happens when you update the container image?

medium

A. Pods update one by one without downtime

B. New pods start first, then old pods terminate, no downtime

C. All old pods are terminated before new pods start, causing downtime

D. Pods scale up and down simultaneously

Solution

1. Step 1: Understand Recreate update behavior on image change

   When the image changes, Recreate deletes all old pods before creating new pods.

2. Step 2: Recognize downtime impact

   Because old pods are deleted first, there is downtime until new pods are ready.

3. Final Answer:

   All old pods are terminated before new pods start, causing downtime -> Option C

4. Quick Check:

   Recreate update = downtime during pod replacement [OK]

Hint: Recreate deletes old pods first, causing downtime on update [OK]

Common Mistakes:

• Assuming pods update without downtime
• Confusing with RollingUpdate behavior
• Thinking pods update one by one

4. You set strategy.type: Recreate but notice pods are not deleted before new ones start. What is the likely issue?

medium

A. The Deployment has maxUnavailable set to 0, causing RollingUpdate behavior

B. The Deployment is using StatefulSet instead of Deployment

C. The pods have readinessProbe misconfigured

D. The strategy type is misspelled or incorrectly set

Solution

1. Step 1: Check strategy type correctness

   If pods are not deleted first, the strategy type may be misspelled or set incorrectly, so Kubernetes defaults to RollingUpdate.

2. Step 2: Rule out other causes

   maxUnavailable affects RollingUpdate, readinessProbe affects pod readiness, and StatefulSet is a different resource type.

3. Final Answer:

   The strategy type is misspelled or incorrectly set -> Option D

4. Quick Check:

   Misspelled strategy.type causes default RollingUpdate [OK]

Hint: Check exact spelling of strategy.type: Recreate [OK]

Common Mistakes:

• Assuming maxUnavailable affects Recreate
• Ignoring YAML syntax errors
• Confusing Deployment with StatefulSet

5. You have an app that cannot run multiple versions simultaneously. How do you configure the Deployment update strategy to avoid version conflicts?

hard

A. Set strategy.type: Recreate to delete old pods before new ones

B. Set strategy.type: RollingUpdate with maxSurge=1

C. Use kubectl rollout restart without changing strategy

D. Set strategy.type: BlueGreen for zero downtime

Solution

1. Step 1: Identify app requirement

   The app cannot run multiple versions at the same time, so pods must not overlap.

2. Step 2: Choose update strategy

   Recreate deletes old pods before creating new ones, ensuring no version overlap.

3. Step 3: Rule out other options

   RollingUpdate allows overlapping versions, kubectl restart doesn't change strategy, BlueGreen is not a built-in Kubernetes strategy.

4. Final Answer:

   Set strategy.type: Recreate to delete old pods before new ones -> Option A

5. Quick Check:

   App needs no overlap = use Recreate [OK]

Hint: Use Recreate strategy to avoid running multiple versions [OK]

Common Mistakes:

• Choosing RollingUpdate which allows overlap
• Thinking kubectl restart changes update strategy
• Assuming BlueGreen is a native Kubernetes strategy