Deployment as higher-level abstraction in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the kind of Kubernetes object for a Deployment.

Kubernetes

apiVersion: apps/v1
kind: [1]
metadata:
  name: nginx-deployment

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

ADeployment

BConfigMap

CPod

DService

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Pod' instead of 'Deployment' causes only one pod to be created.

Using 'Service' does not manage pod replicas.

The kind field specifies the type of Kubernetes object. For managing replicas and updates, Deployment is used.

2fill in blank

medium

Complete the code to set the number of pod replicas in a Deployment.

Kubernetes

spec:
  replicas: [1]

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

A"three"

B3

Creplicas

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the number in quotes makes it a string, which is invalid.

Using a boolean like 'true' is incorrect here.

The replicas field expects a number, not a string or boolean. Here, 3 means three pod copies.

3fill in blank

hard

Fix the error in the selector field to correctly match pod labels.

Kubernetes

spec:
  selector:
    matchLabels:
      app: [1]

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

Anginx

Bapp

CmatchLabels

Dspec

Attempts:

3 left

💡 Hint

Common Mistakes

Using the label key instead of the value causes no pods to be selected.

Using unrelated words breaks the selector.

The selector must match the label value of pods. Here, pods have label app: nginx, so the value should be nginx.

4fill in blank

hard

Fill both blanks to complete the pod template labels and container image.

Kubernetes

spec:
  template:
    metadata:
      labels:
        app: [1]
    spec:
      containers:
      - name: nginx
        image: [2]

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

Anginx

Bnginx:latest

Cnginx:1.21

Dapp

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching labels and selectors causes pods not to be managed.

Using 'nginx:latest' can cause unpredictable updates.

The pod labels must match the selector value, so app: nginx. The container image should specify a valid image tag like nginx:1.21.

5fill in blank

hard

Fill all three blanks to complete the Deployment spec with replicas, selector, and container image.

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
spec:
  replicas: [1]
  selector:
    matchLabels:
      app: [2]
  template:
    metadata:
      labels:
        app: [2]
    spec:
      containers:
      - name: webapp
        image: [3]

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

A2

Bwebapp

Cwebapp:v2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using different labels in selector and template breaks pod matching.

Not specifying replicas as a number causes errors.

Using image without a tag can lead to unexpected versions.

The Deployment runs 3 replicas (3), with pods labeled app: webapp. The container image is webapp:v2 for version control.

Practice

1. What is the main purpose of a Kubernetes Deployment?

easy

A. To provide network access to pods

B. To store data persistently across pods

C. To schedule pods on specific nodes manually

D. To manage multiple copies of an application and keep them running

Solution

1. Step 1: Understand Deployment role

   A Deployment manages the desired number of pod replicas and ensures they stay running.

2. Step 2: Compare other options

   Options A, B, and D describe Services, Persistent Volumes, and manual scheduling, which are not Deployment's main purpose.

3. Final Answer:

   To manage multiple copies of an application and keep them running -> Option D

4. Quick Check:

   Deployment manages pods = C [OK]

Hint: Deployment controls app copies and uptime [OK]

Common Mistakes:

• Confusing Deployment with Service or Volume
• Thinking Deployment schedules pods manually
• Assuming Deployment stores data

2. Which of the following is the correct minimal YAML snippet to define a Deployment selector matching pods with label app: myapp?

easy

A. selector:
matchLabels:
app: myapp

B. selector:
labels:
app: myapp

C. selector:
matchLabels:
name: myapp

D. selector:
matchExpressions:
- key: app
operator: In
values: [myapp]

Solution

1. Step 1: Recall Deployment selector syntax

   The selector must use matchLabels with key-value pairs matching pod labels.

2. Step 2: Check options

   selector: matchLabels: app: myapp uses correct matchLabels with app: myapp. selector: labels: app: myapp uses wrong key labels. selector: matchLabels: name: myapp uses wrong label key name. selector: matchExpressions: - key: app operator: In values: [myapp] uses matchExpressions which is valid but more complex and not minimal.

3. Final Answer:

   selector: matchLabels: app: myapp -> Option A

4. Quick Check:

   Use matchLabels with correct key = A [OK]

Hint: Use matchLabels with exact pod label keys [OK]

Common Mistakes:

• Using 'labels' instead of 'matchLabels'
• Mismatching label keys in selector
• Confusing matchLabels with matchExpressions

3. Given this Deployment YAML snippet, what will be the number of pods running after applying it?

apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-deploy
spec:
  replicas: 3
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      containers:
      - name: nginx
        image: nginx:latest

medium

A. 0 pods running due to label mismatch

B. 1 pod running

C. 3 pods running

D. Deployment will fail to create pods

Solution

1. Step 1: Check replicas and labels

   The Deployment requests 3 replicas and the selector matches pods with label app: test. The pod template labels match this exactly.

2. Step 2: Confirm pod creation

   Since labels match, Kubernetes will create 3 pods as requested.

3. Final Answer:

   3 pods running -> Option C

4. Quick Check:

   Matching labels + replicas 3 = 3 pods [OK]

Hint: Match selector and template labels to get pods [OK]

Common Mistakes:

• Assuming label mismatch causes zero pods
• Thinking Deployment fails without errors
• Ignoring replicas count

4. You applied a Deployment YAML but no pods are created. Which issue is most likely causing this?

medium

A. The Deployment metadata name is missing

B. The Deployment selector labels do not match the pod template labels

C. The replicas field is set to zero

D. The container image name is missing

Solution

1. Step 1: Understand Deployment selector importance

   The Deployment uses the selector to find pods it manages. If selector labels don't match pod template labels, no pods are created.

2. Step 2: Evaluate other options

   Missing image name causes pod creation failure but usually with errors. Replicas zero means no pods but is explicit. Missing metadata name causes YAML validation error.

3. Final Answer:

   The Deployment selector labels do not match the pod template labels -> Option B

4. Quick Check:

   Selector-template label mismatch = no pods [OK]

Hint: Check selector and template labels match exactly [OK]

Common Mistakes:

• Ignoring label mismatch
• Assuming missing image silently creates no pods
• Confusing replicas zero with label mismatch

5. You want to update your app smoothly without downtime using a Deployment. Which feature of Deployment helps achieve this?

hard

A. Rolling update strategy that replaces pods gradually

B. Manual pod deletion to force restart

C. Setting replicas to zero before update

D. Using a StatefulSet instead of Deployment

Solution

1. Step 1: Identify update strategies in Deployment

   Deployment supports rolling updates that replace pods one by one, keeping the app available.

2. Step 2: Compare other options

   Manual deletion causes downtime. Setting replicas to zero stops all pods. StatefulSet is for stateful apps, not smooth rolling updates.

3. Final Answer:

   Rolling update strategy that replaces pods gradually -> Option A

4. Quick Check:

   Rolling update = smooth app update [OK]

Hint: Rolling update replaces pods one by one [OK]

Common Mistakes:

• Deleting pods manually causes downtime
• Scaling replicas to zero stops app
• Confusing StatefulSet with Deployment update