StatefulSets for stateful applications in Kubernetes - Mini Project: Build & Apply

StatefulSets for stateful applications

📖 Scenario: You are managing a database application that needs stable network IDs and persistent storage. You will create a Kubernetes StatefulSet to ensure each database pod has a unique identity and stable storage.

🎯 Goal: Build a Kubernetes StatefulSet manifest for a simple stateful application with 3 replicas, stable network IDs, and persistent volume claims.

📋 What You'll Learn

Create a StatefulSet manifest with 3 replicas

Use a container image nginx:1.21

Set the serviceName to nginx

Add a volumeClaimTemplates for persistent storage

Print the final StatefulSet manifest YAML

💡 Why This Matters

🌍 Real World

StatefulSets are used to deploy databases, caches, and other applications that need stable network IDs and persistent storage in Kubernetes.

💼 Career

Understanding StatefulSets is essential for DevOps engineers managing stateful applications on Kubernetes clusters.

1

Create the basic StatefulSet structure

Create a YAML manifest for a StatefulSet named nginx with 3 replicas and serviceName set to nginx. Include the apiVersion as apps/v1 and kind as StatefulSet. Do not add containers or volumes yet.

Kubernetes

# Your YAML manifest starts here
# Define apiVersion, kind, metadata with name nginx, spec with replicas 3 and serviceName nginx

Need a hint?

Start by defining the basic StatefulSet fields: apiVersion, kind, metadata.name, and spec.replicas with spec.serviceName.

2

Add the container specification

Inside the spec.template.spec, add a container named nginx using the image nginx:1.21. Do not add volume mounts yet.

Kubernetes

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: nginx
spec:
  replicas: 3
  serviceName: nginx
  template:
    spec:
      # Add containers list here
      # Your code here

Need a hint?

Remember to nest containers under spec.template.spec. Use a list with one container named nginx and image nginx:1.21.

3

Add persistent volume claim template

Add a volumeClaimTemplates section under spec with one claim named nginx-pvc. It should request 1Gi storage with access mode ReadWriteOnce.

Kubernetes

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: nginx
spec:
  replicas: 3
  serviceName: nginx
  template:
    spec:
      containers:
      - name: nginx
        image: nginx:1.21
  # Add volumeClaimTemplates here
  # Your code here

Need a hint?

Use volumeClaimTemplates under spec to define persistent storage for each pod. Set accessModes and resources.requests.storage properly.

4

Print the complete StatefulSet manifest

Print the full StatefulSet YAML manifest you created so far.

Kubernetes

# Print the StatefulSet manifest
# Your code here

Need a hint?

Use multiple print statements to output each line of the YAML manifest exactly as written.