What Is a StatefulSet in Kubernetes?

A StatefulSet is a Kubernetes workload API object designed to manage stateful applications. Unlike Deployments, StatefulSets provide:

• Stable pod identities (e.g., mysql-0, mysql-1)

• Stable network hostnames

• Persistent storage using PersistentVolumeClaims (PVCs)

• Ordered deployment and scaling

StatefulSets are commonly used for:

• Databases (MySQL, PostgreSQL)

• Distributed systems (Kafka, Cassandra)

• Applications that require persistent data and stable networking

When Should You Use a StatefulSet?

Use a StatefulSet when your application:

• Requires persistent storage

• Needs stable pod names

• Depends on ordered startup or shutdown

• Maintains state across pod restarts

Creating a StatefulSet in Kubernetes (Step-by-Step)

Step 1: Create a ConfigMap (Optional)

If your application requires configuration values, create a ConfigMap.

apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql-config
data:
  MYSQL_ROOT_PASSWORD: my-secret-password
  MYSQL_DATABASE: mydb
dts

Step 2: Create a Headless Service

A headless service enables stable DNS entries for each pod in the StatefulSet.

apiVersion: v1
kind: Service
metadata:
  name: mysql-service
spec:
  clusterIP: None
  selector:
    app: mysql
  ports:
    - protocol: TCP
      port: 3306
yaml

Step 3: Create the MySQL StatefulSet

This StatefulSet creates three MySQL pods, each with its own persistent volume.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  serviceName: mysql-service
  replicas: 3
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - name: mysql
        image: mysql:5.7
        envFrom:
          - configMapRef:
              name: mysql-config
        ports:
          - containerPort: 3306
        volumeMounts:
          - name: mysql-persistent-storage
            mountPath: /var/lib/mysql
  volumeClaimTemplates:
  - metadata:
      name: mysql-persistent-storage
    spec:
      accessModes:
        - ReadWriteOnce
      resources:
        requests:
          storage: 1Gi
nestedtext

Step 4: Apply the Configuration

Deploy the resources to your Kubernetes cluster:

kubectl apply -f configmap.yaml
kubectl apply -f mysql-service.yaml
kubectl apply -f mysql-statefulset.yaml
coq

Step 5: Verify the StatefulSet

Check the status of your StatefulSet and pods:

kubectl get statefulsets
kubectl get pods
routeros

View logs from individual pods:

kubectl logs mysql-0
kubectl logs mysql-1
kubectl logs mysql-2
apache

Scaling a StatefulSet

You can scale a StatefulSet by updating the replica count.

kubectl scale statefulset mysql --replicas=4
routeros

Pods are created or deleted in order, preserving data integrity.

Accessing StatefulSet Pods

Each pod has a predictable hostname:

kubectl exec -it mysql-0 -- /bin/bash
applescript

StatefulSet vs Deployment (Quick Comparison)

Conclusion

StatefulSets are a core Kubernetes feature for running stateful workloads. They provide stable networking, persistent storage, and ordered scaling—making them ideal for databases and distributed systems.

By following this guide, you now know how to:

• Create a StatefulSet

• Attach persistent storage

• Scale and manage stateful applications

If you’re running databases on Kubernetes, StatefulSets are the right choice