You must see Ready.
STEP 0 — WHAT WE ARE BUILDING (VISUAL FIRST)
Final architecture
mysql-0, mysql-1, mysql-2 STEP 1 — CREATE A NAMESPACE (CLEAN ISOLATION)
kubectl create namespace mysql-lab kubectl config set-context --current --namespace=mysql-lab
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Verify:
kubectl get ns
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STEP 2 — HEADLESS SERVICE (MOST IMPORTANT FILE)
apiVersion: v1 kind: Service metadata: name: mysql-headless spec: clusterIP: None selector: app: mysql ports: - port: 3306 name: mysql
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Apply:
kubectl apply -f mysql-headless.yaml
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Verify:
kubectl get svc
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You must see:
mysql-headless ClusterIP None
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⚠️ Alone this is NOT ENOUGH — identity still missing
STEP 3 — STATEFULSET (THE CORE)
apiVersion: apps/v1 kind: StatefulSet metadata: name: mysql spec: serviceName: mysql-headless replicas: 3 selector: matchLabels: app: mysql template: metadata: labels: app: mysql spec: containers: - name: mysql image: mysql:8.0 env: - name: MYSQL_ROOT_PASSWORD value: rootpass ports: - containerPort: 3306 volumeMounts: - name: data mountPath: /var/lib/mysql volumeClaimTemplates: - metadata: name: data spec: accessModes: ["ReadWriteOnce"] resources: requests: storage: 1Gi
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Apply:
kubectl apply -f mysql-statefulset.yaml
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STEP 4 — WATCH POD CREATION (ORDER MATTERS)
kubectl get pods -w
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You will see:
mysql-0 → Running mysql-1 → Running mysql-2 → Running
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STEP 5 — VERIFY STABLE POD NAMES
kubectl get pods
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Expected:
mysql-0 mysql-1 mysql-2
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Restart one pod:
kubectl delete pod mysql-1
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Watch:
kubectl get pods -w
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Result:
mysql-1 comes backVISUAL: DEPLOYMENT VS STATEFULSET
This is why Deployments are unsafe for databases.
STEP 6 — VERIFY PERSISTENT STORAGE
kubectl get pvc
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Expected:
data-mysql-0 data-mysql-1 data-mysql-2
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Each pod has:
STEP 7 — VERIFY DNS (CRITICAL STEP)
Run a temporary client pod:
kubectl run dns-test --image=busybox:1.36 -it --rm --restart=Never -- sh
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Inside the pod:
nslookup mysql-0.mysql-headless nslookup mysql-1.mysql-headless nslookup mysql-2.mysql-headless
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Each resolves to a different IP.
Exit:
exit
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Format:
<pod-name>.<headless-service>.<namespace>.svc.cluster.local
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STEP 8 — CONNECT TO MYSQL (REAL TEST)
kubectl exec -it mysql-0 -- mysql -uroot -prootpass
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Inside MySQL:
CREATE DATABASE labdb; USE labdb; CREATE TABLE test (id INT); INSERT INTO test VALUES (1); SELECT * FROM test;
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Exit:
exit
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STEP 9 — DELETE POD, DATA MUST SURVIVE
kubectl delete pod mysql-0
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Wait until it comes back:
kubectl get pods -w
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Reconnect:
kubectl exec -it mysql-0 -- mysql -uroot -prootpass
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Check:
USE labdb; SELECT * FROM test;
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✅ Data is still there.
VISUAL: DATA SURVIVES POD DELETION
STEP 10 — WHAT THIS LAB PROVES (LOCK THIS IN)
SENIOR DEVOPS MENTAL MODEL (INTERVIEW READY)
“StatefulSets are required for databases because they provide stable pod identities and ordered lifecycle management. Headless services expose pod-level DNS so clients can target specific replicas. VolumeClaimTemplates ensure each pod has persistent storage that survives restarts.”
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