Day 59: Troubleshoot Deployment Issues in Kubernetes

#kubernetes #devops

Last week, the Nautilus DevOps team deployed a redis app on Kubernetes cluster, which was working fine so far. This morning one of the team members was making some changes in this existing setup, but he made some mistakes and the app went down. We need to fix this as soon as possible. Please take a look.

The deployment name is redis-deployment. The pods are not in running state right now, so please look into the issue and fix the same.

Step 1: Identify the Issue

kubectl get deployments
kubectl get pods
kubectl describe deployment redis-deployment

Issues Found:

Pod stuck in ContainerCreating status
Image: redis:alpin (invalid, should be redis:alpine)
ConfigMap: redis-conig (misspelled, should be redis-config)

Step 2: Delete the Faulty Deployment

kubectl delete deployment redis-deployment

Step 3: Create Corrected YAML

cat > redis-deployment-fixed.yaml << 'EOF'
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis-deployment
  labels:
    app: redis
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis-container
        image: redis:alpine
        ports:
        - containerPort: 6379
        resources:
          requests:
            cpu: 300m
        volumeMounts:
        - mountPath: /redis-master-data
          name: data
        - mountPath: /redis-master
          name: config
      volumes:
      - name: data
        emptyDir: {}
      - name: config
        configMap:
          name: redis-config
EOF

Step 4: Apply the Corrected Deployment

kubectl apply -f redis-deployment-fixed.yaml

Step 5: Verify the Fix

kubectl get deployments

Output:

NAME               READY   UP-TO-DATE   AVAILABLE   AGE
redis-deployment   1/1     1            1           31s

kubectl get pods

Output:

NAME                                READY   STATUS    RESTARTS   AGE
redis-deployment-5476b4ddd6-f7txp   1/1     Running   0          31s

Key Learnings

Common Issues and Fixes

Issue	Symptom	Fix
Invalid image name	`ContainerCreating`	Use correct image name and tag
Misspelled ConfigMap	`ContainerCreating`	Match ConfigMap name exactly
Missing ConfigMap	`ContainerCreating`	Create the ConfigMap
Resource limits	`Pending` or `CrashLoopBackOff`	Adjust resource requests/limits

Troubleshooting Commands

Command	Purpose
`kubectl get deployments`	Check deployment status
`kubectl get pods`	Check pod status
`kubectl describe deployment <name>`	Detailed deployment info
`kubectl describe pod <name>`	Detailed pod info
`kubectl logs <pod-name>`	View pod logs
`kubectl get events`	View cluster events
`kubectl rollout status deployment <name>`	Check rollout status

DEV Community