100-Days-Of-DevOps-Challenge-KodeKloud

Fix Python App Deployed on Kubernetes Cluster

One of the DevOps engineers was trying to deploy a python app on Kubernetes cluster. Unfortunately, due to some mis-configuration, the application is not coming up. Please take a look into it and fix the issues. Application should be accessible on the specified nodePort.

• The deployment name is python-deployment-devops, its using poroko/flask-demo-appimage. The deployment and service of this app is already deployed.
• nodePort should be 32345 and targetPort should be python flask app’s default port.

Note: The kubectl on jump_host has been configured to work with the kubernetes cluster.

Steps

1. Let’s see the pod status

    kubectl get pods
    kubectl describe pod pod-name
   

   In my case the eorror is look like this:

    Events:
    Type     Reason     Age                    From               Message
    ----     ------     ----                   ----               -------
    Normal   Scheduled  37m                    default-scheduler  Successfully assigned default/python-deployment-devops-678b746b7-f25jg to kodekloud-control-plane
    Normal   Pulling    36m (x4 over 37m)      kubelet            Pulling image "poroko/flask-app-demo"
    Warning  Failed     36m (x4 over 37m)      kubelet            Failed to pull image "poroko/flask-app-demo": rpc error: code = Unknown desc = failed to pull and unpack image "docker.io/poroko/flask-app-demo:latest": failed to resolve reference "docker.io/poroko/flask-app-demo:latest": pull access denied, repository does not exist or may require authorization: server message: insufficient_scope: authorization failed
    Warning  Failed     36m (x4 over 37m)      kubelet            Error: ErrImagePull
    Warning  Failed     36m (x6 over 37m)      kubelet            Error: ImagePullBackOff
    Normal   BackOff    2m45s (x152 over 37m)  kubelet            Back-off pulling
   

   docker.io/poroko/flask-app-demo:latest the dpeloyment using wrong docker image

2. Let’s create a k3s-deployment.yaml file from existing deployment

    kubectl get deployments.apps python-deployment-devops -o yaml > k3s-deployment.yaml
   

3. Let’s fix the docker image

    vi k3s-deployment.yaml
   

   replace docker image in container section with accurate image

4. Recreate the deployment

    kubectl delete deployments.apps python-deployment-devops
    kubectl apply -f k3s-deployment.yaml
   

   wait for 1-2 minutes and check status

    kubectl get pods
   

   try to access app, but its not working.

5. Now let’s check the service status

    kubectl get svc
   

     kubectl get svc
    NAME                    TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
    kubernetes              ClusterIP   10.96.0.1       <none>        443/TCP          23m
    python-service-devops   NodePort    10.96.109.187   <none>        8080:32345/TCP   12m
   

   So service is already running but it’s mapped with wrong target port. let’s fix that

6. Fixing service

    kubectl get svc python-service-devops -o yaml > k3s-service.yaml
   

   let’s change the target port in k3s-service.yaml file

    vi k3s-service.yaml
   

   configure service

    kubectl apply -f k3s.-svc.yaml
   

7. Verify results

    kubectl get svc
   

Good to Know?

Application Debugging

• Image Issues: Verify correct image names and tags
• Service Configuration: Check port mappings and selectors
• Network Connectivity: Test service-to-service communication
• Resource Constraints: Ensure adequate resources

Common Misconfigurations

• Wrong Image: Typos in image names or tags
• Port Mismatch: Service targetPort doesn’t match container port
• Label Mismatch: Service selector doesn’t match pod labels
• Resource Limits: Insufficient CPU/memory allocation

Debugging Workflow

• Check Pod Status: Verify pods are running
• Examine Events: Look for error messages
• Validate Configuration: Review YAML specifications
• Test Connectivity: Use port-forward or exec
• Check Logs: Application and system logs

Service Troubleshooting

• Endpoints: kubectl get endpoints shows service targets
• Port Forward: kubectl port-forward for direct access
• Service Discovery: Test DNS resolution within cluster
• Network Policies: Check if network policies block traffic

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