Challenge - Intermediate project

Set up a project combining Deployment, Service and ConfigMap.

Challenge: the intermediate project

In the last challenge you'll repair a broken deployment. The api pods in the magaza namespace are in CrashLoopBackOff and the web service returns empty responses. Steps:

Gather the symptoms (get, describe).
Read the crashed container's log.
Add the missing setting and restart the deployment.
Compare the service selector with the pod labels and fix it.

$ kubectl logs -n magaza deploy/api --previous
Error: DB_HOST tanımlı değil
$ kubectl get svc web -n magaza -o jsonpath='{.spec.selector}'
{"app":"web-on"}       # the pods have app=web

Exercise Diagnosis

Write three commands: list the pods in the magaza namespace; show the previous container log of deploy/api in magaza; print the selector of the web service in magaza with jsonpath='{.spec.selector}'.

Show example solution

kubectl get pods -n magaza
kubectl logs deploy/api -n magaza --previous
kubectl get svc web -n magaza -o jsonpath='{.spec.selector}'

Exercise Repair

Write three commands: apply the patch {"data":{"DB_HOST":"db"}} to the api-ayar ConfigMap in magaza; restart the api deployment in magaza; fix the selector of the web service in magaza with the patch {"spec":{"selector":{"app":"web"}}}.

Show example solution

kubectl patch configmap api-ayar -n magaza -p '{"data":{"DB_HOST":"db"}}'
kubectl rollout restart deployment/api -n magaza
kubectl patch svc web -n magaza -p '{"spec":{"selector":{"app":"web"}}}'

Test yourself

If the service selector is app=web-on and the pods have app=web, why are there "empty responses"?
- The selector matches no pods; the service has no endpoints
- The pods are crashing
- The NodePort is closed
- DNS is broken
Show answer

The selector matches no pods; the service has no endpoints — The EndpointSlice appears empty.

Fix the service's selector.

kubectl ____ svc web -n magaza -p '{"spec":{"selector":{"app":"web"}}}'

Show answer

kubectl patch svc web -n magaza -p '{"spec":{"selector":{"app":"web"}}}'

Match.

CrashLoopBackOff

logs --previous
empty response

Selector and EndpointSlice
missing setting

Add to the ConfigMap
rollout restart

Apply the new setting

Next lesson: Intermediate section exam

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