Pod Design

Updated Dec 29, 2023 ·

Some of the scenario questions here are based on Kodekloud's CKAD course labs.

NOTE

CKAD and CKA can have similar scenario questions. It is recommended to go through the CKA practice tests.

Shortcuts

First run the two commands below for shortcuts.

export do="--dry-run=client -o yaml" 
export now="--force --grace-period=0"

Questions

Upgrade the application by setting the image on the deployment to kodekloud/webapp-color:v2. Do not delete and re-create the deployment. Only set the new image name for the existing deployment.

controlplane ~ ✦ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           6m46s 

Answer

controlplane ~ ✦ ✖ k set image deploy frontend simple-webapp=kodekloud/webapp-color:v2
deployment.apps/frontend image updated

controlplane ~ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   5/4     4            3           5m18s 

Change the deployment strategy to Recreate.

controlplane ~ ✦ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           6m46s 

Answer

controlplane ~ ✦2 ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           8m14s

controlplane ~ ✦2 ➜  k get deployments.apps frontend -o yaml > frontend.yml

controlplane ~ ✦2 ➜  k delete -f frontend.yml 
deployment.apps "frontend" deleted

controlplane ~ ✦2 ➜  k get deployments.apps 
No resources found in default namespace. 

## frontend.yml
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: frontend
  namespace: default
spec:
  replicas: 4
  selector:
    matchLabels:
      name: webapp
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        name: webapp
    spec:
      containers:
      - image: kodekloud/webapp-color:v2
        name: simple-webapp
        ports:
        - containerPort: 8080
          protocol: TCP

controlplane ~ ✦2 ➜  k apply -f frontend.yml 
deployment.apps/frontend created

controlplane ~ ✦2 ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           6s

A pod definition file named throw-dice-pod.yaml is given. The image throw-dice randomly returns a value between 1 and 6. 6 is considered success and all others are failure. Try deploying the POD and view the POD logs for the generated number. File is located at /root/throw-dice-pod.yaml

controlplane ~ ➜  cat throw-dice-pod.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: throw-dice-pod
spec:
  containers:
  - image: kodekloud/throw-dice
    name: throw-dice
restartPolicy: Never 

Next, create a Job using this POD definition file or from the imperative command and look at how many attempts does it take to get a '6'.

Job Name: throw-dice-job
Image Name: kodekloud/throw-dice

Then update the job definition to run as many times as required to get 3 successful 6's

Answer

controlplane ~ ➜  k apply  -f throw-dice-pod.yaml 
pod/throw-dice-pod created

controlplane ~ ➜  k get po
NAME             READY   STATUS              RESTARTS   AGE
throw-dice-pod   0/1     ContainerCreating   0          3s

controlplane ~ ➜  k get po
NAME             READY   STATUS   RESTARTS   AGE
throw-dice-pod   0/1     Error    0          4s

controlplane ~ ➜  k logs throw-dice-pod 
5

Create the job.

controlplane ~ ➜  k create job throw-dice-job --image kodekloud/throw-dice $do
apiVersion: batch/v1
kind: Job
  metadata:
  creationTimestamp: null
  name: throw-dice-job
spec:
  template:
    metadata:
      creationTimestamp: null
    spec:
      containers:
      - image: kodekloud/throw-dice
        name: throw-dice-job
        resources: {}
    restartPolicy: Never
status: {}

controlplane ~ ➜  k create job throw-dice-job --image kodekloud/throw-dice $do > job.yml

## job.yml
apiVersion: batch/v1
kind: Job
metadata:
  creationTimestamp: null
  name: throw-dice-job
spec:
  backoffLimit: 15
  template:
    metadata:
    creationTimestamp: null
    spec:
    containers:
    - image: kodekloud/throw-dice
        name: throw-dice-job
        resources: {}
    restartPolicy: Never
status: {} 

controlplane ~ ➜  k apply -f job.yml 
job.batch/throw-dice-job created

controlplane ~ ➜  k get job
NAME             COMPLETIONS   DURATION   AGE
throw-dice-job   0/1           4s         4s

Update the job definition to run as many times as required to get 3 successful 6's

apiVersion: batch/v1
kind: Job
metadata:
  name: throw-dice-job
spec:
  completions: 3
  backoffLimit: 25 # This is so the job does not quit before it succeeds.
  template:
    spec:
      containers:
      - name: throw-dice
        image: kodekloud/throw-dice
    restartPolicy: Never

Using the same YAML file from the previous question, speed it up by running upto 3 jobs in parallel.

controlplane ~ ✦2 ➜  k get job
NAME             COMPLETIONS   DURATION   AGE
throw-dice-job   3/3           15s        40s 

Answer

controlplane ~ ✦2 ➜  k delete job throw-dice-job 
job.batch "throw-dice-job" deleted

controlplane ~ ✦2 ➜  k get job
No resources found in default namespace. 

## job.yml
apiVersion: batch/v1
kind: Job
metadata:
name: throw-dice-job
spec:
parallelism: 3
completions: 3
backoffLimit: 25 # This is so the job does not quit before it succeeds.
template:
    spec:
    containers:
    - name: throw-dice
        image: kodekloud/throw-dice
    restartPolicy: Never

controlplane ~ ✦2 ➜  k apply -f job.yml 
job.batch/throw-dice-job created

Using the same YAML file from the previous question, schedule that job to run at 21:30 hours every day.

Answer

## cronjob.yml
apiVersion: batch/v1
kind: CronJob
metadata:
name: throw-dice-cron-job
spec:
schedule: "30 21 * * *"
jobTemplate:
    spec:
    completions: 3
    parallelism: 3
    backoffLimit: 25 # This is so the job does not quit before it succeeds.
    template:
        spec:
        containers:
        - name: throw-dice
            image: kodekloud/throw-dice
        restartPolicy: Never 

controlplane ~ ✦5 ➜  k apply -f cronjob.yml
cronjob.batch/throw-dice-cron-job created

controlplane ~ ✦5 ➜  k get cronjobs.batch 
NAME                  SCHEDULE      SUSPEND   ACTIVE   LAST SCHEDULE   AGE
throw-dice-cron-job   30 21 * * *   False     0        <none>          8s

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