DevOps Classroom notes 03/Feb/2024

Jobs and Cronjobs in kubernetes

• In enterprise grade application we have batch jobs and scheduled jobs
• For doing the above mentioned activites we have
  • Job
  • CronJob
• Here Job expects the Pod to get into Completed state and Cron Job schedule the Pod to execute on some schedule
• Refer Here for official docs
• Lets run a cron job which runs every weekday at 1:00 AM which executes a container (sleep 300s)
• Refer Here for cron schedules
• Refer Here for specs
  

Daemonsets

• Refer Here for daemonset
• Daemonsets support rolling updates
• Lets create a daemon set which runs on every node Refer Here for changes.
  
• Note: Metrics Server Refer Here is an add-on in k8s which is enabled in managed k8s where as in kube-adm that is additional installation

kubectl top node
kubectl top pod

Scheduling pods in k8s

• Assigning pods to a node Refer Here
  • nodeSelector
  • Affinity and Anti-Affinity
  • nodeName
  • taints and tolerations
  • Resource Limits based (random)
• NodeSelector

---
apiVersion: v1
kind: Pod
metadata:
  name: web
  labels:
    name: web
    env: dev
spec:
  nodeSelector:
    test: prod
  containers:
  - name: web
    image: nginx
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"
    ports:
      - containerPort: 80

• nodeName

---
apiVersion: v1
kind: Pod
metadata:
  name: nodenamedemo
  labels:
    name: web
    env: dev
spec:
  nodeName: "aks-nodepool1-22765696-vmss000000"
  containers:
  - name: web
    image: nginx
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"
    ports:
      - containerPort: 80

• To be discussed tomorrwo