Resource Requirements & Limits

Resource Requests [Pod]

    - name: myapp
        image: myapp:latest
                memory: "64Mi"
                cpu: "2"

Resource Limits [Pod]

    - name: myapp
        image: myapp:latest
                memory: "1Gi"
                cpu: "1"
                memory: "2Gi"
                cpu: "2"
  • Containers can't user more CPU than it's limit

  • A container can use more memory than its limits

Limit Range

  • Helps us to set a default limit or request.

    - default:
        cpu: "500m"
        cpu: "500m"
        cpu: "1"
        cpu: "100m"
      type: Container

Resource Quotas

  • These are used to define and restrict how much membery & cpu can all pods utilize.

  • Max resource limits are mentioned.

Lab Learning [Resources]

  • We can't change pod resources during its execution hence on changes are saved in /temp/ directory.

  • We can use kubectl replace --force -f </temp/location> it will terminate running pod and create new one.

Static Pods

  • The pods created by kubelet without intervention from kube-apiserver are called as static pods.

  • Manifests for pods are saved in /etc/kubernetes/manifests.

  • We can't create deployments, replicasets, services using this.

Lab Learnings [Static Pods]

  • Static pods are visible by get pods command.

  • It will have node-name after it's name, that's how you find static pods

  • eg: kube-apiserver-controlplane - controlplane is the node name.

  • To delete pod, you have to delete manifest file in location.

  • Similarly update it.

  • To delete static pod in different node

    • ssh into node

    • go to /var/lib/kubelet/config.yaml

    • find staticPodPath

    • Go to the path and you'll find static pod manifest.

    • Delete it using rm command.

Manual Schedules

  • The scheduler config can be found at /etc/kuberenetes/config/...yml

  • If we have multiple mast nodes then only 1 scheduler configuration can run at a time.

  • We can use leaderElection & leaderElect=true to define leader in multiple master scenario.

  • We can specify what scheduler picks up the pod using schedulerName:<name-of-scheduler>

  • kubectl logs <scheduler-name> -n ns

  • kubectl get events

Stages of Scheduling

  • Scheduling Queue

  • Filtering

  • Scoring

  • Binding

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