Manual Scheduling

Labels & Selectors

Taints and Toleration

Node Selectors

Node Affinity

Resources Requirement & Limit

DaemonSets

Static Pods

Multiple Scheduler

ref: https://kubernetes.io/docs/tasks/extend-kubernetes/configure-multiple-schedulers/

Deploy Additional Scheduler

Each scheduler uses a separate configuration file and with each file having its own scheduler name. This is not how you would deploy a cusstom scheduler 99% of the time today because with kubeadm deployment, all the control plane component run as a pod or a deployment within the kubernetes cluster.

Deploy Additional Scheduler As a Pod

pod definition for custom scheduler

apiVersion: v1
kind: Pod
metadata:
  name: annotation-second-scheduler
  labels:
    name: multischeduler-example
spec:
  schedulerName: my-scheduler
  containers:
  - name: pod-with-second-annotation-container
    image: registry.k8s.io/pause:3.8

Exercise

Questions

What is the name of the POD that deploys the default kubernetes scheduler in this environment?
What is the image used to deploy the kubernetes scheduler?
Let’s create a configmap that the new scheduler will employ using the concept of ConfigMap as a volume. We have already given a configMap definition file called my-scheduler-configmap.yaml

apiVersion: v1
data:
  my-scheduler-config.yaml: |
    apiVersion: kubescheduler.config.k8s.io/v1
    kind: KubeSchedulerConfiguration
    profiles:
      - schedulerName: my-scheduler
    leaderElection:
      leaderElect: false    
kind: ConfigMap
metadata:
  creationTimestamp: null
  name: my-scheduler-config
  namespace: kube-system

at /root/ path that will create a configmap with name my-scheduler-config using the content of file /root/my-scheduler-config.yaml. 4. Deploy an additional scheduler to the cluster following the given specification Use the manifest file provided at /root/my-scheduler.yaml.

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: my-scheduler
  name: my-scheduler
  namespace: kube-system
spec:
  serviceAccountName: my-scheduler
  containers:
  - command:
    - /usr/local/bin/kube-scheduler
    - --config=/etc/kubernetes/my-scheduler/my-scheduler-config.yaml
    image: <use-correct-image>
    livenessProbe:
      httpGet:
        path: /healthz
        port: 10259
        scheme: HTTPS
      initialDelaySeconds: 15
    name: kube-second-scheduler
    readinessProbe:
      httpGet:
        path: /healthz
        port: 10259
        scheme: HTTPS
    resources:
      requests:
        cpu: '0.1'
    securityContext:
      privileged: false
    volumeMounts:
      - name: config-volume
        mountPath: /etc/kubernetes/my-scheduler
  hostNetwork: false
  hostPID: false
  volumes:
    - name: config-volume
      configMap:
        name: my-scheduler-config

Use the same image as used by the default kubernetes scheduler. 5. a POD definition file is given. Use it to create a POD with the new custom scheduler.

apiVersion: v1 
kind: Pod 
metadata:
  name: nginx 
spec:
  containers:
  - image: nginx
    name: nginx

Solution

run k get pods -n kube-system -> kube-scheduler-controlplane
run k describe pod kube-scheduler-controlplane
run kubectl create configmap my-scheduler-config --from-file=/root/my-scheduler-config.yaml -n kube-system, then check the result by running k get configmap my-scheduler-config -n kube-system
steps

check the image from pod using k describe pod kube-scheduler-controlplane -n kube-system | grep Image
copy the image to the yaml file
run k create -f my-scheduler.yaml

edit the yaml file

apiVersion: v1 
kind: Pod 
metadata:
  name: nginx 
spec:
  schedulerName: my-scheduler
  containers:
  - image: nginx
    name: nginx

and run k apply -f nginx-pod.yaml

Admission Controllers

Validating & Mutating Admission Controllers

CKA: Scheduler