[cka] Multiple Schedulers

1. What is the name of the POD that deploys the default kubernetes scheduler in this environment?

 

% controlplane ~ ➜  k get pods -A
NAMESPACE      NAME                                   READY   STATUS    RESTARTS   AGE
kube-flannel   kube-flannel-ds-wkmwp                  1/1     Running   0          3m18s
kube-system    coredns-768b85b76f-blx82               1/1     Running   0          3m17s
kube-system    coredns-768b85b76f-p4qf4               1/1     Running   0          3m17s
kube-system    etcd-controlplane                      1/1     Running   0          3m32s
kube-system    kube-apiserver-controlplane            1/1     Running   0          3m32s
kube-system    kube-controller-manager-controlplane   1/1     Running   0          3m32s
kube-system    kube-proxy-txbqd                       1/1     Running   0          3m18s
kube-system    kube-scheduler-controlplane            1/1     Running   0          3m35s

 

answer : kube-scheduler-controlplane

 

2.  What is the image used to deploy the kubernetes scheduler? Inspect the kubernetes scheduler pod and identify the image

 

$ controlplane ~ ➜  k describe pod kube-scheduler-controlplane -n kube-system

...

Events:
  Type    Reason   Age    From     Message
  ----    ------   ----   ----     -------
  Normal  Pulled   5m38s  kubelet  Container image "registry.k8s.io/kube-scheduler:v1.30.0" already present on machine
  Normal  Created  5m37s  kubelet  Created container kube-scheduler
  Normal  Started  5m37s  kubelet  Started container kube-scheduler
...

 

answer : registry.k8s.io/kube-scheduler:v1.30.0

 

3.  We have already created the ServiceAccount and ClusterRoleBinding that our custom scheduler will make use of.

Checkout the following Kubernetes objects:

ServiceAccount: my-scheduler (kube-system namespace)
ClusterRoleBinding: my-scheduler-as-kube-scheduler
ClusterRoleBinding: my-scheduler-as-volume-scheduler

Run the command: kubectl get serviceaccount -n kube-system and kubectl get clusterrolebinding

Note: - Don't worry if you are not familiar with these resources. We will cover it later on.

 

 

 

4. 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 at /root/ path that will create a configmap with name my-scheduler-config using the content of file /root/my-scheduler-config.yaml.

 

$ controlplane ~ ➜  kubectl create -f /root/my-scheduler-configmap.yaml
configmap/my-scheduler-config created

 

 

5. Deploy an additional scheduler to the cluster following the given specification.

Use the manifest file provided at /root/my-scheduler.yaml. Use the same image as used by the default kubernetes scheduler.

 

---
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: registry.k8s.io/kube-scheduler:v1.30.0  # changed
    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
---

$ controlplane ~ ➜  k apply -f /root/my-scheduler.yaml
pod/my-scheduler created

 

6.  A POD definition file is given. Use it to create a POD with the new custom scheduler.

File is located at /root/nginx-pod.yaml

 

$ controlplane ~ ➜  vi nginx-pod.yaml 

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

$ controlplane ~ ➜  k apply -f nginx-pod.yaml
pod/nginx created