[애플리케이션 스케줄링과 라이프사이클 관리] 멀티플 스케줄러

멀티 스케줄러의 필요성

• 기본 스케줄러가 사용자의 필요에 맞지 않으면 사용자 고유의 스케줄러 구현 가능
• 기본 스케줄러와 함께 여러 스케줄러를 동시에 실행 가능
• 각 포드에 사용할 스케줄러를 지정하는 방식도 가능

my-scheduler.yaml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: my-scheduler
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: my-scheduler-as-kube-scheduler
subjects:
- kind: ServiceAccount
  name: my-scheduler
  namespace: kube-system
roleRef:
  kind: ClusterRole
  name: system:kube-scheduler
  apiGroup: rbac.authorization.k8s.io
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: my-scheduler-as-volume-scheduler
subjects:
- kind: ServiceAccount
  name: my-scheduler
  namespace: kube-system
roleRef:
  kind: ClusterRole
  name: system:volume-scheduler
  apiGroup: rbac.authorization.k8s.io
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: my-scheduler-config
  namespace: kube-system
data:
  my-scheduler-config.yaml: |
    apiVersion: kubescheduler.config.k8s.io/v1beta2
    kind: KubeSchedulerConfiguration
    profiles:
      - schedulerName: my-scheduler
    leaderElection:
      leaderElect: false    
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    component: scheduler
    tier: control-plane
  name: my-scheduler
  namespace: kube-system
spec:
  selector:
    matchLabels:
      component: scheduler
      tier: control-plane
  replicas: 1
  template:
    metadata:
      labels:
        component: scheduler
        tier: control-plane
        version: second
    spec:
      serviceAccountName: my-scheduler
      containers:
      - command:
        - /usr/local/bin/kube-scheduler
        - --config=/etc/kubernetes/my-scheduler/my-scheduler-config.yaml
        image: gcr.io/my-gcp-project/my-kube-scheduler:1.0
        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

두 포드 스케줄링

• 멜티 스케줄러를 사용해 두 포드를 스케줄

• schedulerName에 default-scheduluer를 작성하거나 아무 서술이 없는 경우 default-scheduler로 실행됨

• 세 번째 포드는 my-scheduler 사용

pod2.yaml

apiVersion: v1
  kind: Pod
  metadata:
    name: annotation-default-scheduler
    labels:
      name: multischeduler-example
  spec:
    schedulerName: default-scheduler
    containers:
    - name: pod-with-default-annotation-container
      image: registry.k8s.io/pause:2.0
  

pod3.yaml

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:2.0
  

클러스터롤에 권한이 부재

• 클러스터에 API 권한ㅇ르 부여하면 my-scheduler도 활성화 가능
• 다음 명령어로 클러스터 롤을 편집

kubectl edit clusterrole system:kube-scheduler

• ResourceName에 my-scheduler 추가

resourceNames:
- kube-scheduler
- my-scheduler

---

연습문제

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

-> kube-scheduler-controlplane

controlplane ~ ✖ kubectl get pods -A -o wide
NAMESPACE      NAME                                   READY   STATUS    RESTARTS   AGE   IP           NODE           NOMINATED NODE   READINESS GATES
kube-flannel   kube-flannel-ds-rvnw9                  1/1     Running   0          12m   192.4.66.9   controlplane   <none>           <none>
kube-system    coredns-5d78c9869d-gnxjj               1/1     Running   0          12m   10.244.0.2   controlplane   <none>           <none>
kube-system    coredns-5d78c9869d-lgqkz               1/1     Running   0          12m   10.244.0.3   controlplane   <none>           <none>
kube-system    etcd-controlplane                      1/1     Running   0          13m   192.4.66.9   controlplane   <none>           <none>
kube-system    kube-apiserver-controlplane            1/1     Running   0          13m   192.4.66.9   controlplane   <none>           <none>
kube-system    kube-controller-manager-controlplane   1/1     Running   0          13m   192.4.66.9   controlplane   <none>           <none>
kube-system    kube-proxy-hx94t                       1/1     Running   0          12m   192.4.66.9   controlplane   <none>           <none>
kube-system    kube-scheduler-controlplane            1/1     Running   0          13m   192.4.66.9   controlplane   <none>           <none>

What is the image used to deploy the kubernetes scheduler?

-> registry.k8s.io/kube-scheduler:v1.27.0

controlplane ~ ✖ kubectl describe pod kube-scheduler-controlplane -n kube-system
Name:                 kube-scheduler-controlplane
Namespace:            kube-system
Priority:             2000001000
Priority Class Name:  system-node-critical
Node:                 controlplane/192.4.66.9
Start Time:           Mon, 07 Aug 2023 21:21:40 -0400
Labels:               component=kube-scheduler
                      tier=control-plane
Annotations:          kubernetes.io/config.hash: db6b3451d765dd210f8e4065f082b37f
                      kubernetes.io/config.mirror: db6b3451d765dd210f8e4065f082b37f
                      kubernetes.io/config.seen: 2023-08-07T21:21:38.999465344-04:00
                      kubernetes.io/config.source: file
Status:               Running
SeccompProfile:       RuntimeDefault
IP:                   192.4.66.9
IPs:
  IP:           192.4.66.9
Controlled By:  Node/controlplane
Containers:
  kube-scheduler:
    Container ID:  containerd://d5bc333dbd18ab1e80a0025937bcc6dede595d43867831661e996c26b3b36a42
    Image:         registry.k8s.io/kube-scheduler:v1.27.0
    Image ID:      registry.k8s.io/kube-scheduler@sha256:939d0c6675c373639f53f05d61b5035172f95afb47ecffee6baf4e3d70543b66
    Port:          <none>
    Host Port:     <none>
    Command:
      kube-scheduler
      --authentication-kubeconfig=/etc/kubernetes/scheduler.conf
      --authorization-kubeconfig=/etc/kubernetes/scheduler.conf
      --bind-address=127.0.0.1
      --kubeconfig=/etc/kubernetes/scheduler.conf
      --leader-elect=true
    State:          Running
      Started:      Mon, 07 Aug 2023 21:21:30 -0400
    Ready:          True
    Restart Count:  0
    Requests:
      cpu:        100m
    Liveness:     http-get https://127.0.0.1:10259/healthz delay=10s timeout=15s period=10s #success=1 #failure=8
    Startup:      http-get https://127.0.0.1:10259/healthz delay=10s timeout=15s period=10s #success=1 #failure=24
    Environment:  <none>
    Mounts:
      /etc/kubernetes/scheduler.conf from kubeconfig (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kubeconfig:
    Type:          HostPath (bare host directory volume)
    Path:          /etc/kubernetes/scheduler.conf
    HostPathType:  FileOrCreate
QoS Class:         Burstable
Node-Selectors:    <none>
Tolerations:       :NoExecute op=Exists
Events:
  Type    Reason   Age   From     Message
  ----    ------   ----  ----     -------
  Normal  Pulled   15m   kubelet  Container image "registry.k8s.io/kube-scheduler:v1.27.0" already present on machine
  Normal  Created  15m   kubelet  Created container kube-scheduler
  Normal  Started  15m   kubelet  Started container kube-scheduler