Kubernetes DaemonSet

데몬셋

각각의 노드에서 같은 셀렉터(레이블)를 갖고 있는 파드를 한 개씩 생성하고 실행하는 컨트롤러이며 롤링 업데이트 및 롤백 기능 제공

▶ 주로 로그 수집기, 모니터링 에이전트와 같은 프로그램을 실행하는 파드를 생성할 때 사용됨

• 신규 노드가 클러스터에 추가되면 파드도 같이 생성됨
• 신규 노드가 클러스터에서 제거되면 추가되었던 파드는 가비지 상태로 전환됨
• 데몬셋을 삭제하면, 데몬셋이 생성한 파드들은 삭제됨

[root@master ~/kube/07/ds]# kubectl api-resources | grep Daemon
daemonsets                        ds           apps/v1                                true         DaemonSet
[root@master ~/kube/07/ds]# vi nginx-ds.yaml
[root@master ~/kube/07/ds]# cat nginx-ds.yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: nginx-ds
spec:
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      name: nginx-pod
      labels:
        app: webui
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.14
[root@master ~/kube/07/ds]# kubectl apply -f nginx-ds.yaml
daemonset.apps/nginx-ds created
[root@master ~/kube/07/ds]# kubectl get pod -o wide
NAME             READY   STATUS    RESTARTS   AGE   IP               NODE    NOMINATED NODE   READINESS GATES
nginx-ds-7n2lx   1/1     Running   0          8s    10.233.102.159   node1   <none>           <none>
nginx-ds-mm5bg   1/1     Running   0          7s    10.233.71.26     node3   <none>           <none>
nginx-ds-qpsv9   1/1     Running   0          7s    10.233.75.41     node2   <none>           <none>

▶ 각 노드에 하나씩 생긴 것을 확인할 수 있음

[root@master ~/kube/07/ds]# kubectl get daemonsets.apps
NAME       DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
nginx-ds   3         3         3       3            3           <none>          77s
[root@master ~/kube/07/ds]# kubectl describe daemonsets.apps nginx-ds
Name:           nginx-ds
Selector:       app=webui
Node-Selector:  <none>
Labels:         <none>
Annotations:    deprecated.daemonset.template.generation: 1
Desired Number of Nodes Scheduled: 3
Current Number of Nodes Scheduled: 3
Number of Nodes Scheduled with Up-to-date Pods: 3
Number of Nodes Scheduled with Available Pods: 3
Number of Nodes Misscheduled: 0
Pods Status:  3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  app=webui
  Containers:
   nginx-container:
    Image:        nginx:1.14
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Events:
  Type    Reason            Age   From                  Message
  ----    ------            ----  ----                  -------
  Normal  SuccessfulCreate  82s   daemonset-controller  Created pod: nginx-ds-7n2lx
  Normal  SuccessfulCreate  82s   daemonset-controller  Created pod: nginx-ds-qpsv9
  Normal  SuccessfulCreate  82s   daemonset-controller  Created pod: nginx-ds-mm5bg

▶ pod는 daemonset-controller에 의해 생성됨
kube-system에서 daemonset으로 구동되는 리소스 확인

[root@master ~/kube/07/ds]# kubectl get ds -n kube-system
NAME           DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR            AGE
calico-node    4         4         4       4            4           kubernetes.io/os=linux   27h
kube-proxy     4         4         4       4            4           kubernetes.io/os=linux   27h
nodelocaldns   4         4         4       4            4           kubernetes.io/os=linux   27h

▶ kube-system에 있는 pod 들과 다르게 master에 사용자 정의 daemonset이 뜨지 않는 이유는 기본적으로 taint가 걸려있기때문

[root@master ~/kube/07/ds]# kubectl describe nodes | grep Taint
Taints:             node-role.kubernetes.io/control-plane:NoSchedule
Taints:             <none>
Taints:             <none>
Taints:             <none>
[root@master ~/kube/07/ds]# kubectl taint nodes master node-role.kubernetes.io/control-plane:NoSchedule-
node/master untainted
[root@master ~/kube/07/ds]# kubectl get pod
NAME             READY   STATUS              RESTARTS   AGE
nginx-ds-7n2lx   1/1     Running             0          9m12s
nginx-ds-mm5bg   1/1     Running             0          9m11s
nginx-ds-qpsv9   1/1     Running             0          9m11s
nginx-ds-r49tr   0/1     ContainerCreating   0          4s
[root@master ~/kube/07/ds]# kubectl get pod -o wide
NAME             READY   STATUS    RESTARTS   AGE     IP               NODE     NOMINATED NODE   READINESS GATES
nginx-ds-7n2lx   1/1     Running   0          9m20s   10.233.102.159   node1    <none>           <none>
nginx-ds-mm5bg   1/1     Running   0          9m19s   10.233.71.26     node3    <none>           <none>
nginx-ds-qpsv9   1/1     Running   0          9m19s   10.233.75.41     node2    <none>           <none>
nginx-ds-r49tr   1/1     Running   0          12s     10.233.97.133    master   <none>           <none>

▶ Taint를 풀어주면 자동으로 생성되는 것을 확인할 수 있음

[root@master ~/kube/07/ds]# kubectl taint nodes master node-role.kubernetes.io/control-plane:NoSchedule
node/master tainted