如何将k8s中的某些节点单独、仅给某些应用来使用

1、概述

在k8s集群的使用场景中有这样的一种情况，某些机器只给某些特殊的应用来使用。那么，这个时候，需要有以下的2个条件来进行保障：

• 节点不允许其他的pod来使用
• 应用只允许被调度到该节点上

2、实现方法

我们如果要实现上述的目标，节点不被其他的pod应用来使用，那么将节点增加taints就可以，然后，pod在调度的时候有可能会被调度到其他的节点上，那么要保证pod只会被调度到这些的节点上，那么，在打了taints的节点上，在增加label即可。

下面是具体的实现的过程。

2.1、节点上增加taints和标签

kubectl taint nodes nccztsjb-node-23 role=master:NoSchedule

这样节点上就不允许没有toleration的pod运行

kubectl label nodes nccztsjb-node-23 dedicated=prod

2.2、pod上设置toleration和nodeSelector

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-taints
  namespace: default
spec:
  progressDeadlineSeconds: 600
  selector:
    matchLabels:
      app: nginx-taints
  replicas: 5
  template:
    metadata:
      labels:
        app: nginx-taints
    spec:
      containers:
      - image: 172.20.58.152/middleware/nginx:1.21.4
        imagePullPolicy: IfNotPresent
        name: nginx
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      tolerations:
      - key: "role"
        operator: "Exists"
        effect: "NoSchedule"
      nodeSelector:
        dedicated: "prod"

toleration保证pod可以在这个节点上运行，nodeSelector保证pod只在有包含dedicated=prod的标签节点上运行。

运行结果：

kubectl apply -f nginx-taints.yaml

查看pod运行状态

[root@nccztsjb-node-23 ~]# kubectl get pod -l app=nginx-taints -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP               NODE               NOMINATED NODE   READINESS GATES
nginx-taints-78b7978fd5-7sjm5   1/1     Running   0          5s    172.39.209.112   nccztsjb-node-23   <none>           <none>
nginx-taints-78b7978fd5-97hg9   1/1     Running   0          3s    172.39.209.116   nccztsjb-node-23   <none>           <none>
nginx-taints-78b7978fd5-bswrb   1/1     Running   0          5s    172.39.209.113   nccztsjb-node-23   <none>           <none>
nginx-taints-78b7978fd5-lfwzm   1/1     Running   0          5s    172.39.209.114   nccztsjb-node-23   <none>           <none>
nginx-taints-78b7978fd5-vxhfq   1/1     Running   0          3s    172.39.209.115   nccztsjb-node-23   <none>           <none>
[root@nccztsjb-node-23 ~]# 

pod的多个实例都运行在nccztsjb-node-23上了。

OK，以上是基本的配置过程。

如果#1：pod没有设置toleration

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-taints
  namespace: default
spec:
  progressDeadlineSeconds: 600
  selector:
    matchLabels:
      app: nginx-taints
  replicas: 5
  template:
    metadata:
      labels:
        app: nginx-taints
    spec:
      containers:
      - image: 172.20.58.152/middleware/nginx:1.21.4
        imagePullPolicy: IfNotPresent
        name: nginx
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      #tolerations:
      #- key: "role"
      #  operator: "Exists"
      #  effect: "NoSchedule"
      nodeSelector:
        dedicated: "prod"

运行pod及查看结果

[root@nccztsjb-node-23 ~]# kubectl apply -f nginx-taints.yaml 
deployment.apps/nginx-taints created
[root@nccztsjb-node-23 ~]# kubectl get pod -l app=nginx-taints -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP       NODE     NOMINATED NODE   READINESS GATES
nginx-taints-7cfdd85578-67smg   0/1     Pending   0          1s    <none>   <none>   <none>           <none>
nginx-taints-7cfdd85578-877zb   0/1     Pending   0          1s    <none>   <none>   <none>           <none>
nginx-taints-7cfdd85578-nl8p6   0/1     Pending   0          1s    <none>   <none>   <none>           <none>
nginx-taints-7cfdd85578-qgf4t   0/1     Pending   0          1s    <none>   <none>   <none>           <none>
nginx-taints-7cfdd85578-vw987   0/1     Pending   0          1s    <none>   <none>   <none>           <none>
[root@nccztsjb-node-23 ~]# 

都未被调度到节点上。

如果#2:节点上未设置nodeSelector

[root@nccztsjb-node-23 ~]# cat nginx-taints.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-taints
  namespace: default
spec:
  progressDeadlineSeconds: 600
  selector:
    matchLabels:
      app: nginx-taints
  replicas: 5
  template:
    metadata:
      labels:
        app: nginx-taints
    spec:
      containers:
      - image: 172.20.58.152/middleware/nginx:1.21.4
        imagePullPolicy: IfNotPresent
        name: nginx
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      tolerations:
      - key: "role"
        operator: "Exists"
        effect: "NoSchedule"
      #nodeSelector:
       # dedicated: "prod"

运行及查看pod的状态

[root@nccztsjb-node-23 ~]# kubectl apply -f nginx-taints.yaml 
deployment.apps/nginx-taints created
[root@nccztsjb-node-23 ~]# kubectl get pod -l app=nginx-taints -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP               NODE               NOMINATED NODE   READINESS GATES
nginx-taints-6cb85bb844-8ggsc   1/1     Running   0          3s    172.39.209.117   nccztsjb-node-23   <none>           <none>
nginx-taints-6cb85bb844-flbf2   1/1     Running   0          3s    172.39.21.121    nccztsjb-node-25   <none>           <none>
nginx-taints-6cb85bb844-gjlqm   1/1     Running   0          3s    172.39.21.120    nccztsjb-node-25   <none>           <none>
nginx-taints-6cb85bb844-hrxfr   1/1     Running   0          3s    172.39.157.206   nccztsjb-node-24   <none>           <none>
nginx-taints-6cb85bb844-q9vfk   1/1     Running   0          3s    172.39.157.201   nccztsjb-node-24   <none>           <none>
[root@nccztsjb-node-23 ~]# 

这样的结果就是pod可以在任意的节点上运行了，不仅仅是在nccztsjb-node-23节点上。