20.kubernetes笔记 Pod资源调度(三)污点与容忍度

作者: Bigyong | 来源:发表于2021-12-28 07:11 被阅读0次

目录
概述
污点和容忍度
Pod调度顺序
示例1: 把Pod调度到master 对master:NoSchedule标识容忍
示例2: 为节点添加效用标识NoExecute 驱逐所有Pod

概述:

污点taints是定义在节点之上的键值型属性数据，用于让节点拒绝将Pod调度运行于其上，除非该Pod对象具有接纳节点污点的容忍度。而容忍度tolerations是定义在 Pod对象上的键值型属性数据，用于配置其可容忍的节点污点，而且调度器仅能将Pod对象调度至其能够容忍该节点污点的节点之上，如图所示

一个Pod能否被调度到节点上因素有

是否节点有污点
节点上有污点.Pod是否能容忍这个污点

污点和容忍度

污点定义在节点的node Spec中，而容忍度则定义在Pod的podSpec中，它们都是键值型数据，但又都额外支持一个效果effect标记，语法格式为key=value:effect，其中key和value的用法及格式与资源注俯－信息相似，而effect则用于定义对Pod对象的排斥等级，它主要包含以下三种类型效用标识

NoSchedule
不能容忍此污点的新Pod对象不可调度至当前节点，属于强制型约束关系，节点上现存的Pod对象不受影响。
PreferNoSchedule
的柔性约束版本，即不能容忍此污点的新Pod对象尽量不要调度至当前节点，不过无其他节点可供调度时也允许接受相应的Pod对象。节点上现存的Pod对象不受影响。
NoExecute
不能容忍此污点的新Pod对象不可调度至当前节点，属于强制型约束关系，而且节点上现存的Pod对象因节点污点变动或Pod容忍度变动而不再满足匹配规则时，Pod对象将被驱逐。

在Pod对象上定义容忍度时，它支持两种操作符：一种是等值比较Equal,表示容忍度与污点必须在key、value和effect三者之上完全匹配；另一种是存在性判断Exists，表示二者的key和effect必须完全匹配，而容忍度中的value字段要使用空值。

Pod调度顺序

一个节点可以配置使用多个污点，一个Pod对象也可以有多个容忍度，不过二者在进行匹配检查时应遵循如下逻辑。

首先处理每个有着与之匹配的容忍度的污点
不能匹配到的污点上，如果存在一个污点使用了NoSchedule效用标识，则拒绝调度Pod对象至此节点
不能匹配到的污点上，若没有任何一个使用了NoSchedule效用标识，但至少有一个使用了PreferNoScheduler，则应尽量避免将Pod对象调度至此节点
如果至少有一个不匹配的污点使用了NoExecute效用标识，则节点将立即驱逐Pod对象，或者不予调度至给定节点；另外，即便容忍度可以匹配到使用了 NoExecute效用标识的污点，若在定义容忍度时还同时使用tolerationSeconds属性定义了容忍时限，则超出时限后其也将被节点驱逐。

使用kubeadm部署的Kubernetes集群，其Master节点将自动添加污点信息以阻止不能容忍此污点的Pod对象调度至此节点，因此，用户手动创建的未特意添加容忍此污点容忍度的Pod对象将不会被调度至此节点

示例1: Pod调度到master 对master:NoSchedule标识容忍

[root@k8s-master Scheduler]#  kubectl describe node k8s-master.org    #查看master污点 效用标识
...
Taints:             node-role.kubernetes.io/master:NoSchedule
Unschedulable:      false

[root@k8s-master Scheduler]# cat tolerations-daemonset-demo.yaml 
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: daemonset-demo
  namespace: default
  labels:
    app: prometheus
    component: node-exporter
spec:
  selector:
    matchLabels:
      app: prometheus
      component: node-exporter
  template:
    metadata:
      name: prometheus-node-exporter
      labels:
        app: prometheus
        component: node-exporter
    spec:
      tolerations:  #容忍度  容忍master   NoSchedule标识
      - key: node-role.kubernetes.io/master  #是key值
        effect: NoSchedule  #效用标识
        operator: Exists  #存在即可
      containers:
      - image: prom/node-exporter:latest
        name: prometheus-node-exporter
        ports:
        - name: prom-node-exp
          containerPort: 9100
          hostPort: 9100

[root@k8s-master Scheduler]# kubectl apply -f  tolerations-daemonset-demo.yaml 

[root@k8s-master Scheduler]# kubectl get pod -o wide
NAME                                       READY   STATUS    RESTARTS   AGE     IP              NODE             NOMINATED NODE   READINESS GATES
daemonset-demo-7fgnd                       2/2     Running   0          5m15s   10.244.91.106   k8s-node2.org    <none>           <none>
daemonset-demo-dmd47                       2/2     Running   0          5m15s   10.244.70.105   k8s-node1.org    <none>           <none>
daemonset-demo-jhzwf                       2/2     Running   0          5m15s   10.244.42.29    k8s-node3.org    <none>           <none>
daemonset-demo-rcjmv                       2/2     Running   0          5m15s   10.244.59.16    k8s-master.org   <none>           <none>

示例2: 为节点添加effect效用标识NoExecute 驱逐所有Pod

[root@k8s-master Scheduler]# kubectl taint --help
Update the taints on one or more nodes.

  *  A taint consists of a key, value, and effect. As an argument here, it is expressed as key=value:effect.
  *  The key must begin with a letter or number, and may contain letters, numbers, hyphens, dots, and underscores, up to
253 characters.
  *  Optionally, the key can begin with a DNS subdomain prefix and a single '/', like example.com/my-app
  *  The value is optional. If given, it must begin with a letter or number, and may contain letters, numbers, hyphens,
dots, and underscores, up to  63 characters.
  *  The effect must be NoSchedule, PreferNoSchedule or NoExecute.
  *  Currently taint can only apply to node.

Examples:  #示例
  # Update node 'foo' with a taint with key 'dedicated' and value 'special-user' and effect 'NoSchedule'.
  # If a taint with that key and effect already exists, its value is replaced as specified.
  kubectl taint nodes foo dedicated=special-user:NoSchedule
  
  # Remove from node 'foo' the taint with key 'dedicated' and effect 'NoSchedule' if one exists.
  kubectl taint nodes foo dedicated:NoSchedule-
  
  # Remove from node 'foo' all the taints with key 'dedicated'
  kubectl taint nodes foo dedicated-
  
  # Add a taint with key 'dedicated' on nodes having label mylabel=X
  kubectl taint node -l myLabel=X  dedicated=foo:PreferNoSchedule
  
  # Add to node 'foo' a taint with key 'bar' and no value
  kubectl taint nodes foo bar:NoSchedule


[root@k8s-master Scheduler]# kubectl get pod -o wide
NAME                                         READY   STATUS    RESTARTS   AGE   IP               NODE         NOMINATED NODE   READINESS GATES
daemonset-demo-7ghhd                         1/1     Running   0          23m   192.168.113.35   k8s-node1    <none>           <none>
daemonset-demo-cjxd5                         1/1     Running   0          23m   192.168.12.35    k8s-node2    <none>           <none>
daemonset-demo-lhng4                         1/1     Running   0          23m   192.168.237.4    k8s-master   <none>           <none>
daemonset-demo-x5nhg                         1/1     Running   0          23m   192.168.51.54    k8s-node3    <none>           <none>
pod-antiaffinity-required-697f7d764d-69vx4   0/1     Pending   0          8s    <none>           <none>       <none>           <none>
pod-antiaffinity-required-697f7d764d-7cxp2   1/1     Running   0          8s    192.168.51.55    k8s-node3    <none>           <none>
pod-antiaffinity-required-697f7d764d-rpb5r   1/1     Running   0          8s    192.168.12.36    k8s-node2    <none>           <none>
pod-antiaffinity-required-697f7d764d-vf2x8   1/1     Running   0          8s    192.168.113.36   k8s-node1    <none>           <none>

为Node 3打上NoExecute效用标签,驱逐Node所有Pod

[root@k8s-master Scheduler]# kubectl taint node  k8s-node3 diskfull=true:NoExecute 
node/k8s-node3 tainted
[root@k8s-master Scheduler]# kubectl describe node k8s-node3
...
CreationTimestamp:  Sun, 29 Aug 2021 22:45:43 +0800
Taints:             diskfull=true:NoExecute

node节点所有Pod已经被驱逐但因为Pod 定义为每个节点只能存在一个同类型Pod 所以会被挂起,不会被在其它节点创建

[root@k8s-master Scheduler]# kubectl get pod -o wide 
NAME                                         READY   STATUS    RESTARTS   AGE     IP               NODE         NOMINATED NODE   READINESS GATES
daemonset-demo-7ghhd                         1/1     Running   0          31m     192.168.113.35   k8s-node1    <none>           <none>
daemonset-demo-cjxd5                         1/1     Running   0          31m     192.168.12.35    k8s-node2    <none>           <none>
daemonset-demo-lhng4                         1/1     Running   0          31m     192.168.237.4    k8s-master   <none>           <none>
pod-antiaffinity-required-697f7d764d-69vx4   0/1     Pending   0          7m45s   <none>           <none>       <none>           <none>
pod-antiaffinity-required-697f7d764d-l86td   0/1     Pending   0          6m5s    <none>           <none>       <none>           <none>
pod-antiaffinity-required-697f7d764d-rpb5r   1/1     Running   0          7m45s   192.168.12.36    k8s-node2    <none>           <none>
pod-antiaffinity-required-697f7d764d-vf2x8   1/1     Running   0          7m45s   192.168.113.36   k8s-node1    <none>           <none>

删除污点 Pod重新被创建

[root@k8s-master Scheduler]# kubectl taint node  k8s-node3 diskfull- 
node/k8s-node3 untainted
[root@k8s-master Scheduler]# kubectl get pod -o wide
NAME                                         READY   STATUS              RESTARTS   AGE    IP               NODE         NOMINATED NODE   READINESS GATES
daemonset-demo-7ghhd                         1/1     Running             0          34m    192.168.113.35   k8s-node1    <none>           <none>
daemonset-demo-cjxd5                         1/1     Running             0          34m    192.168.12.35    k8s-node2    <none>           <none>
daemonset-demo-lhng4                         1/1     Running             0          34m    192.168.237.4    k8s-master   <none>           <none>
daemonset-demo-m6g26                         0/1     ContainerCreating   0          4s     <none>           k8s-node3    <none>           <none>
pod-antiaffinity-required-697f7d764d-69vx4   0/1     ContainerCreating   0          10m    <none>           k8s-node3    <none>           <none>
pod-antiaffinity-required-697f7d764d-l86td   0/1     Pending             0          9m1s   <none>           <none>       <none>           <none>
pod-antiaffinity-required-697f7d764d-rpb5r   1/1     Running             0          10m    192.168.12.36    k8s-node2    <none>           <none>
pod-antiaffinity-required-697f7d764d-vf2x8   1/1     Running             0          10m    192.168.113.36   k8s-node1    <none>           <none>

参考文档:

https://www.cnblogs.com/ssgeek/p/12768927.html

20.kubernetes笔记 Pod资源调度(三)污点与容忍度

概述:

污点和容忍度

Pod调度顺序

示例1: Pod调度到master 对master:NoSchedule标识容忍

示例2: 为节点添加effect效用标识NoExecute 驱逐所有Pod

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