20.kubernetes笔记 Pod资源调度(三)污点与容忍度
2021-12-28 本文已影响0人
Bigyong
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>
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