k8s-污点和容忍度

Taint 和 Toleration

节点亲和性，是pod的一种属性（偏好或硬性要求），它使pod被吸引到一类特定的节点。Taint 则相反，它使节点能够排斥一类特定的 pod

Taint 和 toleration 相互配合，可以用来避免 pod 被分配到不合适的节点上。每个节点上都可以应用一个或多个taint ，这表示对于那些不能容忍这些 taint 的 pod，是不会被该节点接受的。如果将 toleration 应用于 pod上，则表示这些 pod 可以（但不要求）被调度到具有匹配 taint 的节点上

污点(Taint)

I、污点 ( Taint ) 的组成

使用kubectl taint命令可以给某个 Node 节点设置污点，Node 被设置上污点之后就和 Pod 之间存在了一种相斥的关系，可以让 Node 拒绝 Pod 的调度执行，甚至将 Node 已经存在的 Pod 驱逐出去

每个污点的组成如下：

key=value:effect

每个污点有一个 key 和 value 作为污点的标签，其中 value 可以为空，effect 描述污点的作用。当前 tainteffect 支持如下三个选项：

NoSchedule：表示 k8s 将不会将 Pod 调度到具有该污点的Node 上
PreferNoSchedule：表示 k8s 将尽量避免将 Pod 调度到具有该污点的Node 上
NoExecute：表示 k8s 将不会将 Pod 调度到具有该污点的 Node 上，同时会将 Node 上已经存在的 Pod驱逐出去

II、污点的设置、查看和去除

# 设置污点
kubectl taint nodes node1 key1=value1:NoSchedule
# 节点说明中，查找 Taints 字段
kubectl describe pod  pod-name
#结果：
`Taints:             key1=value1:NoSchedule`
# 去除污点
kubectl taint nodes node1 key1:NoSchedule-

测试启动三个副本的Deployment:

apiVersion: apps/v1
kind: Deployment
metadata:name: myapp-deploynamespace: default
spec:replicas: 3selector:matchLabels:app: myapprelease: stabeltemplate:metadata:labels:app: myapprelease: stabelenv: testspec: containers:- name: myappimage: nginximagePullPolicy: IfNotPresentports:- name: httpcontainerPort: 80

kubectl apply -f dep.yml

发现3个pod都调度到了node2节点上（node1有污点）

[root@master k8s]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-5db79b5cb6-c6phz   1/1     Running   0          26s   10.244.2.30   node2   <none>           <none>
myapp-deploy-5db79b5cb6-gkqlc   1/1     Running   0          26s   10.244.2.29   node2   <none>           <none>
myapp-deploy-5db79b5cb6-qkjb7   1/1     Running   0          26s   10.244.2.28   node2   <none>           <none>

去除污点：

kubectl taint nodes node1 key1:NoSchedule-

删除一个pod后：
服务就可以调度到node1节点

[root@master k8s]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-5db79b5cb6-c6phz   1/1     Running   0          35m   10.244.2.30   node2   <none>           <none>
myapp-deploy-5db79b5cb6-gkqlc   1/1     Running   0          35m   10.244.2.29   node2   <none>           <none>
myapp-deploy-5db79b5cb6-qkjb7   1/1     Running   0          35m   10.244.2.28   node2   <none>           <none>[root@master k8s]# kubectl delete pod myapp-deploy-5db79b5cb6-c6phz
pod "myapp-deploy-5db79b5cb6-c6phz" deleted[root@master k8s]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-5db79b5cb6-dpcjf   1/1     Running   0          6s    10.244.1.34   node1   <none>           <none>
myapp-deploy-5db79b5cb6-gkqlc   1/1     Running   0          35m   10.244.2.29   node2   <none>           <none>
myapp-deploy-5db79b5cb6-qkjb7   1/1     Running   0          35m   10.244.2.28   node2   <none>           <none>

node1节点使用NoExecute：（发现原来在node1节点的pod被驱逐到node2）

[root@master k8s]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-5db79b5cb6-dpcjf   1/1     Running   0          6s    10.244.1.34   node1   <none>           <none>
myapp-deploy-5db79b5cb6-gkqlc   1/1     Running   0          35m   10.244.2.29   node2   <none>           <none>
myapp-deploy-5db79b5cb6-qkjb7   1/1     Running   0          35m   10.244.2.28   node2   <none>           <none>[root@master k8s]# kubectl taint nodes node1 key1=value1:NoExecute
node/node1 tainted[root@master k8s]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-5db79b5cb6-gkqlc   1/1     Running   0          52m   10.244.2.29   node2   <none>           <none>
myapp-deploy-5db79b5cb6-qkjb7   1/1     Running   0          52m   10.244.2.28   node2   <none>           <none>
myapp-deploy-5db79b5cb6-x9kc9   1/1     Running   0          2s    10.244.2.31   node2   <none>           <none>

容忍(Tolerations）

设置了污点的 Node 将根据 taint 的 effect：NoSchedule、PreferNoSchedule、NoExecute 和 Pod 之间产生互斥的关系，Pod 将在一定程度上不会被调度到 Node 上。但我们可以在 Pod 上设置容忍 ( Toleration ) ，意思是设置了容忍的 Pod 将可以容忍污点的存在，可以被调度到存在污点的 Node 上

pod.spec.tolerations

tolerations:- key: "key1"operator: "Equal"value: "value1"  effect: "NoSchedule"  tolerationSeconds: 3600- key: "key1"  operator: "Equal"  value: "value1"  effect: "NoExecute"- key: "key2"  operator: "Exists"  effect: "NoSchedule"

其中 key, vaule, effect 要与 Node 上设置的 taint 保持一致
operator 的值为 Exists 将会忽略 value 值
tolerationSeconds 用于描述当 Pod 需要被驱逐时可以在 Pod 上继续保留运行的时间

1、当不指定 key 值时，表示容忍所有的污点 key（master节点也会部署）：

tolerations:
- operator: "Exists"

2、当不指定 effect 值时，表示容忍所有的污点作用

tolerations:
- key: "key"operator: "Exists"

3、有多个 Master 存在时，防止资源浪费，可以如下设置（还没有测试）

kubectl taint nodes Node-Name node-role.kubernetes.io/master=:PreferNoSchedule

例子1：
使用下面的容忍度：

tolerations:- key: "key1"  operator: "Equal"  value: "value1"  effect: "NoExecute"

[root@master k8s]# cat dep-tolerator.yml

apiVersion: apps/v1
kind: Deployment
metadata:name: myapp-deploynamespace: default
spec:replicas: 3selector:matchLabels:app: myapprelease: stabeltemplate:metadata:labels:app: myapprelease: stabelenv: testspec: tolerations:- key: key1operator: Equalvalue: value1effect: NoExecutecontainers:- name: myappimage: nginximagePullPolicy: IfNotPresentports:- name: httpcontainerPort: 80

查看结果会看到node1和node2都有部署

[root@master k8s]# kubectl apply -f dep-tolerator.yml
deployment.apps/myapp-deploy created
[root@master k8s]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-67d655bffc-7bn6n   1/1     Running   0          12s   10.244.2.32   node2   <none>           <none>
myapp-deploy-67d655bffc-9fqc2   1/1     Running   0          12s   10.244.1.36   node1   <none>           <none>
myapp-deploy-67d655bffc-vmmd4   1/1     Running   0          12s   10.244.1.35   node1   <none>           <none>

例子2：
使用

tolerations:
- operator: "Exists"

[root@master k8s]# cat dep-tolerator-all.yml

apiVersion: apps/v1
kind: Deployment
metadata:name: myapp-deploynamespace: default
spec:replicas: 3selector:matchLabels:app: myapprelease: stabeltemplate:metadata:labels:app: myapprelease: stabelenv: testspec: tolerations:- operator: Existscontainers:- name: myappimage: nginximagePullPolicy: IfNotPresentports:- name: httpcontainerPort: 80

 kubectl apply -f dep-tolerator-all.yml

结果：会发现连master节点也调度了

[root@master k8s]# kubectl get pod -o wide
NAME                          READY   STATUS    RESTARTS   AGE   IP            NODE     NOMINATED NODE   READINESS GATES
myapp-deploy-b9d684ff-2525s   1/1     Running   0          21m   10.244.2.33   node2    <none>           <none>
myapp-deploy-b9d684ff-bsrbg   1/1     Running   0          21m   10.244.0.8    master   <none>           <none>
myapp-deploy-b9d684ff-fggcg   1/1     Running   0          21m   10.244.1.37   node1    <none>           <none>

例子3：(容忍带有key: "key1"的)

tolerations:
- key: "key1"operator: "Exists"