【云原生 | 从零开始学Kubernetes九、k8s的node节点选择器与node节点亲和性

node节点选择器与污点容忍度

• node 节点选择器
• • 1、nodeName
  • 2、nodeSelector
• 污点和污点容忍
• • 污点容忍
  • node 节点亲和性
  • 写在最后

node 节点选择器

我们在创建 pod 资源的时候，pod 会根据 schduler 进行调度，那么默认会调度到随机的一个工作节点，如果我们想要 pod 调度到指定节点或者调度到一些具有相同特点的 node 节点，怎么办呢？ 可以使用 pod 中的 nodeName 或者 nodeSelector 字段指定要调度到的 node 节点

1、nodeName

指定 pod 节点运行在哪个具体 node 上

#node1和2用docker下载tomcat busybox

[root@k8smaster node]# vim pod-node.yml 
apiVersion: v1 
kind: Pod 
metadata: 
  name: demo-pod
  namespace: default 
  labels: 
    app: myapp 
    env: dev 
spec: 
  nodeName: k8snode
  containers: 
  - name: tomcat-pod-java 
    ports: 
    - containerPort: 8080 
    image: tomcat
    imagePullPolicy: IfNotPresent 
  - name: busybox 
    image: busybox:latest 
    command: 
    - "/bin/sh" 
    - "-c" 
    - "sleep 3600" 
 
[root@k8smaster node]# kubectl apply -f pod-node.yml 
pod/demo-pod created

#查看 pod 调度到哪个节点 
[root@k8smaster node]# kubectl get pods -o wide 
NAME                          READY   STATUS    RESTARTS   AGE    IP            NODE       NOMINATED NODE  
demo-pod                      2/2     Running   0          35s    10.244.2.18   k8snode    <none>   

2、nodeSelector

指定 pod 调度到具有哪些标签的 node 节点上

#给 node 节点打标签，打个具有 disk=ceph 的标签
[root@k8smaster node]# kubectl describe nodes k8snode2   查看node属性
[root@k8smaster node]# kubectl label nodes k8snode2 disk=ceph
node/k8snode2 labeled
#然后再查看去label哪里就能看到了

#定义 pod 的时候指定要调度到具有 disk=ceph 标签的 node 上 
[root@k8smaster node]# vim pod-1.yaml 
apiVersion: v1 
kind: Pod 
metadata: 
  name: demo-pod-1 
  namespace: default 
  labels: 
    app: myapp 
    env: dev 
spec: 
  nodeSelector: 
    disk: ceph
  containers: 
  - name: tomcat-pod-java 
    ports: 
    - containerPort: 8080 
    image: tomcat
    imagePullPolicy: IfNotPresent 
 
[root@k8smaster node]# kubectl apply -f pod-1.yaml 
pod/demo-pod-1 created

#查看 pod 调度到哪个节点 
[root@k8smaster node]# kubectl get pods -o wide 
NAME                          READY   STATUS    RESTARTS   AGE     IP            NODE       NOMINATED NODE    demo-pod-1                    1/1     Running   0          8s      10.244.1.19   k8snode2   <none>         
#如果标签和nodename都有的话 优先选择好的node。

污点和污点容忍

污点容忍

污点容忍就是某个节点可能被调度，也可能不被调度

node 节点亲和性

node 节点亲和性调度：nodeAffinity 用帮助文档查看亲和性字段下面的东西

[root@k8smaster node]# kubectl explain pods.spec.affinity 
KIND:     Pod
VERSION:  v1

RESOURCE: affinity <Object>

DESCRIPTION:
     If specified, the pod's scheduling constraints

     Affinity is a group of affinity scheduling rules.

FIELDS:
   nodeAffinity	<Object>
     Describes node affinity scheduling rules for the pod.

   podAffinity	<Object>
   
   podAntiAffinity	<Object>
#有node节点亲和性 pode节点亲和性等，然后我们再详细的看看nodeAffinity 。
 
[root@k8smaster node]# kubectl explain pods.spec.affinity.nodeAffinity 
KIND:     Pod
VERSION:  v1

RESOURCE: nodeAffinity <Object>

DESCRIPTION:
     Describes node affinity scheduling rules for the pod.

     Node affinity is a group of node affinity scheduling rules.

FIELDS:
   preferredDuringSchedulingIgnoredDuringExecution	<[]Object>

   requiredDuringSchedulingIgnoredDuringExecution	<Object>
     
#prefered 表示有节点尽量满足这个位置定义的亲和性，这不是一个必须的条件，软亲和性，没满足也可能调度。
#require 表示必须有节点满足这个位置定义的亲和性，这是个硬性条件，硬亲和性，没满足不可能调度。

[root@k8smaster node]# kubectl explain pods.spec.affinity.nodeAffinity.requiredDuringSchedulingIgnoredDuringExecution
KIND:     Pod
VERSION:  v1

RESOURCE: requiredDuringSchedulingIgnoredDuringExecution <Object>

DESCRIPTION:
     If the affinity requirements specified by this field are not met at
     scheduling time, the pod will not be scheduled onto the node. If the
     affinity requirements specified by this field cease to be met at some point
     during pod execution (e.g. due to an update), the system may or may not try
     to eventually evict the pod from its node.

     A node selector represents the union of the results of one or more label
     queries over a set of nodes; that is, it represents the OR of the selectors
     represented by the node selector terms.

FIELDS:
   nodeSelectorTerms	<[]Object> -required-		#必写字段，对象列表
 
[root@k8smaster node]# kubectl explain pods.spec.affinity.nodeAffinity.requiredDuringSchedulingIgnoredDuringExecution.nodeSelectorTermsKIND:     Pod
VERSION:  v1

RESOURCE: nodeSelectorTerms <[]Object>

DESCRIPTION:
     Required. A list of node selector terms. The terms are ORed.

     A null or empty node selector term matches no objects. The requirements of
     them are ANDed. The TopologySelectorTerm type implements a subset of the
     NodeSelectorTerm.

FIELDS:
   matchExpressions	<[]Object>	#匹配表达式的
     A list of node selector requirements by node's labels.

   matchFields	<[]Object>	#匹配字段的 
     A list of node selector requirements by node's fields.
 
[root@k8smaster node]# kubectl explain pods.spec.affinity.nodeAffinity.requiredDuringSchedulingIgnoredDuringExecution.nodeSelectorTerms.matchExpressions
KIND:     Pod
VERSION:  v1

RESOURCE: matchExpressions <[]Object>

DESCRIPTION:
     A list of node selector requirements by node's labels.

     A node selector requirement is a selector that contains values, a key, and
     an operator that relates the key and values.

FIELDS:
   key	<string> -required-		#检查 label
   
   operator	<string> -required-	#做等值选则还是不等值选则 

   values	<[]string>			#给定的值 
#在做node节点亲和性的时候，values是标签的值，他会通过op匹配相等的key或者不等的key。
 
 
例 1：使用 requiredDuringSchedulingIgnoredDuringExecution 硬亲和性 
#node1 node2都拉nginx
 
[root@k8smaster node]# vim pod-nodeaffinity-demo.yaml
apiVersion: v1
kind: Pod
metadata:
        name: pod-node-affinity-demo
        namespace: default
        labels:
            app: myapp
            tier: frontend
spec:
    containers:
    - name: myapp
      image: nginx
    affinity:
         nodeAffinity:
            requiredDuringSchedulingIgnoredDuringExecution:
                   nodeSelectorTerms:
                   - matchExpressions:
                     - key: zone
                       operator: In
                       values:
                       - foo
                       - bar

affinity:亲和性，下面的node是node亲和性，然后requ硬亲和性，nodeselect是对象列表，我们用-链接，然后match也是对象列表，同上，key是zone，然后等值关系，值是foo和bar。 这个yaml意思是：我们检查当前节点中有任意一个节点拥有 zone 标签的值是 foo 或者 bar，就可以把 pod 调度到这个 node 节点的 foo 或者 bar 标签上的节点上,现在找不到，因为没打标签！

[root@k8smaster node]# kubectl apply -f pod-nodeaffinity-demo.yaml 
pod/pod-node-affinity-demo created
[root@k8smaster node]# kubectl get pods -o wide | grep pod-node 
pod-node-affinity-demo        0/1     Pending   0          11s    <none>        <none>     <none>          

# status 的状态是 pending，上面说明没有完成调度，因为没有一个拥有 zone 的标签的值是 foo 或者 bar，而且使用的是硬亲和性，必须满足条件才能完成调度。
[root@k8smaster node]# kubectl label nodes k8snode zone=foo
node/k8snode labeled
#给这个节点打上标签 zone=foo，在查看 
[root@k8smaster node]# kubectl get pods -o wide 显示running了
pod-node-affinity-demo        1/1     Running   0          4m4s   10.244.2.19   k8snode    <none>           
 
例 2：使用 preferredDuringSchedulingIgnoredDuringExecution 软亲和性 
[root@k8smaster node]# vim pod-nodeaffinity-demo-2.yaml 
apiVersion: v1
kind: Pod
metadata:
        name: pod-node-affinity-demo-2
        namespace: default
        labels:
            app: myapp
            tier: frontend
spec:
    containers:
    - name: myapp
      image: nginx
    affinity:
        nodeAffinity:
            preferredDuringSchedulingIgnoredDuringExecution:
            - preference:
               matchExpressions:
               - key: zone1
                 operator: In
                 values:
                 - foo1
                 - bar1
              weight: 60
          
#用的还是node亲和性，然后是软亲和性，如果所有的工作节点都没有这个标签，pod还是会调度
[root@k8smaster node]# kubectl apply -f pod-nodeaffinity-demo-2.yaml 
pod/pod-node-affinity-demo-2 created

[root@k8smaster node]# kubectl get pods -o wide |grep demo-2
pod-node-affinity-demo-2      1/1     Running   0          29s     10.244.1.20   k8snode2   <none>          


#上面说明软亲和性是可以运行这个 pod 的，尽管没有运行这个 pod 的节点定义的 zone1 标签 
 
Node 节点亲和性针对的是 pod 和 node 的关系，Pod 调度到 node 节点的时候匹配的条件

写在最后

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