nodeName

调度到指定节点
nodeName是节点选择约束的最简单形式，但是由于其限制，通常不使用它。nodeName是PodSpec的一个字段。如果它是非空的，则调度程序将忽略容器，并且在指定节点上运行的kubelet会尝试运行容器。因此，如果 nodeNamePodSpec中指定nodeName，则它优先于上述用于节点选择的方法。

nodeName用于选择节点的一些限制是：
如果指定的节点不存在，则容器将不会运行，并且在某些情况下可能会自动删除。
如果命名节点没有足够的资源来容纳该Pod，则该Pod将失败，其原因将指示原因，例如OutOfmemory或OutOfcpu。
云环境中的节点名称并非总是可预测或稳定的

cat << EOF > nodename.yaml
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  nodeName: node01
EOF

node节点添加label
[root@master01 ~]# kubectl label nodes node01 disktype=ssd
[root@master01 ~]# kubectl get nodes node01 —show-labels
NAME STATUS ROLES AGE VERSION LABELS
删除标签
[liwm@rmaster01 liwm]$ kubectl label nodes node01 disktype-
node/node01 labeled
[liwm@rmaster01 liwm]$

无指定的标签时 pod会一直处于 Pending状态
Warning FailedScheduling default-scheduler 0/5 nodes are available: 5 node(s) didn’t match node selector.
**

nodeSelector

使用yaml创建pod，指定nodeSelector

cat << EOF > pod-nodeSelector.yaml
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    env: test
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  nodeSelector:
    disktype: ssd
EOF

kubectl apply -f pod-nodeSelector.yaml

kubectl label nodes node01 app=nginx
kubectl get nodes node01 —show-labels

cat << EOF > nginx-app.yaml
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    env: test
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  nodeSelector:
    app: nginx
EOF

[liwm@rmaster01 liwm]$ kubectl label nodes node01 app-
node/node01 labeled
[liwm@rmaster01 liwm]$ kubectl get nodes node01 --show-labels 
NAME     STATUS   ROLES    AGE   VERSION   LABELS
node01   Ready    worker   21d   v1.17.2   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node01,kubernetes.io/os=linux,node-role.kubernetes.io/worker=
[liwm@rmaster01 liwm]$

Affinity and anti-affinity

亲和与反亲和

affinity/anti-affinity功能有丰富的约束类型。
比如：
语言更具表现力（不仅是“and或完全匹配”）；
规则除了硬性要求（完全匹配）还可以使用“软性要求”/“偏好要求”；（当硬性要求和软性要求同时出现就出现偏好要求）偏好有权重打分
可以使用Node节点的Label与Pod的Label实现亲和与反亲和；

affinity/anti-affinity的两种类型：
requiredDuringSchedulinglgnoredDuringExecution（硬性要求）
preferredDuringSchedulinglgnoredDuringExecution（软性要求）
运算符（operator）：
In，Notln，Exists，DoesNotExist，Gt，Lt 可以使用NotIn和DoesNotExist实现节点的反亲和行为
等于 不等于 已存在 不存在 大于 小于

Node affinity

# 硬性要求

cat << EOF > node-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity:
    nodeAffinity: # 使用node亲和进行判定
      requiredDuringSchedulingIgnoredDuringExecution: # 硬性要求
        nodeSelectorTerms: # 节点选择器的条件
        - matchExpressions: # 定义匹配的表达式
          - key: app # label的key
            operator: In # 定义判断方式多种：In,NotIn,Exists,DoesNotexist,Gt,Lt。
            values: # label的values
            - nginx
  containers:
  - name: with-node-affinity
    image: nginx
    imagePullPolicy: IfNotPresent
EOF

kubectl create -f node-affinity.yaml
kubectl label nodes node01 app=nginx

删除label 落地后的pod不受影响

# 软性要求

cat << EOF > node-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity:
    nodeAffinity:
      preferredDuringSchedulingIgnoredDuringExecution: # 软性要求      
      - weight: 1 # 设置权重，分数越高优先级越高
        preference:
          matchExpressions:
          - key: disktype
            operator: In
            values:
            - ssd
  containers:
  - name: with-node-affinity
    image: nginx
    imagePullPolicy: IfNotPresent
EOF

kubectl create -f node-affinity.yaml
kubectl label nodes node02 disktype=ssd

kubectl label nodes node02 disktype-

#权重

cat << EOF > weight-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
  name: with-weight
spec:
  affinity:
    nodeAffinity:
      preferredDuringSchedulingIgnoredDuringExecution: # 软性要求      
      - weight: 1  # 设置权重，分数越高优先级越高
        preference:
          matchExpressions:
          - key: disktype
            operator: In
            values:
            - ssd2
      - weight: 10 
        preference:
          matchExpressions:
          - key: disktype
            operator: In
            values:
            - ssd1
  containers:
  - name: with-weight
    image: nginx
    imagePullPolicy: IfNotPresent
EOF

# 偏好要求

kubectl label nodes node02 disktype=ssd
kubectl label nodes node01 app=nginx1
kubectl label nodes node02 app=nginx2

cat << EOF > node-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: app
            operator: In
            values:
            - nginx1
            - nginx2
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 1
        preference:
          matchExpressions:
          - key: disktype
            operator: In
            values:
            - ssd
  containers:
  - name: with-node-affinity
    image: nginx
    imagePullPolicy: IfNotPresent
EOF

**
kubectl create -f node-affinity.yaml

pod affinity

#podaffinity

创建pod-affinity

cat << EOF > pod-affinity.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
spec:
  selector:
    matchLabels:
      app: store
  replicas: 3 #node节点不够有pod无法调度一直pending状态
  template:
    metadata:
      labels:
        app: store
    spec:
      affinity:
        podAntiAffinity: #反亲和、一个节点只运行1个pod
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - store
            topologyKey: "kubernetes.io/hostname"    # 拓扑域，用来判定拥有哪些标签的节点是同一个位置
      containers:
      - name: redis-server
        image: redis:3.2-alpine
        imagePullPolicy: IfNotPresent
EOF

#podantiaffinity

创建web-server

cat << EOF > web-server.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-server
spec:
  selector:
    matchLabels:
      app: web-store
  replicas: 3
  template:
    metadata:
      labels:
        app: web-store
    spec:
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - web-store
            topologyKey: "kubernetes.io/hostname"
        podAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - store
            topologyKey: "kubernetes.io/hostname"
      containers:
      - name: web-app
        image: nginx
        imagePullPolicy: IfNotPresent
EOF