Kubernetes 02.04 pod节点调度

> Node标签，NodeSelector，PodAffinity

# node 标签
```
# 查看标签
kubectl get node -o custom-columns=HOSTNAME:.metadata.name,LABELS:.metadata.labels

# 打标签
kubectl label nodes k8s-node-1 tag=node1
```
# NodeSelector
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: default #默认 default
  labels:
    env: test
spec:
  nodeSelector:
    tag: node1
  containers:
  - image: centos:latest
    name: my-pod-container
    command:
      - /bin/sleep
    args:
      - "86400"
```
# NodeAffinity
**requiredDuringSchedulingIgnoredDuringExecution**
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    tag: deployment-tag
  name: deployment-name
spec:
  replicas: 4
  selector:
    matchLabels:
      tag: pod-tag    
  template: # pod info
    metadata:
      labels:
        tag: pod-tag
    spec:
      affinity:
        nodeAffinity:
          #必须满足条件，否则不部署
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
              - matchExpressions:
                - key: tag
                  operator: In #In,NotIn,Exists,DoesNotExists,Gt,Lt
                  values:
                    - node2           
      containers:
        - image: centos:latest
          name: my-pod-container
          command:
            - /bin/sleep
          args:
            - "86400"
```
**preferredDuringSchedulingIgnoredDuringExecution**
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: default #默认 default
  labels:
    env: test
spec:
  affinity:
    nodeAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
        - weight: 1  # 1 ~ 100
          preference:
            matchExpressions:
              - key: tag
                operator: In #In,NotIn,Exists,DoesNotExists,Gt,Lt
                values:
                  - node2
        - weight: 100
          preference:
            matchExpressions:
              - key: tag
                operator: In #In,NotIn,Exists,DoesNotExists,Gt,Lt
                values:
                  - node1   
  containers:
  - image: centos:latest
    name: my-pod-container
    command:
      - /bin/sleep
    args:
      - "86400"
```
**如果nodeSelector和nodeAffinity同时存在，要都满足**  
**nodeAffinity 中的多个nodeSelectorTerms 是或的关系**  
**nodeSelectorTerms 中多个matchExpressions 是与的关系**    
# PodAffinity
要和哪些pod 部署在一起或者不要部署在一起   
```
#看pod label 
kubectl get pod -o custom-columns=NAME:.metadata.name,NODE:spec.nodeName,LABELS:.metadata.labels
NAME                               NODE         LABELS
special-pod                        k8s-node-2   map[tag:sp_pod]
```
**把满足条件的Pod 放一起**
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: default #默认 default
  labels:
    tag: my-pod
spec:
  affinity:
    podAffinity:
      #必须满足条件，否则不部署
      requiredDuringSchedulingIgnoredDuringExecution:
        - topologyKey: kubernetes.io/hostname
          labelSelector:
            matchExpressions:
              - key: tag
                operator: In #In,NotIn,Exists,DoesNotExists,Gt,Lt
                values:
                  - sp_pod
  containers:
  - image: centos:latest
    name: my-pod-container
    command:
      - /bin/sleep
    args:
      - "86400"
```
一般情况下 topologyKey 可以为非空的任何label, 但是admission controller 配置了LimitPodHardAntiAffinityTopology的话那就只可以是kubernetes.io/hostname  
**满足条件的Pod 不能放一起**  
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: default #默认 default
  labels:
    tag: my-pod
spec:
  affinity:
    podAntiAffinity:
      #必须满足条件，否则不部署
      requiredDuringSchedulingIgnoredDuringExecution:
        - topologyKey: kubernetes.io/hostname
          labelSelector:
            matchExpressions:
              - key: tag
                operator: In #In,NotIn,Exists,DoesNotExists,Gt,Lt
                values:
                  - sp_pod
  containers:
  - image: centos:latest
    name: my-pod-container
    command:
      - /bin/sleep
    args:
      - "86400"
```

乱读天书， 不求甚解

乱读天书，不求甚解