14、kubernetes之资源调度

一、基本概念

1、调度器选择节点的三步

• 预选：先排除所以完全不符合的节点，包括资源需求、端口冲突、污点排除等
• 优选：计算每个节点的优先级并排序，找出最佳匹配（得分最高）的节点
• 选定：如果得分最高的节点不是一个，则随机选择一个，调度完成

2、常用的调度预选策略

• CheckNodeCondition：检查节点状态是否正常
• GeneralPredicates：通用预选策略
  • HostName：检查pod.spec.hostname是否定义，并且检查节点中是否有同名的pod而冲突
  • PodFitsHostPorts ：检查pod.spec.containers.ports.hostPort属性（绑定节点上的某个端口）是否定义，并且检查节点中的节点端口是否冲突
  • MatchNodeSelector：pods.spec.nodeSelector，检查节点选择器
  • PodFitsResources：检查节点是符合pod的资源需求
• NoDiskConflict：检查Pod依赖的存储卷是否能满足需求，默认不检查
• PodToletatesNodeTaints：pods.spec.tolerations可容忍的污点，检查Pod是否能容忍节点上的污点
• PodToletatesNodeExecuteTaints：后期pod无法容忍节点的污点是否驱离，默认不检查
• CheckNodelabelPresence：检查节点的标签的存在性
• CheckServiceAffinity：根据Pod所属的service，将相同所属的service尽可能放在同一个节点，默认不检查
• CheckVolumeBinging：检查符合的vpc
• NoVolumeZoneConflict：检查存储卷区域
• CheckNodeMemoryPressure：检查节点内存是否存在压力
• CheckNodePODPressure：检查节点PID数量是否存在压力
• CheckNodeDiskPressure：检查节点磁盘IO是否存在压力
• MatchInterPodAffinity：检查节点是否能满足Pod的亲和性

3、优选函数

• LeastRequested：节点的资源空闲率高的优选

• MostRequested：与LeastRequested相反，尽可能将一个节点使用完

• BalanceResourceAllocation：CPU和内存资源被占用相近的优选

• NodePreferAvoidPods：根据节点注解判断(scheduler.alpha.kubernetes.io/preferAvoidPods)，节点倾向性得分高的优选

• TaintToleration：将Pod对象的spec.tolerations列表项与节点的taints列表项进行匹配度检查，匹配的越多越优先

• SeletorSpreading：检查标签选择器选择的节点被分布的少的，目的是尽可能将从属于一个标签选择器的节点散开

• InterPodAffinity：遍历Pod亲和性，匹配亲和性越高越优选

• NodeAffinity：节点亲和性

• NodeLabel：根据节点是否拥有特定标签，存在则得分

• ImageLoclity：根据节点本地拥有Pod所使用的镜像大小来计算得分

二、调度配置清单示例

1、nodeSelector：节点选择器

# kubectl label nodes node01 disktype=ssd
# kubectl label nodes node02 disktype=harddisk
# kubectl get nodes --show-labels
# vim pod-demo-ssd.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo-ssd
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
  nodeSelector:  #节点选择器
    disktype: ssd  #调度到拥有disktype=ssd的标签的node上

2、nodeaffinity：节点亲和性

# kubectl label nodes master zone=Beijing   
# kubectl label nodes node01 zone=Shanghai
# kubectl label nodes node02 zone=Guangzhou
# cat pod-demo-nodeaffinity.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo-nodeaffinity
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:  #硬亲和
        nodeSelectorTerms:
        - matchExpressions:  #选择zone在Beijing或Shanghai
          - key: zone
            operator: In
            values:
            - Beijing
            - Shanghai

3、podaffinity：pod亲和性

# cat pod-demo-podaffinity.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo-podaffinity-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
---
apiVersion: v1
kind: Pod
metadata:
  name: pod-demo-podaffinity-2
  namespace: default
  labels:
    app: db
    tier: backend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: busybox
    image: busybox:latest
    imagePullPolicy: IfNotPresent
    command: ["sh","-c","sleep 3600"]
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - {key: app, operator: In, values: ["myapp"]}
        topologyKey: kubernetes.io/hostname

4、taints：节点污点

• taints
  • effect：容忍度
    • NoSchedule：不能容忍则不能调度过来，只影响调度过程，对现存pod无影响
    • PreferNoSchedule：不能容忍则尽量不要调度过来
    • NoExecute：不能容忍则不能调度过来，既影响调度过程，也影响现存pod

# kubectl taint node node01 node-type=production:NoSchedule  #打污点
# kubectl describe node node01 |grep Taints

# cat deploy-damo.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deploy
  namespace: default
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      release: canary
  template:
    metadata:
      labels:
        app: myapp
        release: canary
    spec:
      containers:
      - name: myapp-container
        image: dongfeimg/myapp:v2
        ports:
        - name: http
          containerPort: 80
      tolerations:
      - key: "node-type"
        operator: "Equal"  #完全相同
        value: "production"
        effect: "NoSchedule"