K8S 弹性伸缩

HPA的原理

Kubernetes有一个HPA(Horizontal Pod Autoscaler)的资源，可以实现基于CPU使用率的Pod自动伸缩的功能。HPA基于Master Node上的kube-controller-manager服务启动参数–horizontal-pod-autoscaler-sync-period定义的时长(默认为30秒)，

周期性的检测Pod的CPU使用率(需要事先安装heapster)。如果需要设置–horizontal-pod-autoscaler-sync-period可以在Master Node上的/etc/default/kube-controller-manager中修改，V1.18.1以后监控使用的是Metrics-Server，

一、部署Metrics-Server

1、下载并解压Metrics-Server

https://github.com/kubernetes-sigs/metrics-server/archive/v0.3.6.tar.gz
tar -zxvf v0.3.6.tar.gz 

2、修改metrice-server配置

cd metrics-server-0.3.6/deploy/1.8+/
vim metrics-server-deployment.yaml

3、vim metrics-server-deployment.yaml修改文件内容

apiVersion: v1
kind: ServiceAccount
metadata:
  name: metrics-server
  namespace: kube-system
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: metrics-server
  namespace: kube-system
  labels:
    k8s-app: metrics-server
spec:
  selector:
    matchLabels:
      k8s-app: metrics-server
  template:
    metadata:
      name: metrics-server
      labels:
        k8s-app: metrics-server
    spec:
      serviceAccountName: metrics-server
      volumes:
      # mount in tmp so we can safely use from-scratch images and/or read-only containers
      - name: tmp-dir
        emptyDir: {}
      containers:
      - name: metrics-server
        # 修改image 和 imagePullPolicy
        image: mirrorgooglecontainers/metrics-server-amd64:v0.3.6
        imagePullPolicy: IfNotPresent
        # 新增command配置
        command:
        - /metrics-server
        - --kubelet-insecure-tls
        - --kubelet-preferred-address-types=InternalDNS,InternalIP,ExternalDNS,ExternalIP,Hostname
        volumeMounts:
        - name: tmp-dir
          mountPath: /tmp
        # 新增resources配置
        resources:
          limits:
            cpu: 300m
            memory: 200Mi
          requests:
            cpu: 200m
            memory: 100Mi

4、安装metrics-server

kubectl apply -f metrics-server-0.3.6/deploy/1.8+/

5、查看nodes的信息

[root@k8s-master 1.8+]# kubectl top nodes 
NAME         CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%   
k8s-master   94m          4%     959Mi           55%       
k8s-node1    58m          5%     580Mi           66%       
k8s-node2    39m          3%     552Mi           63%