【K8S 三】部署 metrics-server 插件
目录
Metrics Server
安装前提
下载镜像并配置启动YAML
部署并验证
这篇文章写得比较早，当时是在kubeadm部署环境下实施的，如果您是通过二进制部署（因为这种部署拓扑比较灵活）出现了问题可以移步《【K8S 七】Metrics Server部署中的问题》，可能会对您有帮助。
Metrics Server
Metrics Server是一种可伸缩的、高效的容器资源指标源，用于Kubernetes内置的自动缩放管道。
Metrics服务器从Kubelets收集资源指标，并通过Metrics API在Kubernetes apiserver中公开它们，以便HPA（Horizontal Pod Autoscaler）和VPA（Vertical Pod Autoscaler）使用。Metrics API也可以被kubectl top访问，这使得它更容易调试弹性伸缩管道。
Metrics服务器并不用于非弹性伸缩的目的。例如，不要使用它将指标转发到监视解决方案，或者将其作为监视解决方案指标的来源。
Horizontal Pod Autoscaler：水平Pod弹性伸缩；Vertical Pod Autoscaler：垂直Pod弹性伸缩。
资源消耗：Metrics Server uses 1m core of CPU and 3 MB of memory per node
可扩展支持最多5,000个节点集群
详情参考kubernetes-sigs/metrics-server
安装前提
下面所有操作的前提是已经存在搭建好的Kubernetes集群环境，且apiserver要配置证书，且metrics-server也需要CA证书，不然就会报错（使用kubeadm工具会简单很多）：
Expected to load root CA config from /var/run/secrets/kubernetes.io/serviceaccount/ca.crt, but got err: open /var/run/secrets/kubernetes.io/serviceaccount/ca.crt: no such file or directory
Error: unable to load configmap based request-header-client-ca-file: Get "https://10.254.0.1:443/api/v1/namespaces/kube-system/configmaps/extension-apiserver-authentication": x509: certificate signed by unknown authority
下载镜像并配置启动YAML
目前Metrics-Server的镜像是k8s.gcr.io/metrics-server/metrics-server:v0.4.1，无法科学上网的同学，只能曲线救国，手动下载镜像到本地或推到私有镜像库：
本人已经将镜像推到了实验环境的私有仓库中：192.168.x.x/library/metrics-server:v0.4.1
下载启动配置文件，并对文件进行如下配置，否则metrics-server启动会报错：
unable to fully scrape metrics from node kubeadmin-node: unable to fetch metrics from node kubeadmin-node: Get "https://192.168.x.x:10250/stats/summary?only_cpu_and_memory=true": x509: cannot validate certificate for 192.168.x.x because it doesn't contain any IP SANs, unable to fully scrape metrics from node rhel-8-11.8: unable to fetch metrics from node rhel-8-11.8: Get "https://192.168.x.y:10250/stats/summary?only_cpu_and_memory=true": x509: cannot validate certificate for 192.168.x.y because it doesn't contain any IP SANs
wget https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
cp components.yaml kube-metric-server.yaml
diff components.yaml kube-metric-server.yaml
133a134,135
> - --metric-resolution=30s
> - --kubelet-insecure-tls
136c138
< image: k8s.gcr.io/metrics-server/metrics-server:v0.6.1
---
> image: registry.aliyuncs.com/google_containers/metrics-server:v0.6.1部署并验证
$ kubectl apply -f kube-metrics-server.yaml
$ kubectl get po -o wide -n kube-system
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
metrics-server-6695c86795-gfkhh 1/1 Running 0 58m 172.254.1.14 kubeadmin-node
$ kubectl top node
NAME CPU(cores) CPU% MEMORY(bytes) MEMORY%
kubeadmin-node 57m 0% 2085Mi 27%
rhel-8-11.8 126m 1% 1714Mi 22%
$ kubectl top pod
mysql-gbprd 1m 467Mi
myweb-5478cb4767-gm5k2 1m 195Mi
myweb-5478cb4767-h5snw 1m 195Mi