一、概述
介绍 Metrics Server 前首先介绍一下 Heapster，该工具是用于 Kubernetes 集群监控和性能分析工具，可以收集节点上的指标数据，例如，节点的 CPU、Memory、Network 和 Disk 的 Metric 数据。不过在 Kubernetes V1.11 版本后将被逐渐废弃。而 Metrics Server 正是 Heapster 的代替者。
Metrics Server 是 Kubernetes 集群核心监控数据的聚合器，Metrics Server 从 Kubelet 收集资源指标，并通过 Merics API 在 Kubernetes APIServer 中提供给缩放资源对象 HPA 使用。也可以通过 Metrics API 提供的 Kubectl top 查看 Pod 资源占用情况，从而实现对资源的自动缩放。
需要注意的是：
- metric-server提供的是实时的指标（实际是最近一次采集的数据，保存在内存中），并没有数据库来存储；
- 这些数据指标并非由metric-server本身采集，而是由每个节点上的cadvisor采集，metric-server只是发请求给cadvisor并将metric格式的数据转换成aggregate api；
- 由于需要通过aggregate api来提供接口，需要集群中的kube-apiserver开启该功能
二、部署metrics-server
- 创建components.yaml文件，将内容复制进去
vim components.yaml
--- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: system:aggregated-metrics-reader labels: rbac.authorization.k8s.io/aggregate-to-view: "true" rbac.authorization.k8s.io/aggregate-to-edit: "true" rbac.authorization.k8s.io/aggregate-to-admin: "true" rules: - apiGroups: ["metrics.k8s.io"] resources: ["pods", "nodes"] verbs: ["get", "list", "watch"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: metrics-server:system:auth-delegator roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:auth-delegator subjects: - kind: ServiceAccount name: metrics-server namespace: kube-system --- apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: metrics-server-auth-reader namespace: kube-system roleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: extension-apiserver-authentication-reader subjects: - kind: ServiceAccount name: metrics-server namespace: kube-system --- apiVersion: apiregistration.k8s.io/v1beta1 kind: APIService metadata: name: v1beta1.metrics.k8s.io spec: service: name: metrics-server namespace: kube-system group: metrics.k8s.io version: v1beta1 insecureSkipTLSVerify: true groupPriorityMinimum: 100 versionPriority: 100 --- 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 image: mirrorgooglecontainers/metrics-server-amd64:v0.3.6 imagePullPolicy: IfNotPresent command: - /metrics-server - --kubelet-preferred-address-types=InternalIP - --kubelet-insecure-tls - --v=2 args: - --cert-dir=/tmp - --secure-port=4443 ports: - name: main-port containerPort: 4443 protocol: TCP securityContext: readOnlyRootFilesystem: true runAsNonRoot: true runAsUser: 1000 volumeMounts: - name: tmp-dir mountPath: /tmp nodeSelector: kubernetes.io/os: linux kubernetes.io/arch: "amd64" --- apiVersion: v1 kind: Service metadata: name: metrics-server namespace: kube-system labels: kubernetes.io/name: "Metrics-server" kubernetes.io/cluster-service: "true" spec: selector: k8s-app: metrics-server ports: - port: 443 protocol: TCP targetPort: main-port --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: system:metrics-server rules: - apiGroups: - "" resources: - pods - nodes - nodes/stats - namespaces - configmaps verbs: - get - list - watch --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: system:metrics-server roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:metrics-server subjects: - kind: ServiceAccount name: metrics-server namespace: kube-system
网上有很多是通过从github上下载yaml文件内容，然后进行更改的，但是实际执行起来就会出现这样那样的问题，要不是镜像拉不下来，要不各种报错，这个yaml文件内容已经是经过修改的，可以直接执行，即可成功。
- 执行components.yaml
kubectl apply -f components.yaml
- 验证Metrics Server组件部署成功
- 查看原生apiserver是否有metrics.k8s.io/v1beta1
[root@k8s-master1 ~]# kubectl api-versions|grep metrics metrics.k8s.io/v1beta1
可以看到metrics.k8s.io/v1beta1群组已经注册到原生apiserver上。
- 查看metrics server pod是否运行正常
[root@k8s-master1 ~]# kubectl get pods -n kube-system |grep metrics metrics-server-5dfbdf76fd-hrjdl 1/1 Running 1 12h
可以看到对应pod已经正常运行，接着查看pod日志kubectl logs -f pod/[pod名称] -n kube-system，只要metrics server pod没有出现错误日志，或者无法注册等信息，就表示pod里的容器运行正常。
- 使用kubectl top 命令查看pod的cpu ，内存占比，看看对应命令是否可以正常执行。
[root@k8s-master1 ~]# kubectl top nodes NAME CPU(cores) CPU% MEMORY(bytes) MEMORY% k8s-master1 295m 7% 866Mi 11% k8s-master2 273m 6% 1147Mi 14% k8s-master3 233m 5% 669Mi 8% k8s-node1 92m 2% 483Mi 6%
