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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：

1. 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；
2. 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；
3. 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

1. 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。

2. 执行components.yaml

kubectl apply -f components.yaml

3. 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%