K8S从1.8版本开始，CPU、内存等资源的metrics信息能够通过 Metrics API来获取，用户能够间接获取这些metrics信息（例如通过执行kubect top命令），HPA应用这些metics信息来实现动静伸缩。本文介绍K8S集群基于metric server的HPA。在开始之前咱们须要理解一下Metrics API和Metrics Server。
Metrics API：
1、通过Metrics API咱们能够获取到指定node或者pod的以后资源应用状况，API自身不存储任何信息，所以咱们不可能通过API来获取资源的历史应用状况。
2、Metrics API的获取门路位于：/apis/metrics.k8s.io/
3、获取Metrics API的前提条件是metrics server要在K8S集群中胜利部署
4、更多的metrics材料请参考：https://github.com/kubernetes/metrics
Metrics server：
1、Metrics server是K8S集群资源应用状况的聚合器
2、从1.8版本开始，Metrics server默认能够通过kube-up.sh 脚本以deployment的形式进行部署，也能够通过yaml文件的形式进行部署
3、Metrics server收集所有node节点的metrics信
Plan-A
[root@master49 metrics-images]# cat metrics-applaction.yaml apiVersion: v1kind: ServiceAccountmetadata: name: metrics-server namespace: kube-system labels: kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile---apiVersion: rbac.authorization.k8s.io/v1kind: ClusterRolemetadata: name: system:metrics-serverrules:- apiGroups: - "" resources: - pods - nodes - nodes/stats - namespaces verbs: - get - list - watch- apiGroups: - "extensions" resources: - deployments verbs: - get - list - watch---apiVersion: rbac.authorization.k8s.io/v1kind: ClusterRoleBindingmetadata: name: system:metrics-serverroleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:metrics-serversubjects:- kind: ServiceAccount name: metrics-server namespace: kube-system---apiVersion: rbac.authorization.k8s.io/v1beta1kind: ClusterRoleBindingmetadata: name: metrics-server:system:auth-delegatorroleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:auth-delegatorsubjects:- kind: ServiceAccount name: metrics-server namespace: kube-system---apiVersion: rbac.authorization.k8s.io/v1beta1kind: RoleBindingmetadata: name: metrics-server-auth-reader namespace: kube-systemroleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: extension-apiserver-authentication-readersubjects:- kind: ServiceAccount name: metrics-server namespace: kube-system---apiVersion: apiregistration.k8s.io/v1beta1kind: APIServicemetadata: name: v1beta1.metrics.k8s.iospec: service: name: metrics-server namespace: kube-system group: metrics.k8s.io version: v1beta1 insecureSkipTLSVerify: true groupPriorityMinimum: 100 versionPriority: 100---apiVersion: v1kind: Servicemetadata: name: metrics-server namespace: kube-system labels: kubernetes.io/name: "Metrics-server"spec: selector: k8s-app: metrics-server ports: - port: 443 protocol: TCP targetPort: 443---apiVersion: v1kind: ConfigMapmetadata: name: metrics-server-config namespace: kube-system labels: kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: EnsureExistsdata: NannyConfiguration: |- apiVersion: nannyconfig/v1alpha1 kind: NannyConfiguration---apiVersion: apps/v1kind: Deploymentmetadata: name: metrics-server namespace: kube-system labels: k8s-app: metrics-server-v0.3.1 kubernetes.io/cluster-service: "true" addonmanager.kubernetes.io/mode: Reconcile version: v0.3.1spec: selector: matchLabels: k8s-app: metrics-server version: v0.3.1 template: metadata: name: metrics-server labels: k8s-app: metrics-server version: v0.3.1 annotations: scheduler.alpha.kubernetes.io/critical-pod: '' seccomp.security.alpha.kubernetes.io/pod: 'docker/default' spec: priorityClassName: system-cluster-critical serviceAccountName: metrics-server containers: - name: metrics-server image: htcfive/metrics-server-amd64 command: - /metrics-server - --kubelet-insecure-tls - --kubelet-preferred-address-types=InternalIP ports: - containerPort: 443 name: https protocol: TCP - name: metrics-server-nanny image: wcollin/addon-resizer:1.8.1 resources: limits: cpu: 100m memory: 300Mi requests: cpu: 5m memory: 50Mi env: - name: MY_POD_NAME valueFrom: fieldRef: fieldPath: metadata.name - name: MY_POD_NAMESPACE valueFrom: fieldRef: fieldPath: metadata.namespace volumeMounts: - name: metrics-server-config-volume mountPath: /etc/config command: - /pod_nanny - --cpu=40m - --extra-cpu=0.5m - --memory=40Mi - --extra-memory=4Mi - --threshold=5 - --deployment=metrics-server-v0.2.1 - --container=metrics-server - --poll-period=300000 - --estimator=exponential volumes: - name: metrics-server-config-volume configMap: name: metrics-server-config tolerations: - key: "CriticalAddonsOnly" operator: "Exists"[root@master49 metrics-images]# kubectl apply -f metrics-applaction.yaml serviceaccount/metrics-server createdclusterrole.rbac.authorization.k8s.io/system:metrics-server createdclusterrolebinding.rbac.authorization.k8s.io/system:metrics-server createdclusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator createdrolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader createdapiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io createdservice/metrics-server createdconfigmap/metrics-server-config createderror: unable to recognize "metrics-applaction.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"[root@master49 metrics-images]# kubectl delete -f metrics-applaction.yaml serviceaccount "metrics-server" deletedclusterrole.rbac.authorization.k8s.io "system:metrics-server" deletedclusterrolebinding.rbac.authorization.k8s.io "system:metrics-server" deletedclusterrolebinding.rbac.authorization.k8s.io "metrics-server:system:auth-delegator" deletedrolebinding.rbac.authorization.k8s.io "metrics-server-auth-reader" deletedapiservice.apiregistration.k8s.io "v1beta1.metrics.k8s.io" deletedservice "metrics-server" deletedconfigmap "metrics-server-config" deletederror: unable to recognize "metrics-applaction.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"[root@master49 metrics-images]# vim metrics-applaction.yaml [root@master49 metrics-images]# kubectl apply -f metrics-applaction.yaml serviceaccount/metrics-server createdclusterrole.rbac.authorization.k8s.io/system:metrics-server createdclusterrolebinding.rbac.authorization.k8s.io/system:metrics-server createdclusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator createdrolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader createdapiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io createdservice/metrics-server createdconfigmap/metrics-server-config createddeployment.apps/metrics-server created[root@master49 metrics-images]# [root@master49 metrics-images]# kubectl get pods -n kube-systemNAME READY STATUS RESTARTS AGEcalico-kube-controllers-75d555c48-c66ll 1/1 Running 0 18hcalico-node-4w9rr 1/1 Running 0 18hcalico-node-hrvcq 1/1 Running 0 18hcalico-node-srz5h 1/1 Running 0 18hcalico-node-xmb28 1/1 Running 0 18hcalico-node-zhrs2 1/1 Running 0 18hcoredns-7ff77c879f-46sjv 1/1 Running 0 19hcoredns-7ff77c879f-txpw9 1/1 Running 0 5hetcd-master49 1/1 Running 6 18hetcd-master50 1/1 Running 3 18hetcd-master56 1/1 Running 17 18hkube-apiserver-master49 1/1 Running 1 18hkube-apiserver-master50 1/1 Running 0 18hkube-apiserver-master56 1/1 Running 0 18hkube-controller-manager-master49 1/1 Running 8 18hkube-controller-manager-master50 1/1 Running 6 18hkube-controller-manager-master56 1/1 Running 6 18hkube-proxy-2gcg5 1/1 Running 0 18hkube-proxy-4ckzn 1/1 Running 0 18hkube-proxy-bffn9 1/1 Running 0 18hkube-proxy-kdjtv 1/1 Running 0 18hkube-proxy-w9xzf 1/1 Running 0 18hkube-scheduler-master49 1/1 Running 8 18hkube-scheduler-master50 1/1 Running 5 18hkube-scheduler-master56 1/1 Running 7 18hlog-pilot-2d2s9 1/1 Running 0 5h1mlog-pilot-cnfvq 1/1 Running 0 5h1mlog-pilot-hgbkm 1/1 Running 0 5h1mlog-pilot-vwjtm 1/1 Running 0 5hlog-pilot-zqvnp 1/1 Running 0 5hmetrics-server-99d8bb9cc-m5lp9 2/2 Running 0 3m42s[root@master49 metrics-images]# kubectl top pods -n kube-systemNAME CPU(cores) MEMORY(bytes) calico-kube-controllers-75d555c48-c66ll 2m 9Mi calico-node-4w9rr 41m 25Mi calico-node-hrvcq 44m 39Mi calico-node-srz5h 40m 25Mi calico-node-xmb28 41m 25Mi calico-node-zhrs2 44m 41Mi coredns-7ff77c879f-46sjv 8m 8Mi coredns-7ff77c879f-txpw9 6m 8Mi etcd-master49 64m 99Mi etcd-master50 91m 428Mi etcd-master56 95m 423Mi kube-apiserver-master49 66m 471Mi kube-apiserver-master50 61m 504Mi kube-apiserver-master56 59m 474Mi kube-controller-manager-master49 4m 15Mi kube-controller-manager-master50 27m 67Mi kube-controller-manager-master56 6m 15Mi kube-proxy-2gcg5 1m 13Mi kube-proxy-4ckzn 14m 14Mi kube-proxy-bffn9 20m 14Mi kube-proxy-kdjtv 1m 20Mi kube-proxy-w9xzf 15m 19Mi kube-scheduler-master49 4m 18Mi kube-scheduler-master50 6m 24Mi kube-scheduler-master56 4m 17Mi log-pilot-2d2s9 3m 18Mi log-pilot-cnfvq 3m 21Mi log-pilot-hgbkm 3m 7Mi log-pilot-vwjtm 4m 7Mi log-pilot-zqvnp 3m 7Mi metrics-server-99d8bb9cc-m5lp9 1m 28Mi [root@master49 metrics-images]# kubectl top nodeserror: metrics not available yet###### 别慌，等会就好了[root@master49 metrics-images]# kubectl top nodesNAME CPU(cores) CPU% MEMORY(bytes) MEMORY% master49 378m 9% 1851Mi 15% master50 498m 12% 2476Mi 20% master56 470m 11% 2196Mi 18% node52 2949m 12% 65802Mi 31% node53 1285m 5% 31770Mi 15% [root@master49 metrics-images]# lsmetrics-applaction.yamlPlan-B
[root@master49 metrics-server]# lltotal 32-rw-r--r--. 1 root root 304 Dec 24 13:57 auth-delegator.yaml-rw-r--r--. 1 root root 325 Dec 24 13:57 auth-reader.yaml-rw-r--r--. 1 root root 294 Dec 24 13:57 metrics-apiservice.yaml-rw-r--r--. 1 root root 284 Dec 24 13:57 metrics-server-cluster-role-binding.yaml-rw-r--r--. 1 root root 409 Dec 24 13:57 metrics-server-cluster-role.yaml-rw-r--r--. 1 root root 585 Mar 30 14:31 metrics-server-deployment.yaml-rw-r--r--. 1 root root 94 Dec 24 13:57 metrics-server-service-account.yaml-rw-r--r--. 1 root root 245 Dec 24 13:57 metrics-server-service.yaml[root@master49 metrics-server]# ll|awk '{print $9}'auth-delegator.yamlauth-reader.yamlmetrics-apiservice.yamlmetrics-server-cluster-role-binding.yamlmetrics-server-cluster-role.yamlmetrics-server-deployment.yamlmetrics-server-service-account.yamlmetrics-server-service.yaml[root@master49 metrics-server]# ll|awk '{print $9}' | xargs cat apiVersion: rbac.authorization.k8s.io/v1beta1kind: ClusterRoleBindingmetadata: name: metrics-server:system:auth-delegatorroleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:auth-delegatorsubjects:- kind: ServiceAccount name: metrics-server namespace: kube-systemapiVersion: rbac.authorization.k8s.io/v1beta1kind: RoleBindingmetadata: name: metrics-server-auth-reader namespace: kube-systemroleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: extension-apiserver-authentication-readersubjects:- kind: ServiceAccount name: metrics-server namespace: kube-systemapiVersion: apiregistration.k8s.io/v1beta1kind: APIServicemetadata: name: v1beta1.metrics.k8s.iospec: service: name: metrics-server namespace: kube-system group: metrics.k8s.io version: v1beta1 insecureSkipTLSVerify: true groupPriorityMinimum: 100 versionPriority: 100apiVersion: rbac.authorization.k8s.io/v1kind: ClusterRoleBindingmetadata: name: system:metrics-serverroleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: system:metrics-serversubjects:- kind: ServiceAccount name: metrics-server namespace: kube-systemapiVersion: rbac.authorization.k8s.io/v1kind: ClusterRolemetadata: name: system:metrics-serverrules:- apiGroups: - "" resources: - pods - nodes - nodes/stats - namespaces verbs: - get - list - watch- apiGroups: - "apps" resources: - deployments verbs: - get - list - watch- apiGroups: - "extensions" resources: - deployments verbs: - get - list - watchapiVersion: apps/v1kind: Deploymentmetadata: name: metrics-server namespace: kube-system labels: k8s-app: metrics-serverspec: selector: matchLabels: k8s-app: metrics-server template: metadata: name: metrics-server labels: k8s-app: metrics-server spec: serviceAccountName: metrics-server containers: - name: metrics-server image: docker.io/carlziess/metrics-server-amd64-v0.2.1:latest imagePullPolicy: Always command: - /metrics-server - --source=kubernetes.summary_api:''apiVersion: v1kind: ServiceAccountmetadata: name: metrics-server namespace: kube-systemapiVersion: v1kind: Servicemetadata: name: metrics-server namespace: kube-system labels: kubernetes.io/name: "Metrics-server"spec: selector: k8s-app: metrics-server ports: - port: 443 protocol: TCP targetPort: 443[root@master49 metrics-server]# kubectl apply -f .clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator createdrolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader createdapiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io createdclusterrolebinding.rbac.authorization.k8s.io/system:metrics-server createdclusterrole.rbac.authorization.k8s.io/system:metrics-server createddeployment.apps/metrics-server createdserviceaccount/metrics-server createdservice/metrics-server created