简介： 混合云K8s容器化应用弹性伸缩实战
1. 前提条件
本最佳实践的软件环境要求如下：
应用环境：
①容器服务ACK基于专有云V3.10.0版本。
②公共云云企业网服务CEN。
③公共云弹性伸缩组服务ESS。
配置条件：
1）使用专有云的容器服务或者在ECS上手动部署敏捷PaaS。
2）开通云专线，打通容器服务所在VPC与公共云上的VPC。
3）开通公共云弹性伸缩组服务（ESS）。
2. 背景信息
本实践基于K8s的业务集群运行在专有云上，对测试业务进行压力测试，主要基于以下三种产品和能力：
①利用阿里云的云企业网专线打通专有云和公共云，实现两朵云上VPC网络互通。
②利用K8s（Kubernetes）的HPA能力，实现容器的水平伸缩。
③利用K8s的Cluster Autoscaler和阿里云弹性伸缩组ESS能力实现节点的自动伸缩。
HPA（Horizontal Pod Autoscaler）是K8s的一种资源对象，能够根据CPU、内存等指标对statefulset、deployment等对象中的pod数量进行动态伸缩，使运行在上面的服务对指标的变化有一定的自适应能力。
当被测试业务指标达到上限时，触发HPA自动扩容业务pod；当业务集群无法承载更多pod时，触发公共云的ESS服务，在公共云内扩容出ECS并自动添加到专有云的K8s集群。
图 1：架构原理图
3. 配置HPA
本示例创建了一个支持HPA的nginx应用，创建成功后，当Pod的利用率超过本例中设置的20%利用率时，则会进行水平扩容，低于20%的时候会进行缩容。
1.若使用自建K8s集群，则通过yaml文件配置HPA
1）创建一个nginx应用，必须为应用设置request值，否则HPA不会生效。
apiVersion: app/v1beta2 kind: Deployment spec: template: metadata: creationTimestamp: null labels: app: hpa-test spec: dnsPolicy: ClusterFirst terminationGracePeriodSeconds:30 containers: image: '192.168.**.***:5000/admin/hpa-example:v1' imagePullPolicy: IfNotPresent terminationMessagePolicy:File terminationMessagePath:/dev/termination-log name: hpa-test resources: requests: cpu: //必须设置request值 securityContext: {} restartPolicy:Always schedulerName:default-scheduler replicas: 1 selector: matchLabels: app: hpa-test revisionHistoryLimit: 10 strategy: type: RollingUpdate rollingUpdate: maxSurge: 25% maxUnavailable: 25% progressDeadlineSeconds: 6002）创建HPA。
apiVersion: autoscaling/v1
kind: HorizontalPodAutoscaler
metadata:
annotations:
autoscaling.alpha.kubernetes.io/conditions:'[{"type":"AbleToScale","status":"True","lastTransitionTime":"2020-04-29T06:57:28Z","reason":"ScaleDownStabilized","message":"recent recommendations were higher than current one, applying the highest recent recommendation"},{"type":"ScalingActive","status":"True","lastTransitionTime":"2020-04-29T06:57:28Z","reason":"ValidMetricFound","message":"theHPA was able to successfully calculate a replica count from cpu resource utilization(percentage of request)"},{"type":"ScalingLimited","status":"False","lastTransitionTime":"2020-04-29T06:57:28Z","reason":"DesiredWithinRange","message":"thedesired count is within the acceptable range"}]' autoscaling.alpha.kubernetes.io/currentmetrics:'[{"type":"Resource","resource":{"name":"cpu","currentAverageUtilization":0,"currentAverageValue":"0"}}]' creationTimestamp: 2020-04-29T06:57:13Z name: hpa-test namespace: default resourceVersion: "3092268" selfLink: /apis/autoscaling/v1/namespaces/default/horizontalpodautoscalers/hpa01 uid: a770ca26-89e6-11ea-a7d7-00163e0106e9 spec: maxReplicas: //设置pod数量 minReplicas: 1 scaleTargetRef: apiVersion: apps/v1beta2 kind: Deployment name: centos targetCPUUtilizationPercentage://设置CPU阈值2.若使用阿里云容器服务，需要在部署应用时选择配置HPA
图2：访问设置
4. 配置Cluster Autoscaler
资源请求（Request）的正确、合理设置，是弹性伸缩的前提条件。节点自动伸缩组件基于K8s资源调度的分配情况进行伸缩判断，节点中资源的分配通过资源请（Request）进行计算。
当Pod由于资源请求（Request）无法满足并进入等待（Pending）状态时，节点自动伸缩组件会根据弹性伸缩组配置信息中的资源规格以及约束配置，计算所需的节点数目。
如果可以满足伸缩条件，则会触发伸缩组的节点加入。而当一个节点在弹性伸缩组中且节点上Pod的资源请求低于阈值时，节点自动伸缩组件会将节点进行缩容。
1.配置弹性伸缩组ESS
1）创建ESS弹性伸缩组，记录最小实例数和最大实例数。
图3：修改伸缩组
2）创建伸缩配置，记录伸缩配置的id。
图4：伸缩配置
#!/bin/sh yum install -y ntpdate && ntpdate -u ntp1.aliyun.com && curl http:// example.com/public/hybrid/attach_local_node_aliyun.sh | bash -s -- --docker-version 17.06.2-ce-3 --token 9s92co.y2gkocbumal4fz1z --endpoint 192.168.**.***:6443 --cluster-dns 10.254.**.** --region cn-huhehaote echo "{" > /etc/docker/daemon.json echo "\"registry-mirrors\": [" >> /etc/docker/daemon.json echo "\"https://registry-vpc.cn-huhehaote.aliyuncs.com\"" >> /etc/docker/daemon.json echo "]," >> /etc/docker/daemon.json echo "\"insecure-registries\": [\"https://192.168.**.***:5000\"]" >> /etc/docker/daemon.json echo "}" >> /etc/docker/daemon.json systemctl restart docker 2.K8s集群部署autoscaler
kubectl apply -f ca.yml参考ca.yml创建autoscaler，注意修改如下配置与实际环境相对应。
access-key-id: "TFRBSWlCSFJyeHd2QXZ6****" access-key-secret: "bGIyQ3NuejFQOWM0WjFUNjR4WTVQZzVPRXND****" region-id: "Y24taHVoZWhh****"ca.yal代码如下：
--- apiVersion: v1 kind: ServiceAccount metadata: labels: k8s-addon: cluster-autoscaler.addons.k8s.io k8s-app: cluster-autoscaler name: cluster-autoscaler namespace: kube-system --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: cluster-autoscaler labels: k8s-addon: cluster-autoscaler.addons.k8s.io k8s-app: cluster-autoscaler rules: - apiGroups: [""] resources: ["events","endpoints"] verbs: ["create", "patch"] - apiGroups: [""] resources: ["pods/eviction"] verbs: ["create"] - apiGroups: [""] resources: ["pods/status"] verbs: ["update"] - apiGroups: [""] resources: ["endpoints"] resourceNames: ["cluster-autoscaler"] verbs: ["get","update"] - apiGroups: [""] resources: ["nodes"] verbs: ["watch","list","get","update"] - apiGroups: [""] resources: ["pods","services","replicationcontrollers","persistentvolumeclaims","persistentvolumes"] verbs: ["watch","list","get"] - apiGroups: ["extensions"] resources: ["replicasets","daemonsets"] verbs: ["watch","list","get"] - apiGroups: ["policy"] resources: ["poddisruptionbudgets"] verbs: ["watch","list"] - apiGroups: ["apps"] resources: ["statefulsets"] verbs: ["watch","list","get"] - apiGroups: ["storage.k8s.io"] resources: ["storageclasses"] verbs: ["watch","list","get"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: cluster-autoscaler namespace: kube-system labels: k8s-addon: cluster-autoscaler.addons.k8s.io k8s-app: cluster-autoscaler rules: - apiGroups: [""] resources: ["configmaps"] verbs: ["create","list","watch"] - apiGroups: [""] resources: ["configmaps"] resourceNames: ["cluster-autoscaler-status", "cluster-autoscaler-priority-expander"] verbs: ["delete","get","update","watch"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: cluster-autoscaler labels: k8s-addon: cluster-autoscaler.addons.k8s.io k8s-app: cluster-autoscaler roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: cluster-autoscaler subjects: - kind: ServiceAccount name: cluster-autoscaler namespace: kube-system --- apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: cluster-autoscaler namespace: kube-system labels: k8s-addon: cluster-autoscaler.addons.k8s.io k8s-app: cluster-autoscaler roleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: cluster-autoscaler subjects: - kind: ServiceAccount name: cluster-autoscaler namespace: kube-system --- apiVersion: v1 kind: Secret metadata: name: cloud-config namespace: kube-system type: Opaque data: access-key-id: "TFRBSWlCSFJyeHd2********" access-key-secret: "bGIyQ3NuejFQOWM0WjFUNjR4WTVQZzVP*********" region-id: "Y24taHVoZW********" --- apiVersion: apps/v1 kind: Deployment metadata: name: cluster-autoscaler namespace: kube-system labels: app: cluster-autoscaler spec: replicas: 1 selector: matchLabels: app: cluster-autoscaler template: metadata: labels: app: cluster-autoscaler spec: dnsConfig: nameservers: - 100.XXX.XXX.XXX