通过 AWS EC2 Auto Scaling 组使用 Cluster Autoscaler

本指南介绍如何使用 AWS EC2 Auto Scaling 组在 Rancher 自定义集群上安装和使用 Kubernetes cluster-autoscaler。

我们将安装一个 Rancher RKE 自定义集群，该集群具有固定数量的具有 etcd 和 controlplane 角色的节点，以及数量可变的具有 worker 角色的节点，它们由 cluster-autoscaler 管理。

先决条件

本指南要求：

• Rancher Server 正常运行。
• 你的 AWS EC2 用户具有创建虚拟机、Auto Scaling 组以及 IAM 配置文件和角色的适当权限。

1. 创建自定义集群

在 Rancher Server 上，我们需要创建一个自定义的 K8s 集群。请参阅此处以检查版本兼容性。

请确保 cloud_provider 名称设置为 amazonec2。创建集群后，我们需要获得：

• clusterID：c-xxxxx 将用于 EC2 kubernetes.io/cluster/<clusterID> 实例标签。

• clusterName：将用于 EC2 k8s.io/cluster-autoscaler/<clusterName> 实例标签。

• nodeCommand：将添加到 EC2 实例 user_data 上，以包含集群上的新节点。

  sudo docker run -d --privileged --restart=unless-stopped --net=host -v /etc/kubernetes:/etc/kubernetes -v /var/run:/var/run rancher/rancher-agent:<RANCHER_VERSION> --server https://<RANCHER_URL> --token <RANCHER_TOKEN> --ca-checksum <RANCHER_CHECKSUM> <roles>

2. 配置云提供商

在 AWS EC2 上，我们需要创建一些对象来配置系统。为了在 AWS 上进行配置，我们定义了三个不同的组和 IAM 配置文件。

1. Autoscaling 组：将加入 EC2 Auto Scaling 组 (ASG) 的节点。cluster-autoscaler 将使用 ASG 来进行扩缩容。

• IAM 配置文件：运行 cluster-autoscaler 的 K8s 节点需要该文件。推荐用于 Kubernetes master 节点。此配置文件称为 K8sAutoscalerProfile。

  {
      "Version": "2012-10-17",
      "Statement": [
          {
              "Effect": "Allow",
              "Action": [
                  "autoscaling:DescribeAutoScalingGroups",
                  "autoscaling:DescribeAutoScalingInstances",
                  "autoscaling:DescribeLaunchConfigurations",
                  "autoscaling:SetDesiredCapacity",
                  "autoscaling:TerminateInstanceInAutoScalingGroup",
                  "autoscaling:DescribeTags",
                  "autoscaling:DescribeLaunchConfigurations",
                  "ec2:DescribeLaunchTemplateVersions"
              ],
              "Resource": [
                  "*"
              ]
          }
      ]
  }

1. Master 组：将成为 Kubernetes etcd 和/或 controlplane 的节点。该组不会在 ASG 中。

• IAM 配置文件：集成 Kubernetes cloud_provider 需要该文件。或者，你也可以使用 AWS_ACCESS_KEY 和 AWS_SECRET_KEY 来代替 using-aws-credentials。此配置文件称为 K8sMasterProfile。

  {
      "Version": "2012-10-17",
      "Statement": [
          {
              "Effect": "Allow",
              "Action": [
                  "autoscaling:DescribeAutoScalingGroups",
                  "autoscaling:DescribeLaunchConfigurations",
                  "autoscaling:DescribeTags",
                  "ec2:DescribeInstances",
                  "ec2:DescribeRegions",
                  "ec2:DescribeRouteTables",
                  "ec2:DescribeSecurityGroups",
                  "ec2:DescribeSubnets",
                  "ec2:DescribeVolumes",
                  "ec2:CreateSecurityGroup",
                  "ec2:CreateTags",
                  "ec2:CreateVolume",
                  "ec2:ModifyInstanceAttribute",
                  "ec2:ModifyVolume",
                  "ec2:AttachVolume",
                  "ec2:AuthorizeSecurityGroupIngress",
                  "ec2:CreateRoute",
                  "ec2:DeleteRoute",
                  "ec2:DeleteSecurityGroup",
                  "ec2:DeleteVolume",
                  "ec2:DetachVolume",
                  "ec2:RevokeSecurityGroupIngress",
                  "ec2:DescribeVpcs",
                  "elasticloadbalancing:AddTags",
                  "elasticloadbalancing:AttachLoadBalancerToSubnets",
                  "elasticloadbalancing:ApplySecurityGroupsToLoadBalancer",
                  "elasticloadbalancing:CreateLoadBalancer",
                  "elasticloadbalancing:CreateLoadBalancerPolicy",
                  "elasticloadbalancing:CreateLoadBalancerListeners",
                  "elasticloadbalancing:ConfigureHealthCheck",
                  "elasticloadbalancing:DeleteLoadBalancer",
                  "elasticloadbalancing:DeleteLoadBalancerListeners",
                  "elasticloadbalancing:DescribeLoadBalancers",
                  "elasticloadbalancing:DescribeLoadBalancerAttributes",
                  "elasticloadbalancing:DetachLoadBalancerFromSubnets",
                  "elasticloadbalancing:DeregisterInstancesFromLoadBalancer",
                  "elasticloadbalancing:ModifyLoadBalancerAttributes",
                  "elasticloadbalancing:RegisterInstancesWithLoadBalancer",
                  "elasticloadbalancing:SetLoadBalancerPoliciesForBackendServer",
                  "elasticloadbalancing:AddTags",
                  "elasticloadbalancing:CreateListener",
                  "elasticloadbalancing:CreateTargetGroup",
                  "elasticloadbalancing:DeleteListener",
                  "elasticloadbalancing:DeleteTargetGroup",
                  "elasticloadbalancing:DescribeListeners",
                  "elasticloadbalancing:DescribeLoadBalancerPolicies",
                  "elasticloadbalancing:DescribeTargetGroups",
                  "elasticloadbalancing:DescribeTargetHealth",
                  "elasticloadbalancing:ModifyListener",
                  "elasticloadbalancing:ModifyTargetGroup",
                  "elasticloadbalancing:RegisterTargets",
                  "elasticloadbalancing:SetLoadBalancerPoliciesOfListener",
                  "iam:CreateServiceLinkedRole",
                  "ecr:GetAuthorizationToken",
                  "ecr:BatchCheckLayerAvailability",
                  "ecr:GetDownloadUrlForLayer",
                  "ecr:GetRepositoryPolicy",
                  "ecr:DescribeRepositories",
                  "ecr:ListImages",
                  "ecr:BatchGetImage",
                  "kms:DescribeKey"
              ],
              "Resource": [
                  "*"
              ]
          }
      ]
  }

  • IAM 角色：K8sMasterRole: [K8sMasterProfile,K8sAutoscalerProfile]

  • 安全组：K8sMasterSg。详情请参见 RKE 端口（自定义节点选项卡）

  • 标签： kubernetes.io/cluster/<clusterID>: owned

  • 用户数据：K8sMasterUserData Ubuntu 18.04(ami-0e11cbb34015ff725)，安装 Docker 并将 etcd 和 controlplane 节点添加到 K8s 集群。

    #!/bin/bash -x
    cat <<EOF > /etc/sysctl.d/90-kubelet.conf
    vm.overcommit_memory = 1
    vm.panic_on_oom = 0
    kernel.panic = 10
    kernel.panic_on_oops = 1
    kernel.keys.root_maxkeys = 1000000
    kernel.keys.root_maxbytes = 25000000
    EOF
    sysctl -p /etc/sysctl.d/90-kubelet.conf
    curl -sL https://releases.rancher.com/install-docker/19.03.sh | sh
    sudo usermod -aG docker ubuntu
    TOKEN=$(curl -s -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600")
    PRIVATE_IP=$(curl -H "X-aws-ec2-metadata-token: ${TOKEN}" -s http://169.254.169.254/latest/meta-data/local-ipv4)
    PUBLIC_IP=$(curl -H "X-aws-ec2-metadata-token: ${TOKEN}" -s http://169.254.169.254/latest/meta-data/public-ipv4)
    K8S_ROLES="--etcd --controlplane"
    sudo docker run -d --privileged --restart=unless-stopped --net=host -v /etc/kubernetes:/etc/kubernetes -v /var/run:/var/run rancher/rancher-agent:<RANCHER_VERSION> --server https://<RANCHER_URL> --token <RANCHER_TOKEN> --ca-checksum <RANCHER_CA_CHECKSUM> --address ${PUBLIC_IP} --internal-address ${PRIVATE_IP} ${K8S_ROLES}

1. Worker 组：将加入 K8s worker plane 的节点。Worker 节点将由 cluster-autoscaler 使用 ASG 进行扩缩容。

• IAM 配置文件：提供 cloud_provider worker 集成。 此配置文件称为 K8sWorkerProfile。

  {
      "Version": "2012-10-17",
      "Statement": [
          {
              "Effect": "Allow",
              "Action": [
                  "ec2:DescribeInstances",
                  "ec2:DescribeRegions",
                  "ecr:GetAuthorizationToken",
                  "ecr:BatchCheckLayerAvailability",
                  "ecr:GetDownloadUrlForLayer",
                  "ecr:GetRepositoryPolicy",
                  "ecr:DescribeRepositories",
                  "ecr:ListImages",
                  "ecr:BatchGetImage"
              ],
              "Resource": "*"
          }
      ]
  }

• IAM 角色：K8sWorkerRole：[K8sWorkerProfile]

• 安全组：K8sWorkerSg。详情请参见 RKE 端口（自定义节点选项卡）

• 标签：

  • kubernetes.io/cluster/<clusterID>: owned
  • k8s.io/cluster-autoscaler/<clusterName>: true
  • k8s.io/cluster-autoscaler/enabled: true

• 用户数据：K8sWorkerUserData Ubuntu 18.04(ami-0e11cbb34015ff725)，安装 Docker 并将 worker 节点添加到 K8s 集群。

  #!/bin/bash -x
  cat <<EOF > /etc/sysctl.d/90-kubelet.conf
  vm.overcommit_memory = 1
  vm.panic_on_oom = 0
  kernel.panic = 10
  kernel.panic_on_oops = 1
  kernel.keys.root_maxkeys = 1000000
  kernel.keys.root_maxbytes = 25000000
  EOF
  sysctl -p /etc/sysctl.d/90-kubelet.conf
  curl -sL https://releases.rancher.com/install-docker/19.03.sh | sh
  sudo usermod -aG docker ubuntu
  TOKEN=$(curl -s -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600")
  PRIVATE_IP=$(curl -H "X-aws-ec2-metadata-token: ${TOKEN}" -s http://169.254.169.254/latest/meta-data/local-ipv4)
  PUBLIC_IP=$(curl -H "X-aws-ec2-metadata-token: ${TOKEN}" -s http://169.254.169.254/latest/meta-data/public-ipv4)
  K8S_ROLES="--worker"
  sudo docker run -d --privileged --restart=unless-stopped --net=host -v /etc/kubernetes:/etc/kubernetes -v /var/run:/var/run rancher/rancher-agent:<RANCHER_VERSION> --server https://<RANCHER_URL> --token <RANCHER_TOKEN> --ca-checksum <RANCHER_CA_CHECKCSUM> --address ${PUBLIC_IP} --internal-address ${PRIVATE_IP} ${K8S_ROLES}

详情请参见 AWS 上的 RKE 集群 和 AWS 上的 Cluster Autoscaler。

3. 部署节点

我们配置 AWS 后，我们需要创建虚拟机来引导集群：

• master (etcd+controlplane)：根据需要部署三个适当大小的 master 实例。详情请参见生产就绪集群的建议。

  • IAM 角色：K8sMasterRole
  • 安全组：K8sMasterSg
  • 标签：
    • kubernetes.io/cluster/<clusterID>: owned
  • 用户数据：K8sMasterUserData

• worker：使用以下设置在 EC2 上定义 ASG：

  • 名称：K8sWorkerAsg
  • IAM 角色：K8sWorkerRole
  • 安全组：K8sWorkerSg
  • 标签：
    • kubernetes.io/cluster/<clusterID>: owned
    • k8s.io/cluster-autoscaler/<clusterName>: true
    • k8s.io/cluster-autoscaler/enabled: true
  • 用户数据：K8sWorkerUserData
  • 实例：
    • 最少：2
    • 理想情况：2
    • 最大：10

部署 VM 后，你的 Rancher 自定义集群应该可以正常运行了，其中包含三个 master 节点和两个 worker 节点。

4. 安装 Cluster-autoscaler

此时，我们的 Rancher 集群应该已正常运行。我们将根据 cluster-autoscaler 的建议，在 master 节点和 kube-system 命名空间上安装 cluster-autoscaler。

参数

下表显示了用于微调的 cluster-autoscaler 参数：

部署

基于 cluster-autoscaler-run-on-master.yaml 示例，我们已经创建了自己的 cluster-autoscaler-deployment.yaml 以使用首选的 auto-discovery 设置，更新容忍度、nodeSelector、镜像版本和命令配置：

---
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", "replicasets", "daemonsets"]
    verbs: ["watch", "list", "get"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["storageclasses", "csinodes"]
    verbs: ["watch", "list", "get"]
  - apiGroups: ["batch", "extensions"]
    resources: ["jobs"]
    verbs: ["get", "list", "watch", "patch"]
  - apiGroups: ["coordination.k8s.io"]
    resources: ["leases"]
    verbs: ["create"]
  - apiGroups: ["coordination.k8s.io"]
    resourceNames: ["cluster-autoscaler"]
    resources: ["leases"]
    verbs: ["get", "update"]
---
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: 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
      annotations:
        prometheus.io/scrape: 'true'
        prometheus.io/port: '8085'
    spec:
      serviceAccountName: cluster-autoscaler
      tolerations:
        - effect: NoSchedule
          operator: "Equal"
          value: "true"
          key: node-role.kubernetes.io/controlplane
      nodeSelector:
        node-role.kubernetes.io/controlplane: "true"
      containers:
        - image: eu.gcr.io/k8s-artifacts-prod/autoscaling/cluster-autoscaler:<VERSION>
          name: cluster-autoscaler
          resources:
            limits:
              cpu: 100m
              memory: 300Mi
            requests:
              cpu: 100m
              memory: 300Mi
          command:
            - ./cluster-autoscaler
            - --v=4
            - --stderrthreshold=info
            - --cloud-provider=aws
            - --skip-nodes-with-local-storage=false
            - --expander=least-waste
            - --node-group-auto-discovery=asg:tag=k8s.io/cluster-autoscaler/enabled,k8s.io/cluster-autoscaler/<clusterName>
          volumeMounts:
            - name: ssl-certs
              mountPath: /etc/ssl/certs/ca-certificates.crt
              readOnly: true
          imagePullPolicy: "Always"
      volumes:
        - name: ssl-certs
          hostPath:
            path: "/etc/ssl/certs/ca-certificates.crt"

准备好清单文件后，将该文件部署到 Kubernetes 集群中（也可以使用 Rancher UI 进行操作）：

kubectl -n kube-system apply -f cluster-autoscaler-deployment.yaml

备注

你也可以通过手动配置来设置 Cluster-autoscaler deployment。

测试

此时，cluster-autoscaler 应该已经在 Rancher 自定义集群中启动并运行。当满足以下条件之一时，cluster-autoscaler 需要管理 K8sWorkerAsg ASG，以在 2 到 10 个节点之间进行扩缩容：

• 集群中有 Pod 因资源不足而无法运行。在这种情况下，集群被扩容。
• 集群中有一些节点长时间未得到充分利用，而且它们的 Pod 可以放到其他现有节点上。在这种情况下，集群被缩容。

生成负载

为了在 Kubernetes 集群上产生负载并查看 cluster-autoscaler 是否正常工作，我们准备了一个 test-deployment.yaml。test-deployment 通过三个副本请求 1000m CPU 和 1024Mi 内存。通过调整请求的资源和/或副本以确保耗尽 Kubernetes 集群资源：

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: hello-world
  name: hello-world
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-world
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
      - image: rancher/hello-world
        imagePullPolicy: Always
        name: hello-world
        ports:
        - containerPort: 80
          protocol: TCP
        resources:
          limits:
            cpu: 1000m
            memory: 1024Mi
          requests:
            cpu: 1000m
            memory: 1024Mi

准备好 test deployment 后，将其部署在 Kubernetes 集群的默认命名空间中（可以使用 Rancher UI）：

kubectl -n default apply -f test-deployment.yaml

检查扩缩容

Kubernetes 资源耗尽后，cluster-autoscaler 应该扩容无法调度 pod 的 worker 节点。它应该进行扩容，直到所有 pod 都能被调度。你应该会在 ASG 和 Kubernetes 集群上看到新节点。检查 kube-system cluster-autoscaler pod 上的日志。

检查完扩容后，我们开始检查缩容。为此，请减少 test deployment 的副本数，直到你能释放足够的 Kubernetes 集群资源以进行缩容。你应该能看到 ASG 和 Kubernetes 集群上的节点消失了。检查 kube-system cluster-autoscaler pod 上的日志。