kubernetes 部署高可用 kube-controller-manager 集群

tags: master, kube-controller-manager

06-3.部署高可用 kube-controller-manager 集群

本文档介绍部署高可用 kube-controller-manager 集群的步骤。

该集群包含 3 个节点,启动后将通过竞争选举机制产生一个 leader 节点,其它节点为阻塞状态。当 leader 节点不可用后,剩余节点将再次进行选举产生新的 leader 节点,从而保证服务的可用性。

为保证通信安全,本文档先生成 x509 证书和私钥,kube-controller-manager 在如下两种情况下使用该证书:

  1. 与 kube-apiserver 的安全端口通信时;
  2. 安全端口(https,10252) 输出 prometheus 格式的 metrics;

准备工作

下载最新版本的二进制文件、安装和配置 flanneld 参考:06-0.部署master节点.md

创建 kube-controller-manager 证书和私钥

创建证书签名请求:

cat > kube-controller-manager-csr.json <<EOF
{
    "CN": "system:kube-controller-manager",
    "key": {
        "algo": "rsa",
        "size": 2048
    },
    "hosts": [
      "127.0.0.1",
      "172.27.129.105",
      "172.27.129.111",
      "172.27.129.112"
    ],
    "names": [
      {
        "C": "CN",
        "ST": "BeiJing",
        "L": "BeiJing",
        "O": "system:kube-controller-manager",
        "OU": "4Paradigm"
      }
    ]
}
EOF
  • hosts 列表包含所有 kube-controller-manager 节点 IP;
  • CN 为 system:kube-controller-manager、O 为 system:kube-controller-manager,kubernetes 内置的 ClusterRoleBindings system:kube-controller-manager 赋予 kube-controller-manager 工作所需的权限。

生成证书和私钥:

cfssl gencert -ca=/etc/kubernetes/cert/ca.pem \
  -ca-key=/etc/kubernetes/cert/ca-key.pem \
  -config=/etc/kubernetes/cert/ca-config.json \
  -profile=kubernetes kube-controller-manager-csr.json | cfssljson -bare kube-controller-manager

将生成的证书和私钥分发到所有 master 节点:

source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    scp kube-controller-manager*.pem k8s@${node_ip}:/etc/kubernetes/cert/
  done

创建和分发 kubeconfig 文件

kubeconfig 文件包含访问 apiserver 的所有信息,如 apiserver 地址、CA 证书和自身使用的证书;

source /opt/k8s/bin/environment.sh
kubectl config set-cluster kubernetes \
  --certificate-authority=/etc/kubernetes/cert/ca.pem \
  --embed-certs=true \
  --server=${KUBE_APISERVER} \
  --kubeconfig=kube-controller-manager.kubeconfig

kubectl config set-credentials system:kube-controller-manager \
  --client-certificate=kube-controller-manager.pem \
  --client-key=kube-controller-manager-key.pem \
  --embed-certs=true \
  --kubeconfig=kube-controller-manager.kubeconfig

kubectl config set-context system:kube-controller-manager \
  --cluster=kubernetes \
  --user=system:kube-controller-manager \
  --kubeconfig=kube-controller-manager.kubeconfig

kubectl config use-context system:kube-controller-manager --kubeconfig=kube-controller-manager.kubeconfig

分发 kubeconfig 到所有 master 节点:

source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    scp kube-controller-manager.kubeconfig k8s@${node_ip}:/etc/kubernetes/
  done

创建和分发 kube-controller-manager systemd unit 文件

source /opt/k8s/bin/environment.sh
cat > kube-controller-manager.service <<EOF
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/GoogleCloudPlatform/kubernetes

[Service]
ExecStart=/opt/k8s/bin/kube-controller-manager \\
  --port=0 \\
  --secure-port=10252 \\
  --bind-address=127.0.0.1 \\
  --kubeconfig=/etc/kubernetes/kube-controller-manager.kubeconfig \\
  --service-cluster-ip-range=${SERVICE_CIDR} \\
  --cluster-name=kubernetes \\
  --cluster-signing-cert-file=/etc/kubernetes/cert/ca.pem \\
  --cluster-signing-key-file=/etc/kubernetes/cert/ca-key.pem \\
  --experimental-cluster-signing-duration=8760h \\
  --root-ca-file=/etc/kubernetes/cert/ca.pem \\
  --service-account-private-key-file=/etc/kubernetes/cert/ca-key.pem \\
  --leader-elect=true \\
  --feature-gates=RotateKubeletServerCertificate=true \\
  --controllers=*,bootstrapsigner,tokencleaner \\
  --horizontal-pod-autoscaler-use-rest-clients=true \\
  --horizontal-pod-autoscaler-sync-period=10s \\
  --tls-cert-file=/etc/kubernetes/cert/kube-controller-manager.pem \\
  --tls-private-key-file=/etc/kubernetes/cert/kube-controller-manager-key.pem \\
  --use-service-account-credentials=true \\
  --alsologtostderr=true \\
  --logtostderr=false \\
  --log-dir=/var/log/kubernetes \\
  --v=2
Restart=on
Restart=on-failure
RestartSec=5
User=k8s

[Install]
WantedBy=multi-user.target
EOF
  • --port=0:关闭监听 http /metrics 的请求,同时 --address 参数无效,--bind-address 参数有效;
  • --secure-port=10252--bind-address=0.0.0.0: 在所有网络接口监听 10252 端口的 https /metrics 请求;
  • --kubeconfig:指定 kubeconfig 文件路径,kube-controller-manager 使用它连接和验证 kube-apiserver;
  • --cluster-signing-*-file:签名 TLS Bootstrap 创建的证书;
  • --experimental-cluster-signing-duration:指定 TLS Bootstrap 证书的有效期;
  • --root-ca-file:放置到容器 ServiceAccount 中的 CA 证书,用来对 kube-apiserver 的证书进行校验;
  • --service-account-private-key-file:签名 ServiceAccount 中 Token 的私钥文件,必须和 kube-apiserver 的 --service-account-key-file 指定的公钥文件配对使用;
  • --service-cluster-ip-range :指定 Service Cluster IP 网段,必须和 kube-apiserver 中的同名参数一致;
  • --leader-elect=true:集群运行模式,启用选举功能;被选为 leader 的节点负责处理工作,其它节点为阻塞状态;
  • --feature-gates=RotateKubeletServerCertificate=true:开启 kublet server 证书的自动更新特性;
  • --controllers=*,bootstrapsigner,tokencleaner:启用的控制器列表,tokencleaner 用于自动清理过期的 Bootstrap token;
  • --horizontal-pod-autoscaler-*:custom metrics 相关参数,支持 autoscaling/v2alpha1;
  • --tls-cert-file--tls-private-key-file:使用 https 输出 metrics 时使用的 Server 证书和秘钥;
  • --use-service-account-credentials=true:
  • User=k8s:使用 k8s 账户运行;

kube-controller-manager 不对请求 https metrics 的 Client 证书进行校验,故不需要指定 --tls-ca-file 参数,而且该参数已被淘汰。

完整 unit 见 kube-controller-manager.service

分发 systemd unit 文件到所有 master 节点:

source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    scp kube-controller-manager.service root@${node_ip}:/etc/systemd/system/
  done

kube-controller-manager 的权限

ClusteRole: system:kube-controller-manager 的权限很小,只能创建 secret、serviceaccount 等资源对象,各 controller 的权限分散到 ClusterRole system:controller:XXX 中。

需要在 kube-controller-manager 的启动参数中添加 --use-service-account-credentials=true 参数,这样 main controller 会为各 controller 创建对应的 ServiceAccount XXX-controller。

内置的 ClusterRoleBinding system:controller:XXX 将赋予各 XXX-controller ServiceAccount 对应的 ClusterRole system:controller:XXX 权限。

启动 kube-controller-manager 服务

source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    ssh root@${node_ip} "mkdir -p /var/log/kubernetes && chown -R k8s /var/log/kubernetes"
    ssh root@${node_ip} "systemctl daemon-reload && systemctl enable kube-controller-manager && systemctl restart kube-controller-manager"
  done
  • 必须先创建日志目录;

检查服务运行状态

source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    ssh k8s@${node_ip} "systemctl status kube-controller-manager|grep Active"
  done

确保状态为 active (running),否则查看日志,确认原因:

$ journalctl -u kube-controller-manager

查看输出的 metric

注意:以下命令在 kube-controller-manager 节点上执行。

kube-controller-manager 监听 10252 端口,接收 https 请求:

$ sudo netstat -lnpt|grep kube-controll
tcp        0      0 127.0.0.1:10252         0.0.0.0:*               LISTEN      18377/kube-controll
$ curl -s --cacert /etc/kubernetes/cert/ca.pem https://127.0.0.1:10252/metrics |head
# HELP ClusterRoleAggregator_adds Total number of adds handled by workqueue: ClusterRoleAggregator
# TYPE ClusterRoleAggregator_adds counter
ClusterRoleAggregator_adds 3
# HELP ClusterRoleAggregator_depth Current depth of workqueue: ClusterRoleAggregator
# TYPE ClusterRoleAggregator_depth gauge
ClusterRoleAggregator_depth 0
# HELP ClusterRoleAggregator_queue_latency How long an item stays in workqueueClusterRoleAggregator before being requested.
# TYPE ClusterRoleAggregator_queue_latency summary
ClusterRoleAggregator_queue_latency{quantile="0.5"} 57018
ClusterRoleAggregator_queue_latency{quantile="0.9"} 57268
  • curl --cacert CA 证书用来验证 kube-controller-manager https server 证书;

测试 kube-controller-manager 集群的高可用

停掉一个或两个节点的 kube-controller-manager 服务,观察其它节点的日志,看是否获取了 leader 权限。

查看当前的 leader

$ kubectl get endpoints kube-controller-manager --namespace=kube-system  -o yaml
apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"kube-node2_084534e2-6cc4-11e8-a418-5254001f5b65","leaseDurationSeconds":15,"acquireTime":"2018-06-10T15:40:33Z","renewTime":"2018-06-10T16:19:08Z","leaderTransitions":12}'
  creationTimestamp: 2018-06-10T13:59:42Z
  name: kube-controller-manager
  namespace: kube-system
  resourceVersion: "4540"
  selfLink: /api/v1/namespaces/kube-system/endpoints/kube-controller-manager
  uid: 862cc048-6cb6-11e8-96fa-525400ba84c6

可见,当前的 leader 为 kube-node2 节点。

参考

  1. 关于 controller 权限和 use-service-account-credentials 参数:https://github.com/kubernetes/kubernetes/issues/48208
  2. kublet 认证和授权:https://kubernetes.io/docs/admin/kubelet-authentication-authorization/#kubelet-authorization






发表于: 1月前   最后更新时间: 1月前   游览量:139
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