05-4. 部署高可用 kube-scheduler 集群

本文档介绍部署高可用 kube-scheduler 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-scheduler 在如下两种情况下使用该证书：

  1. 与 kube-apiserver 的安全端口通信;
  2. 在安全端口(https，10251) 输出 prometheus 格式的 metrics；

注意：如果没有特殊指明，本文档的所有操作均在 zhangjun-k8s-01 节点上执行。

创建 kube-scheduler 证书和私钥

创建证书签名请求：

  1. cd /opt/k8s/work
  2. cat > kube-scheduler-csr.json <<EOF
  3. {
  4.     "CN": "system:kube-scheduler",
  5.     "hosts": [
  6.       "127.0.0.1",
  7.       "172.27.138.239",
  8.       "172.27.137.229",
  9.       "172.27.138.251"
  10.     ],
  11.     "key": {
  12.         "algo": "rsa",
  13.         "size": 2048
  14.     },
  15.     "names": [
  16.       {
  17.         "C": "CN",
  18.         "ST": "BeiJing",
  19.         "L": "BeiJing",
  20.         "O": "system:kube-scheduler",
  21.         "OU": "opsnull"
  22.       }
  23.     ]
  24. }
  25. EOF
  • hosts 列表包含所有 kube-scheduler 节点 IP；
  • CN 和 O 均为 system:kube-scheduler，kubernetes 内置的 ClusterRoleBindings system:kube-scheduler 将赋予 kube-scheduler 工作所需的权限；

生成证书和私钥：

  1. cd /opt/k8s/work
  2. cfssl gencert -ca=/opt/k8s/work/ca.pem \
  3.   -ca-key=/opt/k8s/work/ca-key.pem \
  4.   -config=/opt/k8s/work/ca-config.json \
  5.   -profile=kubernetes kube-scheduler-csr.json | cfssljson -bare kube-scheduler
  6. ls kube-scheduler*pem

将生成的证书和私钥分发到所有 master 节点：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. for node_ip in ${NODE_IPS[@]}
  4.   do
  5.     echo ">>> ${node_ip}"
  6.     scp kube-scheduler*.pem root@${node_ip}:/etc/kubernetes/cert/
  7.   done

创建和分发 kubeconfig 文件

kube-scheduler 使用 kubeconfig 文件访问 apiserver，该文件提供了 apiserver 地址、嵌入的 CA 证书和 kube-scheduler 证书：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. kubectl config set-cluster kubernetes \
  4.   --certificate-authority=/opt/k8s/work/ca.pem \
  5.   --embed-certs=true \
  6.   --server="https://##NODE_IP##:6443" \
  7.   --kubeconfig=kube-scheduler.kubeconfig
  9. kubectl config set-credentials system:kube-scheduler \
  10.   --client-certificate=kube-scheduler.pem \
  11.   --client-key=kube-scheduler-key.pem \
  12.   --embed-certs=true \
  13.   --kubeconfig=kube-scheduler.kubeconfig
  15. kubectl config set-context system:kube-scheduler \
  16.   --cluster=kubernetes \
  17.   --user=system:kube-scheduler \
  18.   --kubeconfig=kube-scheduler.kubeconfig
  20. kubectl config use-context system:kube-scheduler --kubeconfig=kube-scheduler.kubeconfig

分发 kubeconfig 到所有 master 节点：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. for node_ip in ${NODE_IPS[@]}
  4.   do
  5.     echo ">>> ${node_ip}"
  6.     sed -e "s/##NODE_IP##/${node_ip}/" kube-scheduler.kubeconfig > kube-scheduler-${node_ip}.kubeconfig
  7.     scp kube-scheduler-${node_ip}.kubeconfig root@${node_ip}:/etc/kubernetes/kube-scheduler.kubeconfig
  8.   done

创建 kube-scheduler 配置文件

  1. cd /opt/k8s/work
  2. cat >kube-scheduler.yaml.template <<EOF
  3. apiVersion: kubescheduler.config.k8s.io/v1alpha1
  4. kind: KubeSchedulerConfiguration
  5. bindTimeoutSeconds: 600
  6. clientConnection:
  7.   burst: 200
  8.   kubeconfig: "/etc/kubernetes/kube-scheduler.kubeconfig"
  9.   qps: 100
  10. enableContentionProfiling: false
  11. enableProfiling: true
  12. hardPodAffinitySymmetricWeight: 1
  13. healthzBindAddress: ##NODE_IP##:10251
  14. leaderElection:
  15.   leaderElect: true
  16. metricsBindAddress: ##NODE_IP##:10251
  17. EOF
  • --kubeconfig：指定 kubeconfig 文件路径，kube-scheduler 使用它连接和验证 kube-apiserver；
  • --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；

替换模板文件中的变量：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. for (( i=0; i < 3; i++ ))
  4.   do
  5.     sed -e "s/##NODE_NAME##/${NODE_NAMES[i]}/" -e "s/##NODE_IP##/${NODE_IPS[i]}/" kube-scheduler.yaml.template > kube-scheduler-${NODE_IPS[i]}.yaml
  6.   done
  7. ls kube-scheduler*.yaml
  • NODE_NAMES 和 NODE_IPS 为相同长度的 bash 数组，分别为节点名称和对应的 IP；

分发 kube-scheduler 配置文件到所有 master 节点：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. for node_ip in ${NODE_IPS[@]}
  4.   do
  5.     echo ">>> ${node_ip}"
  6.     scp kube-scheduler-${node_ip}.yaml root@${node_ip}:/etc/kubernetes/kube-scheduler.yaml
  7.   done
  • 重命名为 kube-scheduler.yaml;

创建 kube-scheduler systemd unit 模板文件

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. cat > kube-scheduler.service.template <<EOF
  4. [Unit]
  5. Description=Kubernetes Scheduler
  6. Documentation=https://github.com/GoogleCloudPlatform/kubernetes
  8. [Service]
  9. WorkingDirectory=${K8S_DIR}/kube-scheduler
  10. ExecStart=/opt/k8s/bin/kube-scheduler \\
  11.   --config=/etc/kubernetes/kube-scheduler.yaml \\
  12.   --bind-address=##NODE_IP## \\
  13.   --secure-port=10259 \\
  14.   --port=0 \\
  15.   --tls-cert-file=/etc/kubernetes/cert/kube-scheduler.pem \\
  16.   --tls-private-key-file=/etc/kubernetes/cert/kube-scheduler-key.pem \\
  17.   --authentication-kubeconfig=/etc/kubernetes/kube-scheduler.kubeconfig \\
  18.   --client-ca-file=/etc/kubernetes/cert/ca.pem \\
  19.   --requestheader-allowed-names="" \\
  20.   --requestheader-client-ca-file=/etc/kubernetes/cert/ca.pem \\
  21.   --requestheader-extra-headers-prefix="X-Remote-Extra-" \\
  22.   --requestheader-group-headers=X-Remote-Group \\
  23.   --requestheader-username-headers=X-Remote-User \\
  24.   --authorization-kubeconfig=/etc/kubernetes/kube-scheduler.kubeconfig \\
  25.   --logtostderr=true \\
  26.   --v=2
  27. Restart=always
  28. RestartSec=5
  29. StartLimitInterval=0
  31. [Install]
  32. WantedBy=multi-user.target
  33. EOF

为各节点创建和分发 kube-scheduler systemd unit 文件

替换模板文件中的变量，为各节点创建 systemd unit 文件：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. for (( i=0; i < 3; i++ ))
  4.   do
  5.     sed -e "s/##NODE_NAME##/${NODE_NAMES[i]}/" -e "s/##NODE_IP##/${NODE_IPS[i]}/" kube-scheduler.service.template > kube-scheduler-${NODE_IPS[i]}.service 
  6.   done
  7. ls kube-scheduler*.service

分发 systemd unit 文件到所有 master 节点：

  1. cd /opt/k8s/work
  2. source /opt/k8s/bin/environment.sh
  3. for node_ip in ${NODE_IPS[@]}
  4.   do
  5.     echo ">>> ${node_ip}"
  6.     scp kube-scheduler-${node_ip}.service root@${node_ip}:/etc/systemd/system/kube-scheduler.service
  7.   done

启动 kube-scheduler 服务

  1. source /opt/k8s/bin/environment.sh
  2. for node_ip in ${NODE_IPS[@]}
  3.   do
  4.     echo ">>> ${node_ip}"
  5.     ssh root@${node_ip} "mkdir -p ${K8S_DIR}/kube-scheduler"
  6.     ssh root@${node_ip} "systemctl daemon-reload && systemctl enable kube-scheduler && systemctl restart kube-scheduler"
  7.   done

检查服务运行状态

  1. source /opt/k8s/bin/environment.sh
  2. for node_ip in ${NODE_IPS[@]}
  3.   do
  4.     echo ">>> ${node_ip}"
  5.     ssh root@${node_ip} "systemctl status kube-scheduler|grep Active"
  6.   done

确保状态为 active (running)，否则查看日志，确认原因：

  1. journalctl -u kube-scheduler

查看输出的 metrics

注意：以下命令在 kube-scheduler 节点上执行。

kube-scheduler 监听 10251 和 10259 端口：

  • 10251：接收 http 请求，非安全端口，不需要认证授权；
  • 10259：接收 https 请求，安全端口，需要认证授权；

两个接口都对外提供 /metrics 和 /healthz 的访问。

  1. $ sudo netstat -lnpt |grep kube-sch
  2. tcp        0      0 172.27.138.251:10251    0.0.0.0:*               LISTEN      114702/kube-schedul
  3. tcp        0      0 172.27.138.251:10259    0.0.0.0:*               LISTEN      114702/kube-schedul
  1. $ curl -s http://172.27.138.251:10251/metrics |head
  2. # HELP apiserver_audit_event_total Counter of audit events generated and sent to the audit backend.
  3. # TYPE apiserver_audit_event_total counter
  4. apiserver_audit_event_total 0
  5. # HELP apiserver_audit_requests_rejected_total Counter of apiserver requests rejected due to an error in audit logging backend.
  6. # TYPE apiserver_audit_requests_rejected_total counter
  7. apiserver_audit_requests_rejected_total 0
  8. # HELP apiserver_client_certificate_expiration_seconds Distribution of the remaining lifetime on the certificate used to authenticate a request.
  9. # TYPE apiserver_client_certificate_expiration_seconds histogram
  10. apiserver_client_certificate_expiration_seconds_bucket{le="0"} 0
  11. apiserver_client_certificate_expiration_seconds_bucket{le="1800"} 0
  1. $ curl -s --cacert /opt/k8s/work/ca.pem --cert /opt/k8s/work/admin.pem --key /opt/k8s/work/admin-key.pem https://172.27.138.251:10259/metrics |head
  2. # HELP apiserver_audit_event_total Counter of audit events generated and sent to the audit backend.
  3. # TYPE apiserver_audit_event_total counter
  4. apiserver_audit_event_total 0
  5. # HELP apiserver_audit_requests_rejected_total Counter of apiserver requests rejected due to an error in audit logging backend.
  6. # TYPE apiserver_audit_requests_rejected_total counter
  7. apiserver_audit_requests_rejected_total 0
  8. # HELP apiserver_client_certificate_expiration_seconds Distribution of the remaining lifetime on the certificate used to authenticate a request.
  9. # TYPE apiserver_client_certificate_expiration_seconds histogram
  10. apiserver_client_certificate_expiration_seconds_bucket{le="0"} 0
  11. apiserver_client_certificate_expiration_seconds_bucket{le="1800"} 0

查看当前的 leader

  1. $ kubectl get endpoints kube-scheduler --namespace=kube-system  -o yaml
  2. apiVersion: v1
  3. kind: Endpoints
  4. metadata:
  5.   annotations:
  6.     control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"zhangjun-k8s-01_ce04632e-64e4-477e-b8f0-4e69020cd996","leaseDurationSeconds":15,"acquireTime":"2020-02-07T07:05:00Z","renewTime":"2020-02-07T07:05:28Z","leaderTransitions":0}'
  7.   creationTimestamp: "2020-02-07T07:05:00Z"
  8.   name: kube-scheduler
  9.   namespace: kube-system
  10.   resourceVersion: "756"
  11.   selfLink: /api/v1/namespaces/kube-system/endpoints/kube-scheduler
  12.   uid: 1b687724-a6e2-4404-9efb-a1f0e201fecc

可见，当前的 leader 为 zhangjun-k8s-01 节点。

测试 kube-scheduler 集群的高可用

随便找一个或两个 master 节点，停掉 kube-scheduler 服务，看其它节点是否获取了 leader 权限。