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手动部署k8s(十)-部署高可用 kube-scheduler 集群

原教程来自 github/opsnull, 现在此基础上记录自己搭建遇到的问题

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：

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

创建 kube-scheduler 证书和私钥

创建证书签名请求

cd /opt/k8s/work
cat > kube-scheduler-csr.json <<EOF
{
    "CN": "system:kube-scheduler",
    "hosts": [
      "127.0.0.1",
      "192.168.1.31",
      "192.168.1.32",
      "192.168.1.33"
    ],
    "key": {
        "algo": "rsa",
        "size": 2048
    },
    "names": [
      {
        "C": "CN",
        "ST": "BeiJing",
        "L": "BeiJing",
        "O": "system:kube-scheduler",
        "OU": "4Paradigm"
      }
    ]
}
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

cd /opt/k8s/work
cfssl gencert -ca=/opt/k8s/work/ca.pem /
  -ca-key=/opt/k8s/work/ca-key.pem /
  -config=/opt/k8s/work/ca-config.json /
  -profile=kubernetes kube-scheduler-csr.json | cfssljson -bare kube-scheduler
ls kube-scheduler*pem

将生成的证书和私钥分发到所有 master 节点

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

cd /opt/k8s/work
source /opt/k8s/bin/environment.sh
kubectl config set-cluster kubernetes /
  --certificate-authority=/opt/k8s/work/ca.pem /
  --embed-certs=true /
  --server=${KUBE_APISERVER} /
  --kubeconfig=kube-scheduler.kubeconfig

kubectl config set-credentials system:kube-scheduler /
  --client-certificate=kube-scheduler.pem /
  --client-key=kube-scheduler-key.pem /
  --embed-certs=true /
  --kubeconfig=kube-scheduler.kubeconfig

kubectl config set-context system:kube-scheduler /
  --cluster=kubernetes /
  --user=system:kube-scheduler /
  --kubeconfig=kube-scheduler.kubeconfig

kubectl config use-context system:kube-scheduler --kubeconfig=kube-scheduler.kubeconfig

分发 kubeconfig 到所有 master 节点

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

创建 kube-scheduler 配置文件

cd /opt/k8s/work
cat >kube-scheduler.yaml.template <<EOF
apiVersion: kubescheduler.config.k8s.io/v1alpha1
kind: KubeSchedulerConfiguration
bindTimeoutSeconds: 600
clientConnection:
  burst: 200
  kubeconfig: "/etc/kubernetes/kube-scheduler.kubeconfig"
  qps: 100
enableContentionProfiling: false
enableProfiling: true
hardPodAffinitySymmetricWeight: 1
healthzBindAddress: ##NODE_IP##:10251
leaderElection:
  leaderElect: true
metricsBindAddress: ##NODE_IP##:10251
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

cd /opt/k8s/work
source /opt/k8s/bin/environment.sh
for (( i=0; i < 3; i++ ))
  do
    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
  done
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

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

创建 kube-scheduler systemd unit 模板文件

cd /opt/k8s/work
cat > kube-scheduler.service.template <<EOF
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/GoogleCloudPlatform/kubernetes

[Service]
WorkingDirectory=${K8S_DIR}/kube-scheduler
ExecStart=/opt/k8s/bin/kube-scheduler //
  --config=/etc/kubernetes/kube-scheduler.yaml //
  --bind-address=##NODE_IP## //
  --secure-port=10259 //
  --port=0 //
  --tls-cert-file=/etc/kubernetes/cert/kube-scheduler.pem //
  --tls-private-key-file=/etc/kubernetes/cert/kube-scheduler-key.pem //
  --authentication-kubeconfig=/etc/kubernetes/kube-scheduler.kubeconfig //
  --client-ca-file=/etc/kubernetes/cert/ca.pem //
  --requestheader-allowed-names="" //
  --requestheader-client-ca-file=/etc/kubernetes/cert/ca.pem //
  --requestheader-extra-headers-prefix="X-Remote-Extra-" //
  --requestheader-group-headers=X-Remote-Group //
  --requestheader-username-headers=X-Remote-User //
  --authorization-kubeconfig=/etc/kubernetes/kube-scheduler.kubeconfig //
  --logtostderr=true //
  --v=2
Restart=always
RestartSec=5
StartLimitInterval=0

[Install]
WantedBy=multi-user.target
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

cd /opt/k8s/work
source /opt/k8s/bin/environment.sh
for (( i=0; i < 3; i++ ))
  do
    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 
  done
ls kube-scheduler*.service
  • 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 systemd unit 文件到所有 master 节点

cd /opt/k8s/work
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    scp kube-scheduler-${node_ip}.service root@${node_ip}:/etc/systemd/system/kube-scheduler.service
  done
  • 重命名为 kube-scheduler.service

启动 kube-scheduler 服务

source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
  do
    echo ">>> ${node_ip}"
    ssh root@${node_ip} "mkdir -p ${K8S_DIR}/kube-scheduler"
    ssh root@${node_ip} "systemctl daemon-reload && systemctl enable kube-scheduler && systemctl restart kube-scheduler"
  done
  • 启动服务前必须先创建工作目录

检查服务运行状态

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

确保状态为 active (running)，否则查看日志，确认原因：

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 10251 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。

[root@ _41_ /opt/k8s/work]# netstat -lnpt |grep kube-sch
tcp        0      0 192.168.1.31:10259      0.0.0.0:*               LISTEN      34130/kube-schedule 
tcp        0      0 192.168.1.31:10251      0.0.0.0:*               LISTEN      34130/kube-schedule 
[root@ _42_ /opt/k8s/work]# 

[root@ _54_ /opt/k8s/work]# curl -s http://192.168.1.31:10251/metrics  | head
# HELP apiserver_audit_event_total Counter of audit events generated and sent to the audit backend.
# TYPE apiserver_audit_event_total counter
apiserver_audit_event_total 0
# HELP apiserver_audit_requests_rejected_total Counter of apiserver requests rejected due to an error in audit logging backend.
# TYPE apiserver_audit_requests_rejected_total counter
apiserver_audit_requests_rejected_total 0
# HELP apiserver_client_certificate_expiration_seconds Distribution of the remaining lifetime on the certificate used to authenticate a request.
# TYPE apiserver_client_certificate_expiration_seconds histogram
apiserver_client_certificate_expiration_seconds_bucket{le="0"} 0
apiserver_client_certificate_expiration_seconds_bucket{le="1800"} 0

[root@ _55_ /opt/k8s/work]# curl -s --cacert /opt/k8s/work/ca.pem --cert /opt/k8s/work/admin.pem --key /opt/k8s/work/admin-key.pem https://192.168.1.31:10259/metrics |head
# HELP apiserver_audit_event_total Counter of audit events generated and sent to the audit backend.
# TYPE apiserver_audit_event_total counter
apiserver_audit_event_total 0
# HELP apiserver_audit_requests_rejected_total Counter of apiserver requests rejected due to an error in audit logging backend.
# TYPE apiserver_audit_requests_rejected_total counter
apiserver_audit_requests_rejected_total 0
# HELP apiserver_client_certificate_expiration_seconds Distribution of the remaining lifetime on the certificate used to authenticate a request.
# TYPE apiserver_client_certificate_expiration_seconds histogram
apiserver_client_certificate_expiration_seconds_bucket{le="0"} 0
apiserver_client_certificate_expiration_seconds_bucket{le="1800"} 0

查看当前的 leader

[root@ _56_ /opt/k8s/work]# kubectl get endpoints kube-scheduler --namespace=kube-system  -o yaml
apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"slave-31_f569773c-b434-11e9-95dc-000c293d1de7","leaseDurationSeconds":15,"acquireTime":"2019-08-01T08:18:37Z","renewTime":"2019-08-01T08:25:22Z","leaderTransitions":0}'
  creationTimestamp: "2019-08-01T08:18:37Z"
  name: kube-scheduler
  namespace: kube-system
  resourceVersion: "64781"
  selfLink: /api/v1/namespaces/kube-system/endpoints/kube-scheduler
  uid: f63b92a9-b434-11e9-8c9a-000c293d1de7

可见，当前的 leader 为 slave-31 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。
slave-31 192.168.1.31 停止kube-scheduler 服务

[root@ _60_ /opt/k8s/work]# kubectl get endpoints kube-scheduler --namespace=kube-system  -o yaml
apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"slave-32_f6830187-b434-11e9-b550-000c29eca111","leaseDurationSeconds":15,"acquireTime":"2019-08-01T08:27:02Z","renewTime":"2019-08-01T08:27:04Z","leaderTransitions":1}'
  creationTimestamp: "2019-08-01T08:18:37Z"
  name: kube-scheduler
  namespace: kube-system
  resourceVersion: "64886"
  selfLink: /api/v1/namespaces/kube-system/endpoints/kube-scheduler
  uid: f63b92a9-b434-11e9-8c9a-000c293d1de7

可以看到leader已经切换为slave-32

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