手动搭建k8s-1-10-4之部署kube-scheduler

文章发布较早，内容可能过时，阅读注意甄别。

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：

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

配置之前需要先安装 kubelet,flannel 等组件，不过前边已经安装，现在直接进入配置。

# 1，创建 kube-scheduler 证书和私钥

创建证书签名请求：

cat > kube-scheduler-csr.json <<EOF
{
    "CN": "system:kube-scheduler",
    "hosts": [
      "127.0.0.1",
      "192.168.106.3",
      "192.168.106.4",
      "192.168.106.5"
    ],
    "key": {
        "algo": "rsa",
        "size": 2048
    },
    "names": [
      {
        "C": "CN",
        "ST": "BeiJing",
        "L": "BeiJing",
        "O": "system:kube-scheduler",
        "OU": "4Paradigm"
      }
    ]
}
EOF

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hosts 列表包含所有 kube-scheduler 节点 IP；
CN 为 system:kube-scheduler、O 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：

$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-scheduler-csr.json | cfssljson -bare kube-scheduler

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# 2，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-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

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上一步创建的证书、私钥以及 kube-apiserver 地址被写入到 kubeconfig 文件中；

分发 kubeconfig 到所有 master 节点：

cat > magic.sh << "EOF"
#!/bin/bash
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
do
    echo ">>> ${node_ip}" 
    scp kube-scheduler.kubeconfig k8s@${node_ip}:/etc/kubernetes/
done
EOF

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# 3，创建和分发 kube-scheduler systemd unit 文件

cat > kube-scheduler.service <<EOF
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
[Service]
ExecStart=/opt/k8s/bin/kube-scheduler \\
  --address=127.0.0.1 \\
  --kubeconfig=/etc/kubernetes/kube-scheduler.kubeconfig \\
  --leader-elect=true \\
  --alsologtostderr=true \\
  --logtostderr=false \\
  --log-dir=/var/log/kubernetes \\
  --v=2
Restart=on-failure
RestartSec=5
User=k8s
[Install]
WantedBy=multi-user.target
EOF

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--address：在 127.0.0.1:10251 端口接收 http /metrics 请求；kube-scheduler 目前还不支持接收 https 请求；
--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；
User=k8s：使用 k8s 账户运行；

分发 systemd unit 文件到所有 master 节点：

cat > magic.sh << "EOF"
#!/bin/bash
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
do
    echo ">>> ${node_ip}" 
    scp kube-scheduler.service root@${node_ip}:/etc/systemd/system/
done
EOF

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# 4，启动 kube-scheduler 服务

cat > magic.sh << "EOF"
#!/bin/bash
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-scheduler && systemctl start kube-scheduler"
done
EOF

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# 5，检查服务运行状态

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

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如果看到如下输出：

$bash magic.sh
>>> 192.168.106.3
   Active: active (running) since Fri 2018-11-23 18:31:30 CST; 6h ago
>>> 192.168.106.4
   Active: active (running) since Fri 2018-11-23 18:29:32 CST; 6h ago
>>> 192.168.106.5
   Active: active (running) since Fri 2018-11-23 18:29:32 CST; 6h ago

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则正常，如果失败，看日志：

journalctl -xu kube-scheduler

# 5，查看输出的 metric

注意：以下命令在 kube-scheduler 节点上执行。

kube-scheduler 监听 10251 端口，接收 http 请求：

$sudo netstat -lnpt|grep kube-sche
tcp        0      0 127.0.0.1:10251         0.0.0.0:*               LISTEN      15377/kube-schedule

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$curl -s http://127.0.0.1:10251/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 go_gc_duration_seconds A summary of the GC invocation durations.
# TYPE go_gc_duration_seconds summary
go_gc_duration_seconds{quantile="0"} 6.3423e-05
go_gc_duration_seconds{quantile="0.25"} 0.000120079
go_gc_duration_seconds{quantile="0.5"} 0.000146495
go_gc_duration_seconds{quantile="0.75"} 0.000174475
go_gc_duration_seconds{quantile="1"} 0.001807813

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# 6，查看当前的 leader

$kubectl get endpoints kube-scheduler --namespace=kube-system  -o yaml
apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"kube-node2_aa57b017-ef0a-11e8-aaf2-5254001a681e","leaseDurationSeconds":15,"acquireTime":"2018-11-23T10:31:09Z","renewTime":"2018-11-23T17:05:31Z","leaderTransitions":1}'
  creationTimestamp: 2018-11-23T10:29:32Z
  name: kube-scheduler
  namespace: kube-system
  resourceVersion: "30835"
  selfLink: /api/v1/namespaces/kube-system/endpoints/kube-scheduler
  uid: aabb2233-ef0a-11e8-9670-525400c7ba97

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可见，当前的 leader 为 kube-node2 节点。

# 7，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（systemd 日志）。

现在就去停掉 kube-node2 上的 kube-scheduler 服务。

$systemctl stop kube-scheduler
$systemctl status kube-scheduler | grep Active
   Active: inactive (dead) since Sat 2018-11-24 01:06:40 CST; 14s ago

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然后再来查看一下现在的 leader 是谁：

$kubectl get endpoints kube-scheduler --namespace=kube-system  -o yaml
apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"kube-node3_aa9017f9-ef0a-11e8-b73d-525400b42484","leaseDurationSeconds":15,"acquireTime":"2018-11-23T17:06:57Z","renewTime":"2018-11-23T17:07:31Z","leaderTransitions":2}'
  creationTimestamp: 2018-11-23T10:29:32Z
  name: kube-scheduler
  namespace: kube-system
  resourceVersion: "30984"
  selfLink: /api/v1/namespaces/kube-system/endpoints/kube-scheduler
  uid: aabb2233-ef0a-11e8-9670-525400c7ba97

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可以看到，已经漂移到了 kube-node3 上去了。

上次更新: 2022/08/19, 09:49:20

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