本文将在前文基础上介绍k8s集群的高可用实践，一般来讲，k8s集群高可用主要包含以下几个内容：
1、etcd集群高可用
2、集群dns服务高可用
3、kube-apiserver、kube-controller-manager、kube-scheduler等master组件的高可用

其中etcd实现的办法较为容易，具体实现办法可参考前文：
https://blog.51cto.com/ylw6006/2095871

集群dns服务高可用，可以通过配置dns的pod副本数为2，通过配置label实现2个副本运行在在不同的节点上实现高可用。

kube-apiserver服务的高可用，可行的方案较多，具体介绍可参考文档：
https://jishu.io/kubernetes/kubernetes-master-ha/

kube-controller-manager、kube-scheduler等master组件的高可用相对容易实现，运行多份实例即可。

一、环境介绍

master节点1： 192.168.115.5/24 主机名：vm1 
master节点2： 192.168.115.6/24 主机名：vm2
VIP地址： 192.168.115.4/24 (使用keepalived实现)
Node节点1: 192.168.115.6/24 主机名：vm2
Node节点2: 192.168.115.7/24 主机名：vm3

操作系统版本：centos 7.2 64bit
K8s版本：1.9.6 二进制部署

本文演示环境是在前文的基础上，已有k8s集群（1个master节点、2个node节点上），实现k8s集群master组件的高可用，关于k8s环境的部署请参考前文链接!
1、配置Etcd集群和TLS认证 ——> https://blog.51cto.com/ylw6006/2095871
2、Flannel网络组件部署 ——> https://blog.51cto.com/ylw6006/2097303
3、升级Docker服务 ——> https://blog.51cto.com/ylw6006/2103064
4、K8S二进制部署Master节点 ——> https://blog.51cto.com/ylw6006/2104031
5、K8S二进制部署Node节点 ——> https://blog.51cto.com/ylw6006/2104692

二、证书更新

在vm1节点上完成证书的更新，重点是要把master相关ip全部全部加入到列表里面

# mkdir api-ha && cd api-ha
# cat k8s-csr.json    
{
  "CN": "kubernetes",
  "hosts": [
    "127.0.0.1",
    "192.168.115.4",
    "192.168.115.5",
    "192.168.115.6",
    "10.254.0.1",
    "kubernetes",
    "kubernetes.default",
    "kubernetes.default.svc",
    "kubernetes.default.svc.cluster",
    "kubernetes.default.svc.cluster.local"
  ],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "CN",
      "ST": "FuZhou",
      "L": "FuZhou",
      "O": "k8s",
      "OU": "System"
    }
  ]
}

# cfssl gencert -ca=/etc/ssl/etcd/ca.pem 
  -ca-key=/etc/ssl/etcd/ca-key.pem 
  -config=/etc/ssl/etcd/ca-config.json 
  -profile=kubernetes k8s-csr.json | cfssljson -bare kubernetes

# mv *.pem /etc/kubernetes/ssl/

三、配置master组件

1、复制vm1的kube-apiserver、kube-controller-manager、kube-scheduler文件到vm2节点上

# cd /usr/local/sbin
# scp -rp  kube-apiserver  kube-controller-manager  kube-scheduler  vm2:/usr/local/sbin/

2、复制vm1的证书文件到vm2节点上

# cd /etc/kubernetes/ssl
# scp -rp ./* vm2:/etc/kubernetes/ssl

3、配置服务并启动服务

# cat /usr/lib/systemd/system/kube-apiserver.service
[Unit]
Description=Kubernetes API Server
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=network.target

[Service]
ExecStart=/usr/local/sbin/kube-apiserver 
  --admission-control=NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,ResourceQuota 
  --advertise-address=0.0.0.0 
  --bind-address=0.0.0.0 
  --insecure-bind-address=127.0.0.1 
  --authorization-mode=RBAC 
  --runtime-config=rbac.authorization.k8s.io/v1alpha1 
  --kubelet-https=true 
  --enable-bootstrap-token-auth=true 
  --token-auth-file=/etc/kubernetes/token.csv 
  --service-cluster-ip-range=10.254.0.0/16 
  --service-node-port-range=1024-65535 
  --tls-cert-file=/etc/kubernetes/ssl/kubernetes.pem 
  --tls-private-key-file=/etc/kubernetes/ssl/kubernetes-key.pem 
  --client-ca-file=/etc/ssl/etcd/ca.pem 
  --service-account-key-file=/etc/ssl/etcd/ca-key.pem 
  --etcd-cafile=/etc/ssl/etcd/ca.pem 
  --etcd-certfile=/etc/ssl/etcd/server.pem 
  --etcd-keyfile=/etc/ssl/etcd/server-key.pem 
  --etcd-servers=https://192.168.115.5:2379,https://192.168.115.6:2379,https://192.168.115.7:2379 
  --enable-swagger-ui=true 
  --allow-privileged=true 
  --apiserver-count=3 
  --audit-log-maxage=30 
  --audit-log-maxbackup=3 
  --audit-log-maxsize=100 
  --audit-log-path=/var/lib/audit.log 
  --event-ttl=1h 
  --v=2
Restart=on-failure
RestartSec=5
Type=notify
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target
# cat /usr/lib/systemd/system/kube-scheduler.service
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/GoogleCloudPlatform/kubernetes

[Service]
ExecStart=/usr/local/sbin/kube-scheduler 
  --address=127.0.0.1 
  --master=http://127.0.0.1:8080 
  --leader-elect=true 
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
# cat /usr/lib/systemd/system/kube-controller-manager.service 
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/GoogleCloudPlatform/kubernetes

[Service]
ExecStart=/usr/local/sbin/kube-controller-manager 
  --address=127.0.0.1 
  --master=http://127.0.0.1:8080 
  --allocate-node-cidrs=true 
  --service-cluster-ip-range=10.254.0.0/16 
  --cluster-cidr=172.30.0.0/16 
  --cluster-name=kubernetes 
  --cluster-signing-cert-file=/etc/ssl/etcd/ca.pem 
  --cluster-signing-key-file=/etc/ssl/etcd/ca-key.pem 
  --service-account-private-key-file=/etc/ssl/etcd/ca-key.pem 
  --root-ca-file=/etc/ssl/etcd/ca.pem 
  --leader-elect=true 
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
# systemctl enable kube-apiserver
# systemctl enable kube-controller-manager
# systemctl enable kube-scheduler
# systemctl start kube-apiserver
# systemctl start kube-controller-manager
# systemctl start kube-scheduler

注意：

vm1上的api-server配置文件需要将--advertise-address、--bind-address两个参数修改为全网监听

四、安装和配置keepalived

# yum -y install keepalived
# cat /etc/keepalived/keepalived.conf   
! Configuration File for keepalived  
global_defs {  
    notification_email {   
        ylw@fjhb.cn
    }   
    notification_email_from admin@fjhb.cn
    smtp_server 127.0.0.1  
    smtp_connect_timeout 30  
    router_id LVS_MASTER  
}  

vrrp_script check_apiserver {
    script "/etc/keepalived/check_apiserver.sh"
    interval 3
}  

vrrp_instance VI_1 {  
    state MASTER
    interface ens33
    virtual_router_id 60  
    priority 100  
    advert_int 1  
    authentication {  
        auth_type PASS  
        auth_pass k8s.59iedu.com
    }  
    virtual_ipaddress {  
        192.168.115.4/24
    }

    track_script {   
        check_apiserver
    }
}
# cat /usr/lib/systemd/system/keepalived.service  
[Unit]
Description=LVS and VRRP High Availability Monitor
After=syslog.target network-online.target kube-apiserver.service
Require=kube-apiserver.service

[Service]
Type=forking
PIDFile=/var/run/keepalived.pid
KillMode=process
EnvironmentFile=-/etc/sysconfig/keepalived
ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS
ExecReload=/bin/kill -HUP $MAINPID

[Install]
WantedBy=multi-user.target

注意:

vm2节点上需要修改state为BACKUP, priority为99 （priority值必须小于master节点配置值）

# cat /etc/keepalived/check_apiserver.sh
#!/bin/bash
flag=$(systemctl status kube-apiserver &> /dev/null;echo $?)
if [[ $flag != 0 ]];then
        echo "kube-apiserver is down,close the keepalived"
        systemctl stop keepalived
fi
# chmod +x /etc/keepalived/check_apiserver.sh 
# systemctl daemon-reload
# systemctl enable keepalived
# systemctl start keepalived

五、修改客户端配置

1、Kubelet.kubeconfig 、bootstrap.kubeconfig、kube-proxy.kubeconfig 配置

# grep 'server' /etc/kubernetes/kubelet.kubeconfig 
server: https://192.168.115.4:6443
# grep 'server' /etc/kubernetes/bootstrap.kubeconfig 
server: https://192.168.115.4:6443
# grep 'server' /etc/kubernetes/kube-proxy.kubeconfig 
    server: https://192.168.115.4:6443

2、confing配置

# grep 'server' /root/.kube/config 
server: https://192.168.115.4:6443

3、重启客户端服务

# systemctl restart kubelet 
# systemctl restart kube-proxy

六、测试

1、关闭服务前的集群状态，VIP在vm1节点上
K8S集群Master高可用实践

K8S集群Master高可用实践

2、在vm1上将kube-apiserver服务停止，可以看到VIP消息，但任何可以连接master获取pod信息
K8S集群Master高可用实践
日志显示vip被自动移除
K8S集群Master高可用实践
3、在vm2上能看到自动注册上了VIP，且kubectl客户端连接正常
K8S集群Master高可用实践
K8S集群Master高可用实践
4、在vm1上将kube-apiserver、keepalived服务启动，由于配置的是主从模式，所以会抢占VIP
K8S集群Master高可用实践
5、在vm2上可以看到VIP的释放，keepalived重新进入backup状态
K8S集群Master高可用实践
6、在整个过程中可以用其他的客户端来连接master VIP来测试服务器的连续性
K8S集群Master高可用实践

七、使用haproxy改进

只用keepalived实现master ha，当api-server的访问量大的时候，会有性能瓶颈问题，通过配置haproxy，可以同时实现master的ha和流量的负载均衡。
1、安装和配置haproxy，两台master做同样的配置

# yum -y install haproxy
# cat /etc/haproxy/haproxy.cfg
global
    log         127.0.0.1 local2
    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon
    stats socket /var/lib/haproxy/stats

defaults
    mode                    tcp
    log                     global
    option                  tcplog
    option                  dontlognull
    option                  redispatch
    retries                 3
    timeout queue           1m
    timeout connect         10s
    timeout client          1m
    timeout server          1m
    timeout check           10s
    maxconn                 3000

listen stats
    mode   http
    bind :10086
    stats   enable
    stats   uri     /admin?stats
    stats   auth    admin:admin
    stats   admin   if TRUE

frontend  k8s_https *:8443
    mode      tcp
    maxconn      2000
    default_backend     https_sri

backend https_sri
    balance      roundrobin
    server s1 192.168.115.5:6443  check inter 10000 fall 2 rise 2 weight 1
    server s2 192.168.115.6:6443  check inter 10000 fall 2 rise 2 weight 1

2、修改kube-apiserver配置,ip地址根据实际情况修改

# grep 'address' /usr/lib/systemd/system/kube-apiserver.service     
  --advertise-address=192.168.115.5 
  --bind-address=192.168.115.5 
  --insecure-bind-address=127.0.0.1

3、修改keepalived启动脚本和配置文件,vrrp脚本的ip地址根据实际情况修改

# cat /usr/lib/systemd/system/keepalived.service            
[Unit]
Description=LVS and VRRP High Availability Monitor
After=syslog.target network-online.target 
Require=haproxy.service
########以下输出省略#########
# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived  
global_defs {  
    notification_email {   
        ylw@fjhb.cn
    }   
    notification_email_from admin@fjhb.cn  
    smtp_server 127.0.0.1  
    smtp_connect_timeout 30  
    router_id LVS_MASTER  
}  

vrrp_script check_apiserver {
    script "curl -o /dev/null -s -w %{http_code} -k  https://192.168.115.5:6443"
    interval 3
    timeout 3
    fall 2
    rise 2
}  
########以下输出省略#########

4、修改kubelet和kubectl客户端配置文件，指向haproxy的端口8443

# grep '192' /etc/kubernetes/bootstrap.kubeconfig 
    server: https://192.168.115.4:8443
# grep '192' /etc/kubernetes/kubelet.kubeconfig 
    server: https://192.168.115.4:8443
# grep '192' /etc/kubernetes/kube-proxy.kubeconfig 
server: https://192.168.115.4:8443
# grep '192' /root/.kube/config 
server: https://192.168.115.4:8443

5、重启服务验证
master

# systemctl daemon-reload
# systemctl enable haproxy 
# systemctl start haproxy 
# systemctl restart keepalived 
# systemctl restart kube-apiserver

kubelet

# systemctl restart kubelet
# systemctl restart kube-proxy

K8S集群Master高可用实践
K8S集群Master高可用实践