之前基于kubeadm 搭建的单master双node 的k8s集群， 问题就是master 节点挂掉之后会导致整个集群不可用， 所以简单研究下多master的搭建方式。

1. 方案简介

 　　用到的高可用技术主要是keepalived 和 haproxy。

1. keepalived

　　Keepalived主要是通过虚拟路由冗余来实现高可用功能。

　　Keepalived一个基于VRRP(Virtual Router Redundancy Protocol - 虚拟路由冗余协议) 协议来实现的 LVS 服务高可用方案，可以利用其来解决单点故障。一个LVS服务会有2台服务器运行Keepalived，一台为主服务器（MASTER），一台为备份服务器（BACKUP），但是对外表现为一个虚拟IP，主服务器会发送特定的消息给备份服务器，当备份服务器收不到这个消息的时候，即主服务器宕机的时候， 备份服务器就会接管虚拟IP，继续提供服务，从而保证了高可用性。

2. haproxy

　　haproxy 类似于nginx， 是一个负载均衡、反向代理软件。 nginx 采用master-workers 进程模型，每个进程单线程，多核CPU能充分利用。 haproxy 是多线程，单进程就能实现高性能，虽然haproxy 也支持多进程。

2. 搭建集群

　　基本上照着下面流程操作就可以了。

1. 安装要求

部署Kubernetes集群机器需要满足以下几个条件：

(1) 一台或多台机器，操作系统 CentOS7.x-86_x64

(2)硬件配置：2GB或更多RAM，2个CPU或更多CPU，硬盘30GB或更多

(3) 可以访问外网，需要拉取镜像，如果服务器不能上网，需要提前下载镜像并导入节点

(4) 禁止swap分区

2. 准备环境

 接下来进行如下操作

# 关闭防火墙
systemctl stop firewalld
systemctl disable firewalld

# 关闭selinux
sed -i 's/enforcing/disabled/' /etc/selinux/config  # 永久
setenforce 0  # 临时

# 关闭swap
swapoff -a  # 临时
sed -ri 's/.*swap.*/#&/' /etc/fstab    # 永久

# 根据规划设置主机名
hostnamectl set-hostname <hostname>

# 在master添加hosts
cat >> /etc/hosts << EOF
192.168.13.110    master.k8s.io   k8s-vip
192.168.13.107    master01.k8s.io k8smaster01
192.168.13.108    master02.k8s.io k8smaster02
192.168.13.109    node01.k8s.io   k8snode01
EOF

# 将桥接的IPv4流量传递到iptables的链
cat > /etc/sysctl.d/k8s.conf << EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system  # 生效

# 时间同步
yum install ntpdate -y
ntpdate time.windows.com

3. 所有master 节点部署keepalived

1. 安装相关包和keepalived

yum install -y conntrack-tools libseccomp libtool-ltdl

yum install -y keepalived

2. 配置master 节点

k8smaster01

cat > /etc/keepalived/keepalived.conf <<EOF 
! Configuration File for keepalived

global_defs {
   router_id k8s
}

vrrp_script check_haproxy {
    script "killall -0 haproxy"
    interval 3
    weight -2
    fall 10
    rise 2
}

vrrp_instance VI_1 {
    state MASTER 
    interface ens33 
    virtual_router_id 51
    priority 250
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass ceb1b3ec013d66163d6ab
    }
    virtual_ipaddress {
        192.168.13.110
    }
    track_script {
        check_haproxy
    }

}
EOF

k8smaster02

cat > /etc/keepalived/keepalived.conf <<EOF 
! Configuration File for keepalived

global_defs {
   router_id k8s
}

vrrp_script check_haproxy {
    script "killall -0 haproxy"
    interval 3
    weight -2
    fall 10
    rise 2
}

vrrp_instance VI_1 {
    state BACKUP 
    interface ens33 
    virtual_router_id 51
    priority 200
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass ceb1b3ec013d66163d6ab
    }
    virtual_ipaddress {
        192.168.13.110
    }
    track_script {
        check_haproxy
    }

}
EOF

3. 启动和检查

# 启动keepalived
systemctl start keepalived.service
# 设置开机启动
systemctl enable keepalived.service
# 查看启动状态
systemctl status keepalived.service

启动后查看master1的网卡信息： 可以看到有vip 相关的信息

ip a s ens33

4. 部署haproxy

1. 安装

yum install -y haproxy

2. 配置

两台master节点的配置均相同，配置中声明了后端代理的两个master节点服务器，指定了haproxy运行的端口为16443等，因此16443端口为集群的入口

cat > /etc/haproxy/haproxy.cfg << EOF
#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global
    # to have these messages end up in /var/log/haproxy.log you will
    # need to:
    # 1) configure syslog to accept network log events.  This is done
    #    by adding the '-r' option to the SYSLOGD_OPTIONS in
    #    /etc/sysconfig/syslog
    # 2) configure local2 events to go to the /var/log/haproxy.log
    #   file. A line like the following can be added to
    #   /etc/sysconfig/syslog
    #
    #    local2.*                       /var/log/haproxy.log
    #
    log         127.0.0.1 local2
    
    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon 
       
    # turn on stats unix socket
    stats socket /var/lib/haproxy/stats
#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------  
defaults
    mode                    http
    log                     global
    option                  httplog
    option                  dontlognull
    option http-server-close
    option forwardfor       except 127.0.0.0/8
    option                  redispatch
    retries                 3
    timeout http-request    10s
    timeout queue           1m
    timeout connect         10s
    timeout client          1m
    timeout server          1m
    timeout http-keep-alive 10s
    timeout check           10s
    maxconn                 3000
#---------------------------------------------------------------------
# kubernetes apiserver frontend which proxys to the backends
#--------------------------------------------------------------------- 
frontend kubernetes-apiserver
    mode                 tcp
    bind                 *:16443
    option               tcplog
    default_backend      kubernetes-apiserver    
#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
backend kubernetes-apiserver
    mode        tcp
    balance     roundrobin
    server      master01.k8s.io   192.168.13.107:6443 check
    server      master02.k8s.io   192.168.13.108:6443 check
#---------------------------------------------------------------------
# collection haproxy statistics message
#---------------------------------------------------------------------
listen stats
    bind                 *:1080
    stats auth           admin:awesomePassword
    stats refresh        5s
    stats realm          HAProxy\ Statistics
    stats uri            /admin?stats
EOF

3. 启动和检查

两台master 都启动

# 设置开机启动
systemctl enable haproxy
# 开启haproxy
systemctl start haproxy
# 查看启动状态
systemctl status haproxy

检查端口

netstat -lntup|grep haproxy

5. 所有节点安装Docker/kubeadm/kubelet

Kubernetes默认CRI（容器运行时）为Docker，因此先安装Docker。

1. 安装docker

wget https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo -O /etc/yum.repos.d/docker-ce.repo
yum -y install docker-ce-18.06.1.ce-3.el7
systemctl enable docker && systemctl start docker
docker --version

修改docker 镜像源:

cat > /etc/docker/daemon.json << EOF
{
  "registry-mirrors": ["https://b9pmyelo.mirror.aliyuncs.com"]
}
EOF

2. 添加阿里云YUM软件源

cat > /etc/yum.repos.d/kubernetes.repo << EOF
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF

3. 安装kubeadm，kubelet和kubectl

yum install -y kubelet-1.21.3 kubeadm-1.21.3 kubectl-1.21.3
systemctl enable kubelet

6. 部署k8smaster

1. 创建kubeadm 配置文件

在具有vip的master上操作，这里为master1

mkdir /usr/local/kubernetes/manifests -p

cd /usr/local/kubernetes/manifests/

vi kubeadm-config.yaml

apiServer:
  certSANs:
    - k8smaster01
    - k8smaster02
    - master.k8s.io
    - 192.168.13.110
    - 192.168.13.107
    - 192.168.13.108
    - 127.0.0.1
  extraArgs:
    authorization-mode: Node,RBAC
  timeoutForControlPlane: 4m0s
apiVersion: kubeadm.k8s.io/v1beta1
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controlPlaneEndpoint: "master.k8s.io:16443"
controllerManager: {}
dns: 
  type: CoreDNS
etcd:
  local:    
    dataDir: /var/lib/etcd
imageRepository: registry.aliyuncs.com/google_containers
kind: ClusterConfiguration
kubernetesVersion: v1.21.3
networking: 
  dnsDomain: cluster.local  
  podSubnet: 10.244.0.0/16
  serviceSubnet: 10.1.0.0/16
scheduler: {}

2. 在k8smaster01 节点执行

kubeadm init --config kubeadm-config.yaml

执行后提示如下：

[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

You can now join any number of control-plane nodes by copying certificate authorities
and service account keys on each node and then running the following as root:

  kubeadm join master.k8s.io:16443 --token piealo.bck99wdpdv14rlo6 \
        --discovery-token-ca-cert-hash sha256:e0579b642a2b62219627f9f19af5227dadb539f9db11992585644d4f126046e5 \
        --control-plane 

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join master.k8s.io:16443 --token piealo.bck99wdpdv14rlo6 \
        --discovery-token-ca-cert-hash sha256:e0579b642a2b62219627f9f19af5227dadb539f9db11992585644d4f126046e5 

按照提示配置环境变量，使用kubectl工具：

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

检查：

[root@k8smaster01 manifests]# kubectl get nodes
NAME          STATUS     ROLES                  AGE    VERSION
k8smaster01   NotReady   control-plane,master   144m   v1.21.3
[root@k8smaster01 manifests]# kubectl get pods -n kube-system
NAME                                  READY   STATUS    RESTARTS   AGE
coredns-59d64cd4d4-62bhq              0/1     Pending   0          144m
coredns-59d64cd4d4-95dl5              0/1     Pending   0          144m
etcd-k8smaster01                      1/1     Running   0          144m
kube-apiserver-k8smaster01            1/1     Running   0          144m
kube-controller-manager-k8smaster01   1/1     Running   0          144m
kube-proxy-df8c8                      1/1     Running   0          144m
kube-scheduler-k8smaster01            1/1     Running   0          145m

3. 安装集群网络

mkdir flannel
cd flannel
wget -c https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

创建以及查看：

kubectl apply -f kube-flannel.yml 
kubectl get pods -n kube-system

4. k8smaster02 加入节点

(1)复制密钥及相关文件

从master1复制密钥及相关文件到master2

ssh root@192.168.13.108 mkdir -p /etc/kubernetes/pki/etcd

scp /etc/kubernetes/admin.conf root@192.168.13.108:/etc/kubernetes

scp /etc/kubernetes/pki/{ca.*,sa.*,front-proxy-ca.*} root@192.168.13.108:/etc/kubernetes/pki

scp /etc/kubernetes/pki/etcd/ca.* root@192.168.13.108:/etc/kubernetes/pki/etcd

(2) master2加入集群

在k8smaster02 执行在k8smaster01上init后输出的join命令,需要带上参数 `--control-plane` 表示把master控制节点加入集群

kubeadm join master.k8s.io:16443 --token piealo.bck99wdpdv14rlo6 \
        --discovery-token-ca-cert-hash sha256:e0579b642a2b62219627f9f19af5227dadb539f9db11992585644d4f126046e5 --control-plane

执行完后输出：

This node has joined the cluster and a new control plane instance was created:

* Certificate signing request was sent to apiserver and approval was received.
* The Kubelet was informed of the new secure connection details.
* Control plane (master) label and taint were applied to the new node.
* The Kubernetes control plane instances scaled up.
* A new etcd member was added to the local/stacked etcd cluster.

To start administering your cluster from this node, you need to run the following as a regular user:

        mkdir -p $HOME/.kube
        sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
        sudo chown $(id -u):$(id -g) $HOME/.kube/config

然后执行上面输出的信息：

        mkdir -p $HOME/.kube
        sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
        sudo chown $(id -u):$(id -g) $HOME/.kube/config

检查状态：

[root@k8smaster02 ~]# kubectl get node
NAME          STATUS     ROLES                  AGE     VERSION
k8smaster01   Ready      control-plane,master   17h     v1.21.3
k8smaster02   NotReady   control-plane,master   6m21s   v1.21.3
[root@k8smaster02 ~]# kubectl get pods --all-namespaces
NAMESPACE     NAME                                  READY   STATUS                  RESTARTS   AGE
kube-system   coredns-59d64cd4d4-62bhq              1/1     Running                 0          17h
kube-system   coredns-59d64cd4d4-95dl5              1/1     Running                 0          17h
kube-system   etcd-k8smaster01                      1/1     Running                 0          17h
kube-system   etcd-k8smaster02                      1/1     Running                 0          6m22s
kube-system   kube-apiserver-k8smaster01            1/1     Running                 0          17h
kube-system   kube-apiserver-k8smaster02            1/1     Running                 0          6m25s
kube-system   kube-controller-manager-k8smaster01   1/1     Running                 1          17h
kube-system   kube-controller-manager-k8smaster02   1/1     Running                 0          6m26s
kube-system   kube-flannel-ds-p2std                 1/1     Running                 0          15h
kube-system   kube-flannel-ds-vc2w2                 0/1     Init:ImagePullBackOff   0          6m27s
kube-system   kube-proxy-df8c8                      1/1     Running                 0          17h
kube-system   kube-proxy-nx8dg                      1/1     Running                 0          6m27s
kube-system   kube-scheduler-k8smaster01            1/1     Running                 1          17h
kube-system   kube-scheduler-k8smaster02            1/1     Running                 0          6m26s

3. k8snode01 加入集群

(1) 在k8snode01 节点上执行之前输出的信息：

kubeadm join master.k8s.io:16443 --token piealo.bck99wdpdv14rlo6 \
        --discovery-token-ca-cert-hash sha256:e0579b642a2b62219627f9f19af5227dadb539f9db11992585644d4f126046e5

执行完后输出如下：

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

(2) 在master 节点查看

[root@k8smaster01 manifests]# kubectl get nodes
NAME          STATUS     ROLES                  AGE     VERSION
k8smaster01   Ready      control-plane,master   17h     v1.21.3
k8smaster02   NotReady   control-plane,master   11m     v1.21.3
k8snode01     NotReady   <none>                 2m26s   v1.21.3

(3) 重新安装网络

[root@k8smaster01 flannel]# pwd
/root/flannel
[root@k8smaster01 flannel]# kubectl apply -f kube-flannel.yml

(4) 再次查看集群状态

[root@k8smaster01 flannel]# kubectl cluster-info
Kubernetes control plane is running at https://master.k8s.io:16443
CoreDNS is running at https://master.k8s.io:16443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
[root@k8smaster01 flannel]# kubectl get nodes -o wide
NAME          STATUS   ROLES                  AGE   VERSION   INTERNAL-IP      EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION                CONTAINER-RUNTIME
k8smaster01   Ready    control-plane,master   18h   v1.21.3   192.168.13.107   <none>        CentOS Linux 7 (Core)   3.10.0-1160.49.1.el7.x86_64   docker://18.6.1
k8smaster02   Ready    control-plane,master   38m   v1.21.3   192.168.13.108   <none>        CentOS Linux 7 (Core)   3.10.0-1160.49.1.el7.x86_64   docker://18.6.1
k8snode01     Ready    <none>                 28m   v1.21.3   192.168.13.109   <none>        CentOS Linux 7 (Core)   3.10.0-1160.49.1.el7.x86_64   docker://18.6.1

4. 测试集群

[root@k8smaster01 flannel]# kubectl create deployment nginx --image=nginx
deployment.apps/nginx created
[root@k8smaster01 flannel]# kubectl get pods -o wide
NAME                     READY   STATUS              RESTARTS   AGE   IP       NODE        NOMINATED NODE   READINESS GATES
nginx-6799fc88d8-g7vcg   0/1     ContainerCreating   0          11s   <none>   k8snode01   <none>           <none>
[root@k8smaster01 flannel]# kubectl expose deployment nginx --port=80 --type=NodePort
service/nginx exposed
[root@k8smaster01 flannel]# kubectl get pod,svc
NAME                         READY   STATUS    RESTARTS   AGE
pod/nginx-6799fc88d8-g7vcg   1/1     Running   0          98s

NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)        AGE
service/kubernetes   ClusterIP   10.1.0.1     <none>        443/TCP        18h
service/nginx        NodePort    10.1.49.27   <none>        80:32367/TCP   60s

　　然后从外部查看任意一个节点的32367 端口即可查看到nginx。 107、08、09、110 四个ip都可以访问到。