Centos7部署k8s[v1.16]高可用[keepalived]集群

实验目的

       一般情况下，k8s集群中只有一台master和多台node，当master故障时，引发的事故后果可想而知。

       故本文目的在于体现集群的高可用，即当集群中的一台master宕机后，k8s集群通过vip的转移，又会有新的节点被选举为集群的master，并保持集群的正常运作。

       因本文体现的是master节点的高可用，为了实现效果，同时因资源条件限制，故总共采用4台服务器完成本次实验，3台master，1台node。

       看到这也需有人有疑惑，总共有4台机器的资源，为啥不能2台master呢？这是因为通过kubeadm部署的集群，当中的etcd集群默认部署在master节点上，3节点方式最多能容忍1台服务器宕机。如果是2台master，当中1台宕机了，直接导致etcd集群故障，以至于k8s集群异常，这些基础环境都over了，vip漂移等高可用也就在白瞎。

环境说明

基本信息

# 主机列表

10.2.2.137 master1

10.2.2.166 master2

10.2.2.96 master3

10.2.3.27 node0

# 软件版本

docker version：18.09.9

k8s version：v1.16.4

架构信息

       本文采用kubeadm方式搭建集群，通过keepalived的vip策略实现高可用，架构图如下：

　　

# 主备模式高可用架构说明

 

a）apiserver通过keepalived实现高可用，当某个节点故障时触发vip转移；

b）controller-manager和scheduler在k8s内容通过选举方式产生领导者（由leader-elect选型控制，默认为true），同一时刻集群内只有一个scheduler组件运行；

c）etcd在kubeadm方式实现集群时，其在master节点会自动创建etcd集群，来实现高可用，部署的节点为奇数，3节点方式最多容忍一台机器宕机。

环境准备

说明

1、大多数文章都是一步步写命令写步骤，而对于有部署经验的人来说觉得繁琐化了，故本文大部分服务器shell命令操作都将集成到脚本；

2、本文相关shell脚本地址： https://gitee.com/kazihuo/k8s-install-shell

3、所有要加入到k8s集群的机器都执行本部分操作。

操作

a）将所有服务器修改成对应的主机名，master1示例如下；

# hostnamectl set-hostname master1 #重新登录后显示新设置的主机名

b）配置master1到master2、master3免密登录，本步骤只在master1上执行；

[root@master1 ~]# ssh-keygen -t rsa  # 一路回车

[root@master1 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub root@10.2.2.166

[root@master1 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub root@10.2.2.96

c）脚本实现环境需求配置；

# sh set-prenv.sh

#!/bin/bash
#====================================================
# Author: LuoMuRui
# Blog: https://www.cnblogs.com/kazihuo
# Create Date: 2020-04-02
# Description: System environment configuration. 
#====================================================

# Stop firewalld
firewall-cmd --state #查看防火墙状态
systemctl stop firewalld.service #停止firewall
systemctl disable firewalld.service #禁止firewall开机启动

# Close selinux
getenforce  #查看selinux状态
setenforce 0  #临时关闭selinux
sed -i 's/^ *SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config  #永久关闭（需重启系统）

# Set localhost's dns
cat >> /etc/hosts << EOF
10.2.2.137 master1
10.2.2.166 master2
10.2.2.96 master3
10.2.3.27 node0
EOF

# Disable swap
swapoff -a  #临时禁用
sed -i.bak '/swap/s/^/#/' /etc/fstab  #永久禁用

# Kernel parameter modification
# k8s网络使用flannel，该网络需要设置内核参数bridge-nf-call-iptables=1，修改这个参数需要系统有br_netfilter模块
lsmod |grep br_netfilter  # 查看模块
modprobe br_netfilter  # 临时新增
# 永久新增模块
cat > /etc/rc.sysinit << EOF
#!/bin/bash
for file in /etc/sysconfig/modules/*.modules ; do
[ -x $file ] && $file
done
EOF
cat > /etc/sysconfig/modules/br_netfilter.modules << EOF
modprobe br_netfilter
EOF
chmod 755 /etc/sysconfig/modules/br_netfilter.modules
cat <<EOF >  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl -p /etc/sysctl.d/k8s.conf

# Set the yum of k8s
cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64/
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF
yum clean all && yum -y makecache

软件安装

docker安装

说明：所有节点都执行本部分操作！

# sh install-docker.sh

#!/bin/bash
#====================================================
# Author: LuoMuRui
# Blog: https://www.cnblogs.com/kazihuo
# Create Date: 2020-04-02
# Description: Install docker. 
#====================================================

# Install dependency package
yum install -y yum-utils device-mapper-persistent-data lvm2

# Add repo
yum-config-manager 
    --add-repo 
    https://download.docker.com/linux/centos/docker-ce.repo

# Looking the version of docker
yum list docker-ce --showduplicates | sort -r

# Install docker 
yum install docker-ce-18.09.9 docker-ce-cli-18.09.9 containerd.io -y

# Mirror acceleration & change Cgroup Driver
# 修改cgroupdriver是为了消除告警：[WARNING IsDockerSystemdCheck]: detected “cgroupfs” as the Docker cgroup driver. The recommended driver is “systemd”. Please follow the guide at https://kubernetes.io/docs/setup/cri/
cat > daemon.json <<EOF
{
  "registry-mirrors": ["https://registry.docker-cn.com"],
  "exec-opts": ["native.cgroupdriver=systemd"]
}
EOF

# Start && enable 
systemctl daemon-reload
systemctl start docker
systemctl enable docker
docker --version

# Others
yum -y install bash-completion
source /etc/profile.d/bash_completion.sh

keepalived安装

说明：三台master节点执行本部分操作！

# 安装

# yum -y install keepalived

# 配置

# master1上keepalived配置

[root@master1 ~]# cat /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id master1
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.2.2.6
    }
}

# master2上keepalived配置

[root@master2 ~]# cat /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id master2
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.2.2.6
    }
}

# master3上keepalived配置

[root@master3 ~]# cat /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id master3
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 50
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.2.2.6
    }
}

# 启动

# service keepalived start

# systemctl enable keepalived

# vip查看

[root@master1 ~]# ip a

# 功能功验

将master1上的keepalived服务器停止或者master1服务器关机后，master2上接管vip，同时master2也关机后，master3接管vip。

k8s安装

说明：所有节点都执行本部分操作！

组件:

kubelet

运行在集群所有节点上，用于启动Pod和容器等对象的工具

kubeadm

用于初始化集群，启动集群的命令工具

kubectl

用于和集群通信的命令行，通过kubectl可以部署和管理应用，查看各种资源，创建、删除和更新各种组件

# sh install-k8s.sh

#!/bin/bash
#====================================================
# Author: LuoMuRui
# Blog: https://www.cnblogs.com/kazihuo
# Create Date: 2020-04-02
# Description: Install the soft of k8s.
#====================================================

# Looking the version
yum list kubelet --showduplicates | sort -r

# Install 
yum install -y kubelet-1.16.4 kubeadm-1.16.4 kubectl-1.16.4

# Start && enable 
systemctl enable kubelet && systemctl start kubelet

# Bash env
echo "source <(kubectl completion bash)" >> ~/.bash_profile
source /root/.bash_profile

镜像下载

说明：所有节点都执行本部分操作！

       因国内网络的限制，故从阿里云镜像仓库下载镜像后本地打回默认标签名的方式，让kubeadm在部署集群时能正常使用镜像。

# sh download-images.sh

#!/bin/bash
#====================================================
# Author: LuoMuRui
# Blog: https://www.cnblogs.com/kazihuo
# Create Date: 2020-04-02
# Description: Download images.
#====================================================

url=registry.cn-hangzhou.aliyuncs.com/loong576
version=v1.16.4
images=(`kubeadm config images list --kubernetes-version=$version|awk -F '/' '{print $2}'`)
for imagename in ${images[@]} ; do
  docker pull $url/$imagename
  docker tag $url/$imagename k8s.gcr.io/$imagename
  docker rmi -f $url/$imagename
done

master初始化

初始化操作

[root@master1 ~]# cat kubeadm-config.yaml

apiVersion: kubeadm.k8s.io/v1beta2
kind: ClusterConfiguration
kubernetesVersion: v1.16.4
apiServer:
  certSANs:
  - 10.2.2.6
controlPlaneEndpoint: "10.2.2.6:6443"
networking:
  podSubnet: "10.244.0.0/16"

[root@master01 ~]# kubeadm init --config=kubeadm-config.yaml

# 初始化成功后末尾显示kubeadm join的信息，记录下来；

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 10.2.2.6:6443 --token 2ccecd.v72vziyzdfnbr46u 
    --discovery-token-ca-cert-hash sha256:eb92768acb748d722ef7d97bc60751a375b67b12a46c7a7232c54cdb378d2e61 
    --control-plane       

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

kubeadm join 10.2.2.6:6443 --token 2ccecd.v72vziyzdfnbr46u 
    --discovery-token-ca-cert-hash sha256:eb92768acb748d722ef7d97bc60751a375b67b12a46c7a7232c54cdb378d2e61

# 初始化失败后可重新初始化

# kubeadm reset

# rm -rf $HOME/.kube/config

添加环境变量

echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> ~/.bash_profile

source ~/.bash_profile

安装flannel插件

# wget https://raw.githubusercontent.com/coreos/flannel/2140ac876ef134e0ed5af15c65e414cf26827915/Documentation/kube-flannel.yml

# kubectl apply -f kube-flannel.yml

control plane节点加入

证书分发

# master1将认证文件同步到其他master节点

[root@master1 ~]# sh cert-others-master.sh

USER=root
CONTROL_PLANE_IPS="master2 master3"
#CONTROL_PLANE_IPS="master2 master3"
for host in ${CONTROL_PLANE_IPS}; do
    scp  /etc/kubernetes/pki/ca.crt "${USER}"@$host:
    scp  /etc/kubernetes/pki/ca.key "${USER}"@$host:
    scp  /etc/kubernetes/pki/sa.key "${USER}"@$host:
    scp  /etc/kubernetes/pki/sa.pub "${USER}"@$host:
    scp  /etc/kubernetes/pki/front-proxy-ca.crt "${USER}"@$host:
    scp  /etc/kubernetes/pki/front-proxy-ca.key "${USER}"@$host:
    scp  /etc/kubernetes/pki/etcd/ca.crt "${USER}"@$host:etcd-ca.crt
    # Quote this line if you are using external etcd
    scp  /etc/kubernetes/pki/etcd/ca.key "${USER}"@$host:etcd-ca.key
done

# master2和master3节点配置证书

[root@master2 ~]# sh cert-set.sh

[root@master3 ~]# sh cert-set.sh

mv /${USER}/ca.crt /etc/kubernetes/pki/
mv /${USER}/ca.key /etc/kubernetes/pki/
mv /${USER}/sa.pub /etc/kubernetes/pki/
mv /${USER}/sa.key /etc/kubernetes/pki/
mv /${USER}/front-proxy-ca.crt /etc/kubernetes/pki/
mv /${USER}/front-proxy-ca.key /etc/kubernetes/pki/
mv /${USER}/etcd-ca.crt /etc/kubernetes/pki/etcd/ca.crt
# Quote this line if you are using external etcd
mv /${USER}/etcd-ca.key /etc/kubernetes/pki/etcd/ca.key

others master加入集群

# master2和master3加入集群，下文以master2为示例，master3按部就班即可；

[root@master2 ~]#  kubeadm join 10.2.2.6:6443 --token 2ccecd.v72vziyzdfnbr46u

    --discovery-token-ca-cert-hash sha256:eb92768acb748d722ef7d97bc60751a375b67b12a46c7a7232c54cdb378d2e61

    --control-plane

[root@master2 ~]# scp master1:/etc/kubernetes/admin.conf /etc/kubernetes/

[root@master2 ~]# echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> ~/.bash_profile && source .bash_profile

集群节点查看

# kubectl get nodes

NAME                            STATUS   ROLES    AGE   VERSION
master1                          Ready    master   20h   v1.16.4
master2                          Ready    master   20h   v1.16.4
master3                          Ready    master   19h   v1.16.4

node节点加入

加入操作

[root@node0 ~]# kubeadm join 10.2.2.6:6443 --token 2ccecd.v72vziyzdfnbr46u

    --discovery-token-ca-cert-hash sha256:eb92768acb748d722ef7d97bc60751a375b67b12a46c7a7232c54cdb378d2e61

节点查看

# kubectl get nodes

NAME                             STATUS   ROLES    AGE   VERSION
node0                           Ready    <none>   18h   v1.16.4
master1                          Ready    master   20h   v1.16.4
master2                          Ready    master   20h   v1.16.4
master3                          Ready    master   19h   v1.16.4

集群功能验证

操作

# 关机master1，模拟宕机

[root@master1 ~]# init 0

# vip飘到master2

[root@master2 ~]# ip a |grep '2.6'

    inet 10.2.2.6/32 scope global eth0

# 组件controller-manager和scheduler发生迁移

# kubectl get endpoints kube-controller-manager -n kube-system -o yaml |grep holderIdentity

    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"master3_885468ec-f9ce-4cc6-93d6-235508b5a130","leaseDurationSeconds":15,"acquireTime":"2020-04-01T10:15:28Z","renewTime":"2020-04-02T06:02:46Z","leaderTransitions":8}'

# kubectl get endpoints kube-scheduler -n kube-system -o yaml |grep holderIdentity

    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"master2_cf16fd61-0202-4610-9a27-3cd9d26b4141","leaseDurationSeconds":15,"acquireTime":"2020-04-01T10:15:25Z","renewTime":"2020-04-02T06:03:09Z","leaderTransitions":9}'

# 集群创建pod，依旧正常使用

# cat nginx.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-test
spec:
  selector:
    matchLabels:
      app: nginx 
  replicas: 3
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:               
      - name: nginx
        image: nginx:latest

# kubectl apply -f nginx.yaml

# kubectl get pods

 

结论

1、集群中3个master节点，无论哪个节点宕机，都不影响集群的正常使用；

2、当集群中3个master节点有2个故障，则造成etcd集群故障，直接影响集群，导致异常！