Keepalived+Nginx high availability utilization

Introduction to Linux Clusters

• By function: high availability and load balancing
• A high-availability cluster usually consists of two servers, one working and the other as redundant.
• Load balancing cluster: A server is required as a distributor (distributing user requests to the back-end server for processing), and a server that provides services to users, at least 2 servers
• Highly available open source software: heartbeat, keepalived
• Load balancing software: LVS, keepalived, haproxy, nginx, commercial: F5, Netsacler

keepalived+Nginx experimental part

Master: 192.168.206.128

From (backup): 192.168.206.129

Virtual IP (VIP): 192.168.206.200

Use keepalived to achieve high availability of Nginx

echo 'this is master' > /usr/share/nginx/html/index.html master node

echo 'this is slave' > /usr/share/nginx/html/index.html standby node

Keepalived+Nginx installation

Keepalived configuration

There are three main modules: core, check, vrrp

Two machines are required to install keepalived+Nginx

yum -y install keepalived  nginx

Nginx configuration  

Two options to configure Nginx

#下载
wget  http://nginx.org/download/nginx-1.18.0.tar.gz
tar -zxvf nginx-1.18.0.tar.gz 
cd  nginx-1.18.0.tar.gz
#所需安装包
yum -y install gcc pcre-devel zlib zlib-devel
#编译运行
./configure  --prefix=/usr/local/nginx
#安装
make && make install

Nginx service configuration

#进入对应文件
cd /usr/local/nginx/sbin
./nginx                                 #启动nginx
./nginx -s  quit 或者  ./nginx  -s stop #结束nginx
./nginx -s  reload                      #重启nginx

keepalived configuration file

main configuration file

!Configuration File for keepalived

global_defs {
   notification_email {
     [email protected]
     [email protected]
     [email protected]
   }
   notification_email_from [email protected]
   smtp_server 192.168.200.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

#keepalived会定时执行脚本并对脚本执行的结果进行分析，动态调整vrrp_instance的优先级。
vrrp_script chk_nginx {
    #运行脚本，脚本内容下面有，就是起到一个nginx宕机以后，自动开启服务
    script "/etc/keepalived/nginx_check.sh" 
    interval 1 #检测时间间隔
    weight -2 #如果条件成立的话，则权重 -2
}

vrrp_instance VI_1 {
    state MASTER #来决定主从 
    interface ens33 # 绑定 IP 的网卡口，根据自己的机器填写    （修）
    virtual_router_id 120 # 虚拟路由的 ID 号， 两个节点设置必须一样
    mcast_src_ip 192.168.206.128  #填写本机ip    （修）
    priority 100 # 节点优先级,主要比从节点优先级高
    advert_int 1 # 组播信息发送间隔，两个节点设置必须一样，默认 1s
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    # 将 track_script 块加入 instance 配置块
    track_script {
        chk_nginx #执行 Nginx 监控的服务
    }

    virtual_ipaddress {
        192.168.206.200/24 # 虚拟ip，通过虚拟Ip切换进行nginx主备切换功能（修）
    }
}

configuration file

! Configuration File for keepalived

vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh" #运行脚本，脚本内容下面有，就是起到一个nginx宕机以后，自动开启服务
    interval 1 #检测时间间隔
    weight -2 #如果条件成立的话，则权重 -20
}

vrrp_instance VI_1 {
    state BACKUP #来决定主从
    interface ens33 # 绑定 IP 的网卡名称，根据自己的机器填写
    virtual_router_id 120 # 虚拟路由的 ID 号， 两个节点设置必须一样
    mcast_src_ip 192.168.206.129  #填写本机ip
    priority 99 # 节点优先级,主要比从节点优先级高
    advert_int 1 # 组播信息发送间隔，两个节点设置必须一样，默认 1s
    #nopreempt #设置为不抢夺VIP
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    # 将 track_script 块加入 instance 配置块
    track_script {
        chk_nginx #执行 Nginx 监控的服务
    }

    virtual_ipaddress {
        192.168.206.200/24 # 虚拟ip
    }
}

Configure monitoring script

Command configuration

vi /etc/keepalived/nginx_check.sh
chmod 755 /etc/keepalived/nginx_check.sh

Monitoring script

#文件位置 /usr/local/sbin/check.sh
#!/bin/bash
#时间变量，用于记录日志
d=`date  --date  today +%Y%m%d_$H:%M:%S`
#计算Nginx进程数量
n=`ps  -C  nginx --no-heading | wc -l`
#如果进程为0，则启动nginx，并且再次检测nginx进程数量
if[$n -eq "0"];  then
	/etc/init.d/nginx  start
	n2=`ps  -C  nginx  --no-heading|wc -l`
	#如果还是为0，说明nginx无法启动，此时需要关闭keepalived
	if[$n2  -eq  "0"]; then 
		echo  "$d  nginx  down,keepalived  will stop"  >> /var/log/check.log
		systemctl  stop keepalived
	fi
fi

Keepalived+Nginx achieves high availability

#主从配置都开启keepalived服务+Nginx服务
# 启动 | 停止 | 重启
service keepalived start |  stop |  restart
#主从设备同时开启keepalived服务，访问VIP地址
#两个设备同时ip a，显示VIP地址为192.168.206.200
curl  192.168.206.200
#输出结果this  is  master
#主设备关闭Nginx，访问VIP地址
#从设备显示VIP地址为从设备的IP地址
curl  192.168.206.200
#输出结果 this is slave