Centos7 安装 Keepalived+Nginx 双机热备HA 的正确姿势 并开机自启 实践笔记

我使用centos7X64最小化安装
CentOS-7-x86_64-Minimal-1708

挂在github上的个人博客：由hexo强力驱动 个人博客

这样配置的作用，我简单描述下：
①比如一台nginx提供负载均衡到后端服务器集群，假设这台ngixn挂了，那后端的服务器集群也就报销了
②再换句话说，Keepalived+Nginx是防止挂了一台nginx之后，还有一台nginx继续提供负载均衡服务

准备：两台机子，三个ip(能互通{一般同一个网段})

nginx_01 ip:192.168.59.128 主机
nginx_02 ip:192.168.59.129 从机
漂浮ip：192.168.59.130

1.配置防火墙：

关闭防火墙和加入放行端口二选一

1.1 直接关闭防火墙(nginx_01 和 nginx_02 都执行)

systemctl stop firewalld.service #停止firewall
systemctl disable firewalld.service #禁止firewall开机启动
firewall-cmd --state #查看默认防火墙状态（关闭后显示notrunning，开启后显示running）

[root@localhost ~]# firewall-cmd --state
not running
[root@localhost ~]#

1.2 加入放行端口(nginx_01 和 nginx_02 都执行)

firewall-cmd --zone=public --add-port=80/tcp --permanent #添加放行端口(--permanent永久生效，没有此参数重启后失效)

firewall-cmd –reload #刷新防火墙 使其生效

```
firewall-cmd --zone=public --list-ports #查看防火墙放行端口列表

[root@localhost ~]# firewall-cmd --zone=public --add-port=18080/tcp --permanent #添加放行端口(--permanent永久生效，没有此参数重启后失效)
success
[root@localhost ~]# firewall-cmd --reload #刷新防火墙 使其生效
success
[root@localhost ~]# firewall-cmd --zone=public --list-ports #查看防火墙放行端口列表
80/tcp
[root@localhost ~]#

2、安装keepalived(nginx_01 和 nginx_02 都执行)

yum install keepalived
keepalived -v

3.先备份配置文件

在nginx_01上配置

cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak

vim /etc/keepalived/keepalived.conf

修改成如下内容

! Configuration File for keepalived
global_defs {
    router_id nginx_server_1
}
vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh"
    interval 2
    weight 20
    !weight为正数
    !如果脚本执行结果为0,,Master:weight+priority>Backup:weight+priority(不切换)
    !如果脚本执行结果不为0,Master:priority:priority+weight(切换)
    !weight为负数
    !如果脚本执行结果为0,,Master:priority>Backup:priority(不切换)
    !如果脚本执行结果不为0,Master:priority+weight:priority(切换)
    !一般来说,weight的绝对值要大于Master和Backup的priority之差
}
vrrp_instance VI_1 {
    state MASTER
    interface ens33 !网卡接口地址
    virtual_router_id 51
    mcast_src_ip 192.168.59.128 !nginx01 ip
    priority 100
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111 !认密码 两台nginx密码要一致
    }
    track_script {
        chk_nginx
    }
    virtual_ipaddress {
        192.168.59.222/24 !漂浮ip 可以有多个 回车隔开
    }
}

在nginx_02上配置

cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak

vi /etc/keepalived/keepalived.conf

修改成如下内容

注意:

state 和主不一样，是BACKUP
route_id 和主不一样
priority 小于主机

! Configuration File for keepalived
global_defs {
    router_id nginx_server_2
}
vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh"
    interval 2
    weight 20
    !weight为正数
    !如果脚本执行结果为0,,Master:weight+priority>Backup:weight+priority(不切换)
    !如果脚本执行结果不为0,Master:priority:priority+weight(切换)
    !weight为负数
    !如果脚本执行结果为0,,Master:priority>Backup:priority(不切换)
    !如果脚本执行结果不为0,Master:priority+weight:priority(切换)
    !一般来说,weight的绝对值要大于Master和Backup的priority之差
}
vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 51
    mcast_src_ip 192.168.59.129
    priority 90
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    track_script {
        chk_nginx
    }
    virtual_ipaddress {
        192.168.59.222/24
    }
}

4.检查nginx进程的代码,当nginx进程奔溃后，keepalived自动启动nginx

在nginx_01和nginx_02上都配置一遍

vim /etc/keepalived/nginx_check.sh

添加如下代码

#!/bin/bash

A=`ps -C nginx --no-header |wc -l`
if [ $A -eq 0 ];then
    /usr/sbin/nginx
    sleep 2
    if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
        killall keepalived
    fi
fi

5.改成可执行文件

在nginx_01和nginx_02上都配置一遍

chmod +xxx /etc/keepalived/nginx_check.sh

6.启动和开机自启动

在nginx_01和nginx_02上都配置一遍

systemctl start keepalived //启动
systemctl enable keepalived //开机自启动