Nginx+keepalived实现七层的负载均衡-CSDN博客

1.keepalived VRRP 介绍

keepalived是什么

         keepalived是集群管理中保证集群高可用的一个服务软件用来防止单点故障。

keepalived工作原理
          keepalived是以VRRP协议为实现基础的VRRP全称Virtual Router Redundancy Protocol即虚拟路由冗余协议。

虚拟路由冗余协议可以认为是实现路由器高可用的协议即将N台提供相同功能的路由器组成一个路由器组这个组里面有一个master和多个backupmaster上面有一个对外提供服务的vip该路由器所在局域网内其他机器的默认路由为该vipmaster会发组播当backup收不到vrrp包时就认为master宕掉了这时就需要根据VRRP的优先级来选举一个backup当master。这样的话就可以保证路由器的高可用了。

keepalived主要有三个模块分别是core、check和vrrp。core模块为keepalived的核心负责主进程的启动、维护以及全局配置文件的加载和解析。check负责健康检查包括常见的各种检查方式。vrrp模块是来实现VRRP协议的。

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脑裂  split  barin

Keepalived的BACKUP主机在收到不MASTER主机报文后就会切换成为master如果是它们之间的通信线路出现问题无法接收到彼此的组播通知但是两个节点实际都处于正常工作状态这时两个节点均为master强行绑定虚拟IP导致不可预料的后果这就是脑裂。

关于脑裂问题的解决方法

1. 添加更多的检测手段比如冗余的心跳线两块网卡做健康监测ping对方等等。尽量减少"裂脑"发生机会。(指标不治本只是提高了检测到的概率)
2. 设置仲裁机制。两方都不可靠那就依赖第三方。比如启用共享磁盘锁ping网关等。(针对不同的手段还需具体分析)
3. 爆头将master停掉。然后检查机器之间的防火墙。网络之间的通信。

2.Nginx+keepalived实现七层的负载均衡

通过Nginx的upstream实现负载均衡

proxy-master:        192.168.134.165

proxy-slave:        192.168.134.166

real-server1:        192.168.134.163        

real-server2:        192.168.134.164

VIP                        192.168.1345.160

2.1准备工作

• 关闭四台机器上的防火墙和selinux

systemctl stop firewalld
sed -i 's/^SELINUX=.*/SELINUX=disabled/' /etc/sysconfig/selinux        //关闭selinux重启生效

• 在四台机器上安装nginx

[root@proxy-master ~]# cd /etc/yum.repos.d/
[root@proxy-master yum.repos.d]# vim nginx.repo
[nginx-stable]
name=nginx stable repo
baseurl=http://nginx.org/packages/centos/$releasever/$basearch/
gpgcheck=0
enabled=1
[root@proxy-master ~]# yum install yum-utils -y
[root@proxy-master ~]# yum install nginx -y
[root@proxy-master ~]# systemctl start nginx

2.2两台服务器做代理

proxy-master:192.168.134.165和proxy-slave:192.168.134.166做代理。

在两台代理机器上都配置

[root@master ~]# vim /etc/nginx/conf.d/default.conf
 
       upstream aren {
                server 192.168.134.163:80 weight=1 max_fails=3 fail_timeout=20s;
                server 192.168.134.164:80 weight=1 max_fails=3 fail_timeout=20s;

}
    server {
        listen       80;   
        root         /usr/share/nginx/html;
        location /{
                proxy_pass http://aren;
                proxy_set_header Host $host:$proxy_port;
                proxy_set_header X-Forwarded-For $remote_addr;
}
   
[root@master ~]# nginx -s reload

2.3在两台Keepalived实现调度器HA

注主/备调度器均能够实现正常调度
1. 主/备调度器安装软件

主

[root@proxy-master ~]# yum install -y keepalived
[root@proxy-slave ~]# yum install -y keepalived
[root@proxy-master ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak    ##备份

! Configuration File for keepalived


global_defs {
   router_id directory1        
}

vrrp_instance VI_1 {
    state MASTER            #定义为主
    interface ens33        #VIP绑定接口
    virtual_router_id 80       #整个集群的调度器一致 
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.134.160/24        #VIP
    }
}

备

[root@proxy-slave ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@proxy-slave ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
   router_id directory2        #
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 80
    priority 50        #back的优先级为50 小于master
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.134.160/24
    }
}

 此时可以看到VIP在master上

2.4在real-server上写入测试页面

[root@server03 ~]# echo "lvs-RS1" > /usr/share/nginx/html/index.html
[root@server03 ~]# systemctl  start nginx


[root@server04 ~]# echo "lvs-RS2" > /usr/share/nginx/html/index.html
[root@server04 ~]# systemctl  start nginx

2.5测试

• 当我们关闭master上的keepalived可以发现VIP会转移到slave上这就实现了高可用当master挂掉后slave会顶替master继续提供服务

##关闭master的nginx 和 keepalived
[root@master ~]# systemctl  stop   keepalived

• 查看slave可以发现VIP在slave上。

•  访问VIP192.168.134.160可以访问到。
• 

 3.解决nginx故障

• 可以解决心跳故障keepalived但不能解决Nginx服务故障。这是我们要添加对nginx健康检查。两台都设置

思路
让Keepalived以一定时间间隔执行一个外部脚本脚本的功能是当Nginx失败则关闭本机的Keepalived

[root@proxy-master ~]# vim /etc/keepalived/check_nginx_status.sh
#!/bin/bash												        
/usr/bin/curl -I http://localhost &>/dev/null	
if [ $? -ne 0 ];then										    
#	/etc/init.d/keepalived stop
	systemctl stop keepalived
fi

•  keepalived使用script

! Configuration File for keepalived


global_defs {
   router_id directory1
}

vrrp_script check {
        script "/etc/keepalived/check-nginx.sh"
        interval 5        #每5秒检测一次
}


vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 80
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123
    }
    virtual_ipaddress {
        192.168.134.160/24
    }
        track_script {
                check
        }

}

•  测试

关闭master上的nginx服务过5秒后会检测到nginx挂掉随后会关闭master上的keepalived并且VIP会转移到slave上面让slave继续提供服务。

master

 slave