[笔记]使用Keepalived实现Nginx主从热备

HA(High Available), 高可用性集群，是保证业务连续性的有效解决方案，一般有两个或两个以上的节点，且分为活动节点及备用节点。

1.1. 高可靠软件keepalived

keepalive是一款可以实现高可靠的软件，通常部署在2台服务器上，分为一主一备。Keepalived可以对本机上的进程进行检测，一旦Master检测出某个进程出现问题，将自己切换成Backup状态，然后通知另外一个节点切换成Master状态。

1.2. keepalived安装

下载keepalived官网:http://keepalived.org

将keepalived解压到/usr/local/src目录下

tar -zxvf  keepalived-1.2..tar.gz -C /usr/local/src

进入到/usr/local/src/keepalived-1.2.19目录

cd /usr/local/src/keepalived-1.2.

开始configure

./configure --prefix=/usr/local/keepalived

编译并安装

make && make install

1.3. 将keepalived添加到系统服务中

拷贝执行文件

cp /usr/local/keepalived/sbin/keepalived /usr/sbin/

将init.d文件拷贝到etc下,加入开机启动项

cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/keepalived

将keepalived文件拷贝到etc下

cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/

创建keepalived文件夹

mkdir -p /etc/keepalived

将keepalived配置文件拷贝到etc下

cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf

添加可执行权限

chmod +x /etc/init.d/keepalived

##以上所有命令一次性执行：

cp /usr/local/keepalived/sbin/keepalived /usr/sbin/

cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/keepalived

cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/

mkdir -p /etc/keepalived

cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf

chmod +x /etc/init.d/keepalived

chkconfig --add keepalived

chkconfig keepalived on

添加keepalived到开机启动

chkconfig --add keepalived

chkconfig keepalived on

1.4. 配置keepalived虚拟IP

修改配置文件： /etc/keepalived/keepalived.conf

MASTER节点

global_defs {

}

vrrp_instance VI_1 {

    state MASTER   #指定A节点为主节点 备用节点上设置为BACKUP即可

    interface eth0    #绑定虚拟IP的网络接口

    virtual_router_id    #VRRP组名，两个节点的设置必须一样，以指明各个节点属于同一VRRP组

    priority    #主节点的优先级（-254之间），备用节点必须比主节点优先级低

    advert_int   #组播信息发送间隔，两个节点设置必须一样

    authentication {    #设置验证信息，两个节点必须一致

        auth_type PASS

        auth_pass 

    }

    virtual_ipaddress {    #指定虚拟IP, 两个节点设置必须一样

        192.168.33.60/    #如果两个nginx的ip分别是192.168.33.,,...，则此处的虚拟ip跟它俩同一个网段即可

    }

}

BACKUP节点 

global_defs {

}

vrrp_instance VI_1 {

    state BACKUP

    interface eth0

    virtual_router_id 

    priority 

    advert_int 

    authentication {

        auth_type PASS

        auth_pass 

    }

    virtual_ipaddress {

        192.168.33.60/

    }

}

#分别启动两台机器上的keepalived

service keepalived start

测试：

杀掉master上的keepalived进程，你会发现，在slave机器上的eth0网卡多了一个ip地址

查看ip地址的命令：  ip addr

1.5. 配置keepalived心跳检查

原理：

Keepalived并不跟nginx耦合，它俩完全不是一家人

但是keepalived提供一个机制：让用户自定义一个shell脚本去检测用户自己的程序，返回状态给keepalived就可以了

MASTER节点

global_defs {

}

vrrp_script chk_health {

    script "[[ `ps -ef | grep nginx | grep -v grep | wc -l` -ge 2 ]] && exit 0 || exit 1"

    interval     #每隔1秒执行上述的脚本，去检查用户的程序ngnix

    weight -

}

vrrp_instance VI_1 {

    state MASTER

    interface eth0

    virtual_router_id 

    priority 

    advert_int 

    authentication {

        auth_type PASS

        auth_pass 

    }

    track_script {

        chk_health

    }

    virtual_ipaddress {

        10.0.0.10/

    }

    notify_master "/usr/local/keepalived/sbin/notify.sh master"

    notify_backup "/usr/local/keepalived/sbin/notify.sh backup"

    notify_fault "/usr/local/keepalived/sbin/notify.sh fault"

}

#添加切换通知脚本

vi /usr/local/keepalived/sbin/notify.sh

#!/bin/bash

case "$1" in

    master)

        /usr/local/nginx/sbin/nginx

        exit 

    ;;

backup)

        /usr/local/nginx/sbin/nginx -s stop

        /usr/local/nginx/sbin/nginx

        exit 

    ;;

    fault)

        /usr/local/nginx/sbin/nginx -s stop

        exit 

    ;;

    *)

        echo 'Usage: notify.sh {master|backup|fault}'

        exit 

    ;;

esac

#添加执行权限

chmod +x /usr/local/keepalived/sbin/notify.sh

global_defs {

}

vrrp_script chk_health {

    script "[[ `ps -ef | grep nginx | grep -v grep | wc -l` -ge 2 ]] && exit 0 || exit 1"

    interval 

    weight -

}

vrrp_instance VI_1 {

    state BACKUP

    interface eth0

    virtual_router_id 

    priority 

    advert_int 

    authentication {

        auth_type PASS

        auth_pass 

    }

    track_script {

        chk_health

    }

    virtual_ipaddress {

        10.0.0.10/

    }

    notify_master "/usr/local/keepalived/sbin/notify.sh master"

    notify_backup "/usr/local/keepalived/sbin/notify.sh backup"

    notify_fault "/usr/local/keepalived/sbin/notify.sh fault"

}

#在第二台机器上添加notify.sh脚本

#分别在两台机器上启动keepalived

service keepalived start

chkconfig keepalived on