linux高可用（HA）keepalived 主從備份

    利用keepalived可以實作對linux伺服器的高可用性，即主從備份，一台線上伺服器出故障另外一台伺服器頂替它，當出故障的伺服器恢複時又自動轉換成主伺服器，頂替它的伺服器再次轉換為備胎，當主伺服器當機、主伺服器網卡壞掉、甚至主伺服器服務挂掉（要用腳本監控實作轉換）都可以自動切換到從伺服器

yum install gcc gcc-c++ openssl-devel httpd kernel-devel -y

tar zxf keepalived-1.1.20.tar.gz

cd keepalived-1.1.20/

./configure --sysconf=/etc/ --with-kernel-dir=/usr/src/kernels/2.6.18-238.el5-i686/

make &&make install

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

! 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
}

vrrp_instance VI_1 {
    state MASTER  #設定為主伺服器
    interface eth0  #監測網絡接口
    virtual_router_id 51  #主、備必須一樣
    priority 100  #(主、備機取不同的優先級，主機值較大，備份機值較小,值越大優先級越高) 
    advert_int 1  #VRRP Multicast廣播周期秒數 
    authentication {
        auth_type PASS  #VRRP認證方式，主備必須一緻
        auth_pass 1111  #(密碼)  
    }
    virtual_ipaddress {
        192.168.65.65  #VRRP HA虛拟位址 
    }
}
      

　　

####将keepalived.conf配置檔案修改成以上配置，即修改虛拟位址為192.168.65.65，這個虛拟位址是虛拟不存在的，使用者在通路網頁的時候通路的就是這個虛拟位址，本配置檔案要注意修改伺服器的主從狀态、優先級、組id以及虛拟ip，還可以修改Email位址通知自己等。

# service keepalived start
# service httpd start
# chkconfig --add httpd
# chkconfig --add keepalived
# chkconfig httpd on
# chkconfig keepalived on      

從伺服器配置：

[root@web1_slave keepalived]# cat /etc/keepalived/keepalived.conf 

! 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
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.65.65
    }
}
      

#####從伺服器keepalived.conf的主配置檔案，優先級改為比主的優先級（100）小，這裡是90.

# echo "slave" > /var/www/html/index.html

######其他配置内容和主伺服器相同

當主伺服器當機或是網卡出問題，從伺服器都會取代它變成主伺服器

上圖是當主伺服器網卡重新開機時，在從伺服器日志記錄上顯示從伺服器先是切換成主伺服器，後又切換成從伺服器。

當web站點挂了時，還想讓從伺服器自動切換成主伺服器就需要腳本來執行。

下面建立一個腳本，名叫check_httpd.sh ，其位置都放在主從伺服器的/etc/keepalived/下面，（主從伺服器使用相同的腳本，腳本放的位置也都相同，在keepalived.conf修改的地方、内容也都相同）

下面是check_httpd.sh 腳本的内容

[root@web1_master keepalived]# cat check_httpd.sh 

#!/bin/bash
CHECK_TIME=2

check()
{
        curl http://127.0.0.1/ >/dev/null 2>&1
        ret=$?
        if [ $ret -ne 0 ];then
                return $ret;
        fi
}

while [ $CHECK_TIME -ne 0 ]
do
        let "CHECK_TIME -= 1"
        check
        HTTP_OK=$?
        if [ $HTTP_OK -eq 0 ];then
                exit 0
        fi
        if [ $HTTP_OK -ne 0 ] &&  [ $CHECK_TIME -eq 0 ]
        then
            exit 1
        fi
done
      

修改主伺服器keepalived.conf配置檔案，結果如下：

[root@web1_master keepalived]# cat keepalived.conf 

! 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
}

vrrp_script check_http {
        script "/etc/keepalived/check_httpd.sh"
        weight -5
        interval 1
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
track_script {
                check_http
        }
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.65.65
    }
}
      

修改從伺服器keepalived.conf配置檔案，結果如下：

[root@web1_slave keepalived]# cat keepalived.conf 

! 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
}

vrrp_script check_http {
        script "/etc/keepalived/check_httpd.sh"
        weight -5
        interval 1
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 90
    advert_int 1
track_script {
                check_http
        }
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.65.65
    }
}
      

    分别重新開機兩台伺服器的keepalived服務

#service keepalivedrestart

    到這裡，如果主伺服器的web程式出現故障，則從伺服器會在1秒鐘後自動切換成主伺服器，當主伺服器恢複時，從伺服器會自動切換成備胎，主伺服器依然是主伺服器。

腦裂#

firewall-cmd --direct --permanent --add-rule ipv4 filter INPUT 0 --destination 224.0.0.18 --protocol vrrp -j ACCEPT
firewall-cmd --direct --permanent --add-rule ipv4 filter OUTPUT 0 --destination 224.0.0.18 --protocol vrrp -j ACCEPT
firewall-cmd --reload      

Keepalived使用vrrp多點傳播，預設位址是224.0.0.18，是以要配置防火牆放過。