使用 keepalived 的ip漂移搭建主從web

• keepalived 的原理請自行百度，這裡利用其ip漂移功能，實現 主從web的高可用。

ip漂移指一個虛擬ip，在2個真實ip（主從機）之間漂移，外部訪問這個虛擬ip。

達到的效果：主從機的web都開啟服務。主機web宕機，從機web開始接管服務。等待主機開始服務後，主機開始對外服務，從機待命。

apt-get install keepalived或其他方式安裝

主機：

xlj@ubuntu:~$ cat /etc/keepalived/keepalived.conf

global_defs {
notification_email {
acassen@firewall.loc
failover@firewall.loc
sysadmin@firewall.loc
}
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 127.0.0.1
smtp_connect_timeout 4
router_id LVS_DEVEL
}

vrrp_script chk_nc {
script "/home/xlj/check.sh"
interval 6
weight -20
}

vrrp_instance VI_1 {
state MASTER

interface eth0
virtual_router_id 51
priority 100
advert_int 1

authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.111.111
}
track_script {
chk_nc
}
#notify_master /home/yonyou/nchome0509xin/keepalive/start.sh
#notify_backup /home/yonyou/nchome0509xin/keepalive/stop.sh
}

從機：

xlj@ubuntu:~$ cat /etc/keepalived/keepalived.conf

global_defs {
notification_email {
acassen@firewall.loc
failover@firewall.loc
sysadmin@firewall.loc
}
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 127.0.0.1
smtp_connect_timeout 4
router_id LVS_DEVEL
}

vrrp_script chk_nc {
script "/home/xlj/check.sh"
interval 6
weight -20
}

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 {
192.168.111.111
}
track_script {
chk_nc
}
#notify_master /home/yonyou/nchome0509xin/keepalive/start.sh
#notify_backup /home/yonyou/nchome0509xin/keepalive/stop.sh
}

配置提示：

1. state為 MASTER或BACKUP
2. virtual_router_id 2機要相同
3. authentication 為防止非法加入要求的授權，2機要相同。
4. virtual_ipaddress 為要虛擬的ip，2機相同。
5. track_script 是健康檢查腳本配置，本例是調用check.sh判斷。
6. 其他參數可以百度

其中，健康檢查腳本主從機都相同：

xlj@ubuntu:~$ cat /home/xlj/check.sh
#!/bin/bash
COUNT=1
COUNT=`ps -ef | grep java | grep -v grep | wc -l`
if [ $COUNT -gt 0 ] ; then
exit 0
else
exit 1
fi
xlj@ubuntu:~$

意思是檢查java進程是否存在，存在則返回0，代表ok。

主從機分別啟動服務：service keepalived restart

• 查看keepalived日誌。默認日誌在 /var/log/syslog:

xlj@ubuntu:~$ tail -f /var/log/syslog
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Registering gratuitous ARP shared channel
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Opening file "/etc/keepalived/keepalived.conf".
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Configuration is using : 69085 Bytes
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Registering Kernel netlink command channel
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Opening file "/etc/keepalived/keepalived.conf".
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Configuration is using : 11714 Bytes
Jun 17 16:26:08 ubuntu Keepalived_healthcheckers[9305]: Using LinkWatch kernel netlink reflector...
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: Using LinkWatch kernel netlink reflector...
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: VRRP_Instance(VI_1) Entering BACKUP STATE
Jun 17 16:26:08 ubuntu Keepalived_vrrp[9306]: VRRP_Script(chk_nc) succeeded

注意，訪問的是虛擬ip：

http://192.168.111.111:8080/

web頁面看不出到底訪問的是主機還是從機，建議你的web應用提供一個頁面針對主機還是從機顯示不同的信息。

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