keepalived实现nginx的高可用

keepalived实现nginx
HA的做法，首先参考博文http://quenlang.blog.51cto.com/4813803/1570352，搭建好nginx反向代理tomcat并利用自身模块proxy_cache实现web缓存的架构，该博文中的nginx安
装在hadoop1节点上，按照博文中的nginx的安装配置，配置好hadoop0，这样就有两个节点安装了nginx并实现了web缓存和反向代理。
这里hadoop0作为nginx的master，而hadoop1作为nginx的backup，以此来配置keepalived。
在hadoop0、hadoop1上安装keepalived

yum install keepalived -y

hadoop0上keepalived的配置如下

[root@hadoop0 ~]# cat  /etc/keepalived/keepalived.conf
! Configuration File for keepalived

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 30
router_id LVS_DEVEL
}

vrrp_script check_nginx {
script "/opt/check_nginx.sh"
interval 2
}

vrrp_instance VI_2 {
state MASTER
interface eth0
virtual_router_id 52
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}

virtual_ipaddress {
192.168.0.207
}

track_script {
check_nginx
}
}

hadoop1上keepalived的配置如下

[root@hadoop1 ~]# cat  /etc/keepalived/keepalived.conf
! Configuration File for keepalived

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 30
router_id LVS_DEVEL
}

vrrp_instance VI_2 {
state BACKUP
interface eth0
virtual_router_id 52
priority 80
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}

virtual_ipaddress {
192.168.0.207
}
}

从上面的配置看到，keepalived代理nginx实现HA之后的虚拟IP为192.168.0.207，监控nginx的脚本内容如下

[root@hadoop0 ~]# cat  /opt/check_nginx.sh
#!/bin/bash
#author: kora
#date: 2014-10-21
#description: check service such as nginx
#

#set -x

CHECK_TIME=3
NGINX_OK=1
NOW=`date`
STATUS='OK!'

procnum=`ps -ef |grep "/usr/local/nginx/sbin/nginx"|grep -v "grep"|wc -l`

while [ "$CHECK_TIME" -ne 0 ]
do
let "CHECK_TIME-=1"
if [ "$procnum" -eq 1 -a -f /usr/local/nginx/logs/nginx.pid ]
then
NGINX_OK=1
CHECK_TIME=0
else
NGINX_OK=0
fi
done

if [ "$NGINX_OK" -eq 0 ]
then
status='fail!'
/etc/init.d/keepalived stop
fi

echo "$NOW:$STATUS" >> /usr/local/nginx/logs/keepalived.log
exit 0

当master上的nginx挂掉之后，脚本会停调keepalived服务，从而将虚拟IP浮动到hadoop1上，实现高可用，而用户需要使用虚拟IP192.168.0.207来访问web应用。