keepalived高可用web
----------------------------------一、前言
二、环境
三、Keepalived体系架构
四、安装Keepalived
五、案例配置
----------------------------------
一、前言
keepalived是一个类似于layer3,4&5交换机制的软件，也就是我们平时说的第3层、第4层和第5层交换。Keepalived的作用是检测web服务器的状态，如果有一台web服务器死机，或工作出现故障，Keepalived将检测到，并将有故障的web服务器从系统中剔除，当web服务器工作正常后Keepalived自动将web服务器加入到服务器群中，这些工作全部自动完成，不需要人工干涉，需要人工做的只是修复故障的web服务器。
二、环境
系统：CentOS6.4 32位
软件包：keepalived-1.2.1.tar.gz
Keepalived官网：http://www.keepalived.org/
三、Keepalived体系架构
1）WatchDog 负责监控checkers和VRRP进程的状况。
2）Checkers 负责真实服务器的健康检查healthchecking，是keepalived最主要的功能。换句话说—可以没有VRRP Stack,但健康检查healthchecking是一定要有的。
3）VRRP Stack负责负载均衡器之间失败切换FailOver。如果只用一个负载均衡器，则VRRP不是必须的。
4) IPVS wrapper 用来发送设定的规则到内核ipvs代码。
5) Netlink Reflector 用来设定 vrrp 的vip地址等。
四、安装Keepalived
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# yum groupinstall "Additional Development" //安装开发工具
# yum groupinstall "Development tools"
# tar -zxvf keepalived-1.2.1.tar.gz -C /usr/local/src/
# cd /usr/local/src/keepalived-1.2.1
# ./cnfigure
Keepalived configuration
------------------------
Keepalived version : 1.2.1
Compiler : gcc
Compiler flags : -g -O2
Extra Lib : -lpopt -lssl -lcrypto
Use IPVS Framework : No //配置出现错误
IPVS sync daemon support : No
Use VRRP Framework : Yes
Use Debug flags : No
解决方法：
# yum install kernel-devel ipvsadm
# ln -s /usr/src/kernels/2.6.32-358.el6.i686/ /usr/src/linux
# ./cnfigure //再次配置环境
# make //编译
# make install //安装
# cd /usr/local/etc //keepalived默认安装路径
# ll
drwxr-xr-x. 3 root root 4096 May 24 00:37 keepalived
drwxr-xr-x. 3 root root 4096 May 24 00:29 rc.d
drwxr-xr-x. 2 root root 4096 May 24 00:29 sysconfig
配置以系统方式service启动
# cp /usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
# cp /usr/local/etc/sysconfig/keepalived/etc/sysconfig/
# mkdir /etc/keepalived
# cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/
# cp /usr/local/sbin/keepalived /usr/sbin/
# service keepalived start
Starting keepalived:
# ps aux |grep keepalived
root 48090.00.0 6480 764 ? Ss 00:51 0:00 keepalived -D
root 48110.20.1 65361788 ? S 00:51 0:00 keepalived -D
root 48120.10.1 65361192 ? S 00:51 0:00 keepalived -D
root 48190.00.0 4356 756 pts/0 S+ 00:52 0:00 grep keepalived
五、案例配置
案例简介：
两台服务器实现高可用web，每台服务器均一张网卡。
（1）前端：当任一服务器的网卡宕掉后，web服务切换到另一web服务器。
（2）后端：当任一服务器的web服务宕掉后，web服务切换到另一web服务器。
1.拓扑图：
IP规划：
MASTER：
eth0:192.168.2.20/24
BACKUP:
eth0:192.168.2.30/24
VIP:192.168.2.10/24
2.MASTER配置:
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# cat /etc/keepalived/keepalived.conf//keepalived主配置文档
#guration File for keepalived
#global define
global_defs {
router_id Haweb_1
}
vrrp_sync_group VGM {
group {
VI_HA
}
}
vrrp_script chk_http_port {
script "killall -0 httpd"
#script "/tcp/127.0.0.1/80"
interval 1
}
# vvrp_instance define #
vrrp_instance VI_HA {
state MASTER
interface eth1
lvs_sync_daemon_inteface eth1
virtual_router_id 51
priority 100
advert_int 5
authentication {
auth_type PASS
auth_pass 123456
}
track_script {
chk_http_port
}
virtual_ipaddress {
192.168.2.10/24 dev eth1
}
}
安装web服务器：
# yum install httpd
# service httpd start
# cd /var/www/html/
# echo "This is Master web.">index.html
# service keepalived start //启动keepalived
# tail -f /var/log/messages //查看日志状态
May 24 23:32:25 localhost Keepalived_vrrp: VRRP_Group(VGM) Syncing instances to MASTER state
3.BACKUP配置：
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# cat /etc/keepalived/keepalived.conf
#guration File for keepalived
#global define
global_defs {
router_id Haweb_1
}
vrrp_sync_group VGM {
group {
VI_HA
}
}
vrrp_script chk_http_port {
script "killall -0 httpd"
# script "/tcp/127.0.0.1/80"
interval 1
}
# vvrp_instance define #
vrrp_instance VI_HA {
state BACKUP
interface eth2
lvs_sync_daemon_inteface eth2
virtual_router_id 51
priority 90
advert_int 5
authentication {
auth_type PASS
auth_pass 123456
}
track_script {
chk_http_port
}
virtual_ipaddress {
192.168.2.10/24 dev eth2
}
}
安装web服务器：
# yum install httpd
# service httpd start
# cd /var/www/html/
# echo "This is Backup web.">index.html
# service keepalived start
# tail -f /var/log/messages
May 24 23:40:33 localhost Keepalived_vrrp: VRRP_Instance(VI_HA) Entering BACKUP STATE
4.测试
（1）前端master服务器的网卡宕掉
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# ip addr //master端，查看IP绑定。
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:0c:29:08:52:3f brd ff:ff:ff:ff:ff:ff
inet 192.168.2.20/24 brd 192.168.2.255 scope global eth0
inet 192.168.2.10/24 scope global secondary eth0
inet6 fe80::20c:29ff:fe08:523f/64 scope link
valid_lft forever preferred_lft forever
浏览器访问VIPhttp://192.168.2.10
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# ifconfig eth1 down //模拟master端网卡宕掉（模拟后请再次打开）
# ip addr //backup端，查看IP绑定。
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:0c:29:6c:f9:45 brd ff:ff:ff:ff:ff:ff
inet 192.168.2.30/24 brd 192.168.2.255 scope global eth0
inet 192.168.2.10/24 scope global secondary eth0
inet6 fe80::20c:29ff:fe6c:f945/64 scope link
valid_lft forever preferred_lft forever
刷新页面：
（2）后端web服务宕掉
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# ip addr //master端，查看IP绑定。
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:0c:29:08:52:3f brd ff:ff:ff:ff:ff:ff
inet 192.168.2.20/24 brd 192.168.2.255 scope global eth0
inet 192.168.2.10/24 scope global secondary eth0
inet6 fe80::20c:29ff:fe08:523f/64 scope link
valid_lft forever preferred_lft forever
浏览器访问VIPhttp://192.168.2.10
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# service httpd stop //模拟master端web服务宕掉
Stopping httpd:
# ip addr //backup端，查看IP绑定。
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:0c:29:6c:f9:45 brd ff:ff:ff:ff:ff:ff
inet 192.168.2.30/24 brd 192.168.2.255 scope global eth0
inet 192.168.2.10/24 scope global secondary eth0
inet6 fe80::20c:29ff:fe6c:f945/64 scope link
valid_lft forever preferred_lft forever
刷新页面：案例总结：
1) 当停止MASTER的网卡或web服务时，由BACKUP接管VIP，提供WEB服务。
2) 当停止BACKUP的网卡或web服务时，由MASTER接管VIP，提供WEB服务。
3）从上可以看出故障切换是由keepalived进程的存活而产生的IP飘移。
ps:关于Keepalived抢占问题如何优化？
两台服务器组成高可用集群，分别处于Master与Backup状态，当Master出现故障时由Backup来接管
所有任务，那么当Master恢复时，Master会抢回所有权。虽然是高可用，但是对客户来说，来回的切换是比较烦恼的事。 如何让master状态的主机挂掉后不抢占的办法：可将两服务器均设成backup状态是因为nopreempt(不抢占)只支持backup模式，而让哪一台backup成为master，这个由优先级priority为决定。
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