（一）keepalived介绍：
Keepalived是Linux下轻量级的高可用的解决方案。Keepalived主要是通过虚拟路由冗余来实现高可用功能，具有部署和使用非常简单，只需一个配置文件即可。它是根据TCP/IP参考模型的第三，第四和第五层交换机检测到每个服务接点的状态，如果某个服务节点出现异常，或者出现故障，keepalived将检测到，并将出现故障的服务节点从集群中剔除，而在故障节点恢复后，keepalived又可以自动将此服务节点重新加入服务器集群中，这些工作全部自动完成，不需要人工干涉，需要人工完成的只是修复出现故障的服务节点。（2台服务器运行Keepalived，一台为主服务器（MASTER），一台为备份服（BACKUP），但是对外表现为一个虚拟IP，主服务器会发送特定的消息给备份服务器，当备份服务器收不到这个消息的时候，即主服务器宕机的时候， 备份服务器就会接管虚拟IP，继续提供服务，从而保证了高可用性）。keepalived采用的是vrrp来实现的。
Keepalived是一个高可用解决方案，主要是用来防止服务器单点发生故障，可以通过和Nginx配合来实现Web服务的高可用。（其实，Keepalived不仅仅可以和Nginx配合，还可以和很多其他服务配合）
Keepalived+Nginx实现高可用的思路：
第一：请求不要直接打到Nginx上，应该先通过Keepalived（这就是所谓虚拟IP，VIP）
第二：Keepalived应该能监控Nginx的生命状态（提供一个用户自定义的脚本，定期检查Nginx进程状态，进行权重变化,，从而实现Nginx故障切换）
（二）安装和配置：
1，编译安装：
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[root@localhost
install
]
#cd /tmp/install
[root@localhost
install
]
# yum install gcc gcc-c++ openssl* kernel-devel net-snmp* libnl* -y
[root@localhost
install
]
#yum install -y libnfnetlink-devel
[root@localhost
install
]
#wget http://www.keepalived.org/software/keepalived-1.2.19.tar.gz
###或者直接在官网上下载
[root@localhost
install
]
#tar zxvf keepalived-1.2.19.tar.gz
[root@localhost
install
]
#cd keepalived-1.2.19
[root@localhost
install
]
#./configure --prefix=/usr/local/keepalived
[root@localhost
install
]
#make && make install
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2,配置：
（1）环境说明
| hostname |
PI | 安装软件 | OS |
| Master |
192.168.122.120 | nginx（已安装).keepalived | Centos6.5 |
| backup | 192.168.122.121 | nginx（已安装).keepalived | Centos6.5 |
| vip（虚拟IP） |
192.168.122.130 |
备注：依次在192.168.122.120和192.168.122.121进行编译安装如上边的步骤,安装完成之后，会在/usr/local下生成bin、etc、sbin三个文件夹，主要的配置文件在etc目录下，执行文件在sbin目录下
（2）依次在120和121上操作：
(a)####keepalive启动时默认会去读/etc/keepalived/keepalived.conf配置文件，但编译安转后，没有自动创建这个文件，而是放到了/usr/local/etc/keepalived/keepalived.conf
为了以后配置方便，我们手动将/usr/local/etc/keepalived/keepalived.conf放到/etc/keepalived/下
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[root@localhost
install
]
#mkdir /etc/keepalived/
[root@localhost
install
]
#cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
[root@localhost
install
]
#cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/keepalived
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(b)#####建立服务启动脚本
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[root@localhost
install
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#cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
[root@localhost
install
]
#chmod +x /etc/init.d/keepalived
####下边是centos7.x版本做成服务
[root@localhost
install
]
#cp /tmp/install/keepalived-1.4.0/keepalived/keepalived.service /lib/systemd/system/keepalived.service
[root@localhost
install
]
#systemctl enable keepalived.service
Created
symlink
from
/etc/systemd/system/multi-user
.target.wants
/keepalived
.service to
/usr/lib/systemd/system/keepalived
.service.
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(c)####更改启动脚本中keepalive启动参数文件的位置，脚本文件路径是/etc/sysconfig/keepalived（如果是通过yum安装，则这个位置就是正确的），而实际文件是在/usr/local/keepalived/etc/sysconfig/keepalived
#sed -i 's#/etc/sysconfig/keepalived#/usr/local/etc/sysconfig/keepalived#g' /etc/init.d/keepalived
[root@localhost install]#vi /etc/init.d/keepalived
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#!/bin/sh
#
# Startup script for the Keepalived daemon
#
# processname: keepalived
# pidfile: /var/run/keepalived.pid
# config: /etc/keepalived/keepalived.conf
# chkconfig: - 21 79
# description: Start and stop Keepalived
# Source function library
.
/etc/rc
.d
/init
.d
/functions
# Source configuration file (we set KEEPALIVED_OPTIONS there)
.
/usr/local/keepalived/etc/sysconfig/keepalived
RETVAL=0
prog=
"keepalived"
start() {
echo
-n $
"Starting $prog: "
daemon keepalived ${KEEPALIVED_OPTIONS}
RETVAL=$?
echo
[ $RETVAL -
eq
0 ] &&
touch
/var/lock/subsys/
$prog
}
"/etc/init.d/keepalived"
74L, 1329C
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（d)给/usr/local/keepalived/sbin/keepalived做个软连接，否则会报错
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[root@localhost sbin]
# /etc/init.d/keepalived start
Starting keepalived:
/bin/bash
: keepalived:
command
not found
[FAILED]
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[root@localhost sbin]
# ln -s /usr/local/keepalived/sbin/keepalived /usr/bin/
[root@localhost sbin]
# /etc/init.d/keepalived start
Starting keepalived: [ OK ]
[root@localhost sbin]
#
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（3)配置keepalived.conf 主要配置三个地方：global_defs、vrrp_instance、virtual_ip address
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root@localhost sbin]
# vi /etc/keepalived/keepalived.conf
! Configuration File
for
keepalived
global_defs {
#全局设置
router_id LVS_DEVEL
#定义路由标识信息，相同局域网唯一，可自定义
}
vrrp_script check_http {
#首先在vrrp_script区域定义脚本名字和脚本执行的间隔和脚本执行的优先级变更
script
"/opt/nginx_pid.sh"
#然后在实例(vrrp_instance)里面引用，有点类似脚本里面的函数引用一样：先定义，后引用函数名
interval 2
#脚本执行间隔时间
weight 10
#利用权重值和优先级进行运算，从而降低主服务优先级使之变为备服务器（建议先忽略）
}
vrrp_instance VI_1 {
#定义一个vrrp实例名，可自定义
state MASTER
#设定初始状态，可以是MASTER或BACKUP，不过当其他节点keepalived启动时会将priority比较大的节点选举为MASTER，因此该项其实没有实质用途。
interface eth0
#具有固定ip的网卡，用来接收和发送vrrp包。如果没有设定mcast_src_ip发送多播数据包的地址，那么将使用这个网卡的ip来发送。
virtual_router_id 51
#虚拟路由的id号，范围为0-255，取值在0-255之间，用来区分多个instance的VRRP组播。相同的VRID为一个组，他将决定多播的MAC地址
priority 99
#当前keepalived的优先级，数字越大，优先级越高
advert_int 1
#组播信息发送间隔，两个节点设置必须一样，默认为1秒
authentication {
#设置节点间验证信息，所以所有节点必须一致
auth_type PASS
#验证类型
auth_pass 1111
#密码
}
track_script {
#调用上面定义的检测脚本
chk_http_port
weight 20
}
virtual_ipaddress {
#设置vip，如果不指定网卡，那么默认绑定到interface指定的网卡，可以通过添加dev ethx的方式，绑定到指定的网卡。
192.168.122.130
}
}
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同理，在121上进行操作：
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vi
/etc/keepalived/keepalived
.conf
! Configuration File
for
keepalived
global_defs {
router_id LVS_DEVEL
}
vrrp_script chk_http_port {
script
"/root/chk_httpd.sh"
interval 2
weight 10
}
vrrp_instance VI_1 {
state BACKUP
#此处为BACKUP
interface eth0
virtual_router_id 51
priority 96
#此处比MASTER要小
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
/opt/nginx_pid
.sh
weight 20
}
virtual_ipaddress {
192.168.122.130
}
}
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（4）在两台服务器上创建定义 vrrp_script check_http的脚本(nginx_pid.sh脚本的作用是当nginx关闭时自动启动nginx)
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[root@zabbix ~]# cat /opt/nginx_pid.sh
#!/bin/bash
A=`ps -C nginx --no-header |wc -l`
if
[ $A -eq 0 ];then
/usr/local/nginx/sbin/nginx
sleep 3
if
[ `ps -C nginx --no-header |wc -l` -eq 0 ];then
killall keepalived
fi
fi
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(5）120和121同时启动keepalived
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[root@hadoop1 ~]
# /etc/init.d/keepalived start
Starting keepalived: [ OK ]
[root@hadoop1 ~]
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link
/loopback
00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1
/8
scope host lo
inet6 ::1
/128
scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
52:54:00:05:7b:31 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.120
/24
brd 192.168.122.255 scope global eth0
inet 192.168.122.130
/32
scope global eth0
inet6 fe80::5054:ff:fe05:7b31
/64
scope link
valid_lft forever preferred_lft forever
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[root@hadoop2 ~]
# /etc/init.d/keepalived start
Starting keepalived: [ OK ]
[root@hadoop2 ~]
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link
/loopback
00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1
/8
scope host lo
inet6 ::1
/128
scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
52:54:00:c6:65:80 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.121
/24
brd 192.168.122.255 scope global eth0
inet6 fe80::5054:ff:fec6:6580
/64
scope link
valid_lft forever preferred_lft forever
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打开浏览器进行查看：
(5)验证实验结果：
实验一：关闭120的keepalived服务看是否切换：
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[root@hadoop1 ~]
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link
/loopback
00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1
/8
scope host lo
inet6 ::1
/128
scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
52:54:00:05:7b:31 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.120
/24
brd 192.168.122.255 scope global eth0
inet6 fe80::5054:ff:fe05:7b31
/64
scope link
valid_lft forever preferred_lft forever
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在查看下121的IP地址：
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[root@hadoop2 ~]
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link
/loopback
00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1
/8
scope host lo
inet6 ::1
/128
scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
52:54:00:c6:65:80 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.121
/24
brd 192.168.122.255 scope global eth0
inet 192.168.122.130
/32
scope global eth0
inet6 fe80::5054:ff:fec6:6580
/64
scope link
valid_lft forever preferred_lft forever
[root@hadoop2 ~]
#
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已成功切换，在打开浏览器：
本文转自 lqbyz 51CTO博客，原文链接:http://blog.51cto.com/liqingbiao/1735397
