高可用：两台业务系统启动着相同的服务，如果有一台故障，另一台自动接管,我们将将这个称之为高可用；
Keekpalived工作原理：通过vrrp协议实现
vrrp原理
vrrp抓包
Keepalived工作方式：抢占式、非抢占式
安装：yum install keepalived -y
日志存放位置：/var/log/messages
1、keepaliaved 抢占式配置
master配置
[root@lb01 ~]# rpm -qc keepalived
/etc/keepalived/keepalived.conf
/etc/sysconfig/keepalived
[root@lb01 ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb02 #标识信息，一个名字而已；
}
vrrp_instance VI_1 {
state MASTER #角色是master
interface eth0 #vip 绑定端口
virtual_router_id 50 #让master 和backup在同一个虚拟路由里，id 号必须相同；
priority 150 #优先级,谁的优先级高谁就是master ;
advert_int 1 #心跳间隔时间
authentication {
auth_type PASS #认证
auth_pass 1111 #密码
}
virtual_ipaddress {
10.0.0.3 #虚拟ip
}
}
backup配置
[root@lb02 ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb02
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 50
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.0.0.3
}
}
[root@lb02 ~]#
2、Keepalived非抢占式配置：
非抢占式不再有主从之分，全部都为BACKUP,并且配置文件中添加nopreempt，用来标识为非抢占式；
[root@lb01 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb01
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 50
priority 150
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.0.0.3
}
}
[root@lb02 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb02
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 50
priority 100
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.0.0.3
}
}
You have new mail in /var/spool/mail/root
[root@lb02 /etc/nginx/upstream]#
3、nginx+keepalived
实现思路：将keepalived 中的vip作为nginx负载均衡的监听地址，并且域名绑定的也是vip的地址。
说明：Nginx 负载均衡实现高可用，需要借助Keepalived地址漂移功能。
在不考虑后端数据库和存储的时候如下架构
keepalived+Nginx
两台负载均衡配置：
[root@lb01 /etc/nginx/upstream]# ip add show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:97:e1:ff brd ff:ff:ff:ff:ff:ff
inet 10.0.0.5/24 brd 10.0.0.255 scope global eth0
valid_lft forever preferred_lft forever
inet 10.0.0.3/32 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe97:e1ff/64 scope link
valid_lft forever preferred_lft forever
[root@lb01 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb01
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 50
priority 150
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.0.0.3
}
}
[root@lb01 /etc/nginx/upstream]#
[root@lb02 /etc/nginx/upstream]# ip add show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:6f:18:48 brd ff:ff:ff:ff:ff:ff
inet 10.0.0.6/24 brd 10.0.0.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe6f:1848/64 scope link
valid_lft forever preferred_lft forever
[root@lb02 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb02
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 50
priority 100
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.0.0.3
}
}
[root@lb02 /etc/nginx/upstream]#
4、keepalived脑裂现象
由于某些原因，导致两台keepalived高可用服务器在指定时间内，无法检测到对方存活心跳信息，从而导致互相抢占对方的资源和服务所有权，然而此时两台高可用服务器有都还存活。
可能出现的原因：
1、服务器网线松动等网络故障；
2、服务器硬件故障发生损坏现象而崩溃；
3、主备都开启了firewalld 防火墙。
4、在Keepalived+nginx 架构中，当Nginx宕机，会导致用户请求失败，但是keepalived不会进行切换，
所以需要编写一个检测nginx的存活状态的脚本，如果nginx不存活，则kill掉宕掉的nginx主机上面的keepalived。(所有的keepalived都要配置)
架构如下：
image.png
脚本如下：
[root@lb01 /server/scripts]# cat /server/scripts/check_list
#!/bin/sh
nginxpid=$(ps -C nginx --no-header|wc -l)
#1.判断Nginx是否存活,如果不存活则尝试启动Nginx
if [ $nginxpid -eq 0 ];then
systemctl start nginx
sleep 3
#2.等待3秒后再次获取一次Nginx状态
nginxpid=$(ps -C nginx --no-header|wc -l)
#3.再次进行判断, 如Nginx还不存活则停止Keepalived,让地址进行漂移,并退出脚本
if [ $nginxpid -eq 0 ];then
systemctl stop keepalived
fi
fi
[root@lb01 /server/scripts]#
配置文件如下：
[root@lb01 /server/scripts]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id lb01
}
vrrp_script check {
script "/server/scripts/check_list"
interval 10
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 50
priority 150
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.0.0.3
}
track_script {
check
}
}
[root@lb01 /server/scripts]#
