# 什么是高可用?
nginx做负载均衡,能达到分发请求的目的,但是不能很好的避免单点故障
## nginx集群单点问题
分发器宕机怎么处理?
假如nginx服务器挂掉了,那么所有的服务也会跟着瘫痪
一种方法是人为监控,发现主分发器宕机后,立马登录备分发器,并给它分配虚ip
另一种办法是用软件来替代人来监控,自动登录备分发器,分配虚ip
数据服务器宕机怎么处理?
分发器可以自动判断数据服务器的存活状态,不对宕机服务器要数据
## Keepalived介绍
Keepalived的作用是检测服务器的状态,如果有一台web服务器宕机,或工作出现故障,Keepalived将检测到,并将有故障的服务器从系统中剔除,同时使 其他服务器代替该服务器的工作,当服务器工作正常后Keepalived自动将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服务器。
总结来说:Keepalived软件是一个监控+自愈的软件。
运行协议是VRRP,主分发器的keepalived会向网络中发组播,宣告自己还活着,组播地址:224.0.0.18
# 环境介绍
|主机名 |IP |角色 |系统 |配置 |软件|
|-------|-------|-------|-------|-------|-------|
nginx01|192.168.179.128|主分发器|centos7.5|2核4G|Nginx+keepalived|
nginx02|192.168.179.129|备分发器|centos7.5|2核4G|Nginx+keepalived|
# 安装nginx和keepalived
两台虚机都安装nginx+keepalived
## 下载nginx
```bash
[root@nginx01]# yum -y install nginx
[root@nginx01]# systemctl start nginx
[root@nginx01]# systemctl enable nginx
[root@nginx01]# systemctl status nginx
● nginx.service - nginx - high performance web server
Loaded: loaded (/usr/lib/systemd/system/nginx.service; disabled; vendor preset: disabled)
Active: active (running) since Wed 2019-09-18 22:57:11 EDT; 4h 7min ago
Docs: http://nginx.org/en/docs/
Process: 11299 ExecStop=/bin/kill -s TERM $MAINPID (code=exited, status=0/SUCCESS)
Process: 11302 ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf (code=exited, status=0/SUCCESS)
Main PID: 11303 (nginx)
CGroup: /system.slice/nginx.service
├─11303 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
└─11304 nginx: worker process
Sep 18 22:57:11 A2 systemd[1]: Stopped nginx - high performance web server.
Sep 18 22:57:11 A2 systemd[1]: Starting nginx - high performance web server...
Sep 18 22:57:11 A2 systemd[1]: PID file /var/run/nginx.pid not readable (yet?) after start.
Sep 18 22:57:11 A2 systemd[1]: Started nginx - high performance web server.
```
## 安装keepalived
keepalived官网地址:https://www.keepalived.org/download.html
```bash
#yum安装
[root@nginx01]# yum -y insatll keepalived
[root@nginx01]# systemctl start keepalived
#编译安装
[root@nginx01]# wget http://www.keepalived.org/software/keepalived-2.0.8.tar.gz
[root@nginx01]# sh keepalived_install.sh
[root@nginx01]# cat keeepalived_install.sh
#keepalived安装脚本
#!/bin/bash
pkg=keepalived-2.0.8.tar.gz tar xf $pkg
yum -y install kernel-devel
ln -s /usr/src/kernels/3.10.0-862.14.4.el7.x86_64/ /usr/src/linux
cd keepalived-2.0.8/
yum install openssl-* -y
./configure --prefix=/usr/local/keepalived
make
make install
mkdir -pv /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/
[root@nginx01]# systemctl start keepalived
```
# 配置keepalived
主备区别在设置优先级
```bash
[root@nginx01]# cd /etc/keepalived
#备份keepalived配置文件
[root@nginx01 keepalived]# cp keepalived.conf keepalived.conf.bak
[root@nginx01 keepalived]# cat keepalived.conf
! Configuration File for keepalived
global_defs {
router_id nginx01
}
vrrp_script check_nginx { # 定义一个脚本
script "/etc/keepalived/check_nginx.sh" # 脚本路径
interval 2 # 探针,此处是每两秒执行一次脚本
fall 1 # 失败次数 1
}
vrrp_instance nginx { # 定义名为nginx实例
state MASTER # 主机状态
interface ens33 # 网卡名
mcast_src_ip 192.168.179.128 # 发组播
virtual_router_id 51 # 虚拟id
priority 100 # 优先级
advert_int 1 # 探针,一秒发一次组播
authentication {
auth_type PASS
auth_pass 1111 # 密码
}
track_script {
check_nginx
}
virtual_ipaddress { # 虚拟ip
192.168.179.200/24
}
}
```
备keepalived配置
```bash
[root@nginx02 keepalived]# cat keepalived.conf
! Configuration File for keepalived
global_defs {
router_id nginx02
}
vrrp_script check_nginx {
script "/etc/keepalived/check_nginx.sh"
interval 2
fall 1
}
vrrp_instance nginx {
state BACKUP
interface ens33
mcast_src_ip 192.168.179.129
virtual_router_id 51
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
check_nginx
}
virtual_ipaddress {
192.168.179.200/24
}
}
```
# 编写检查脚本
两台都操作
```bash
[root@nginx01]# cd /etc/keepalived
[root@nginx01 keepalived]# cat check_nginx.sh
#!/bin/bash
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
then
killall keepalived
fi
[root@nginx01 keepalived]# chmod 777 check_nginx.sh
```
启动nginx和keepalived
```bash
[root@nginx01 keepalived]# ps -ef|grep [n]ginx
root 11303 1 0 Sep18 ? 00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
nginx 11304 11303 0 Sep18 ? 00:00:00 nginx: worker process
[root@nginx01 keepalived]# ps -ef|grep [k]eepalived
root 11329 1 0 Sep18 ? 00:00:00 /usr/sbin/keepalived -D
root 11330 11329 0 Sep18 ? 00:00:00 /usr/sbin/keepalived -D
root 11331 11329 0 Sep18 ? 00:00:01 /usr/sbin/keepalived -D
```
测试
访问vip192.168.179.200正常
在nginx01上:
```bash
[root@nginx01 keepalived]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:17:3a:d8 brd ff:ff:ff:ff:ff:ff
inet 192.168.179.128/24 brd 192.168.179.255 scope global noprefixroute dynamic ens33
valid_lft 1486sec preferred_lft 1486sec
inet 192.168.179.200/24 scope global secondary ens33
valid_lft forever preferred_lft forever
inet6 fe80::8e71:7c12:c808:104d/64 scope link noprefixroute
valid_lft forever preferred_lft forever
```

```bash
[root@nginx01 keepalived]# Killall nginx
[root@nginx01 keepalived]# ps –ef|grep keepalived #发现keepalive也被杀掉
```
ip addr show ens33 nginx01释放掉VIP

访问vip192.168.179.200正常

只不过切到了备用keepalived服务器了,vip也漂移到nginx02

Nginx+Keepalived高可用