1. 概念
keepalived是什么
keepalived是集群管理中保证集群高可用的一个服务软件，用来防止单点故障。
keepalived工作原理
keepalived是以VRRP协议为实现基础的，VRRP全称Virtual Router Redundancy Protocol，即虚拟路由冗余协议。
虚拟路由冗余协议，可以认为是实现路由器高可用的协议，即将N台提供相同功能的路由器组成一个路由器组，这个组里面有一个master和多个backup，master上面有一个对外提供服务的vip（该路由器所在局域网内其他机器的默认路由为该vip），master会发组播，当backup收不到vrrp包时就认为master宕掉了，这时就需要根据VRRP的优先级来选举一个backup当master。这样的话就可以保证路由器的高可用了。
2、Nginx+keepalived实现七层的负载均衡
Nginx通过Upstream模块实现负载均衡
| 主机名 | ip | 系统 | 用途 |
|---|---|---|---|
| Proxy-master | 172.16.147.155 | centos7.5 | 主负载 |
| Proxy-slave | 172.16.147.156 | centos7.5 | 主备 |
| Real-server1 | 172.16.147.153 | Centos7.5 | web1 |
| Real-server2 | 172.16.147.154 | centos7.5 | Web2 |
| Vip for proxy | 172.16.147.100 |
一、实施过程
1、选择两台nginx服务器作为代理服务器。
2、给两台代理服务器安装keepalived制作高可用生成VIP
3、配置nginx的负载均衡
# 两台配置完全一样
[root@proxy-master ~]# vim /etc/nginx/nginx.conf
user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;
include /usr/share/nginx/modules/*.conf;
events {
worker_connections 1024;
}
http {
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
include /etc/nginx/mime.types;
default_type application/octet-stream;
include /etc/nginx/conf.d/*.conf;
upstream backend {
server 172.16.147.154:80 weight=1 max_fails=3 fail_timeout=20s;
server 172.16.147.153:80 weight=1 max_fails=3 fail_timeout=20s;
}
server {
listen 80;
server_name localhost;
location / {
proxy_pass http://backend;
proxy_set_header Host $host:$proxy_port;
proxy_set_header X-Forwarded-For $remote_addr;
}
}
}Keepalived实现调度器HA
1. 主/备调度器安装软件
[root@proxy-master ~]# yum install -y keepalived
[root@proxy-slave ~]# yum install -y keepalived
[root@proxy-master ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@proxy-master ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id directory1 #辅助改为directory2
}
vrrp_instance VI_1 {
state MASTER #定义主还是备
interface ens33 #VIP绑定接口
virtual_router_id 80 #整个集群的调度器一致
priority 100 #back改为50
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.16.147.100/24 # vip
}
}备用机器也添加配置文件
[root@proxy-slave ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@proxy-slave ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
router_id directory2
}
vrrp_instance VI_1 {
state BACKUP #设置为backup
interface ens33
nopreempt #设置到back上面，不抢占资源
virtual_router_id 80
priority 50 #辅助改为50
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.16.147.100/24
}
}启动keepalived 主备都启动
[root@proxy-master ~]# systemctl enable keepalived
[root@proxy-slave ~]# systemctl start keepalived
[root@proxy-master ~]# ip a
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
inet 172.16.147.100/32 scope global 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:ec:8a:fe brd ff:ff:ff:ff:ff:ff
inet 172.16.147.155/24 brd 172.16.147.255 scope global noprefixroute dynamic ens33
valid_lft 1115sec preferred_lft 1115sec
inet 172.16.147.101/24 scope global secondary ens33
valid_lft forever preferred_lft forever现在就实现了两台机器的高可用，两台高可用的机器都作为另外两台nginx服务器的负载均衡器，一台机器down掉了，会自动漂移到另一台备用机器上继续访问