高可用集群HA、LVS+Keepalived、健康检测

keepalived是集群管理中保证集群高可用(HA)的一个服务软件，其功能类似于heartbeat，用来防止单点故障。

2.工作原理

keepalived是以VRRP协议为实现基础的,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。这样我们就可以保证集群的高可用

keepalived主要有三个模块，分别是core、check和vrrp。core模块为keepalived的核心，负责主进程的启动、维护以及全局配置文件的加载和解析。check负责健康检查，包括常见的各种检查方式。vrrp模块是来实现VRRP协议的

如何判断谁是master：看vip，vip在谁上谁就是master

什么是脑裂

脑裂（split-brain）：指在一个高可用（HA）系统中，当联系着的两个节点断开联系时，本来为一个整体的系统，分裂为两个独立节点，这时两个节点开始争抢共享资源，结果会导致系统混乱，数据损坏

脑裂：backup强资源，master不认为自己会死，他俩抢着为客户端服务

解决方案：爆头 master

二：LVS+Keepalived

web-1

加载缓存

yum -y install httpd //安装阿帕奇

systemctl start httpd

切换到默认发布目录：cd /var/www/html/

写内容 echo

systemctl enable httpd

web-2

加载缓存

yum -y install httpd

systemctl enable httpd

2台负载均衡服务器

Nginx-Master（默认master对外提供服务）

仓库文件

yum -y install nginx

systemctl start nginx

systemctl enable nginx

创建池子

调用地址池

nginx -t 检查语法错误

nginx -s reload

安装keepalived软件

yum -y install keepalived

加配置文件

! Configuration File for keepalived

global_defs {
router_id director1
}

vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 80
priority 100 // master优先级
advert_int 1 //每隔一秒检查一次
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress { //VIP
10.0.0.110/24 //注意与IP为同一个网段
}
}

systemctl start keepalived

systemctl enable keepalived

Nginx-Backup

vi /etc/yum.repos.d/nginx.repo

yum -y install keepalived

! Configuration File for keepalived

global_defs {
router_id director2
}

vrrp_instance VI_1 {
state BACKUP
interface ens33
virtual_router_id 80
priority 60
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.142.110/24
}
}

systemctl start keepalived

systemctl enable keepalived

测试：

负载均衡出现问题，keepalived正常

解决问题：keepalived停止，在keepalived做健康检测

健康检测

Nginx-Master

systemctl stop nginx

#!/bin/bash
#+检查nginx进程是否存在 ps查看进程
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}" = "0" ]; then
systemctl stop keepalived
fi

vi keepalived.conf

systemctl restart keepalived

Nginx-Backup

测试：

可以访问

二：LVS+Keepalived

给2lvs做高可用

web-1、web-2环境同上

测试是否可以用

web-1

在回环接口lo绑定VIP

永久开始忽略arp广播（前两条）and永久开始路由转发（最后一条）

web-2

在回环接口lo绑定VIP

永久开始忽略arp广播（前两条）and永久开始路由转发（最后一条）

实现负载均衡

设置VIP10.9.12.110

生成配置文件

创建ipvsadm的文件用来存放lvs的规则

添加规则

访问测试

lvs高可用部署

! Configuration File for keepalived

global_defs {
router_id lvs-keepalived-master
}

vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 80
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.142.110/24
}
}

virtual_server 192.168.142.110 80 {
   delay_loop 3
   lb_algo rr
   lb_kind DR
   nat_mask 255.255.255.0
   protocol TCP
   real_server 192.168.142.145 80 {
       weight 1
       inhibit_on_failure
       TCP_CHECK {
           connect_port 80
           connect_timeout 3
           }
       }
   real_server 192.168.142.149 80 {
       weight 1
       inhibit_on_failure
       TCP_CHECK {
           connect_timeout 3
           connect_port 80
           }
       }
}

nginx-backup

lvs高可用部署

! Configuration File for keepalived

global_defs {
router_id lvs-keepalived-backup
}

vrrp_instance VI_1 {
state BACKUP
interface ens33
nopreempt #不抢占资源
virtual_router_id 80
priority 50
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.142.110/24
}
}
virtual_server 192.168.142.110 80 {
   delay_loop 3
   lb_algo rr
   lb_kind DR
   nat_mask 255.255.255.0
   persistence_timeout 20
   protocol TCP
   real_server 192.168.142.145 80 {
       weight 1
       inhibit_on_failure
       TCP_CHECK {
           connect_port 80
           connect_timeout 3
           }
       }
   real_server 192.168.142.149 80 {
       weight 1
       inhibit_on_failure
       TCP_CHECK {
           connect_timeout 3
           connect_port 80
           }
       }
}