keepalived结合nginx状态检测脚本实现对web服务器集群的高可用

两台CentOS-7.5虚拟机
web1：10.0.11.203
web2：10.0.11.204
VIP ：10.0.11.210
web类型：nginx
客户端：自用笔记本(win10)
nginx状态检测脚本：ck_nginx.sh

实验一、使用keepalived简单实现web集群的高可用功能

1、准备两台web服务器

1）web1网卡情况
[ ~]#
[ ~]# ip a

2）web2网卡情况
[ ~]#
[ ~]# ip a

3）安装nginx

web1端：
[ ~]#
[ ~]# yum install nginx
[ ~]# rpm -qa nginx
nginx-1.16.1-1.el7.x86_64
[ ~]#
[ ~]#
[ ~]# > /usr/share/nginx/html/index.html #清空默认网页
[ ~]# echo web1 > /usr/share/nginx/html/index.html #让网页显示web1
[ ~]# cat /usr/share/nginx/html/index.html
web1
[ ~]#
[ ~]# systemctl start nginx #启动nginx
[ ~]# systemctl enable nginx #设置nginx开机自启动
C:\Users\Administrator>curl 10.0.11.203

web2端：
[ ~]#
[ ~]# yum install nginx
[ ~]# rpm -qa nginx
nginx-1.16.1-1.el7.x86_64
[ ~]#
[ ~]#
[ ~]# > /usr/share/nginx/html/index.html
[ ~]# echo web2 > /usr/share/nginx/html/index.html
[ ~]# cat /usr/share/nginx/html/index.html
web2
[ ~]#
[ ~]# systemctl start nginx
[ ~]# systemctl enable nginx
C:\Users\Administrator>curl 10.0.11.204

4）安装keepalived
说明：两台web服务器都需要安装keepalived服务

web1端：
[ ~]#
[ ~]# yum install keepalived
[ ~]# rpm -qa keepalived
keepalived-1.3.5-16.el7.x86_64
[ ~]#

web2端：
[ ~]#
[ ~]# yum install keepalived
[ ~]# rpm -qa keepalived
keepalived-1.3.5-16.el7.x86_64
[ ~]#

5）配置两台keepalived并启动

web1端：
[ ~]#
[ ~]# > /etc/keepalived/keepalived.conf #清空原来的配置
[ ~]# vim /etc/keepalived/keepalived.conf #编辑配置文件，自定义keepalived配置文件
[ ~]# cat /etc/keepalived/keepalived.conf

[ ~]#
[ ~]# systemctl start keepalived #启动
[ ~]# systemctl enable keepalived #设置开机启动

web2端：
[ ~]#
[ ~]# > /etc/keepalived/keepalived.conf
[ ~]# vim /etc/keepalived/keepalived.conf
[ ~]# cat /etc/keepalived/keepalived.conf

[ ~]#
[ ~]# systemctl start keepalived #启动
[ ~]# systemctl enable keepalived #设置开机启动

3、测试访问
方法：用客户端通过VIP测试访问web

C:\Users\Administrator>curl 10.0.11.210 #个人笔记本通过VIP测试访问web

拔掉web1服务器的网线，用客户端通过VIP测试访问web：
C:\Users\Administrator>curl 10.0.11.210

再次将web1服务器的网线接好，用客户端通过VIP测试访问web：
C:\Users\Administrator>curl 10.0.11.210

4、实验一结论：
1）利用keepalived成功实现了web服务器集群的高可用
2）虽然可以实现在服务器发生异常高故障的情况下web的高可用，但是遗憾的是此时无法实现针对web服务异常故障所引发的主备高可用切换；因为keepalived无法感知nginx服务的运行状态和健康状态。

实验二、使用keepalived结合nginx监控检测脚本实现更加灵活的高可用集群功能

实验环境：基于实验一的环境，以实验一的环境为基础进行
与实验一的唯一区别：需要准备nginx的健康状态检测脚本

1、编写nginx的健康检测脚本

web1端执行：
[ ~]#
[ ~]# vim /etc/keepalived/ck_nginx.sh #编写keepalived检测nginx健康状态的脚本

#!/bin/bash
#检查ngin进程是否存在
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}"="0" ]; then
#尝试启动一次ngnx,停止5秒后再次检测
systemctl start nginx
sleep 5
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}"="0" ]; then
#如果启动没成功,就杀掉keepave触发主备切换
systemctl stop nginx
fi
fi
[ ~]#
[ ~]# cat /etc/keepalived/ck_nginx.sh #查看脚本内容

[ ~]#
[ ~]# chmod +x /etc/keepalived/ck_nginx.sh #授予脚本可执行权限
[ ~]#

web2端执行：
[ ~]#
[ ~]# vim /etc/keepalived/ck_nginx.sh

#!/bin/bash
#检查ngin进程是否存在
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}"="0" ]; then
#尝试启动一次ngnx,停止5秒后再次检测
systemctl start nginx
sleep 5
counter=$(ps -C nginx --no-heading|wc -l)
if [ "${counter}"="0" ]; then
#如果启动没成功,就杀掉keepave触发主备切换
systemctl stop nginx
fi
fi

[ ~]#
[ ~]#
[ ~]# cat /etc/keepalived/ck_nginx.sh

[ ~]#
[ ~]# chmod +x /etc/keepalived/ck_nginx.sh
[ ~]#

2、编辑修改nginx的配置文件
web1端：
[ ~]#
[ ~]# vim /etc/keepalived/keepalived.conf #自定义配置文件

! Configuration File for keepalived

global_defs {
notification_email {

vrrp_script chk_nginx {
script "/etc/keepalived/ck_nginx.sh"
interval 2
weight -5
fail 3
}

vrrp_instance VI_1 {
state MASTER
interface ens32
mcast_src_ip 10.0.11.203
virtual_router_id 55
priority 100
advert_int 1

authentication {
auth_type PASS
auth_pass 123456
}

virtual_ipaddress {
    10.0.11.210/24
}

track_script {
     chk_nginx
}

}

[[email protected] ~]#
[[email protected] ~]# systemctl restart keepalived #重启keepalived使配置生效
[[email protected] ~]#

web2端：
[[email protected] ~]#
[[email protected] ~]# vim /etc/keepalived/keepalived.conf #自定义配置文件

! Configuration File for keepalived

global_defs {
notification_email {

vrrp_script chk_nginx {
script "/etc/keepalived/ck_nginx.sh"
interval 2
weight -5
fail 3
}

vrrp_instance VI_1 {
state MASTER
interface ens32
mcast_src_ip 10.0.11.204
virtual_router_id 55
priority 95
advert_int 1

authentication {
auth_type PASS
auth_pass 123456
}

virtual_ipaddress {
    10.0.11.210/24
}

track_script {
     chk_nginx
}

}

[[email protected] ~]#
[[email protected] ~]#
[[email protected] ~]# systemctl restart keepalived #重启keepalived使配置生效

测试keepalived功能：
由于脚本内容里边，nginx服务在停止以后会立马自启动，所以我们模拟服务器异常关闭导致nginx服务没有办法实现自启动
[[email protected] ~]#
[[email protected] ~]# init 0 #关闭web1服务器

[[email protected] ~]#
[[email protected] ~]# ping 10.0.11.203 #用web2去pingweb1，发现web1已经被关闭

此时使用客户端去测试验证keepalived功能：
C:\Users\Administrator>curl 10.0.11.210 #用客户端通过VIP去访问web服务器

3、实验二结论
使用keepalived服务结合nginx健康状态检测脚本成功实现了对web服务器集群的高可用