keepalived+nginx实现高可用

搭建说明

1. 服务器：192.168.117.97、192.168.117.98、192.168.117.99
2. VIP：192.168.117.100

搭建Nginx环境

1. 下载安装包：https://pan.baidu.com/s/1eAJHe0c_jvcwvjhRzgdlsw，密码：x4jo
2. 解压安装包：tar -xf /opt/module/nginx-1.19.4.tar.gz && rm -rf /opt/module/nginx-1.19.4.tar.gz
3. 检查openssl-devel：yum list installed openssl-devel，如果没有需要先安装：yum -y install openssl openssl-devel
4. 编译安装：cd /opt/module/nginx-1.19.4 && ./configure && make && make install
5. 创建软连接：ln -s /usr/local/nginx /opt/module/nginx
6. 启动Nginx：/opt/module/nginx/sbin/nginx
7. 查看是否启动成功：ps -ef | grep nginx

Keepalived实现高可用

1. keepalived安装：yum install keepalived -y

2. killall命令：用于杀死一个进程，包括其子进程，如果命令未找到，则需要下载：yum install psmisc

3. 添加Nginx检查脚本：vi /etc/keepalived/check_nginx.sh，查看nginx是否启动，如果没启动则先杀掉nginx所有进程，然后启动，如果启动不起来，停掉keepalived服务，此时心跳断掉，VIP进行转移。

   #!/bin/bash
   counter=$(ps -C nginx --no-heading|wc -l)
   if [ "${counter}" != "2" ]; then
       killall nginx
       sleep 0.5
       /opt/module/nginx/sbin/nginx
       sleep 2
       counter=$(ps -C nginx --no-heading|wc -l)
       if [ "${counter}" != "2" ]; then
           service keepalived stop
       fi
   fi
   

4. 给脚本添加执行权限：chmod +x /etc/keepalived/check_nginx.sh

5. 配置keepalived：vi /etc/keepalived/keepalived.conf

   ! Configuration File for keepalived
   global_defs {
      router_id LVS_NGINX
   }
   
   vrrp_script check_nginx {
     script "/etc/keepalived/check_nginx.sh"          #表示将一个脚本信息赋值给变量check_web
     interval 5                                     #执行监控脚本的间隔时间
     weight 2                                       #利用权重值和优先级进行运算，从而降低主服务优先级使之变为备服务器（建议先忽略）
   }
   
   vrrp_instance VI_1 {
       state MASTER         # 备机选BACKUP
       #nopreempt            # 配置不竞争，旧主来了，VIP不会离开飘走
       interface eth0      # 表示keepalived家族表示信息
       virtual_router_id 51
       priority 100        # 后面备机需要依次往下减
       advert_int 1          # 主服务器组播包发送间隔时间
       authentication {
           auth_type PASS
           auth_pass 1111
       }
       virtual_ipaddress {
           192.168.117.100/24 dev eth0 label eth0:2
       }
       track_script {
          check_nginx        #调用执行脚本
       }
   }
   

6. 启动keepalived：service keepalived start

7. 查看keepalived状态：service keepalived status

8. 查看VIP挂载情况：ip addr

9. 如果nginx想要使用VIP，因为备机是没有VIP的，所有Nginx无法监听，此时则需要修改内核文件

   • 实现监听本地不存在的ip地址：echo 'net.ipv4.ip_nonlocal_bind = 1' >>/etc/sysctl.conf
   • sysctl -p
   • echo "1" >/proc/sys/net/ipv4/ip_nonlocal_bind

实验测试

1. 调整nginx首页，便于观察VIP的移动路径，vi /opt/module/nginx/html/index.html

   <h1>Welcome to nginx!(192.168.117.94)h1>
   

2. 网页访问VIP：http://192.168.117.100/

3. 主节点关闭nginx：killall nginx，然后刷新网页，预期VIP不漂移，因为keepalived重启nginx成功了

4. 主节点重启keepalived：service keepalived restart，预期VIP会漂移

5. 主节点模拟nginx损坏，启动不成功，预计会漂移

   • 模拟nginx损坏：mv /opt/module/nginx/conf/nginx.conf /opt/module/nginx/conf/nginx.conf-back
   • 关闭nginx：killall nginx
   • 刷新网页，查看VIP是否漂移
   • 恢复nginx：mv /opt/module/nginx/conf/nginx.conf-back /opt/module/nginx/conf/nginx.conf
   • 重启keepalived：service keepalived restart
   • 查看nginx是否自动启动：ps -ef | grep nginx