Nginx双机热备

Keepalived高可用概述

1.什么是高可用

什么是高可用双击热备, 一般指2台机器启动着相同的业务系统,当有一台机器down机了, 另外一台服务器能快速的接管, 对于访问的用户是无感知的。

2.高可用使用场景

那么高可用使用在什么场景，业务系统需要保证7x24小时不DOWN机, 作为业务来说随时都可用, 让你的业务系统更顽强。

Keepalived高可用安装

1.环境准备

服务器系统   角色  外网IP    内网IPCentOS 7.5  keepalived-master   eth0:10.0.0.5   eth1:172.16.1.5CentOS 7.5  keepalived-slave    eth0:10.0.0.6   eth1:172.16.1.6

2.在lb01与lb02上分别安装keepalived

[root@lb01 ~]# yum install keepalived -y[root@lb02 ~]# yum install keepalived -y

3.配置lb01, keepalived-master

[root@lb01 ~]# cat /etc/keepalived/keepalived.confglobal_defs {         router_id lb01   }vrrp_instance VI_1 {    state MASTER    interface eth0    virtual_router_id 50    priority 150    advert_int 1    authentication {        auth_type PASS        auth_pass 1111}    virtual_ipaddress {        10.0.0.3/24 dev eth0    }}

4.配置lb02, keepalived-backup

[root@lb02 ~]# cat /etc/keepalived/keepalived.confglobal_defs {    router_id lb02}vrrp_instance VI_1 {    state BACKUP    interface eth0    virtual_router_id 50    priority 100    advert_int 1    authentication {        auth_type PASS        auth_pass 1111    }    virtual_ipaddress {        10.0.0.3/24 dev eth0    }}

5.对比keepalived的master与backup配置的区别

Keepalived配置区别  Master配置    Backup节配置route_id(唯一标识)  route_id lb01   route_id lb02state(角色状态) state Master    state Backuppriority(竞选优先级) priority 150    priority 100

6.启动lb01与lb02的keepalived

#lb01[root@lb01 ~]# systemctl enable keepalived[root@lb01 ~]# systemctl start keepalived#lb02[root@lb02 ~]# systemctl enable keepalived[root@lb02 ~]# systemctl start keepalived

7.检查keepalived的虚拟IP地址是否漂移

# lb01存在vip地址[root@lb01 ~]# ip addr |grep 10.0.0.3    inet 10.0.0.3/24 scope global secondary eth0# 停止lb01上的keepalived, 检测vip已不存在[root@lb01 ~]# systemctl stop keepalived[root@lb01 ~]# ip addr |grep 10.0.0.3

在lb02上进行如下操作

[root@lb02 ~]# ip addr|grep 10.0.0.3    inet 10.0.0.3/24 scope global secondary eth0

lb01重新启动keepalived,发现地址被重新接管

[root@lb01 ~]# systemctl start keepalived[root@lb01 ~]# ip addr |grep 10.0.0.3    inet 10.0.0.3/24 scope global secondary eth0

Keepalived高可用配置

keepalived高可用列脑

由于某些原因，导致两台keepalived高可用服务器在指定时间内，无法检测到对方的心跳消息，各自取得资源及服务的所有权，而此时的两台高可用服务器又都还活着。服务器网线松动等网络故障服务器硬件故障发生损坏现象而崩溃主备都开启firewalld防火墙Nginx服务死掉等

1.在备上编写检测脚本, 测试如果能ping通主并且备节点还有VIP的话则认为产生了列脑

[root@lb02 ~]# cat check_split_brain.sh#!/bin/shlb01_vip=10.0.0.3lb01_ip=10.0.0.5while true;do    ping -c 2 -W 3 $lb01_ip &>/dev/null    if [ $? -eq 0 -a `ip add|grep "$lb01_vip"|wc -l` -eq 1 ];then        echo "ha is split brain.warning."    else        echo "ha is ok"    fisleep 5done

2.如果Nginx宕机, 会导致用户请求失败, 但Keepalived并不会进行切换, 所以需要编写一个脚本检测Nginx的存活状态, 如果不存活则kill nginx和keepalived

[root@lb01 ~]# mkdir /server/scripts[root@lb01 ~]# vim /server/scripts/check_web.sh#!/bin/sh#使用while死循环while true;donginxpid=$(ps -C nginx --no-header|wc -l)#1.判断Nginx是否存活,如果不存活则尝试启动Nginxif [ $nginxpid -eq 0 ];then    systemctl start nginx    sleep 5    #2.5秒后再次获取一次Nginx状态    nginxpid=$(ps -C nginx --no-header|wc -l)     #3.再次进行判断, 如Nginx还不存活则停止Keepalived,让地址进行漂移,并退出脚本      if [ $nginxpid -eq 0 ];then        systemctl stop keepalived        exit 1   fifi     sleep 5done[root@lb01 ~]# chmod +x /server/scripts/check_web.sh

在keepalived配置文件中调用此脚本，lb01与lb02都需操作

[root@lb01 ~]# cat /etc/keepalived/keepalived.confglobal_defs {         router_id LVS_01      }vrrp_script check_web {   script "/server/scripts/check_web.sh"   interval 2   weight 50}vrrp_instance VI_1 {    state MASTER    interface ens33    virtual_router_id 51    priority 150    advert_int 1    authentication {        auth_type PASS        auth_pass 1111    }    virtual_ipaddress {        10.0.0.3/24 dev ens33    }    track_script {        check_web    }}