双机热备并不是真正意义上的集群模式，但是相比于单机模式优势是可以实现高可用，在主机出现故障的状态下，可以快速的切换到备机，备机替代主机的工作，保证服务可用。这里主要介绍基于KeepAlive实现的双机热备（本质是一种负载均衡的软实现）同时做好监控报警，在自动故障转移的同时能通知到相关的应用负责人检查相关应用，排查隐患。
虚拟机Vmware workstation
CentOS-7-x86_64-Minimal-1804.iso 下载地址
主备节点
| 资源 | 节点 | IP | 备注 |
|---|---|---|---|
| CentOS 7 | node1 | 192.168.17.131 | 主机 |
| CentOS 7 | node2 | 192.168.17.132 | 备机 |
基本工具安装
yum install openssl-devel libnl3-devel ipset-devel iptables-devel libnfnetlink-devel wget lsof
安装JDK
yum install -y java-1.8.0-openjdk
下载tomcat
wget https://archive.apache.org/dist/tomcat/tomcat-8/v8.0.35/bin/apache-tomcat-8.0.35.tar.gz
拷贝到node2节点当前目录
scp apache-tomcat-8.0.35.tar.gz root@192.168.17.131:`pwd`
分别在node1，node2节点解压tomcat
tar -zxvf apache-tomcat-8.0.35.tar.gz
修改tomcat文件，文件路径/home/tomcat/apache-tomcat-8.0.35/webapps/ROOT
安装Nginx
添加yum源
sudo rpm -Uvh http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm
安装
yum install -y nginx
安装keepalive，两台节点都需要安装
yum install -y keepalived
虚拟IP / VIP 192.168.17.133
修改配置文件，vim /etc/keepalived/keepalived.conf
节点 node1 master
! Configuration File for keepalived
vrrp_script check_nginx_alive {
script "/etc/keepalived/check_nginx_alive.sh"
interval 2
weight -10
}
global_defs {
notification_email {
xiangxc@csizg.com
}
#notification_email_from Alexandre.Cassen@firewall.loc
#smtp_server 127.0.0.1
#smtp_connect_timeout 30
router_id LVS_DEVEL_31
#vrrp_skip_check_adv_addr
#vrrp_strict
#vrrp_garp_interval 0
#vrrp_gna_interval 0
}
vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_interface {
ens33
}
track_script {
check_nginx_alive
}
virtual_ipaddress {
192.168.17.133
}
}
virtual_server 192.168.17.133 80 {
delay_loop 6
lb_algo rr
lb_kind DR
nat_mask 255.255.255.0
#persistence_timeout 50
protocol TCP
real_server 192.168.17.131 80 {
weight 1
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
retry 3
delay_before_retry 3
connect_port 80
}
}
}
节点 node2 backup
! Configuration File for keepalived
vrrp_script check_nginx_alive {
script "/etc/keepalived/check_nginx_alive.sh"
interval 2
weight -10
}
global_defs {
notification_email {
xiangxc@csizg.com
}
#smtp_server 127.0.0.1
#smtp_connect_timeout 30
router_id LVS_DEVEL_32
#vrrp_skip_check_adv_addr
#vrrp_strict
#vrrp_garp_interval 0
#vrrp_gna_interval 0
}
vrrp_instance VI_1 {
state BACKUP
interface ens33
virtual_router_id 51
priority 50
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_interface {
ens33
}
virtual_ipaddress {
192.168.17.133
}
track_script {
check_nginx_alive
}
}
virtual_server 192.168.17.133 80 {
delay_loop 6
lb_algo rr
lb_kind DR
nat_mask 255.255.255.0
#persistence_timeout 50
protocol TCP
real_server 192.168.17.132 80 {
weight 1
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
retry 3
delay_before_retry 3
connect_port 80
}
}
}
配置脚本文件
编辑Nginx监控脚本
vim /etc/keepalived/check_nginx_alive.sh
脚本内容
#!/bin/bash
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
then
service keepalived stop
service nginx start
sleep 5
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" != "" ]
then
service keepalived start
fi
fi
授予执行权限
chmod +x /etc/keepalived/check_nginx_alive.sh
service nginx restart && service keepalived restart
节点2
虚拟ip
异常状况
关闭节点1的服务，关闭节点1的keepalived（此处可以利用脚本实现），访问虚拟主机，可以看到已经切换到备机
备机切换
服务恢复
恢复主机服务，恢复主机keepalive，可以看到主机上线。
Tomcat和Nginx实现主备同理。
keepalived+nginx（Tomcat）实现双机热备
原文：https://www.cnblogs.com/towards/p/15017279.html