双机热备

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。

服务器准备

• 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

环境准备

• 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

  • 将node1中ROOT项目index.jsp添加标签

    node1

  • 将node1中ROOT项目index.jsp添加标签

    node2

• 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
  

配置keepalived

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
  

启动服务

service nginx restart && service keepalived restart

服务验证

• 正常状况
  节点1

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