原理简述

本篇主要学习
keepalived
配合
nginx
实现nginx的高可用, 也就是需要keepalived检测到nginx宕机时停用keepalived, 备用keepalived会自动接收过来.

简单的原理(如下图), 主备服务器会配置相同的vip(虚拟ip), 谁的优先级高谁来接收vip的请求, 然后nginx和keepalived部署在同一个服务器上面, keeplived控制机器接收到vip的请求, 交给了nginx来处理请求. nginx的功能主要是负责负载均衡, nginx的安装配置在此不再赘述, 可以参考这个:
ngix安装与使用

keepalived功能有很多, 此篇只是最简单的配合ngxin实现高可用的demo.

安装

  • 安装常用的的指令包:
    yum install -y curl gcc openssl-devel libnl3-devel net-snmp-devel

  • 安装:
    yum install -y keepalived

  • 启动:
    systemctl start keepalived

  • 重启:
    systemctl restart keepalived

  • 关闭:
    systemctl stop keepalived

  • 开机自启:
    systemctl enable keepalived

  • 修改配置文件:
    vim /etc/keepalived/keepalived.conf

    ! Configuration File for keepalived
    
    # 定义虚拟路由, 必须叫VI_1
    vrrp_instance VI_1 {
        state MASTER #设置为主服务器, 备份服务器设置为BACKUP
        interface enp0s3 #监控的网络接口(ifconfig或者ip addr指令找出网卡)
        priority 100 #(优先级, 主机大一点, 备份机小一点)
        virtual_router_id 99 #同一个vrrp_instance下routerId必须是一致的
    
        authentication {
            auth_type PASS #vrrp认证方式主备必须一致
            auth_pass 12345 #密码
        }
    
        virtual_ipaddress {
            192.168.0.99 #虚拟ip, 主从一致, 可配置多个
        }
    }
    
  • 另外一台机相同方法, 相同配置(state改成
    BACKUP
    , priority调整调一下, 此例中是80)

vrrp 的主从并不是通过stat配置的 MASTER BACKUP 决定的, 是通过优先级决定的

参考1:
Linux下Keepalived安装与配置

参考2:
Keepalived原理介绍和配置实践

参考3:
keepalived介绍、安装及配置详解

参考4:
https://codor.lanzoue.com/b012qnsvc
密码:1i77

检查是否脑裂

  • 使用
    tcpdump -i enp0s3 -nn host 224.0.0.18
    或者
    tcpdump -i enp0s3 | grep VRRP
    进行查看, 默认的广播通道为
    224.0.0.18
    (我把时间删除了, 内容是我改的)

    192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    192.168.0.117 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 80, authtype simple, intvl 1s, length 20
    192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    192.168.0.117 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 80, authtype simple, intvl 1s, length 20
    192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    192.168.0.117 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 80, authtype simple, intvl 1s, length 20
    
  • 如果结果如上, 说明出现了脑裂(主备都向外宣誓我是老大),

    出现这种情况的原因是防火墙或者iptables拦截了vrrp请求, 进行放行即可.

    防火墙(推荐):

    firewall-cmd --add-rich-rule='rule protocol value="vrrp" accept' --permanent
    firewall-cmd --reload
    

    iptables:

    iptables -A INPUT -s 192.168.1.0/24 -d 224.0.0.18 -j ACCEPT
    iptables -A INPUT -s 192.168.1.0/24 -p vrrp -j ACCEPT
    

    不存在可以进行安装,
    yum install iptables-services


  • 最后附上正常运行结果, 即只有100或者80优先级的机器来广播自己是老大

    09:26:55.782258 IP 192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    09:26:56.782910 IP 192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    09:26:57.783787 IP 192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    09:26:58.784709 IP 192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    09:26:59.784792 IP 192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    09:27:00.785171 IP 192.168.0.666666 > 224.0.0.18: VRRPv2, Advertisement, vrid 99, prio 100, authtype simple, intvl 1s, length 20
    

测试ip漂移

ip漂移
: 就是主备切换过程成, vip漂到真实ip上的过程. 也称为
主备切换
.

测试过程就是停用master机器上面的keepalived或者关机master机器, 查看backup机器是否正常接过来, 一般1s左右可以切换过去. 当出现脑裂情况的时候切换过程也能实现, 只是很慢大约7s左右. 具体原因未深究.

漂移过程可以通过抓包实现, 也可以通过两给ngxin转发到不同tomcat中的项目或网页, 或者修改ngxin的默认网页进行测试都可.

至此位置简单使用就完成了, 下面介绍几个功能配置

VRRP脚本

  • 签到keepalived的配置文件夹:
    cd /etc/keepalived/

  • 创建一个脚本文件:
    vim nginx_check.sh

    #!/bin/bash
    count=`ps -C nginx --no-header |wc -l`
    if [ $count -eq 0 ];then
    		killall keepalived
    fi
    
  • 赋予执行权限:
    chmode +x nginx_check.sh

  • 引入脚本:
    vim keepalived.conf


    vrrp_instance
    同级, 其中


    • chk_nginx
      : 脚本名称, 自定义的

    • script
      : 脚本位置

    • interval
      : 执行间隔

    • weight
      : 权重, 如果是负数, 当执行失败时候会影响vrrp_instance中的优先级priority, 因为主备切换是通过优先级的高低的进行切换的, 所以也可以通过这个优先级来进行主动控制主备切换. 而脚本中的内容可以很灵活地实现很多功能. 此个demo中只是简单实现检测到ngxin关闭后自动关闭keepalived, 也可以实现检测启动后进行开启, 然后延迟2s后查看是否启动成功, 未成功再进行关闭keepalived或者降低优先级(配合右键通知).

      vrrp_script chk_nginx {
      	script "/etc/keepalived/nginx_check.sh"
      	interval 2
      	#weight -30
      }
      
  • 配置到vrrp_instance中, 与authentication和virtual_ipaddress同级

    track_script {
    	chk_nginx
    }
    
  • 修改后的配置文件

    ! Configuration File for keepalived
    
    vrrp_script chk_nginx {
        script "/etc/keepalived/nginx_check.sh"
        interval 2
        #weight -30
    }
    
    vrrp_instance VI_1 {
        state MASTER
        interface enp0s3
        priority 100
        advert_int 1
        virtual_router_id 99
        authentication {
            auth_type PASS
            auth_pass 221531
        }
    
        track_script {
            chk_nginx
        }
    
        virtual_ipaddress {
            192.168.0.99
        }
    }
    
  • 测试

    正常启动时候, 手动关闭nginx, 查看keepalived的状态.

  • 参考:


邮件配置

邮件功能是linux上面的
mail
指令.

  • 安装
    mail
    :
    yum -y install mailx

  • 编辑配置文件(设置发送人信息):
    vim /etc/mail.rc
    , 在末尾处添加

    set from=xxx@163.com
    set smtp=smtp.163.com
    set smtp-auth-user=xxx@qq.com
    set smtp-auth-password=KJFHTOSXZQPNFAIU  #邮箱需要开启POP3/SMTP服务并设置密钥
    set smtp-auth=login
    set ssl-verify=ignore
    
  • 测试mail功能:
    echo test mail | mail -s testa 收件人id@qq.com


    • -s
      后面是主题的意思

    • echo test maill
      中的test mail 是邮件正文.

    • 最后跟着收件人

  • 配置到keepalived中, 方法1


    • 创建脚本
      vim mail_send.sh
      (记得赋予执行权限)

      可以使用
      ./mail_send.sh master
      进行测试

      #!/bin/bash
      contact='收件人邮箱@qq.com'
      notify() {
        	  mailsubject="$(hostname) to be $1, vip  转移"
        	  mailbody="$(date +'%F %T'): vrrp transition, $(hostname) changed to be $1"
        	  echo "$mailbody" | mail -s "$mailsubject" $contact
      }
      case $1 in
        	  master)
        			  notify master
        			  ;;
        	  backup)
        			  notify backup
        			  ;;
        	  fault)
        			  notify fault
        			  ;;
        	  *)
        			  echo "Usage: $(basename $0) {master|backup|fault}"
        			  exit 1
        			  ;;
      esac
      
    • 修改配置文件:
      vim keepalived.conf

      vrrp_instance下与authentication同级处

      notify_master "/etc/keepalived/mail_send.sh master"
      notify_backup "/etc/keepalived/mail_send.sh backup"
      notify_fault "/etc/keepalived/mail_send.sh fault"
      
    • 整体配置文件

      ! Configuration File for keepalived
      
      vrrp_script chk_nginx {
          script "/etc/keepalived/nginx_check.sh"
          interval 2
          #weight -30
      }
      
      vrrp_instance VI_1 {
          state MASTER
          interface enp0s3
          priority 100
          advert_int 1
          virtual_router_id 99
          # 当进入master/backup/fault状态时触发脚本, 可携带参数
          notify_master "/etc/keepalived/mail_send.sh master"
          notify_backup "/etc/keepalived/mail_send.sh backup"
          notify_fault "/etc/keepalived/mail_send.sh fault"
          authentication {
              auth_type PASS
              auth_pass 221531
          }
      
          track_script {
              chk_nginx
          }
      
          virtual_ipaddress {
              192.168.0.99
          }
      }
      
  • 配置到keepalived中, 方法2


    • 脚本内容, 下面这个是漂移到master时, 另外创建backup和fault

      #!/bin/bash
      contacts='收件人邮箱1, 收件人邮箱2'
      ip a > ipa_temp.txt
      
      echo "$(date +'%F %T'): Keepalived instance I became MASTER on $(hostname).    --- from master" | mail -s "Master Keepalived notification" -a ipa_temp.txt "$contacts"
      
    • 修改配置文件:
      vim keepalived.conf

      vrrp_instance下与authentication同级处, 后面的
      root
      是执行人和所在组

      notify_master /etc/keepalived/mail_send_master.sh root root
      notify_backup /etc/keepalived/mail_send_backup.sh root root
      notify_fault /etc/keepalived/mail_send_fault.sh root root
      
  • 测试状态转移时有没有邮箱接收到即可, 通过重启, 停用

  • 参考:



学习链接

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