Linux keepalive部署HA高可用环境

一. 高可用环境部署思路

配置两台Apache环境的服务器，提供相同的web页面服务，在这两台Apache服务器上运行keepalive，虚拟出来一个VIP，用户通过VIP访问web服务，这样当一台Apache服务器故障的时候，VIP会飘到另外一台Apache服务器。

二. keepalive部署前准备

1. 安装开发环境

[root@study01 ~]# yum -y install gcc-* glibc-*  *c++* -y 
[root@study01 ~]# yum -y install openssl-devel

[root@study02 ~]# yum -y install gcc-* glibc-*  *c++* -y 
[root@study02 ~]# yum -y install openssl-devel

  [root@study01 ~]# uname -a
  Linux study01.linux.com 2.6.32-754.el6.x86_64 #1 SMP Tue Jun 19 21:26:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
  [root@study01 ~]# cat /etc/redhat-release
  CentOS release 6.10 (Final)

提示：以上是我的server缺少的环境，如果你在以上环境安装完成后，再安装keepalive时还有报错，请根据报错进行环境补充安装；

2. 部署Apache基本环境

[root@study01 ~]#/etc/init.d/httpd restart
[root@study01 ~]#chkconfig --level 35 httpd on
[root@study01 ~]#echo "this is linux01" > /var/www/html/index.html

[root@study02 ~]#/etc/init.d/httpd restart
[root@study02 ~]#chkconfig --level 35 httpd on
[root@study02 ~]#echo "this is linux02" > /var/www/html/index.html

三. keepalive环境部署

1. 获取keepalive的安装链接

从官网https://www.keepalived.org/download.html页面获取。

2. 使用源码部署keepalive

[root@study01 ~]# cd /usr/local/src/
[root@study01 src]#wget https://www.keepalived.org/software/keepalived-2.0.20.tar.gz
[root@study01 src]#tar -zxvf keepalived-2.0.20.tar.gz
[root@study01 src]#cd keepalived-2.0.20
[root@study01 src]#./configure --prefix=/usr/local/keepalived
[root@study01 src]#make && make install
[root@study01 src]#cp /usr/local/src/keepalived-2.0.20/keepalived/etc/init.d/keepalived /etc/init.d/
[root@study01 src]#chmod 755 /etc/init.d/keepalived
[root@study01 src]#cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
[root@study01 src]#chmod 755 /usr/sbin/keepalived
[root@study01 src]#cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
[root@study01 src]#mkdir /etc/keepalived
[root@study01 src]#cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/

提示：第二台linux服务器的keepalive环境部署方法请重复第一台的部署方法。

3. 配置keepalive

[root@study01 ~]# vim /etc/keepalived/keepalived.conf
#以下为第一台环境的keepalive配置内容
! Configuration File for keepalived

global_defs {
   notification_email {
     wang_zengyi@126.com    #接收告警的邮箱
   }                                     #注意需要单独配置smtp_send邮箱
   notification_email_from 647956023@qq.com  #发送告警的邮箱
   smtp_server 182.254.38.18   #发送邮件的服务器地址
   smtp_connect_timeout 30
   router_id study01
}

vrrp_script check_httpd {
    script "/usr/bin/killall -0 httpd"   #检测http服务是否正常
    interval 2
}

vrrp_instance VI_1 {
    state MASTER         #状态为主，默认抢占
    interface eth0         #监听的服务接口
    virtual_router_id 51   #主备必须一致，VRRPID
    priority 100          #优先级，越大越优先
    advert_int 1       #心跳报文通告间隔
    authentication {
        auth_type PASS    #keepalive认证类型
        auth_pass 1111    #keepalive认证密码
    }
    notify_master "/etc/keepalived/master.sh"   #主状态通告脚本
    notify_backup "/etc/keepalived/backup.sh"   #备状态通告脚本
    notify_fault "/etc/keepalived/fault.sh"          #故障状态通过脚本

    track_script {
    check_httpd                 #track http的检测脚本
    }

    virtual_ipaddress {
　　　　　192.168.31.9                            #虚拟IP的写法一，不推荐这种写法。只能用ip add看
        192.168.31.10/24 dev eth0 label eth0:0   #虚拟IP的写法一，推荐这种写法。
    }
}    

#以下脚本内容为测试看状态的简单编写方法，实际环境请根据需要编写；
[root@study01 ~]# cat /etc/keepalived/master.sh
#!/bin/bash
LOGFILE=/var/log/keepalived-state.log
echo "[Master]" >> $LOGFILE
date >> $LOGFILE
[root@study01 ~]# cat /etc/keepalived/backup.sh
#!/bin/bash
LOGFILE=/var/log/keepalived-state.log
echo "[Backup]" >> $LOGFILE
date >> $LOGFILE
[root@study01 ~]# cat /etc/keepalived/fault.sh
#!/bin/bash
LOGFILE=/var/log/keepalived-state.log
echo "[Fault]" >> $LOGFILE
date >> $LOGFILE
[root@study01 ~]#

提示：第二台keepalive配置方法同第一台一样，注意角色定义为BACKUP，优先级要低于角色Master的优先级；

vi /etc/keepalived/keepalived.conf    # 参照下面配置修改配置文件

! Configuration File for keepalived

global_defs {
    notification_email {
        wangbiao@youxuanbao.cn    # 设置报警邮件地址，可以设置多个，每行一个
    }
    # 需开启本机的sendmail服务
    notification_email_from Alexandre.Cassen@firewall.loc    # 设置邮件的发送地址
    smtp_server 127.0.0.1    # 设置smtp server地址
    smtp_connect_timeout 30    # 设置连接smtp server的超时时间
    router_id LVS_DEVEL    # 表示运行keepalived服务器的一个标识。发邮件时显示在邮件主题的信息
    vrrp_skip_check_adv_addr
    vrrp_strict
    vrrp_garp_interval 0
    vrrp_gna_interval 0
}

vrrp_instance VI_1 { # 定义的VRRP热备实例
    state MASTER    # 标示状态为MASTER 备份机为BACKUP
    interface eth0     # 承载VIP地址的物理接口
    virtual_router_id 51    # 虚拟路由器的id号，每个热备组保持一致
    priority 100    # MASTER权重要高于BACKUP 比如BACKUP为99
    advert_int 1    # 通告间隔秒数，（心跳频率）  注意通告的组播地址224.0.0.18
    # mcast_src_ip 172.16.1.99    # Master服务器IP，如果是备份机请填写备份机的IP

    authentication {
        auth_type PASS    # 主从服务器认证类型
        auth_pass 1111    # 认证字串
    }
    virtual_ipaddress {
        172.16.1.100    # 可以多个虚拟IP，换行即可
    }

    # 虚拟服务器 80端口的配置
    virtual_server 172.16.1.100 80 {
        delay_loop 6    # 每隔6秒查询realserver状态
        lb_algo rr    # lvs 算法
        lb_kind DR    # Direct Route
        nat_mask 255.255.255.0
        persistence_timeout 50    # 同一IP的连接50秒内被分配到同一台realserver
        protocol TCP    # 用TCP协议检查realserver状态

        # 实际服务器的IP和端口
        real_server 172.16.1.101 80 {
            weight 3
            TCP_CHECK {
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
            }
        }

        real_server 172.16.1.102 80 {
            weight 3
            TCP_CHECK {
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
            }
        }
    }
}

4. 启动keepalive服务

[root@study01 ~]#chkconfig --level 35 keepalived on
[root@study01 ~]#/etc/init.d/keepalived restart
[root@study02 ~]#chkconfig --level 35 keepalived on
[root@study02 ~]#/etc/init.d/keepalived restart

Mar 15 17:26:35 study01 Keepalived[8582]: Starting Keepalived v2.0.20 (01/22,2020)
Mar 15 17:26:35 study01 Keepalived[8582]: Running on Linux 2.6.32-754.el6.x86_64 #1 SMP Tue Jun 19 21:26:04 UTC 2018 (built for Linux 2.6.32)
Mar 15 17:26:35 study01 Keepalived[8582]: Command line: 'keepalived' '-D'
Mar 15 17:26:35 study01 Keepalived[8582]: Opening file '/etc/keepalived/keepalived.conf'.
Mar 15 17:26:35 study01 Keepalived[8583]: Starting VRRP child process, pid=8585
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: Registering Kernel netlink reflector
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: Registering Kernel netlink command channel
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: Opening file '/etc/keepalived/keepalived.conf'.
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: WARNING - default user 'keepalived_script' for script execution does not exist - please create.
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: SECURITY VIOLATION - scripts are being executed but script_security not enabled.
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: Assigned address 192.168.31.5 for interface eth0
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: Assigned address fe80::a00:27ff:fe8c:afb for interface eth0
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: Registering gratuitous ARP shared channel
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: (VI_1) removing VIPs.
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: VRRP sockpool: [ifindex(2), family(IPv4), proto(112), unicast(0), fd(11,12)]
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: VRRP_Script(check_httpd) succeeded
Mar 15 17:26:35 study01 Keepalived_vrrp[8585]: (VI_1) Entering BACKUP STATE
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: (VI_1) Receive advertisement timeout
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: (VI_1) Entering MASTER STATE
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: (VI_1) setting VIPs.
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: Sending gratuitous ARP on eth0 for 192.168.31.10
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: (VI_1) Sending/queueing gratuitous ARPs on eth0 for 192.168.31.10
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: Sending gratuitous ARP on eth0 for 192.168.31.10
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: Sending gratuitous ARP on eth0 for 192.168.31.10
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: Sending gratuitous ARP on eth0 for 192.168.31.10
Mar 15 17:26:39 study01 Keepalived_vrrp[8585]: Sending gratuitous ARP on eth0 for 192.168.31.10
Mar 15 17:26:44 study01 Keepalived_vrrp[8585]: Sending gratuitous ARP on eth0 for 192.168.31.10

Mar 15 17:28:38 study02 Keepalived_vrrp[6661]: VRRP sockpool: [ifindex(2), family(IPv4), proto(112), unicast(0), fd(11,12)]
Mar 15 17:28:38 study02 Keepalived_vrrp[6661]: VRRP_Script(check_httpd) succeeded
Mar 15 17:28:38 study02 Keepalived_vrrp[6661]: (VI_1) Entering BACKUP STATE

四. 验证高可用

[root@study01 ~]#/etc/init.d/httpd stop

#观察第一台和第二台linux server的keepalive日志，会发现server01会从master变为fault状态，server02会从backup状态变为master状态，此时访问web页面访问的变成了第二台服务器的web页面；


[root@study01 ~]#/etc/init.d/httpd start

#观察第一台和第二台linux server的keepalive日志，会发现server01会从fault变为backup，然后再变为master状态，server02会从master状态变为backup状态，此时访问web页面访问的变成了第一台服务器的web页面；

至此实现了高可用功能，但是你有没有发现这样主机恢复是会抢占服务的，实际业务要求稳定性高，不希望主恢复时主动抢占，那么请看第五部分的更多介绍。

提示：如果要看VIP，需要使用“ip add”命令。

五. keepalive主备切换介绍

1. 通过vrrp_script实现对资源的监控

#1. 通过killall命令监控服务的运行状态
vrrp_script check_httpd {
    script "/usr/bin/killall -0 httpd"   #进程存在$?会返回0，否则$?会返回1
    interval 2
}
……(track部分省略)……

#2. 检测端口允许状态
vrrp_script check_httpd {
    script "</dev/tcp/127.0.0.1/80"   #对本机的80端口检测
    interval 2            #监控间隔2秒一次
    fall 2                            #如果失败两次则认为失败
    rise 1                          #如果成功一次则认为成功
}
……(track部分省略)……

#3. 通过shell语句进行状态监控
vrrp_script check_httpd {
    script "if [ -f /var/run/httpd/httpd.pid ]; then exit 0; else exit 1; fi"
    interval 2
}
……(track部分省略)……

#4. 通过脚本进行服务状态监控 
vrrp_script check_httpd {
    script "/etc/keepalived/check_mysql.sh"  #脚本根据需要写
    interval 2
}
……(track部分省略)……        

2. master和backup的角色切换

• 角色指定为master（master的优先级要配置的比backup大），master恢复时一定会抢占（默认抢占），想不抢占需要将所有的角色配置为backup（通过优先级决定谁是主角色），并指定nopreempt参数。
• 实际上决定keepalive状态的并不是角色state定义的master或者backup，而是priority和weight计算后决定的。weight可以配置为正数或者负数。
  • weight配置为正数时，如果检测成功，那么master节点的优先级为priority和weight之和，如果检测失败，那么master节点的优先级为priority；
  • weight配置为负数时，如果检测成功，那么master节点的优先级仍为priority，如果检测失败那么master节点的优先级为priority减去weight；
  • 配置weight有个准则，那就是weight无论正负，weight的绝对值要大于master与backup节点的priority的差。