物联网架构成长之路(9)-双机热备Keepalived了解

1. 前言
　　负载均衡LB，高可用HA，这一小结主要讲双机热备方案保证高可用。这里选择Keepalived作为双机热备方案，下面就对具体的配置进行了解。
2. 下载Keepalived
　　wget http://www.keepalived.org/software/keepalived-1.4.0.tar.gz
　　文档 http://www.keepalived.org/doc
　　参考 https://www.cnblogs.com/abclife/p/7909818.html
　　https://www.cnblogs.com/kevingrace/p/6138185.html
　　系统 Debian 8

 ./configure --prefix=/opt/keepalive #这一步，可能要额外安装一些依赖

 make
 make install
 mkdir /etc/keepalived
 cp ./etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf
 cp ./sbin/keepalived /usr/sbin/
 vim /etc/init.d/keepalived
 chmod a+x /etc/init.d/keepalived
 service keepalived start

　　/etc/init.d/keepalived 加入如下内容

 #!/bin/sh
 #
 # keepalived   High Availability monitor built upon LVS and VRRP
 #
 # chkconfig:   -
 # description: Robust keepalive facility to the Linux Virtual Server project \
 #              with multilayer TCP/IP stack checks. 

 ### BEGIN INIT INFO
 # Provides: keepalived
 # Required-Start: $local_fs $network $named $syslog
 # Required-Stop: $local_fs $network $named $syslog
 # Should-Start: smtpdaemon httpd
 # Should-Stop: smtpdaemon httpd
 # Default-Start:
 # Default-Stop:
 # Short-Description: High Availability monitor built upon LVS and VRRP
 # Description:       Robust keepalive facility to the Linux Virtual Server
 #                    project with multilayer TCP/IP stack checks.
 ### END INIT INFO 

 # Source function library.
 . /etc/rc.d/init.d/functions 

 exec="/usr/sbin/keepalived"
 prog="keepalived"
 config="/etc/keepalived/keepalived.conf" 

 [ -e /etc/sysconfig/$prog ] && . /etc/sysconfig/$prog 

 lockfile=/var/lock/subsys/keepalived 

 start() {
     [ -x $exec ] || exit
     [ -e $config ] || exit
     echo -n $"Starting $prog: "
     daemon $exec $KEEPALIVED_OPTIONS
     retval=$?
     echo
     [ $retval -eq  ] && touch $lockfile
     return $retval
 } 

 stop() {
     echo -n $"Stopping $prog: "
     killproc $prog
     retval=$?
     echo
     [ $retval -eq  ] && rm -f $lockfile
     return $retval
 } 

 restart() {
     stop
     start
 } 

 reload() {
     echo -n $"Reloading $prog: "
     killproc $prog -
     retval=$?
     echo
     return $retval
 } 

 force_reload() {
     restart
 } 

 rh_status() {
     status $prog
 } 

 rh_status_q() {
     rh_status &>/dev/null
 } 

 case "$1" in
     start)
         rh_status_q && exit
         $
         ;;
     stop)
         rh_status_q || exit
         $
         ;;
     restart)
         $
         ;;
     reload)
         rh_status_q || exit
         $
         ;;
     force-reload)
         force_reload
         ;;
     status)
         rh_status
         ;;
     condrestart|try-restart)
         rh_status_q || exit
         restart
         ;;
     *)
         echo $"Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload}"
         exit
 esac
 exit $?

3. 双机热备（主从模式）
　　修改配置文件 keepalived.conf
　　vim /etc/keeplived/keeplived.conf

 global_defs {
     notification_email { #指定Keepalived在发生事情的时候，发送邮件通知，每行一个地址
         [e-mail]
 　　}
     notification_email_from [e-mail] #指定发件人
     smtp_server 192.168.8.208 #发送email的smtp地址
     smtp_connect_timeout  #超时时间
     router_id nginx_dev #运行Keepalived的机器标识号，可以相同也可以不同
 }

 vrrp_instance nginx_dev {
     state MASTER
     interface eth1
     #mcast_src_ip 172.16.23.203
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.222
     }
 }

　　然后 service keepalived restart
　　然后就可以通过 172.16.23.222 访问当前主机了。如果访问不了的要判断是否所处于同个网络中，即可以通过路由访问到的。这个Keepalived就是通过发广播包这里的通知内网机器实现的。
　　同理在另外一台电脑上配置上面信息 把state MASTER 改为 state BACKUP
4. 双机热备（主主模式）
　　主从模式的话，由于一般情况下是不会出现宕机，所以往往会有一台机器浪费，这样是对机器的浪费，所以现在双机热备主主模式是比较推荐的。所谓的主主模式，就是建立两个实例，互为主从而已。
　　172.16.23.203 配置如下

 global_defs {
     notification_email {  #指定Keepalived在发生事情的时候，发送邮件通知，每行一个地址
         [e-mail]
     }
     notification_email_from [e-mail]   #指定发件人
     smtp_server 192.168.8.208   #发送email的smtp地址
     smtp_connect_timeout      #超时时间
     router_id nginx_dev_1       #运行Keepalived的机器标识号，可以相同也可以不同
     router_id nginx_dev_2
 }

 vrrp_instance nginx_dev_1 {
     state MASTER
     interface eth1
     mcast_src_ip 172.16.23.203
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.222
     }
 }

 vrrp_instance nginx_dev_2 {
     state BACKUP
     interface eth1
     mcast_src_ip 172.16.23.203
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.223
     }
 }

　　172.16.23.204 配置如下

 global_defs {
     notification_email {  #指定Keepalived在发生事情的时候，发送邮件通知，每行一个地址
         [e-mail]
     }
     notification_email_from [e-mail]   #指定发件人
     smtp_server 192.168.8.208   #发送email的smtp地址
     smtp_connect_timeout      #超时时间
     router_id nginx_dev_1         #运行Keepalived的机器标识号，可以相同也可以不同
     router_id nginx_dev_2
 }

 vrrp_instance nginx_dev_2 {
     state MASTER
     interface eth1
     mcast_src_ip 172.16.23.204
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.223
     }
 }

 vrrp_instance nginx_dev_1 {
     state BACKUP
     interface eth1
     mcast_src_ip 172.16.23.204
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.222
     }
 }

　　就是这两份配置，基本是一样的，互为主备，里面一个比较重要修改的是virtual_router_id

　　上面实现的效果是访问172.16.23.222 时先转到172.16.20.203主机上，访问172.16.23.223时转到172.16.20.204主机上。当其中一台主机宕机时，就会自动切换，切换到好的主机上，这个过程就几秒的时间。
　　这里是需要两个IP地址，需要客户端进行负载选择，这一步可以通过DNS进行分发处理。

 root@debian-t6:/usr/local/nginx/html# ip addr
 : lo: <LOOPBACK,UP,LOWER_UP> mtu  qdisc noqueue state UNKNOWN group default
     link/loopback ::::: brd :::::
     inet 127.0.0.1/ scope host lo
        valid_lft forever preferred_lft forever
 : eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu  qdisc pfifo_fast state UP group default
     link/ether fc:aa::9d:d9:5a brd ff:ff:ff:ff:ff:ff
     inet 172.16.23.204/ brd 172.16.23.255 scope global eth1
        valid_lft forever preferred_lft forever
     inet 172.16.23.223/ scope global eth1
        valid_lft forever preferred_lft forever
     inet 172.16.23.222/ scope global eth1
        valid_lft forever preferred_lft forever

　　日志在 /var/log/message

 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) Sending/queueing gratuitous ARPs on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) sent  priority
 Jan  :: debian-t6 Keepalived_healthcheckers[]: Stopped
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) removing protocol VIPs.
 Jan  :: debian-t6 Keepalived_vrrp[]: Stopped
 Jan  :: debian-t6 Keepalived_healthcheckers[]: Opening file '/etc/keepalived/keepalived.conf'.
 Jan  :: debian-t6 Keepalived_vrrp[]: Registering Kernel netlink reflector
 Jan  :: debian-t6 Keepalived_vrrp[]: Registering Kernel netlink command channel
 Jan  :: debian-t6 Keepalived_vrrp[]: Registering gratuitous ARP shared channel
 Jan  :: debian-t6 Keepalived_vrrp[]: Opening file '/etc/keepalived/keepalived.conf'.
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) removing protocol VIPs.
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) removing protocol VIPs.
 Jan  :: debian-t6 Keepalived_vrrp[]: Using LinkWatch kernel netlink reflector...
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) Entering BACKUP STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP sockpool: [ifindex(), proto(), unicast(), fd(,)]
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) forcing a new MASTER election
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) Transition to MASTER STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) Received advert with higher priority , ours
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) Entering BACKUP STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) Transition to MASTER STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) Transition to MASTER STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) Entering MASTER STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) setting protocol VIPs.
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.223
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_2) Sending/queueing gratuitous ARPs on eth1 for 172.16.23.223
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.223
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.223
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.223
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.223
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) Entering MASTER STATE
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) setting protocol VIPs.
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: VRRP_Instance(nginx_dev_1) Sending/queueing gratuitous ARPs on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222
 Jan  :: debian-t6 Keepalived_vrrp[]: Sending gratuitous ARP on eth1 for 172.16.23.222

5. KeepAlived其他配置

　　下面讲解一些其他配置和高级应用
　　（1）email通知，这里就不做了，建议用第三方独立监控服务，如Nagios、Zabbix进行监控
　　（2）router_id 用户标识本节点名称，通常为hostname
　　（3）vrrp_instance 实例定义
　　（4）state 实例状态，只有MASTER 和 BACKUP两种状态，并且需要全部大写。抢占模式下其中MASTER为工作状态，BACKUP为备用状态。当MASTER所在服务器失效时，BACKUP所在服务器会自动把它的状态由BACKUP切换到MASTER状态。当失效的MASTER所在的服务恢复时，BACKUP从MASTER恢复到BACKUP状态
　　（5）interface 对望提供服务网卡接口，即VIP绑定的网卡接口。一些服务器都有两个以上的网卡接口，在选择接口时要正确选择
　　（6）mcast_src_ip 本机IP地址
　　（7）virtual_router_id 虚拟路由的ID号，每个节点必须设置一样。相同的VRID为一个组，将决定多播的MAC地址，不同的实例节点必须不一样
　　（8）priority 节点优先级，取值0~254， MASTER 要比BACKUP高
　　（9）advert_int MASTER 与 BACKUP 节点间同步检查的时间间隔，单位秒
　　（10）authentication 验证类型和验证密码。主要用PASS 密码模式 {auth_type PASS auth_pass 123456} 同一个vrrp实例MASTER与BACKUP使用相同的密码才能正常通信
　　（11）nopreempt 禁止抢占服务。默认情况，当MASTER服务挂掉之后，BACKUP自动升级为MASTER并接替其任务，当MASTER服务恢复后，升级为MASTER的BACKUP服务又自动降为BACKUP，把工作权交给原MASTER。当配置了nopreempt，MASTER从挂到到恢复，不再将服务抢占过来
　　（12）virtual_ipaddress 虚拟IP地址池，可以有多个IP，每个IP占一行，不需要指定子网掩码。注意这里的IP必须与我们设定的VIP保持一致 VRRP HA虚拟地址
　　（13）notify_master 表示当切换到master状态时，要执行的脚本
　　（14）notify_backup 表示当切换到backup状态时，要执行的脚本
　　（15）notify_fault 表示切换出现故障是要执行的脚本(这里也可以发送邮件什么的)
　　（16）track_script 执行监控的服务
　　（17）vrrp_script VRRP 脚本检测
6. KeepAlived 高级应用
　　172.16.23.203

　　/etc/keepalived/keepalived.conf

 global_defs {
     router_id nginx_dev_1
 }

 #用于监控Nginx、Redis等应用是否在运行
 vrrp_script chk_nginx_port {
     script "/etc/keepalived/check.sh" #通过脚本检测，根据返回值进行判断
     interval                         #脚本执行间隔 每2秒执行一次
     weight -                         #检测失败，优先级变更
     fall                             #连续检测2次失败才算失败
     rise                             #检测一次成功算成功，但不修改优先级
 }

 vrrp_instance nginx_dev_1 {
     state MASTER
     interface eth1
     mcast_src_ip 172.16.23.203
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {  #VRRP HA 虚拟地址，可以写多个
         172.16.23.222
     }

     notify_master "/etc/keepalived/run.sh master1"
     notify_backup "/etc/keepalived/run.sh backup1"
     notify_fault  "/etc/keepalived/run.sh fault1"

     track_script {
         chk_nginx_port     #执行对于脚本
     }
 }

 vrrp_instance nginx_dev_2 {
     state BACKUP
     interface eth1
     mcast_src_ip 172.16.23.203
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.223  #VRRP HA虚拟地址
     }

     notify_master "/etc/keepalived/run.sh master2"
     notify_backup "/etc/keepalived/run.sh backup2"
     notify_fault  "/etc/keepalived/run.sh fault2"
 }

　　/etc/keepalived/check.sh

 #!/bin/bash
 counter=$(ps -C nginx --no-heading | wc -l)
 if [ "${counter}" = "" ]; then
     service nginx start
     #sleep   # 这个在执行过程中有问题
     counter=$(ps -C nginx --no-heading | wc -l)
     if [ "${counter}" = "" ]; then
         service keepalived stop
     fi
 fi

　　/etc/keepalived/run.sh

 #!/bin/sh
 echo $(date +%H:%M:%S) $ >> /etc/keepalived/time.txt

　　172.16.23.204

　　/etc/keepalived/keepalived.conf

 global_defs {
     router_id nginx_dev_2         #运行Keepalived的机器标识号，可以相同也可以不同
 }

 #用于监控Nginx、Redis等应用是否在运行
 vrrp_script chk_nginx_port {
     script "/etc/keepalived/check.sh"
     interval
     weight -
     fall
     rise
 }

 vrrp_instance nginx_dev_2 {
     state MASTER
     interface eth1
     mcast_src_ip 172.16.23.204
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.223
     }

     notify_master "/etc/keepalived/run.sh master1"
     notify_backup "/etc/keepalived/run.sh backup1"
     notify_fault "/etc/keepalived/run.sh fault1"

     track_script {
         chk_nginx_port
     }
 }

 vrrp_instance nginx_dev_1 {
     state BACKUP
     interface eth1
     mcast_src_ip 172.16.23.204
     virtual_router_id
     priority
     advert_int
     authentication {
         auth_type PASS
         auth_pass
     }
     virtual_ipaddress {
         172.16.23.222
     }

     notify_master "/etc/keepalived/run.sh master2"
     notify_backup "/etc/keepalived/run.sh backup2"
     notify_fault "/etc/keepalived/run.sh fault2"

     track_script {
         chk_nginx_port
     }
 }

　　/etc/keepalived/check.sh

 #!/bin/bash
 counter=$(ps -C nginx --no-heading | wc -l)
 if [ "${counter}" = "" ]; then
     service nginx start
     counter=$(ps -C nginx --no-heading | wc -l)
     if [ "${counter}" = "" ]; then
         service keepalived stop
     fi
 fi

　　/etc/keepalived/run.sh

 #!/bin/sh
 echo $(date +%H:%M:%S) $ >> /etc/keepalived/time.txt

　　上面的那些sh文件要 chmod a+x *.sh ，在keepalived.conf 文件中最好是使用绝对路径

　　测试过程:
　　先启动203 的KeepAlived和Nginx
　　然后启动204的KeepAlived和Nginx
　　用浏览器访问 172.16.23.223 / 172.16.23.222 都是没有问题，基本被负载到两台主机上去了
　　场景一
　　　　然后204机器 service nginx stop && service nginx status 模拟异常退出并查看状态
　　　　过几秒后再查看204 service nginx status 发现nginx 自动重启了
　　场景二
　　　　修改check.sh 文件 把service nginx start 这一行注释掉
　　　　然后204 机器 service nginx stop && service nginx status 模拟异常退出并查看状态
　　　　过几秒后再查看204 service nginx status / service keepalived status 发现nginx关闭、对于的204上的KeepAlived也被关闭
　　　　这个时候，203服务器 tail -f time.txt 会出现一条master切换信息 表示VIP进行切换
　　　　浏览器访问 172.16.23.223/172.16.23.222 访问正常，不过都是指向同一个机器
　　　　取消check.sh 文件的注释
　　　　启动204的 KeepAlived service keepalived start 由于取消注释，对于的nginx也自动启动了
　　　　这时，203服务器 tail -f time.txt 会出现一条backup切换信息，表示203主机切换为Backup状态了。
　　　　这时浏览器访问以上两个IP，同样被负载的两台主机上