keepalived

1、工作原理

keepalived主要作用：
1、管理LVS负载均衡软件
2、实现对LVS集群节点健康检查功能 
3、作为系统网络服务的高可用功能

keepalived服务工作原理：
    keepalived高可用对之间是通过VRRP进行通信的，VRRP是通过精选机制来确定主备的，主的优先级高于备，因此，工作时主会优先获得所有的资源，备节点处于等待状态，当主挂了的时候，备节点就会接管主节点的资源，然后顶替主节点对外提供服务。
    在keepalived服务对之间，只有作为主的服务器会一直发送VRRP广播包，告诉备它还活着，此时备不会抢占主，当主不可用时，即备监听不到主发送的广播包时，就会启动相关服务接管资源，保证业务的连续性，接管速度最快可以小于1秒
    
1）VRRP协议，全称Virtual Router Redundancy Protocol，中文名为虚拟路由冗余协议，VRRP的出现是为了解决静态路由的单点故障。
2）VRRP是通过一种竞选协议机制来讲路由任务交给某台VRRP路由器的
3）VRRP是用过IP多播的方式（默认多播地址（224.0.0.18））实现高可用对之间通信的。
4）工作时主节点发包，备节点接包，当备节点接收不到主节点发的数据包的时候，就启动接管程序接管主节点的资源。备节点可以有多个，通过优先级竞选，但一般Keepalived系统运维工作中都是一对。
5）VRRP使用了加密协议加密数据，但keepalived官方目前还是推荐使用铭文的方式配置认证类型和密码

2、部署

安装包：keepalived-2.2.0.tar.gz

前置条件
# yum install gcc openssl-devel -y   支持openssl、c的依赖包
# yum -y install libnl libnl-devel   支持ipv6的依赖包
安装
# ./configure --prefix=/usr/local/keepalived
# make && make install
配置成服务：
# cd /usr/local/keepalived
# cp etc/sysconfig/keepalived /etc/sysconfig/
# cp etc/keepalived/keepalived.conf /etc/keepalived/
# cp sbin/keepalived /usr/sbin/
加入开机启动项：
# vim /etc/init.d/keepalived
#!/bin/sh  
#  
# keepalived   High Availability monitor built upon LVS and VRRP  
#  
# chkconfig:   - 86 14  
# 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: 0 1 2 3 4 5 6  
# 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 5
    [ -e $config ] || exit 6
    echo -n $"Starting $prog: "  
    daemon $exec $KEEPALIVED_OPTIONS
    retval=$?
    echo  
    [ $retval -eq 0 ] && touch $lockfile
    return $retval
}

stop() {
    echo -n $"Stopping $prog: "  
    killproc $prog
    retval=$?
    echo  
    [ $retval -eq 0 ] && rm -f $lockfile
    return $retval
}

restart() {
    stop
    start
}

reload() {
    echo -n $"Reloading $prog: "  
    killproc $prog -1
    retval=$?
    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 0
        $1
        ;;
    stop)
        rh_status_q || exit 0
        $1
        ;;
    restart)
        $1
        ;;
    reload)
        rh_status_q || exit 7
        $1
        ;;
    force-reload)
        force_reload
        ;;
    status)
        rh_status
        ;;
    condrestart|try-restart)
        rh_status_q || exit 0
        restart
        ;;
    *)
        echo $"Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload}"  
        exit 2
esac
exit $?
# chmod a+x /etc/init.d/keepalived

修改配置文件
# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id LVS_02
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.105.233/24
    }
}

virtual_server 192.168.105.233 80 {
    delay_loop 6
    lb_algo rr
    lb_kind NAT
    persistence_timeout 50
    nat_mask 255.255.255.0
    protocol TCP

    real_server 192.168.105.231 80 {
        weight 1
        TCP_CHECK {
        connect_timeout 8
        nb_get_retry 3
        delay_before_retry 3
        connect_port 80
        }
    }
    real_server 192.168.105.232 80 {
        weight 1
        TCP_CHECK {
        connect_timeout 8
        nb_get_retry 3
        delay_before_retry 3
        connect_port 80
        }
    }
}
启动
# systemctl start keepalived

3、测试

当关闭keepalived032后，keepalived033迅速接管192.168.105.233