高可用集群技术之Keepalived实现LVS高可用并负载均衡Web服务

Keepalived概述:
Keepalived的作用是检测服务器的状态，如果有一台web服务器死机，或工作出现故障，Keepalived将检测到，并将有故障的服务器从系统中剔除，同时使用其他服务器代替该服务器的工作，当服务器工作正常后Keepalived自动将服务器加入到服务器群中，这些工作全部自动完成，不需要人工干涉，需要人工做的只是修复故障的服务器.

keepalived实现lvs高可用并负载均衡web服务：
准备工作:
2台keepalived节点为: node1.samlee.com node2.samlee.com
2台realserver服务为: node3.samlee.com node4.samlee.com

1、配置RSserver过程如下(node3.samlee.com\node4.samlee.com):
(1)部署web服务(使用nginx配置)
# yum -y install nginx-1.10.0-1.el6.ngx.x86_64.rpm

(2)禁用防火墙及主机名修改
# service iptables stop
# chkconfig iptables off

(3)配置路由转发及转发模块配置
# echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce 
# echo 2 > /proc/sys/net/ipv4/conf/eth0/arp_announce
# echo 1 > /proc/sys/net/ipv4/conf/eth0/arp_ignore 
# echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore
 
--添加路由条目
# ifconfig lo:0 172.16.100.99 netmask 255.255.255.255 broadcast 172.16.100.99 up
# route add -host 172.16.100.99 dev lo:0

2、配置keepalived服务器
(1)安装ipvsadm负载均衡管理器

# yum -y install ipvsadm

(2)安装keepalived
# yum -y install keepalived
# chkconfig keepalived on

(3)配置keepalived默认初始状态如下:(主节点:master状态)
# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
  notification_email {
    root@localhost
  }
  notification_email_from root@localhost 
  smtp_server 127.0.0.1 
  smtp_connect_timeout 30
  router_id LVS_DEVEL            #物理路由id，一般指定为本机的hostname
}
vrrp_instance VI_1 {                #vrrp实例配置段
    state MASTER                    #指定keepalived服务运行状态
    interface eth0                  #指定keepalived的心跳口
    virtual_router_id 51            #指定虚拟路由id（1~255），同一vrrp实例的主备keepalived必须配置为一样
    priority 101                    ##指定起始优先级，优先级高的会成为master
    advert_int 1                    #vrrp通告的发送间隔
    authentication {                #配置通过密码认证
        auth_type PASS
        auth_pass keepalivedpass
    }
    virtual_ipaddress {
    172.16.100.99 dev eth0 label eth0:0    #定义VIP
    }
}

(4)配置keepalived默认初始状态如下:(备节点:backuo状态)
# vim /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
 
global_defs {
  notification_email {
    root@localhost
  }
  notification_email_from root@localhost 
  smtp_server 127.0.0.1 
  smtp_connect_timeout 30
  router_id LVS_DEVEL
}
 
vrrp_instance VI_1 {
    state BACKUP 
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass keepalivedpass
    }
    virtual_ipaddress {
    172.16.100.99 dev eth0 label eth0:0
    }
}

(5)调用周期性检测down文件是否存在来控制keepalived服务的主备切换
在keepalived.conf添加如下内容:
全局配置的段下添加如下:
vrrp_script chk_downfile {        #服务状态检测脚本配置段
    script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"        #通过周期性检测down文件是否存在来控制keepalived服务的主备切换
    interval 1    #指定检测间隔为1秒
    weight -2    #指定检测失败时，优先级减2；检测的成功或失败是由script后面指定的命令或脚本执行返回的状态码决定的，0表示成功，非0表示失败
}
 
在vrrp_instance VI_1 ##vrrp实例配置段添加如下:
track_script {
    chk_downfile          #通过指定上面定义监控脚本来监控服务状态，以完成主备切换
}

重启keepalived服务创建down文件测试:
# service keepalived restart
# touch /etc/keepalived/down
 
---在/etc/keepalived/下建立down文件可实现主备模式切换

(6)调用外部脚本检测web(nginx)健康状态
建立/etc/keepalived/chkngx.sh脚本
#/bin/bash
#/etc/keepalived/chkngx.sh
#
if pkill -0 nginx>/dev/null; then
        [ `curl -sL -w %{http_code} http://localhost -o /dev/null` -eq 200 ] && exit 0
else
        service nginx start
fi
exit $?

授予脚本执行权限:
# chmod +x /etc/keepalived/chkngx.sh

配置keepalived.conf调用外部脚本
全局配置的段下添加如下:
vrrp_script chkngx {
    script "/etc/keepalived/chkngx.sh"    #指定用于检测nginx服务的执行脚本路径
    interval 1        #监测间隔
    weight -2        #失败时，优先级减2
    fall 3          # 指定nginx检测脚本连续执行失败次数为3，才进行Failover
    rise 3          # 指定nginx检测脚本连续执行成功次数为3，才进行Failback
}
 
在vrrp_instance VI_1 ##vrrp实例配置段添加如下:
track_script {
    chkngx          #通过指定上面定义监控脚本来监控服务状态，监控nginx监控状态
}

(7)使用通知脚本实现如何在vrrp事务发生时，发送警告邮件给指定的管理员？ 比如：主从节点故障时
建立脚本监控脚本如下:
# vim /etc/keepalived/notify.sh 
#!/bin/bash
#
 
declare -a vips=(172.16.100.98 172.16.100.99)
contact='root@localhost'
Usage() {
        echo "Usage:`basename $0`{master|backup|fault}"
}
 
Notify() {
    if [ "$2" = "VI_1" ]; then
        vip=${vips[0]}
    echo $vip
    elif [ "$2" = "VI_2" ]; then
        vip=${vips[1]}
    echo $vip
    fi
    suject="`hostname`'s state chaged to $1"
    mailbody="`date  +%F--%H:%M:%S`: `hostname`'s state chage to $1,vip floating..."
    echo $mailbody | mail -s  "$subject" $contact 
    echo $mailbody >> /tmp/keepalived.log
}
 
case $1 in
    master)
    Notify master
        exit 0
    ;;
    backup)
    Notify backup
        exit 0
    ;;
    fault)
    Notify fault
        exit 0
    ;;
    *)
        Usage 
        exit 1
    ;;
esac

授予脚本执行权限:
# chmod +x /etc/keepalived/notify.sh

配置keepalived.conf调用外部脚本
在vrrp_instance VI_1 ##vrrp实例配置段最后添加如下:
notify_master "/etc/keepalived/notify.sh master"        #状态变为master时，触发的通知脚本
notify_backup "/etc/keepalived/notify.sh backup"        #状态变为backup时，触发的通知脚本
notify_fault "/etc/keepalived/notify.sh fault"          #状态变为fault时，触发的通知脚本
notify "/etc/keepalived/notify.sh"    #当发生所有的状态改变时，会先触发对应的状态通知脚本后，再触发该脚本

(8)使用脚本根据down文件检测实现主从状态转换
# vim /etc/keepalived/convert_state.sh
#!/bin/bash
#
 
usage() {
    echo "./`basename $0` {master|backup}"
    exit 1
}
 
if [ $# -eq 0 ]; then
    usage
fi
 
if [[ "$1" = "master" ]]; then
    [ -f /etc/keepalived/down ] && rm -f /etc/keepalived/down
elif [[ "$1" = "backup" ]]; then
    [ ! -f /etc/keepalived/down ] && touch /etc/keepalived/down
else
    usage
fi
sleep 1
 
# chmod +x /etc/keepalived/convert_state.sh

执行脚本convert_state进行备节点转换:
# /etc/keepalived/convert_state.sh backup
# ls /etc/keepalived/ | grep down
down

执行脚本convert_state进行主节点转换:
# /etc/keepalived/convert_state.sh master

(9)LVS+keepalived配置ipvs规则实现负载均衡高可用
配置如下:
virtual_server 172.16.100.99 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    nat_mask 255.255.0.0
    # persistence_timeout 50
    protocol TCP
    sorry_server 127.0.0.1 80        #如果所有节点都down机，将转向本地web服务
 
    real_server 172.16.100.8 80 {
        weight 1
        HTTP_GET {                    #web健康状态检测
            url {
              path /
              status_code 200 
            }
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
    real_server 172.16.100.9 80 {
        weight 1
        HTTP_GET {                    #web健康状态检测
            url {
              path /
              status_code 200 
            }
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

最后查询ipvs规则，如下所示:
# ipvsadm -L -n --stats
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port              Conns  InPkts  OutPkts  InBytes OutBytes
  -> RemoteAddress:Port
TCP  172.16.100.99:80                    3      22        0    4657        0
  -> 172.16.100.8:80                    0        0        0        0        0
  -> 172.16.100.9:80                    0        0        0        0        0

以上为keepalived+lvs+web服务实现所有内容。

keepalived双主模型配置案例如下:
master1为:
vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 101
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass keepalivedpass
    }
    virtual_ipaddress {
    172.16.100.99 dev eth0 label eth0:0
    }
    track_script {
    chk_downfile
    }
    track_script {
    chkngx
    }
    notify_master "/etc/keepalived/notify.sh master"
    notify_backup "/etc/keepalived/notify.sh backup"
    notify_fault "/etc/keepalived/notify.sh fault"
    notify "/etc/keepalived/notify.sh"
}
vrrp_instance VI_2 {
    state BACKUP
    interface eth0
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass keepalivedpass
    }
    virtual_ipaddress {
        172.16.100.98 dev eth0 label eth0:1
    }
    track_script {
        chk_downfile
    }
    track_script {
        chkngx
    }
        notify_master "/etc/keepalived/notify.sh master"
        notify_backup "/etc/keepalived/notify.sh backup"
        notify_fault "/etc/keepalived/notify.sh fault"
        notify "/etc/keepalived/notify.sh"
}

master2为:
vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass keepalivedpass
    }
    virtual_ipaddress {
    172.16.100.99 dev eth0 label eth0:0
    }
    track_script {
    chk_downfile
    chkngx
    }
    track_script {
    chkngx
    }
    notify_master "/etc/keepalived/notify.sh master"
    notify_backup "/etc/keepalived/notify.sh backup"
    notify_fault "/etc/keepalived/notify.sh fault"
    notify "/etc/keepalived/notify.sh"
}
vrrp_instance VI_2 {
    state MASTER
    interface eth0
    virtual_router_id 52
    priority 101
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass keepalivedpass
    }
    virtual_ipaddress {
        172.16.100.98 dev eth0 label eth0:1
    }
    track_script {
        chk_downfile
    }
    track_script {
        chkngx
    }
        notify_master "/etc/keepalived/notify.sh master"
        notify_backup "/etc/keepalived/notify.sh backup"
        notify_fault "/etc/keepalived/notify.sh fault"
        notify "/etc/keepalived/notify.sh"
}

学习LVS+Keepalived必须阅读的三个文档。