keepalived实现lvs的高可用

keepalived的简介

keepalived介绍

Keepalived 软件起初是专为LVS负载均衡软件设计的，用来管理并监控LVS集群系统中各个服务节点的状态，后来又加入了可以实现高可用的VRRP功能。因此，Keepalived除了能够管理LVS软件外，还可以作为其他服务（例如：Nginx、Haproxy、MySQL等）的高可用解决方案软件。

Keepalived软件主要是通过VRRP协议实现高可用功能的。VRRP是Virtual Router RedundancyProtocol(虚拟路由器冗余协议）的缩写，VRRP出现的目的就是为了解决静态路由单点故障问题的，它能够保证当个别节点宕机时，整个网络可以不间断地运行。

所以，Keepalived 一方面具有配置管理LVS的功能，同时还具有对LVS下面节点进行健康检查的功能，另一方面也可实现系统网络服务的高可用功能。

keepalived的重要功能

keepalived 有三个重要的功能，分别是：

• 管理LVS负载均衡软件
• 实现LVS集群节点的健康检查
• 作为系统网络服务的高可用性（failover）

keepalived高可用故障转移原理

Keepalived 高可用服务之间的故障切换转移，是通过 VRRP (Virtual Router Redundancy Protocol ,虚拟路由器冗余协议）来实现的。

在 Keepalived 服务正常工作时，主 Master 节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备 Backup 节点自己还活看，当主 Master 节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检测到来自主 Master 节点的心跳了，于是调用自身的接管程序，接管主 Master 节点的 IP 资源及服务。而当主 Master 节点恢复时，备 Backup 节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。

那么，什么是VRRP呢？
VRRP ,全 称 Virtual Router Redundancy Protocol ,中文名为虚拟路由冗余协议 ，VRRP的出现就是为了解决静态踣甶的单点故障问题，VRRP是通过一种竞选机制来将路由的任务交给某台VRRP路由器的。

keepalived高可用架构图

工作原理
Keepalived高可用对之间是通过VRRP通信的，因此，我们从 VRRP开始了解起：

1. VRRP,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是通过一种竟选协议机制来将路由任务交给某台 VRRP路由器的。

3. VRRP用 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。

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开源。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官方目前还是推荐用明文的方式配置认证类型和密码

Keepalived服务的工作原理：

Keepalived高可用是通过 VRRP 进行通信的， VRRP是通过竞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，此时备不会枪占主，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。

环境：

类型	主机名	ip地址
主	master	192.168.147.20
备	slave	192.168.147.44
RS	RS1	192.168.147.55
RS	RS2	192.168.147.66
VIP		192.168.147.100

配置LVS

在主服务器上

//修改网卡配置文件
[root@master ~]# cat /etc/sysconfig/network-scripts/ifcfg-ens33 
TYPE=Ethernet
BOOTPROTO=static
NAME=ens33
DEVICE=ens33
ONBOOT=yes
IPADDR=192.168.147.20
NETMASK=255.255.255.0
GATEWAY=192.168.147.2
DNS1=114.114.114.114

//安装ipvsadm
[root@master ~]# yum -y install ipvsadm

//添加节点
[root@master ~]# ipvsadm -A -t 192.168.147.100:80 -s rr
[root@master ~]# ipvsadm -a -t 192.168.147.100:80 -r 192.168.147.55 -g
[root@master ~]# ipvsadm -a -t 192.168.147.100:80 -r 192.168.147.66 -g
[root@master ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.168.147.100:80 rr
  -> 192.168.147.55:80            Route   1      0          0         
  -> 192.168.147.66:80            Route   1      0          0       


//关闭防火墙
[root@master ~]# systemctl stop firewalld
[root@master ~]# setenforce 0

在备服务器上

[root@savle ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:e3:00:67 brd ff:ff:ff:ff:ff:ff
    inet 192.168.147.44/24 brd 192.168.147.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet 192.168.147.100/24 brd 192.168.147.255 scope global secondary noprefixroute ens33
       valid_lft forever preferred_lft forever



[root@savle ~]# cat /etc/sysconfig/network-scripts/ifcfg-ens33 
TYPE=Ethernet
BOOTPROTO=static
NAME=ens33
DEVICE=ens33
ONBOOT=yes
IPADDR0=192.168.147.44
NETMASK=255.255.255.0
GATEWAY=192.168.147.2
DNS1=114.114.114.114


//添加节点
[root@savle ~]# ipvsadm -A -t 192.168.147.100:80 -s rr
[root@savle ~]# ipvsadm -a -t 192.168.147.100:80 -r 192.168.100.55:80 -g
[root@savle ~]# ipvsadm -a -t 192.168.147.100:80 -r 192.168.100.66:80 -g
[root@savle ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.168.147.100:80 rr
  -> 192.168.100.55:80            Route   1      0          0         
  -> 192.168.100.66:80            Route   1      0          0   

//关闭防火墙
[root@savle ~]# systemctl stop firewalld
[root@savle ~]# setenforce 0

在RS1与RS2上

//在RS1上
//安装httpd
[root@RS1 ~]# yum -y install httpd
[root@RS1 ~]# systemctl start httpd
[root@RS1 ~]# echo 'r1' > /var/www/html/index.html

//关闭防火墙
[root@RS1 ~]# systemctl stop firewalld
[root@RS1 ~]# setenforce 0

//编写arp
[root@RS1 ~]# cat >> /etc/sysctl.conf <<EOF
> net.ipv4.conf.all.arp_ignore=1
> net.ipv4.conf.all.arp_announce=2
> EOF
[root@RS1 ~]# sysctl -p
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2

//添加IP与路由
[root@RS1 ~]# yum -y install net-tools
[root@RS1 ~]# ifconfig lo:0 192.168.147.100/32 broadcast 192.168.147.100 up
[root@RS1 ~]# route add -host 192.168.147.100 dev lo:0



//在RS2上
//编写arp
[root@RS2 ~]# yum -y install httpd
[root@RS2 ~]# which httpd
/usr/sbin/httpd
[root@RS2 ~]# cat >> /etc/sysctl.conf <<EOF
> net.ipv4.conf.all.arp_ignore=1
> net.ipv4.conf.all.arp_announce=2
> EOF
[root@RS2 ~]# sysctl -p
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2

//安装httpd
[root@RS2 ~]# yum -y install httpd
[root@RS2 ~]# systemctl start httpd
[root@RS2 ~]# echo 'r2' > /var/www/html/index.html

//关闭防火墙
[root@RS2 ~]# systemctl stop firewalld
[root@RS2 ~]# setenforce 0

//添加IP与路由
[root@RS2 ~]# yum -y install net-tools
[root@RS2 ~]# ifconfig lo:0 192.168.147.100/32 broadcast 192.168.147.100 up
[root@RS2 ~]# route add -host 192.168.147.100 dev lo:0

配置keepalived

在主服务器上

//安装keepalived
[root@master ~]# yum -y install keepalived

//编写keepalived配置文件
! Configuration File for keepalived

global_defs {     //全局配置
   router_id lb01
}

vrrp_instance VI_1 {    //定义实例
    state BACKUP        //指定keepalived节点的初始状态
    interface ens33     //VRRP实例绑定网卡接口，用户发送VRRP包
    virtual_router_id 51   //虚拟路由的ID，同一集群要一致
    priority 100       //定义优先级，按优先级来界定主备角色，优先级越大越优先
    advert_int 1       //主备通讯时间间隔
    authentication {    //配置方式
        auth_type PASS  //认证方式。密码
        auth_pass P@ssw0rd  //同一集群的keepalived配置此处必须一致，推荐使用八位随机密码
    }
    virtual_ipaddress {    //配置要使用的VIP地址
        192.168.147.100
    }
}

virtual_server 192.168.147.100 80 {   //配置虚拟服务器
    delay_loop 6    //健康检查时间间隔
    lb_algo rr    //lvs调度算法
    lb_kind DR    //lvs模式
    persistence_timeout 50   //持久化超时时间，单位是秒
    protocol TCP    //四层协议
 
    real_server 192.168.147.20 80 {  //定义备用服务器，当所有RS都故障时，用sorry_server来响应客户端
        weight 1    //给服务器指定权重，默认为1
        TCP_CHECK {  
            connect_port 80    
            connect_timeout 3   //连接超时时间
            nb_get_retry 3     //get尝试次数
            delay_before_retry 3  //在尝试之前延迟多长时间 
        }
    }

    real_server 192.168.147.44 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

[root@master keepalived]# systemctl restart keepalived

在备服务器上

//安装keepalived
[root@slave ~]# yum -y install keepalived

//编写keepalived配置文件
[root@salve keepalived]# vim keepalived.conf
! Configuration File for keepalived

global_defs {    
   router_id lb01
}

vrrp_instance VI_1 {    
    state BACKUP       
    interface ens33    
    virtual_router_id 51   
    priority 90     
    advert_int 1      
    authentication {   
        auth_type PASS  
        auth_pass P@ssw0rd  
    }
    virtual_ipaddress {   
        192.168.147.100
    }
}

virtual_server 192.168.147.100 80 {   
    delay_loop 6   
    lb_algo rr    
    lb_kind DR    
    persistence_timeout 50   
    protocol TCP    
 
    real_server 192.168.147.20 80 {  
        weight 1   
        TCP_CHECK {  
            connect_port 80    
            connect_timeout 3   
            nb_get_retry 3     
            delay_before_retry 3  
        }
    }

    real_server 192.168.147.44 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

[root@slave keepalived]# systemctl restart keepalived

测试：

//将主服务器上的keepalvied停止
[root@master keepalived]# systemctl stop keepalived
[root@master keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:74:8b:b9 brd ff:ff:ff:ff:ff:ff
    inet 192.168.147.20/24 brd 192.168.147.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
//可以看到主服务器上没有VIP


//查看备服务器上的keepalived状态
[root@salve keepalived]# systemctl status keepalived
● keepalived.service - LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; disabled; vendor preset: disab>
   Active: active (running) since Mon 2021-06-21 09:27:51 EDT; 2min 7s ago
  Process: 313019 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/S>
 Main PID: 313020 (keepalived)
    Tasks: 3 (limit: 4615)
   Memory: 2.6M
   CGroup: /system.slice/keepalived.service
           ├─313020 /usr/sbin/keepalived -D
           ├─313021 /usr/sbin/keepalived -D
           └─313022 /usr/sbin/keepalived -D
           
[root@salve keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet 192.168.100.250/0 brd 192.168.100.250 scope global lo:0
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:e3:00:67 brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.77/24 brd 192.168.100.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet 192.168.100.251/24 brd 192.168.100.255 scope global secondary noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fee3:67/64 scope link 
       valid_lft forever preferred_lft forever
//可以看到有VIP

//停止RS2上的httpd服务
[root@RS2 ~]# systemctl stop httpd
[root@RS2 ~]# ss -antl
State     Recv-Q    Send-Q         Local Address:Port         Peer Address:Port    Process                     
LISTEN    0         128                  0.0.0.0:22                0.0.0.0:*                                  
LISTEN    0         128                     [::]:22                   [::]:*                  

keepalived通过脚本来监控lvs负载均衡机的状态

编写脚本

在主服务器上

[root@master scripts]# cat check_httpd.sh 
#!/bin/bash
status=$(ps -ef|grep -Ev "grep|$0"|grep -c httpd)
if [ $status -eq 0 ];then
    systemctl stop keepalived
fi
[root@master scripts]# chmod +x check_httpd.sh 


[root@master scripts]# cat notify.sh 
#!/bin/bash
VIP=$2
case "$1" in
  master)
        httpd_status=$(ps -ef|grep -Ev "grep|$0"|grep 'httpd'|wc -l)
        if [ $httpd_status -lt 1 ];then
            systemctl start httpd
        fi
  ;;
  backup)
        httpd_status=$(ps -ef|grep -Ev "grep|$0"|grep 'httpd'|wc -l)
        if [ $httpd_status -gt 0 ];then
            systemctl stop httpd
        fi
  ;;
  *)
        echo "Usage:$0 master|backup VIP"
  ;;
esac

[root@master scripts]# chmod +x notify.sh

在备服务器上

[root@salve scripts]# cat notify.sh 
#!/bin/bash
VIP=$2
case "$1" in
  master)
        httpd_status=$(ps -ef|grep -Ev "grep|$0"|grep 'httpd'|wc -l)
        if [ $httpd_status -lt 1 ];then
            systemctl start httpd
        fi
  ;;
  backup)
        httpd_status=$(ps -ef|grep -Ev "grep|$0"|grep 'httpd'|wc -l)
        if [ $httpd_status -gt 0 ];then
            systemctl stop httpd
        fi
  ;;
  *)
        echo "Usage:$0 master|backup VIP"
  ;;
esac

[root@master scripts]# chmod +x notify.sh

配置keepalvied加入监控脚本的配置

主服务器上

[root@master keepalived]# cat keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id lb01
}

vrrp_script nginx_check {
    script "/scripts/check_httpd.sh"
    interval 1
    weight -20
}
//加入上面五行

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass P@ssw0rd
    }
    virtual_ipaddress {
        192.168.147.100
    }
    track_script {
        httpd_check
    }
    notify_master "/scripts/notify.sh master 192.168.147.100"
    notify_backup "/scripts/notify.sh backup 192.168.147.100"
}
//加入上面四行

virtual_server 192.168.147.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.100.20 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.100.44 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}


[root@master keepalived]# systemctl restart keepalived

备服务器上

[root@salve keepalived]# cat keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id lb02
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 51
    priority 90
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass P@ssw0rd
    }
    virtual_ipaddress {
        192.168.147.100
    }
    notify_master "/scripts/notify.sh master 192.168.147.100"
    notify_backup "/scripts/notify.sh backup 192.168.147.100"
//加入上面两行

}

virtual_server 192.168.147.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.147.20 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.147.44 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}



[root@salve keepalived]# systemctl restart keepalived

测试

//关闭主上的keepalived
//关闭RS1上的httpd服务
[root@master keepalived]# systemctl stop keepalived
[root@master keepalived]# systemctl status keepalived
● keepalived.service - LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; disabled; vendor preset: disab>
   Active: inactive (dead)

[root@r1 ~]# systemctl stop httpd
[root@r1 ~]# systemctl status httpd
● httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
   Active: inactive (dead)
     Docs: man:httpd.service(8)