一、keepalived简介

keepalived是分布式部署解决系统高可用的软件，结合lvs(LinuxVirtual Server)使用，解决单机宕机的问题。
keepalived是一个基于VRRP协议来实现IPVS的高可用的解决方案。对于LVS负载均衡来说，如果前端的调度器direct发生故障，则后端的realserver是无法接受请求并响应的。因此，保证前端direct的高可用性是非常关键的，否则后端的服务器是无法进行服务的。而我们的keepalived就可以用来解决单点故障（如LVS的前端direct故障）问题。keepalived的主要工作原理是：运行keepalived的两台服务器，其中一台为MASTER，另一台为BACKUP，正常情况下，所有的数据转换功能和ARP请求响应都是由MASTER完成的，一旦MASTER发生故障，则BACKUP会马上接管MASTER的工作，这种切换时非常迅速的。

 

二、测试环境

下面拿4台虚拟机进行环境测试,实验环境为centos6.6 x86_64,在lvs NAT模式环境下只有前端两台keepalived调度机有公网ip，后端真实机只有内网ip，具体用途和ip如下

服务器类型

公网ip

内网ip

LVS VIP

192.168.214.70

192.168.211.254

Keepalived Master

192.168.214.76

192.168.211.76

Keepalived Backup

192.168.214.77

192.168.211.77

Realserver A

192.168.211.79

        Realserver B

192.168.211.83

 

三、软件安装

1、安装lvs所需包ipvsadm

yum install -y ipvsadm

ln -s /usr/src/kernels/`uname -r`  /usr/src/linux

lsmod |grep ip_vs

 

#注意Centos 6.X安装lvs，使用1.26版本。并且需要先安装yuminstall libnl* popt* -y

 

执行ipvsadm(modprobe ip_vs)把ip_vs模块加载到内核

[root@test85 ~]# ipvsadm -L -n

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

 -> RemoteAddress:Port          Forward Weight ActiveConn InActConn

 

#IP Virtual Server version 1.2.1 ---- ip_vs内核模块版本

 

 

2、安装keepalived

yum install -y keepalived

chkconfig keepalived on

注：在centos7系列系统中开机自动启动使用systemctl enable keepalived


四、开启路由转发 

在lvs/NAT模式下前端两台调度机192.168.211.76和192.168.211.77上需要开启路由转发功能

vi /etc/sysctl.conf

修改net.ipv4.ip_forward = 0为net.ipv4.ip_forward= 1

保存退出后，使用systcl –p命令让其生效

 

五、keepalived配置

先看下211.76 keepalivedmaster主机上的配置

具体详细的参数说明见上篇LVS/DR + keepalived负载均衡实现

[root@localhost ~]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived

global_defs {
   notification_email {
     [email protected] 
   }
   notification_email_from [email protected] 
   #smtp_server 127.0.0.1 
   #smtp_connect_timeout 30
    router_id LVS_1
   #lvs_id LVS_EXAMPLE_01 
}

vrrp_sync_group VG1 {
   group {
      VI_1
      VI_GATEWAY
   }
} 

vrrp_instance VI_1 {
    state MASTER
    interface eth0    #公网ip网口
    virtual_router_id 51
    priority 150
    advert_int 1
    lvs_sync_daemon_inteface eth0
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.214.70    #公网vip地址
    }
}

vrrp_instance VI_GATEWAY {
    state MASTER
    interface eth1         #内网ip网口
    lvs_sync_daemon_inteface eth1
    virtual_router_id 52
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.211.254  #内网vip地址
    }
}

virtual_server 192.168.214.70 80 {
    delay_loop 6
    lb_algo rr
    lb_kind NAT         #使用lvs的NAT工作模式
    #nat_mask 255.255.255.0
    persistence_timeout 10 
    protocol TCP

    real_server 192.168.211.79 80 {
        TCP_CHECK {
            connect_timeout 3
            connect_port 80
            nb_get_retry 3
            delay_before_retry 3
        }
    }
   real_server 192.168.211.83 80 {
        TCP_CHECK {
            connect_timeout 3
            connect_port 80
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}


再看下211.77 keepalived BACKUP主机上的配置

[root@localhost ~]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
global_defs {
   notification_email {
     [email protected] 
   }
   notification_email_from [email protected] 
   #smtp_server 127.0.0.1 
   #smtp_connect_timeout 30
   router_id LVS_1
   #lvs_id LVS_EXAMPLE_02 
}

vrrp_sync_group VG1 {
   group {
      VI_1
      VI_GATEWAY
   }
} 

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    lvs_sync_daemon_inteface eth0
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.214.70 
    }
}

vrrp_instance VI_GATEWAY {
    state BACKUP
    interface eth1
    lvs_sync_daemon_inteface eth1
    virtual_router_id 52
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.211.254 
    }
}

virtual_server 192.168.214.70 80 {
    delay_loop 6
    lb_algo rr
    lb_kind NAT
    #nat_mask 255.255.255.0
    persistence_timeout 10
    protocol TCP

 real_server 192.168.211.79 80 {
        TCP_CHECK {
            connect_timeout 3
            connect_port 80
            nb_get_retry 3
            delay_before_retry 3
        }
    }
real_server 192.168.211.83 80 {
        TCP_CHECK {
            connect_timeout 3
            connect_port 80
            nb_get_retry 3
            delay_before_retry 3
        }
    }

}

六、后端真实机配置

后端两台web服务真实机192.168.211.79和192.168.211.83需要配置默认网关为vip内网ip地址192.168.211.254。

注意，线上环境如果更改默认网关为vip内网地址后，可能会造成连接不上服务器，需要提前添加相关静态路由。

 

七、启动keepalived服务及查看相关信息

在211.76和211.77上分别启动keepalived服务

 

在211.76keepalived Master主机上查看信息

通过ip addr可以看到vip 地址已经绑定在eth0和eth1网口

[root@localhost ~]# ip addr
1: lo:  mtu65536 qdisc noqueue state UNKNOWN 
   link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
   inet 127.0.0.1/8 scope host lo
   inet6 ::1/128 scope host 
      valid_lft forever preferred_lft forever
2: eth0: mtu 1500 qdisc pfifo_fast state UP qlen1000
   link/ether 52:54:00:55:b2:d4 brd ff:ff:ff:ff:ff:ff
   inet 192.168.214.76/24 brd 192.168.214.255 scope global eth0
   inet 192.168.214.70/32 scope global eth0
   inet6 fe80::5054:ff:fe55:b2d4/64 scope link 
      valid_lft forever preferred_lft forever
3: eth1: mtu 1500 qdisc pfifo_fast state UP qlen1000
   link/ether 52:54:00:85:11:95 brd ff:ff:ff:ff:ff:ff
   inet 192.168.211.76/24 brd 192.168.211.255 scope global eth1
   inet 192.168.211.254/32 scope global eth1
   inet6 fe80::5054:ff:fe85:1195/64 scope link 
      valid_lft forever preferred_lft forever

在211.76上查看日志信息，看到已成功进入keepalived主机模式
[root@localhost ~]# tail -f/var/log/messages
May 10 10:25:47 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_GATEWAY) setting protocol VIPs.
May 10 10:25:47 localhost Keepalived_healthcheckers[6209]:Netlink reflector reports IP 192.168.211.254 added
May 10 10:25:47 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_GATEWAY) Sending gratuitous ARPs oneth1 for 192.168.211.254
May 10 10:25:47 localhostKeepalived_vrrp[6210]: VRRP_Group(VG1) Syncing instances to MASTER state
May 10 10:25:47 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_1) EnteringMASTER STATE
May 10 10:25:47 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_1) setting protocol VIPs.
May 10 10:25:47 localhost Keepalived_healthcheckers[6209]:Netlink reflector reports IP 192.168.214.70 added
May 10 10:25:47 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_1) Sendinggratuitous ARPs on eth0 for 192.168.214.70
May 10 10:25:52 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_GATEWAY) Sendinggratuitous ARPs on eth1 for 192.168.211.254
May 10 10:25:52 localhostKeepalived_vrrp[6210]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for192.168.214.70


在211.77上查看日志信息，看到已成功进入keepalived备机模式

[root@localhost ~]# tail -f/var/log/messages
May 10 10:27:54 localhostKeepalived_vrrp[6249]: Opening file '/etc/keepalived/keepalived.conf'.
May 10 10:27:54 localhostKeepalived_vrrp[6249]: Configuration is using : 69554 Bytes
May 10 10:27:54 localhostKeepalived_vrrp[6249]: Using LinkWatch kernel netlink reflector...
May 10 10:27:54 localhostKeepalived_vrrp[6249]: VRRP_Instance(VI_1) Entering BACKUP STATE
May 10 10:27:54 localhostKeepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) Entering BACKUP STATE
May 10 10:27:54 localhost Keepalived_vrrp[6249]:VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)]
May 10 10:27:54 localhostKeepalived_vrrp[6249]: VRRP sockpool: [ifindex(3), proto(112), unicast(0),fd(12,13)]
May 10 10:27:54 localhostKeepalived_healthcheckers[6248]: Using LinkWatch kernel netlink reflector...
May 10 10:27:54 localhostKeepalived_healthcheckers[6248]: Activating healthchecker for service[192.168.211.79]:80
May 10 10:27:54 localhostKeepalived_healthcheckers[6248]: Activating healthchecker for service[192.168.211.83]:80

通过ipvsadm -L –n 查看相应lvs连接信息
[root@localhost ~]# ipvsadm -L -n
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.168.214.70:80 rr persistent 10
  -> 192.168.211.79:80            Masq    1      0          0         
  -> 192.168.211.83:80            Masq    1      3          0


八、keepalived测试

使用vip地址192.168.214.70访问后端192.168.211.79和192.168.211.83的页面

LVS/NAT + keepalived负载均衡实现_第1张图片

LVS/NAT + keepalived负载均衡实现_第2张图片

正常访问没问题后，我们来模拟lvs集群故障，让主备进行自动切换下

首先把keepalived master主机211.76宕机，看备机能否接管过来，vip地址是否会漂移过来

在211.77上查看日志，发现备机成功切换成了主机状态，vip地址成功漂移了过来

[root@localhost ~]# ip addr

1: lo: mtu65536 qdisc noqueue state UNKNOWN

   link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

   inet 127.0.0.1/8 scope host lo

   inet6 ::1/128 scope host

      valid_lft forever preferred_lft forever

2: eth0: mtu 1500 qdisc pfifo_fast state UP qlen1000

   link/ether 52:54:00:1b:a2:11 brd ff:ff:ff:ff:ff:ff

   inet 192.168.214.77/24 brd 192.168.214.255 scope global eth0

   inet 192.168.214.70/32 scope global eth0

   inet6 fe80::5054:ff:fe1b:a211/64 scope link

      valid_lft forever preferred_lft forever

3: eth1: mtu 1500 qdisc pfifo_fast state UP qlen 1000

   link/ether 52:54:00:64:47:7d brd ff:ff:ff:ff:ff:ff

   inet 192.168.211.77/24 brd 192.168.211.255 scope global eth1

   inet 192.168.211.254/32 scope global eth1

   inet6 fe80::5054:ff:fe64:477d/64 scope link

      valid_lft forever preferred_lft forever


[root@localhost ~]# tail -f /var/log/messages
May 10 10:27:54 localhost Keepalived_vrrp[6249]: Opening file '/etc/keepalived/keepalived.conf'.
May 10 10:27:54 localhost Keepalived_vrrp[6249]: Configuration is using : 69554 Bytes
May 10 10:27:54 localhost Keepalived_vrrp[6249]: Using LinkWatch kernel netlink reflector...
May 10 10:27:54 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_1) Entering BACKUP STATE
May 10 10:27:54 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) Entering BACKUP STATE
May 10 10:27:54 localhost Keepalived_vrrp[6249]: VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)]
May 10 10:27:54 localhost Keepalived_vrrp[6249]: VRRP sockpool: [ifindex(3), proto(112), unicast(0), fd(12,13)]
May 10 10:27:54 localhost Keepalived_healthcheckers[6248]: Using LinkWatch kernel netlink reflector...
May 10 10:27:54 localhost Keepalived_healthcheckers[6248]: Activating healthchecker for service [192.168.211.79]:80
May 10 10:27:54 localhost Keepalived_healthcheckers[6248]: Activating healthchecker for service [192.168.211.83]:80
May 10 11:09:26 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_1) Transition to MASTER STATE
May 10 11:09:26 localhost Keepalived_vrrp[6249]: VRRP_Group(VG1) Syncing instances to MASTER state
May 10 11:09:26 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) Transition to MASTER STATE
May 10 11:09:27 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) Entering MASTER STATE
May 10 11:09:27 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) setting protocol VIPs.
May 10 11:09:27 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) Sending gratuitous ARPs on eth1 for 192.168.211.254
May 10 11:09:27 localhost Keepalived_healthcheckers[6248]: Netlink reflector reports IP 192.168.211.254 added
May 10 11:09:27 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_1) Entering MASTER STATE
May 10 11:09:27 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_1) setting protocol VIPs.
May 10 11:09:27 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.214.70
May 10 11:09:27 localhost Keepalived_healthcheckers[6248]: Netlink reflector reports IP 192.168.214.70 added
May 10 11:09:32 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_GATEWAY) Sending gratuitous ARPs on eth1 for 192.168.211.254
May 10 11:09:32 localhost Keepalived_vrrp[6249]: VRRP_Instance(VI_1) Sending


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LVS/NAT + keepalived负载均衡实现_第3张图片