小知识：LVS+Keepalived构建高可用负载均衡(测试篇)

一、 启动LVS高可用集群服务

首先，启动每个real server节点的服务：

[root@localhost ~]# /etc/init.d/lvsrs start

start LVS of REALServer

然后，分别在主备Director Server启动Keepalived服务：

[root@DR1 ~]#/etc/init.d/Keepalived start

[root@DR1 ~]#/ ipvsadm -L

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

-> RemoteAddress:Port Forward Weight ActiveConn InActConn

TCP bogon:http rr

-> real-server1:http Route 1 1 0

-> real-server2:http Route 1 1 0

此时查看Keepalived服务的系统日志信息如下:

[root@localhost ~]# tail -f /var/log/messages

Feb 28 10:01:56 localhost Keepalived: Starting Keepalived v1.1.19 (02/27,2011)

Feb 28 10:01:56 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.12.25 added

Feb 28 10:01:56 localhost Keepalived_healthcheckers: Opening file /etc/keepalived/keepalived.conf.

Feb 28 10:01:56 localhost Keepalived_healthcheckers: Configuration is using : 12063 Bytes

Feb 28 10:01:56 localhost Keepalived: Starting Healthcheck child process, pid=4623

Feb 28 10:01:56 localhost Keepalived_vrrp: Netlink reflector reports IP 192.168.12.25 added

Feb 28 10:01:56 localhost Keepalived: Starting VRRP child process, pid=4624

Feb 28 10:01:56 localhost Keepalived_healthcheckers: Activating healtchecker for service [192.168.12.246:80]

Feb 28 10:01:56 localhost Keepalived_vrrp: Opening file /etc/keepalived/keepalived.conf.

Feb 28 10:01:56 localhost Keepalived_healthcheckers: Activating healtchecker for service [192.168.12.237:80]

Feb 28 10:01:57 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE

Feb 28 10:01:58 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE

Feb 28 10:01:58 localhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.

Feb 28 10:01:58 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.12.135 added

Feb 28 10:01:58 localhost avahi-daemon[2778]: Registering new address record for 192.168.12.135 on eth0.

二、 高可用性功能测试

高可用性是通过LVS的两个Director Server完成的，为了模拟故障，我们先将主Director Server上面的Keepalived服务停止，然后观察备用Director Server上Keepalived的运行日志，信息如下：

Feb 28 10:08:52 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE

Feb 28 10:08:54 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE

Feb 28 10:08:54 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.

Feb 28 10:08:54 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.12.135

Feb 28 10:08:54 lvs-backup Keepalived_vrrp: Netlink reflector reports IP 192.168.12.135 added

Feb 28 10:08:54 lvs-backup Keepalived_healthcheckers: Netlink reflector reports IP 192.168.12.135 added

Feb 28 10:08:54 lvs-backup avahi-daemon[3349]: Registering new address record for 192.168.12.135 on eth0.

Feb 28 10:08:59 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.12.135

从日志中可以看出，主机出现故障后，备机立刻检测到，此时备机变为MASTER角色，并且接管了主机的虚拟IP资源，最后将虚拟IP绑定在eth0设备上。

接着，重新启动主Director Server上的Keepalived服务，继续观察备用Director Server的日志状态：

备用Director Server的日志状态：

Feb 28 10:12:11 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) Received higher prio advert

Feb 28 10:12:11 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE

Feb 28 10:12:11 lvs-backup Keepalived_vrrp: VRRP_Instance(VI_1) removing protocol VIPs.

Feb 28 10:12:11 lvs-backup Keepalived_vrrp: Netlink reflector reports IP 192.168.12.135 removed

Feb 28 10:12:11 lvs-backup Keepalived_healthcheckers: Netlink reflector reports IP 192.168.12.135 removed

Feb 28 10:12:11 lvs-backup avahi-daemon[3349]: Withdrawing address record for 192.168.12.135 on eth0.

从日志可知，备机在检测到主机重新恢复正常后，重新返回BACKUP角色，并且释放了虚拟IP资源。

三、 负载均衡测试

这里假定两个real server节点配置www服务的网页文件根目录均为/webdata/www目录，然后分别执行如下操作：

在real server1 执行：

echo “This is real server1” /webdata/www/index.html

在real server2 执行：

echo “This is real server2” /webdata/www/index.html

接着打开浏览器，访问http://192.168.12.135这个地址，然后不断刷新此页面，如果能分别看到“This is real server1”和“This is real server2”就表明LVS已经在进行负载均衡了。

四、 故障切换测试

故障切换是测试当某个节点出现故障后，Keepalived监控模块是否能及时发现，然后屏蔽故障节点，同时将服务转移到正常节点来执行。

这里我们将real server 1节点服务停掉，假定这个节点出现故障，然后查看主、备机日志信息，相关日志如下：

Feb 28 10:14:12 localhost Keepalived_healthcheckers: TCP connection to [192.168.12.246:80] failed !!!

Feb 28 10:14:12 localhost Keepalived_healthcheckers: Removing service [192.168.12.246:80] from VS [192.168.12.135:80]

Feb 28 10:14:12 localhost Keepalived_healthcheckers: Remote SMTP server [192.168.12.1:25] connected.

Feb 28 10:14:12 localhost Keepalived_healthcheckers: SMTP alert successfully sent.

通过日志可以看出，Keepalived监控模块检测到192.168.12.246这台主机出现故障后，将此节点从集群系统中剔除掉了。

此时访问http://192.168.12.135这个地址，应该只能看到“This is real server2”了，这是因为节点1出现故障，而Keepalived监控模块将节点1从集群系统中剔除了。

下面重新启动real server 1节点的服务，可以看到Keepalived日志信息如下：

Feb 28 10:15:48 localhost Keepalived_healthcheckers: TCP connection to [192.168.12.246:80] success.

Feb 28 10:15:48 localhost Keepalived_healthcheckers: Adding service [192.168.12.246:80] to VS [192.168.12.135:80]

Feb 28 10:15:48 localhost Keepalived_healthcheckers: Remote SMTP server [192.168.12.1:25] connected.

Feb 28 10:15:48 localhost Keepalived_healthcheckers: SMTP alert successfully sent.

从日志可知，Keepalived监控模块检测到192.168.12.246这台主机恢复正常后，又将此节点加入了集群系统中。

此时再次访问http://192.168.12.135这个地址，然后不断刷新此页面，应该又能分别看到“This is real server1”和“This is real server2”页面了，这说明在real server 1节点恢复正常后，Keepalived监控模块将此节点加入了集群系统中。

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