七层负载均衡
七层就是基于URL等应用层信息的负载均衡。从第七层"应用层"开始，根据虚拟的url或IP，主机名接收请求，再转向相应的处理服务器。七层负载均衡器也称作七层交换机，即L7 switch（七层交换），OSI的最高层，应用层。此时，该Load Balancer能理解应用协议。如：HAProxy、Nginx等。
四层负载均衡
四层就是基于IP+端口的负载均衡，是在三次负载均衡的基础上，即从第四层"传输层"开始，使用"ip+port"接收请求，再转发到对应的机器。四层负载均衡器也称作四层交换机，即L4 switch（四层交换），在OSI第4层工作，此种Load Balance不理解应用协议（如HTTP/FTP/MySQL等等）。如：LVS、F5、深信服AD等。
nginx进程基于Master+Slave(worker)多进程模型，自身具有非常稳定的子进程管理功能。在Master进程分配模式下，Master进程永远不进行业务处理，只是进行任务分发，从而达到Master进程的存活高可靠性，Slave(worker)进程所有的业务信号都 由主进程发出，Slave(worker)进程所有的超时任务都会被Master中止，属于非阻塞式任务模型。
Keepalived是Linux下面实现VRRP备份路由的高可靠性运行件。基于Keepalived设计的服务模式能够真正做到主服务器和备份服务器故障时IP瞬间无缝交接。二者结合，可以构架出比较稳定的软件LB(LoadBalance)方案。
Keepalived是一个基于VRRP协议来实现的服务高可用方案，可以利用其来避免IP单点故障，类似的工具还有heartbeat、corosync、pacemaker。但是它一般不会单独出现，而是与其它负载均衡技术（如lvs、haproxy、nginx）一起工作来达到集群的高可用。
VRRP协议
VRRP全称 Virtual Router Redundancy Protocol，即 虚拟路由冗余协议。可以认为它是实现路由器高可用的容错协议，即将N台提供相同功能的路由器组成一个路由器组(Router Group)，这个组里面有一个master和多个backup，但在外界看来就像一台一样，构成虚拟路由器，拥有一个虚拟IP（vip，也就是路由器所在局域网内其他机器的默认路由），占有这个IP的master实际负责ARP相应和转发IP数据包，组中的其它路由器作为备份的角色处于待命状态。master会发组播消息，当backup在超时时间内收不到vrrp包时就认为master宕掉了，这时就需要根据VRRP的优先级来选举一个backup当master，保证路由器的高可用。
在VRRP协议实现里，虚拟路由器使用 00-00-5E-00-01-XX 作为虚拟MAC地址，XX就是唯一的 VRID （Virtual Router IDentifier），这个地址同一时间只有一个物理路由器占用。在虚拟路由器里面的物理路由器组里面通过多播IP地址 224.0.0.18 来定时发送通告消息。每个Router都有一个 1-255 之间的优先级别，级别最高的（highest priority）将成为主控（master）路由器。通过降低master的优先权可以让处于backup状态的路由器抢占（pro-empt）主路由器的状态，两个backup优先级相同的IP地址较大者为master，接管虚拟IP。
【1】基础环境准备
两台服务器：192.168.88.129(主) 192.168.88.130(从)，每台服务器上分别安装nginx 、keepalived。
首先要关闭防火墙、关闭selinux。
当然，你可以选择不关闭，但是可能会遇到各种奇怪问题。
安装keepalived可使用yum直接安装：yum -y install keepalived
默认keepalived.conf配置文件
! Configuration File for keepalived global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 192.168.200.1 smtp_connect_timeout 30 router_id LVS_DEVEL vrrp_skip_check_adv_addr vrrp_strict vrrp_garp_interval 0 vrrp_gna_interval 0 } vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.200.16 192.168.200.17 192.168.200.18 } } virtual_server 192.168.200.100 443 { delay_loop 6 lb_algo rr lb_kind NAT persistence_timeout 50 protocol TCP real_server 192.168.201.100 443 { weight 1 SSL_GET { url { path / digest ff20ad2481f97b1754ef3e12ecd3a9cc } url { path /mrtg/ digest 9b3a0c85a887a256d6939da88aabd8cd } connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } } virtual_server 10.10.10.2 1358 { delay_loop 6 lb_algo rr lb_kind NAT persistence_timeout 50 protocol TCP sorry_server 192.168.200.200 1358 real_server 192.168.200.2 1358 { weight 1 HTTP_GET { url { path /testurl/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } url { path /testurl2/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } url { path /testurl3/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } real_server 192.168.200.3 1358 { weight 1 HTTP_GET { url { path /testurl/test.jsp digest 640205b7b0fc66c1ea91c463fac6334c } url { path /testurl2/test.jsp digest 640205b7b0fc66c1ea91c463fac6334c } connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } } virtual_server 10.10.10.3 1358 { delay_loop 3 lb_algo rr lb_kind NAT persistence_timeout 50 protocol TCP real_server 192.168.200.4 1358 { weight 1 HTTP_GET { url { path /testurl/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } url { path /testurl2/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } url { path /testurl3/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } real_server 192.168.200.5 1358 { weight 1 HTTP_GET { url { path /testurl/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } url { path /testurl2/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } url { path /testurl3/test.jsp digest 640205b7b0fc66c1ea91c463fac6334d } connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } }
接下来就是要对该配置文件进行修改，该配置文件在/etc/keepalived/路径下。在默认的keepalive.conf里面还有 virtual_server,real_server 这样的配置，它是为lvs准备的。
首先开始配置主从模式，实例图如下：
【2】修改keepalived.conf配置文件
① 修改主机keepalived.conf配置
global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 192.168.88.129 #这里修改为本机IP smtp_connect_timeout 30 router_id LVS_DEVEL } #添加检测脚本 vrrp_script chk_http_port { script "/usr/local/nginx/nginx_check.sh" interval 2 weight 2 } vrrp_instance VI_1 { state MASTER #主机这里是MASTER 从机是BACKUP interface ens33 #网卡 virtual_router_id 51 # 主、从机的virtual_router_id必须相同 priority 100 # 主备机取不同的优先级，主机优先级大 advert_int 1 #心跳检测间隔时间 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.50 # VRRP 虚拟IP ；可换行输入多个进行绑定 } }
在默认的keepalive.conf里面还有 virtual_server,real_server 这样的配置，我们这用不到，它是为lvs准备的。
/usr/local/nginx/nginx_check.sh 脚本内容如下：
#!/bin/bash counter=$(ps -C nginx --no-heading|wc -l) if [ "${counter}" = "0" ]; then /usr/local/nginx/sbin/nginx sleep 2 counter=$(ps -C nginx --no-heading|wc -l) if [ "${counter}" = "0" ]; then systemctl stop keepalived fi fi
如果发现nginx进程不存在，则尝试启动；sleep2秒后再次检测，如果还是不存在则认为启动失败，就停止keepalived服务。
② 修改从机keepalived.conf配置文件
! Configuration File for keepalived global_defs { notification_email { #指定keepalived在发生事件时(比如切换)发送通知邮件的邮箱 acassen@firewall.loc #设置报警邮件地址，可以设置多个，每行一个。 需开启本机的sendmail服务 failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc #keepalived在发生诸如切换操作时需要发送email通知地址 smtp_server 192.168.88.129 #指定发送email的smtp服务器 smtp_connect_timeout 30 #设置连接smtp server的超时时间 router_id LVS_DEVEL #运行keepalived的机器的一个标识，通常可设为hostname。故障发生时，发邮件时显示在邮件主题中的信息。 } vrrp_script chk_http_port { script "/usr/local/nginx/nginx_check.sh" interval 2 #检测脚本执行间隔时间 weight 2 #设置当前服务器权重增量 } vrrp_instance VI_1 { state BACKUP interface ens33 virtual_router_id 51 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.50 } }
同样需要在/usr/local/nginx/路径下放上nginx_check.sh脚本文件。
③ 启动nginx、keepalived
/usr/local/nginx/sbin/nginx #启动nginx systemctl start keepalived #启动keepalived
【3】测试
① 浏览器访问http://192.168.88.50/
192.168.88.129主nginx访问日志打印如下：
查看主服务器keepalived日志
Keepalived默认所有的日志都是写入到/var/log/message ，你可以使用命令 tail -f /var/log/messages|grep Keepalived 进行查看
尝试访问主服务器部署的页面http://192.168.88.50/edu/index.html：
主机192.168.88.129使用ip address命令检测可以发现虚拟ip已经飘到了主机上面：
② 停掉主机的keepalived
查看主机日志信息：
Jun 30 15:42:34 bogon Keepalived[5789]: Stopping Jun 30 15:42:34 bogon Keepalived_healthcheckers[5791]: Stopped Jun 30 15:42:34 bogon Keepalived_vrrp[5792]: VRRP_Instance(VI_1) sent 0 priority Jun 30 15:42:34 bogon Keepalived_vrrp[5792]: VRRP_Instance(VI_1) removing protocol VIPs. Jun 30 15:42:35 bogon Keepalived_vrrp[5792]: Stopped Jun 30 15:42:35 bogon Keepalived[5789]: Stopped Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2
查看从机日志信息：
#当主服务器停掉后，从机将会切换为MASTER状态 Jun 30 13:26:14 bogon avahi-daemon[731]: Withdrawing address record for 192.168.88.50 on ens33. Jun 30 13:28:55 bogon Keepalived_vrrp[2966]: VRRP_Instance(VI_1) Transition to MASTER STATE Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: VRRP_Instance(VI_1) Entering MASTER STATE Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: VRRP_Instance(VI_1) setting protocol VIPs. Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.50 Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:28:56 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:28:56 bogon avahi-daemon[731]: Registering new address record for 192.168.88.50 on ens33.IPv4. Jun 30 13:29:01 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:29:01 bogon Keepalived_vrrp[2966]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.50 Jun 30 13:29:01 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:29:01 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:29:01 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 13:29:01 bogon Keepalived_vrrp[2966]: Sending gratuitous ARP on ens33 for 192.168.88.50 #当主服
检测从机ip地址:
可以发现从机的keepalived已经切换为了MASTER状态，且从机的ip address检测时发现VIP绑定到了ens33上面。此时访问http://192.168.88.50/就会跑到从服务器的nginx上面！
再次启动主服务器的keepalived，查看主机日志：
主服务器的keepalived进入MASTER STATE，从服务器的keepalived进入BACKUP STATE：
#从服务器日志 Jun 30 15:01:24 bogon Keepalived_vrrp[1900]: VRRP_Instance(VI_1) Received advert with higher priority 100, ours 90 Jun 30 15:01:24 bogon Keepalived_vrrp[1900]: VRRP_Instance(VI_1) Entering BACKUP STATE Jun 30 15:01:24 bogon Keepalived_vrrp[1900]: VRRP_Instance(VI_1) removing protocol VIPs.
③ 停掉主服务器的nginx，不停keepalived
则会执行脚本nginx_check.sh进行nginx启动！
总结
master没挂，则master占有vip且nginx运行在master上
master挂了，则slave抢占vip且在slave上运行nginx服务
如果master上的nginx服务挂了，则nginx会自动重启，重启失败后会自动关闭keepalived，这样vip资源也会转移到slave上。
master和slave两边都开启nginx服务，无论master还是slave，当其中的一个keepalived服务停止后，vip都会漂移到keepalived服务还在的节点上；
如果要想使nginx服务挂了，vip也漂移到另一个节点，则必须用脚本或者在配置文件里面用shell命令来控制。（nginx服务宕停后会自动启动，启动失败后会强制关闭keepalived，从而致使vip资源漂移到另一台机器上）
一种常见的主从热备应用实例如下图所示：
主从的缺点在于如果主机一直稳定，那么从机就会一直处于空闲状态，造成了资源的浪费。
【4】问题总结
① 不能完全停掉keepalived进程
使用yum 安装的keepalived，当使用命令systemctl stop keepalived 停掉keepalived服务时，使用ps命令检测发现还存，如下图示：
当使用命令systemctl status keepalived检测状态，会发现有一条警告信息，如下所示：
Jun 30 11:52:20 bogon systemd[1]: Stopped LVS and VRRP High Availability Monitor. Jun 30 11:52:20 bogon systemd[1]: Stopping LVS and VRRP High Availability Monitor... Jun 30 11:52:20 bogon systemd[1]: Starting LVS and VRRP High Availability Monitor... Jun 30 11:52:20 bogon systemd[1]: Can't open PID file /var/run/keepalived.pid (yet?) after start: No such file or directory Jun 30 11:52:20 bogon systemd[1]: Started LVS and VRRP High Availability Monitor. Jun 30 12:30:57 bogon systemd[1]: Stopped LVS and VRRP High Availability Monitor.
查看其服务脚本信息vim /usr/lib/systemd/system/keepalived.service：
[Unit] Description=LVS and VRRP High Availability Monitor After=syslog.target network-online.target [Service] Type=forking PIDFile=/var/run/keepalived.pid KillMode=process EnvironmentFile=-/etc/sysconfig/keepalived ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS ExecReload=/bin/kill -HUP $MAINPID [Install] WantedBy=multi-user.target
KillMode=process的大致意思是当停止keepalived的时候只会停掉主进程，而主进程产生的子进程是不会被干掉的。而killmode的默认值是control-group，意思时所有进程都会被干掉，这里选择把这项注释掉。
重载配置
systemctl daemon-reload
杀掉keepalived所有进程，然后再次启动keepalived即可：
pkill -9 keepalived
② Unsafe permissions found for script ‘/usr/local/nginx/nginx_check.sh’.
说明你赋予的权限太高了，可以使用如下命令尝试：
chmod 755 /usr/local/nginx/nginx_check.sh
【5】keepalived与heartbeat/corosync等比较
Heartbeat、Corosync、Keepalived这三个集群组件我们到底选哪个好呢？
首先要说明的是，Heartbeat、Corosync是属于同一类型，Keepalived与Heartbeat、Corosync，根本不是同一类型的。
Keepalived使用的vrrp协议方式，虚拟路由冗余协议 (Virtual Router Redundancy Protocol，简称VRRP)；Heartbeat或Corosync是基于主机或网络服务的高可用方式。
简单的说就是，Keepalived的目的是模拟路由器的高可用，Heartbeat或Corosync的目的是实现Service的高可用。
所以一般Keepalived是实现前端高可用，常用的前端高可用的组合有LVS+Keepalived、Nginx+Keepalived、HAproxy+Keepalived。
而Heartbeat或Corosync是实现服务的高可用。常见的组合有Heartbeat v3(Corosync)+Pacemaker+NFS+Httpd 实现Web服务器的高可用、Heartbeat v3(Corosync)+Pacemaker+NFS+MySQL 实现MySQL服务器的高可用。
总结一下，Keepalived中实现轻量级的高可用，一般用于前端高可用，且不需要共享存储，一般常用于两个节点的高可用。而Heartbeat(或Corosync)一般用于服务的高可用，且需要共享存储，一般用于多节点的高可用。这个问题我们说明白了。
那heartbaet与corosync又应该选择哪个好？
一般用corosync，因为corosync的运行机制更优于heartbeat，就连从heartbeat分离出来的pacemaker都说在以后的开发当中更倾向于corosync，所以现在corosync+pacemaker是最佳组合。
【6】主主模式配置实践
主主模式相对于主从模式而言区别在于，每个机器都互为主从。示意图如下：
① 修改192.168.88.129的keepalived.conf配置
添加如下配置：
vrrp_instance VI_2 { state BACKUP #这里修改为BACKUP interface ens33 virtual_router_id 52 #这里修改为52 priority 90 #修改优先级 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.60 #绑定另外一个VIP } track_script { chk_http_port } }
完整配置如下：
global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL } vrrp_script chk_http_port { script "/usr/local/nginx/nginx_check.sh" interval 2 weight 2 } vrrp_instance VI_1 { state MASTER interface ens33 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.50 } track_script { chk_http_port } } vrrp_instance VI_2 { state BACKUP interface ens33 virtual_router_id 52 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.60 } track_script { chk_http_port } }
② 修改192.168.88.130的keepalived.conf配置
添加配置如下：
vrrp_instance VI_2 { state MASTER interface ens33 virtual_router_id 52 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.60 } track_script { chk_http_port } }
完整配置如下：
global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL } vrrp_script chk_http_port { script "/usr/local/nginx/nginx_check.sh" interval 2 weight 2 } vrrp_instance VI_1 { state BACKUP interface ens33 virtual_router_id 51 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.50 } track_script { chk_http_port } } vrrp_instance VI_2 { state MASTER interface ens33 virtual_router_id 52 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.88.60 } track_script { chk_http_port } }
分别重启两台服务器上的keepalived服务，查看对应的日志信息。
192.168.88.129上keepalived日志信息如下：
Jun 30 17:00:13 bogon Keepalived[7503]: Stopping Jun 30 17:00:13 bogon Keepalived_healthcheckers[7504]: Stopped Jun 30 17:00:13 bogon Keepalived_vrrp[7505]: VRRP_Instance(VI_1) sent 0 priority Jun 30 17:00:13 bogon Keepalived_vrrp[7505]: VRRP_Instance(VI_1) removing protocol VIPs. Jun 30 17:00:14 bogon Keepalived_vrrp[7505]: Stopped Jun 30 17:00:14 bogon Keepalived[7503]: Stopped Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2 Jun 30 17:00:14 bogon Keepalived[16827]: Starting Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2 Jun 30 17:00:14 bogon Keepalived[16827]: Opening file '/etc/keepalived/keepalived.conf'. Jun 30 17:00:14 bogon Keepalived[16828]: Starting Healthcheck child process, pid=16830 Jun 30 17:00:14 bogon Keepalived[16828]: Starting VRRP child process, pid=16831 Jun 30 17:00:14 bogon Keepalived_healthcheckers[16830]: Opening file '/etc/keepalived/keepalived.conf'. Jun 30 17:00:14 bogon Keepalived_vrrp[16831]: Registering Kernel netlink reflector Jun 30 17:00:14 bogon Keepalived_vrrp[16831]: Registering Kernel netlink command channel Jun 30 17:00:14 bogon Keepalived_vrrp[16831]: Registering gratuitous ARP shared channel Jun 30 17:00:14 bogon Keepalived_vrrp[16831]: Opening file '/etc/keepalived/keepalived.conf'. Jun 30 17:00:14 bogon Keepalived_vrrp[16831]: WARNING - default user 'keepalived_script' for script execution does not exist - please create. Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: SECURITY VIOLATION - scripts are being executed but script_security not enabled. Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) removing protocol VIPs. Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) removing protocol VIPs. Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: Using LinkWatch kernel netlink reflector... Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Entering BACKUP STATE Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)] Jun 30 17:00:15 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) Transition to MASTER STATE Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) Entering MASTER STATE Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) setting protocol VIPs. Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.50 Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:16 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:17 bogon Keepalived_vrrp[16831]: /usr/local/nginx/nginx_check.sh exited due to signal 15 Jun 30 17:00:17 bogon Keepalived_vrrp[16831]: VRRP_Script(chk_http_port) succeeded Jun 30 17:00:18 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) Changing effective priority from 100 to 102 Jun 30 17:00:18 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Changing effective priority from 90 to 92 Jun 30 17:00:18 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Transition to MASTER STATE Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Entering MASTER STATE Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) setting protocol VIPs. Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.60 Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:19 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:21 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:21 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.50 Jun 30 17:00:21 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:21 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:21 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:21 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:24 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:24 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.60 Jun 30 17:00:24 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:24 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:24 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:24 bogon Keepalived_vrrp[16831]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:28 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Received advert with higher priority 100, ours 92 Jun 30 17:00:28 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) Entering BACKUP STATE Jun 30 17:00:28 bogon Keepalived_vrrp[16831]: VRRP_Instance(VI_2) removing protocol VIPs.
可以看到 对VRRP_Instance(VI_1)而言，192.168.88.129为MASTER；对VRRP_Instance(VI_2)而言，192.168.88.129为BACKUP
192.168.88.130上keepalived日志信息如下：
Jun 30 17:00:13 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) Transition to MASTER STATE Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) Entering MASTER STATE Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) setting protocol VIPs. Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.50 Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:14 bogon Keepalived_vrrp[5752]: Sending gratuitous ARP on ens33 for 192.168.88.50 Jun 30 17:00:15 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) Received advert with higher priority 100, ours 92 Jun 30 17:00:15 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) Entering BACKUP STATE Jun 30 17:00:15 bogon Keepalived_vrrp[5752]: VRRP_Instance(VI_1) removing protocol VIPs. Jun 30 17:00:26 bogon Keepalived[5749]: Stopping Jun 30 17:00:26 bogon Keepalived_healthcheckers[5751]: Stopped Jun 30 17:00:27 bogon Keepalived_vrrp[5752]: Stopped Jun 30 17:00:27 bogon Keepalived[5749]: Stopped Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2 Jun 30 17:00:27 bogon Keepalived[19665]: Starting Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2 Jun 30 17:00:27 bogon Keepalived[19665]: Opening file '/etc/keepalived/keepalived.conf'. Jun 30 17:00:27 bogon Keepalived[19666]: Starting Healthcheck child process, pid=19668 Jun 30 17:00:27 bogon Keepalived[19666]: Starting VRRP child process, pid=19669 Jun 30 17:00:27 bogon Keepalived_healthcheckers[19668]: Opening file '/etc/keepalived/keepalived.conf'. Jun 30 17:00:27 bogon Keepalived_vrrp[19669]: Registering Kernel netlink reflector Jun 30 17:00:27 bogon Keepalived_vrrp[19669]: Registering Kernel netlink command channel Jun 30 17:00:27 bogon Keepalived_vrrp[19669]: Registering gratuitous ARP shared channel Jun 30 17:00:27 bogon Keepalived_vrrp[19669]: Opening file '/etc/keepalived/keepalived.conf'. Jun 30 17:00:27 bogon Keepalived_vrrp[19669]: WARNING - default user 'keepalived_script' for script execution does not exist - please create. Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: SECURITY VIOLATION - scripts are being executed but script_security not enabled. Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_1) removing protocol VIPs. Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) removing protocol VIPs. Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: Using LinkWatch kernel netlink reflector... Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_1) Entering BACKUP STATE Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: VRRP sockpool: [ifindex(2), proto(112), unicast(0), fd(10,11)] Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: VRRP_Script(chk_http_port) succeeded Jun 30 17:00:28 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) Transition to MASTER STATE Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_1) Changing effective priority from 90 to 92 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) Changing effective priority from 100 to 102 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) Entering MASTER STATE Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) setting protocol VIPs. Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.60 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:29 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:34 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:34 bogon Keepalived_vrrp[19669]: VRRP_Instance(VI_2) Sending/queueing gratuitous ARPs on ens33 for 192.168.88.60 Jun 30 17:00:34 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:34 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:34 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60 Jun 30 17:00:34 bogon Keepalived_vrrp[19669]: Sending gratuitous ARP on ens33 for 192.168.88.60
可以看到 对VRRP_Instance(VI_1)而言，192.168.88.130为BACKUP；对VRRP_Instance(VI_2)而言，192.168.88.130为MASTER。
浏览器访问http://192.168.88.50/，192.168.88.129上的nginx会处理该请求；浏览器访问http://192.168.88.60/，192.168.88.130上的nginx会处理该请求 !
当任何一台服务器上面的keepalived服务停掉后，另外一台服务器上面的keepalived都会进入MASTER状态处理请求。如这里停掉192.168.88.129上的keepalived服务，则192.168.88.130上的keepalived服务的VRRP_Instance(VI_1)进入MASTER状态，并对http://192.168.88.50/ http://192.168.88.60/进行处理！
查看192.168.88.130此时ip 地址如下：
