keepalived+nginx

我们先来谈谈keepalived的工作原理：

keepalived的工作原理基于三个层面，分别时IP层，TCP层和应用层
IP 层：keepalived会定期向服务器集群中的服务器发送一个类似于ping程序的ICMP数据包。通俗理解就是我keepalived来ping你服 务器，我要是ping通了，那我知道你还活着，咱们可以继续合作，如果不幸发现你挂了，那就得把这台服务器踢了。该层就是确保服务器ip地址有效，一次来 判断这台服务器可否继续在岗谋职。
TCP层：这一层和IP层类似，只不过IP层检查的是IP，该层检查TCP端口。keepalived在IP层 且报你服务器的IP有效，然后继续看你的TCP端口，比如说你是web server，那你的80端口就应该开启，如果keepalived发现你的80端口没有启动。那么它就会认为你已经挂掉，然后剔除。
应用层：这一层就是具体的工作程序了，keepalived是个恪尽职守的检察官，应用层的程序与用户的设定息息相关，keepalived则通过检查服务器的运行是否和用户设定一致，如果不一致，keepalived就会宣判这台服务器牺牲。

keepalived + nginx

主机：172.25.44.3 server3
备机：172.25.44.4 server4

配置虚拟ip

[root@server3 ～]# vim /etc/sysconfig/network-scripts/ifcfg-eth0:0DEVICE=eth0:0TYPE=EthernetONBOOT=yesBOOTPROTO=staticDNS1=172.25.44.44IPADDR=172.25.44.100NETMASK=255.255.255.0GETWAY=172.25.44.44[root@server3 ～]# /etc/init.d/network restart[root@server3 ～]# ifconfigeth0      Link encap:Ethernet  HWaddr 52:54:00:48:60:3E          inet addr:172.25.44.4  Bcast:172.25.44.255  Mask:255.255.255.0          inet6 addr: fe80::5054:ff:fe48:603e/64 Scope:Link          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          RX packets:11926 errors:0 dropped:0 overruns:0 frame:0          TX packets:6533 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:1000          RX bytes:25662550 (24.4 MiB)  TX bytes:876645 (856.0 KiB)eth0:0    Link encap:Ethernet  HWaddr 52:54:00:48:60:3E          inet addr:172.25.44.100  Bcast:172.25.44.255  Mask:255.255.255.0          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1lo        Link encap:Local Loopback          inet addr:127.0.0.1  Mask:255.0.0.0          inet6 addr: ::1/128 Scope:Host          UP LOOPBACK RUNNING  MTU:16436  Metric:1          RX packets:36283 errors:0 dropped:0 overruns:0 frame:0          TX packets:36283 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:0          RX bytes:1982812 (1.8 MiB)  TX bytes:1982812 (1.8 MiB)

安装nginx

安装包：nginx-1.10.3.tar.gz
解压安装包：tar zxf nginx-1.10.3.tar.gz

[root@server3 software]# cd nginx-1.10.3 -prefix=/usr/local/lnmp/nignx[root@server3 nginx-1.10.3]# ./configure[root@server3 nginx-1.10.3]# make[root@server3 nginx-1.10.3]# make install[root@server3 nginx-1.10.3]# ln -s /usr/local/lnmp/nginx/sbin/nginx /usr/local/sbin/#创建nginx的软链接

配置nginx

[root@server3 nginx-1.10.3]# cd /usr/local/lnmp/nginx/conf[root@server3 conf]# vim nginx.conf/#访问8088端口是的发布目录为/var/www/html，而nginx的默认发布目录还是/usr/local/lnmp/nginx/htmlserver {        listen       8088；#监听8088端口        server_name  localhost;    location / {        root   /var/www/html;        index  index.html index.htm;    }    error_page   500 502 503 504  /50x.html;    location = /50x.html {        root   /usr/local/lnmp/nginx/html;    }}[root@server3 conf]# cd /var/www/html[root@server3 html]# vim index.html
Welcome to nginx! 172.25.44.3[root@server3 html]# nginx

安装keepalived

安装包：keepalived-1.2.2.tar.gz

[root@server3 software]# wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz[root@server3 software]# tar zxf keepalived-1.2.2.tar.gz[root@server3 software]# cd keepalived-1.2.2[root@server3 keepalived-1.2.2]# ./configure[root@server3 keepalived-1.2.2]# make[root@server3 keepalived-1.2.2]# make install[root@server3 keepalived-1.2.2]# cp /usr/local/sbin/keepalived /usr/sbin/[root@server3 keepalived-1.2.2]# cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/[root@server3 keepalived-1.2.2]# cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/[root@server3 keepalived-1.2.2]# cp -r /usr/local/etc/keepalived/ /etc/

配置leepalived

[root@server3 keepalived-1.2.2]# vim /var/www/html/index.htmlglobal_defs {    router_id LVS_DEVEL}vrrp_script chk_http_port {    script "#state MASTER:MASTER主机，BACKUP备机#priority 100:优先级指定，数字越大优先级越高#virtual_ipaddress:指定vip#track_scrip:检查端口
[root@server3 keepalived-1.2.2]# /etc/init.d/keepalived start
备机次同步主机的操作步骤：keepalived的配置文件中，主机的state为MASTER，备机的state为BACKUP，备机的priority要小于主机
测试
验证nginx启动正常
访问主机nginx的默认页
访问主机nginx的指定页
访问备机nginx的默认页
访问备机nginx的指定页
访问vip
主机server3的优先级更高，在主机完好的情况下，有server3来负载nginx运行
[root@server3 software]# /etc/init.d/keepalived stopStopping keepalived:                                       [  OK  ]
当主机的keeplived服务挂掉的时候，在则访问vip，则由备机自动负载nginx运行
[root@server4 conf]# ip a1: lo:  mtu 16436 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 forever2: eth0:  mtu 1500 qdisc pfifo_fast state UP qlen 1000    link/ether 52:54:00:48:60:3e brd ff:ff:ff:ff:ff:ff    inet 172.25.44.4/24 brd 172.25.44.255 scope global eth0    inet 172.25.254.104/24 brd 172.25.254.255 scope global eth0    inet 172.25.44.100/32 scope global eth0    inet 172.25.44.100/24 brd 172.25.44.255 scope global secondary eth0:0    inet6 fe80::5054:ff:fe48:603e/64 scope link       valid_lft forever preferred_lft forever
同时可以看到vip浮动在备机server4上
[root@server3 software]# /etc/init.d/keepalived startStarting keepalived:                                       [  OK  ]
启动主机server3上的keepalived服务，再次访问vip，则nginx的负载运行又回到主机server3上
[root@server3 software]# ip a1: lo:  mtu 16436 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 forever2: eth0:  mtu 1500 qdisc pfifo_fast state UP qlen 1000    link/ether 52:54:00:b4:14:0d brd ff:ff:ff:ff:ff:ff    inet 172.25.44.3/24 brd 172.25.44.255 scope global eth0    inet 172.25.254.103/24 brd 172.25.254.255 scope global eth0    inet 172.25.44.100/32 scope global eth0    inet6 fe80::5054:ff:feb4:140d/64 scope link       valid_lft forever preferred_lft forever
该情况下查看ip，发现vip浮动在主机server3上
在应用层出问题的情况下，如停掉主机server3的nginx服务，则备机server4也会自动接管nginx支持前端的访问
[root@server3 software]# killall nginx

问题补充：在备机keepalived的配合配置文件中，如果补修改state的情况下实验也是可以成功的，我觉得应该时两个机子通过priority优先级竞争。