使用keepalived实现nginx的高可用性
一，简介nginx是一款轻量级的web服务器和反向代理服务器，它拥有较强的并发能力，较为简单灵活的配置，以及超强的性能。nginx越来越受到人们的关注，国内许多站点都采用nginx作为其web服务器或者反向代理。
keepalived是linux中使用vrrp协议实现高可用功能的一个软件，vrrp可以将两台或者多台路由设备虚拟成一台设备，并提供vip供外网访问，内部通过相应算法选举出MASTER，将vip配置在MASTER上，向外提供相应服务，当MASTER宕机时，BACKUP在一定时间内接收不到MASTER传递过来的信息时，此时，选举会再次发生，BACKUP节点就会取代MASTER节点，成为新的MASTER，并继续向外提供服务，这就实现了服务的高可用性。
二，实验环境
两台linux主机，系统版本为redhat5.8 32位
node1的ip地址为： 192.168.1.85
node2的ip地址为： 192.168.1.86
vip为： 192.168.1.90
keepalived软件版本 keepalived-1.2.7.tar.gz 下载地址：http://www.keepalived.org/download.html
nginx软件版本为：nginx-1.4.7.tar.gz下载地址为 http://nginx.org/
三，实验过程
1，解压并安装相应软件
keepalived:
tar xf keepalived-1.2.7.tar.gz
cd keepalived-1.2.7
./configure
make
make install
(1)拷贝相应文件到相应目录中
cp /usr/local/sbin/keepalived /usr/sbin/
cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/etc/keepalived/ /etc/ -r
(2)编辑keepalived.conf配置文件
cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bkup 保存一份配置 编辑如下
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost #定义收件人
}
notification_email_from keepalived@localhost #定义发件人
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_nginx {
script "killall -0 nginx" #检测nginx是否在线
interval 1 #检测周期为1秒
weight 2 #如果nginx不在线，则权重降低2
}
vrrp_script chk_keepalived_down {
script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"#测试keepalived的主备切换情况
interval 1
weight 2
}
vrrp_instance VI_1 {
state MASTER #node1为主节点
interface eth0 #监听的接口
virtual_router_id 52 #虚拟路由ID，两端必须一致
priority 101 #优先级，MASTER端要高于BACKUP端
advert_int 1 #通告周期 1 秒
authentication {
auth_type PASS #认证方式
auth_pass 1111 #认证秘钥
}
virtual_ipaddress {
192.168.1.90 #vip的设定
}
track_script { #要执行的检测脚本
chk_nginx
chk_mantaince_down
}
keepalived.conf中还有许多内容，但都是为lvs准备，这里并没有启动lvs功能，所以都删掉了。
node2的配置和node1类似，只不过要把state MASTER改为BACKUP,把优先级调的比MASTER小一些即可。
nginx:
(1)解决依赖关系
yum install pcre-devel -y (2)添加用户和组
groupadd -r nginx
useradd -r -g nginx nginx
(3)解压并编译安装
tar xfnginx-1.4.7.tar.gz
cd nginx-1.4.7
./configure --prefix=/usr --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx/nginx.pid --lock-path=/var/lock/nginx.lock --user=nginx --group=nginx --with-http_ssl_module --with-http_flv_module --with-http_stub_status_module --with-http_gzip_static_module --http-client-body-temp-path=/var/tmp/nginx/client/ --http-proxy-temp-path=/var/tmp/nginx/proxy/ --http-fastcgi-temp-path=/var/tmp/nginx/fcgi/ --http-uwsgi-temp-path=/var/tmp/nginx/uwsgi --http-scgi-temp-path=/var/tmp/nginx/scgi --with-pcre
make && make install
(4)修改下主页后就可以启动服务了
在两个节点上启动keepalived
service keepalived start 在node1上查看日志
tail /var/log/messages
Aug 19 19:12:16 localhost Keepalived_vrrp: VRRP_Script(chk_nginx) succeeded
Aug 19 19:12:16 localhost Keepalived_vrrp: VRRP_Script(chk_mantaince_down) succeeded
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Aug 19 19:12:18 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Aug 19 19:12:18 localhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.
Aug 19 19:12:18 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.1.90 added
Aug 19 19:12:18 localhost avahi-daemon: Registering new address record for 192.168.1.90 on eth0.
Aug 19 19:12:18 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.90
Aug 19 19:12:18 localhost Keepalived_vrrp: Netlink reflector reports IP 192.168.1.90 added
Aug 19 19:12:23 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.90
可以看到node1被选举为master，vip配置在node1上
使用ip addr 查看
...
2: eth0:mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:0c:29:a3:12:75 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.85/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.90/32 scope global eth0
查看node2上日志信息
Aug 19 19:12:17 localhost Keepalived_vrrp: Registering Kernel netlink reflector
Aug 19 19:12:17 localhost Keepalived_vrrp: Registering Kernel netlink command channel
Aug 19 19:12:17 localhost Keepalived_vrrp: Registering gratuitous ARP shared channel
Aug 19 19:12:17 localhost Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Aug 19 19:12:17 localhost Keepalived_vrrp: Configuration is using : 40529 Bytes
Aug 19 19:12:17 localhost Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP sockpool:
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP_Script(chk_nginx) succeeded
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP_Script(chk_mantaince_down) succeeded
为backup状态
此时打开浏览器访问vip 192.168.1.90 提供页面的是node1
将node1上的nginx服务down掉
service nginx stop 再次查看node1 上的日志
Aug 19 19:18:15 localhost Keepalived_vrrp: VRRP_Script(chk_nginx) failed
Aug 19 19:18:16 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Received higher prio advert
Aug 19 19:18:16 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE
Aug 19 19:18:16 localhost Keepalived_vrrp: VRRP_Instance(VI_1) removing protocol VIPs.
Aug 19 19:18:16 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.1.90 removed
Aug 19 19:18:16 localhost avahi-daemon: Withdrawing address record for 192.168.1.90 on eth0.
Aug 19 19:18:16 localhost Keepalived_vrrp: Netlink reflector reports IP 192.168.1.90 removed
Aug 19 19:18:17 localhost Keepalived_vrrp: VRRP_Script(chk_nginx) succeeded
此时，node1已经变为backup状态，vip也已经被移除
查看node2的日志信息
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP_Script(chk_nginx) succeeded
Aug 19 19:12:17 localhost Keepalived_vrrp: VRRP_Script(chk_mantaince_down) succeeded
Aug 19 19:18:16 localhost Keepalived_vrrp: VRRP_Instance(VI_1) forcing a new MASTER election
Aug 19 19:18:17 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Aug 19 19:18:18 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Aug 19 19:18:18 localhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.
Aug 19 19:18:18 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.90
node2成为master节点，整个切换过程完成。
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