这篇文章简单介绍利用keepalived软件，实现对nginx服务器的高可用，即实现故障自动切换。假设你已经安装好nginx，下面介绍keepalived的安装和使用。
keepalived安装
- yum install openssl-devel
- cd /tmp
- wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz
- tar xzf keepalived-1.2.2.tar.gz
- cd keepalived-1.2.2
- ./configure
- make && make install
- cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/
- cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
- chmod +x /etc/init.d/keepalived
- chkconfig --add keepalived
- chkconfig keepalived on
- mkdir /etc/keepalived
- ln -s /usr/local/sbin/keepalived /usr/sbin/
keepalived的配置
更详细的keepalived配置文件说明可以执行man keepalived.conf查看。
我们假设主服务器IP:192.168.1.103,从服务器ip:192.168.1.101 虚拟ip:192.168.1.110
下面对主服务器的keepalived进行配置：
- vi /etc/keepalived/keepalived.conf
- global_defs {
- notification_email {
- admin@centos.bz
- }
- notification_email_from keepalived@domain.com
- smtp_server 127.0.0.1
- smtp_connect_timeout 30
- router_id LVS_DEVEL
- }
- vrrp_script chk_http_port {
- script "/opt/nginx_pid.sh"
- interval 2
- weight 2
- }
- vrrp_instance VI_1 {
- state MASTER ############ 辅机为 BACKUP
- interface eth0
- virtual_router_id 51
- mcast_src_ip 192.168.1.103
- priority 102 ########### 权值要比 back 高
- advert_int 1
- authentication {
- auth_type PASS
- auth_pass 1111
- }
- track_script {
- chk_http_port ### 执行监控的服务
- }
- virtual_ipaddress {
- 192.168.1.110
- }
- }
从服务器：
- global_defs {
- notification_email {
- admin@centos.bz
- }
- notification_email_from keepalived@domain.com
- smtp_server 127.0.0.1
- smtp_connect_timeout 30
- router_id LVS_DEVEL
- }
- vrrp_script chk_http_port {
- script "/opt/nginx_pid.sh"
- interval 2
- weight 2
- }
- vrrp_instance VI_1 {
- state BACKUP
- interface eth0
- virtual_router_id 51
- mcast_src_ip 192.168.1.101
- priority 101 ##########权值 要比 master 低。。
- advert_int 1
- authentication {
- auth_type PASS
- auth_pass 1111
- }
- track_script {
- chk_http_port ### 执行监控的服务
- }
- virtual_ipaddress {
- 192.168.1.110
- }
- }
之后分别在主从服务器建立nginx的监控脚本：
- vi /opt/nginx_pid.sh
- #!/bin/bash
- A=`ps -C nginx --no-header |wc -l`
- if [ $A -eq 0 ];then
- /usr/local/nginx/sbin/nginx
- sleep 3
- if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
- killall keepalived
- fi
- fi
然后分别启动主从服务器的keepalived:
- service keepalived start
keepalived的测试
我们在主服务器上执行命令ip a，显示如下：
- 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
- link/ether 00:0c:29:aa:a1:e4 brd ff:ff:ff:ff:ff:ff
- inet 192.168.1.103/24 brd 255.255.255.255 scope global eth0
- inet 192.168.1.110/32 scope global eth0
证明主服务器已经绑定了虚拟ip 192.168.1.110
在从服务器上执行命令ip a,显示如下：
- 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
- link/ether 00:0c:29:2b:94:3b brd ff:ff:ff:ff:ff:ff
- inet 192.168.1.101/24 brd 255.255.255.255 scope global eth0
显示表明从服务器上没有绑定vip 192.168.1.110,只有本机真实ip192.168.1.101
下面我们停止主服务器的nginx进程，再看看ip绑定情况:
主服务器的情况：
- 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
- link/ether 00:0c:29:aa:a1:e4 brd ff:ff:ff:ff:ff:ff
- inet 192.168.1.103/24 brd 255.255.255.255 scope global eth0
从服务器的情况：
- 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
- link/ether 00:0c:29:2b:94:3b brd ff:ff:ff:ff:ff:ff
- inet 192.168.1.101/24 brd 255.255.255.255 scope global eth0
- inet 192.168.1.110/32 scope global eth0
由此可见vip已经指向了从服务器。
参考：http://www.keepalived.org/pdf/UserGuide.pdf