nginx + keepalived 双机热备

序

双机热备是指两台机器都在运行，但并非两台机器同时在提供服务。
当提供服务的一台出现故障的时候，另外一台会马上自动接管并且提供服务，且切换的时间非常短。

keepalived的工作原理是VRRP——虚拟路由冗余协议。

测试环境如下：

	ip	vip
master	192.168.174.135	192.168.174.140
backup	192.168.174.137	192.168.174.140

nginx

安装

sudo apt-get install nginx

查找配置文件位置

sudo find / -name nginx.conf
/etc/nginx/nginx.conf

修改配置文件（nginx.conf）

user www-data;
worker_processes 4;
pid /run/nginx.pid;

events {
    worker_connections 1024;
}

http {
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    server {
        listen 80 default_server;
        server_name test;
        charset utf-8;

        location / {
        root html;
        index index.html index.htm;
        proxy_set_header X-Real_IP $remote_addr;
        client_max_body_size 100m;
        }
    }
}

文件/usr/share/nginx/html/index.html

在192.168.174.135上加上 <h1>Welcome to nginx! 135 </h1>

在192.168.174.137上加上 <h1>Welcome to nginx! ***137*** </h1>

启动

sudo service nginx start

关闭

sudo service nginx stop

keepalived

安装

下载keepalived-1.2.19.tar.gz

tar –zxvf keepalived-1.2.19.tar.gz
cd keepalived-1.2.19
./configure --prefix=/usr/local/keepalived
make
sudo make install

期间可能出现问题：

!!! OpenSSL is not properly installed on your system. !!!
!!! Can not include OpenSSL headers files. !!!

解决

sudo apt-get install libssl.dev

建立软链接

sudo ln -s /usr/local/keepalived/sbin/keepalived /sbin/
sudo ln -s /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
sudo ln -s /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/

启动

sudo keepalived -D -f /usr/local/keepalived/etc/keepalived/keepalived.conf

关闭

sudo killall keepalived

配置（keepalived.conf）：

global_defs {
    router_id NODEA
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0        #监测网络接口
    virtual_router_id 50  #主、备必须一样
    priority 100          #优先级：主＞备
    advert_int 1
    authentication {
        auth_type PASS #VRRP认证，主备一致
        auth_pass 1111  #密码
}

virtual_ipaddress {
        192.168.174.140/24 #VRRP HA虚拟地址
    }
}

备用节点的配置

global_defs {
   router_id NODEB
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 50
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }

 virtual_ipaddress {
    192.168.174.140/24
    }
}

测试

双击热备

两台机子均启动nginx和keepalived，浏览器各自访问

浏览器访问：http://192.168.174.140/，显示的是MASTER的页面。

同样用ip appr可以验证：

135机器：

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo