[置顶] Keepalived+Nginx实现高可用(HA)

环境介绍

1.服务器(192.168.20.112)：安装keepalived和nginx  主节点

2.服务器(192.168.20.113)：安装keepalived和nginx  从节点

3.服务器(192.168.20.114)：安装tomcat

4.服务器(192.168.20.115)：安装tomcat

5.两台Nginx端口：80

6.两台tomcat端口：8080

7.VIP：192.168.20.116

配置文件

1.Nginx配置文件(两个节点Nginx配置文件一致，Nginx端口可以与tomcat不一致)：

worker_processes  1;

events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    sendfile        on;

    keepalive_timeout  65;

    #gzip  on;
upstream serverpool {
    server 192.168.20.114:8080;
    server 192.168.20.115:8080;
    }

    server {
        listen       80;
        server_name  localhost;

        location / {
            proxy_pass http://serverpool;
            proxy_set_header   Host    $host;
            proxy_set_header   X-Real-IP   $remote_addr; 
            proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for; 
        }

        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }

}

2.主节点keeaplived配置文件

! Configuration File for keepalived

global_defs {
notification_email {
        [e-mail]
        [e-mail]
   }

   notification_email_from [e-mail]
   smtp_server smtp.163.com
   smtp_connect_timeout 30
   router_id nginx_master

}
#检测nginx端口是否故障的脚本
vrrp_script chk_http_port {  
        script "</dev/tcp/127.0.0.1/80"  
        interval 1  
        weight -2  
} 
#为了避免启动keepalived之前没有启动nginx , 在start中首先启动nginx
start() {
    /usr/local/nginx/sbin/nginx
    sleep 3
    echo -n $"Starting $prog: "
    daemon keepalived ${KEEPALIVED_OPTIONS}
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog
} 

vrrp_instance VI_1 {
    state MASTER
    interface eth1#注意网卡要与本机网卡名称一致
    virtual_router_id 51
    priority 100#优先权权重,值大的会被先启用
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.20.116#自己设置的VIP
    }
track_script {  
        chk_http_port  #启用脚本检测
    } 
}

3.从节点keeaplived配置文件

! Configuration File for keepalived

global_defs {
notification_email {
        [e-mail]
        [e-mail]
   }

   notification_email_from [e-mail]
   smtp_server smtp.163.com
   smtp_connect_timeout 30
   router_id nginx_backup

}
#检测nginx端口是否故障的脚本
vrrp_script chk_http_port {  
        script "</dev/tcp/127.0.0.1/80"  
        interval 1  
        weight -2  
} 
#为了避免启动keepalived之前没有启动nginx , 在start中首先启动nginx
start() {
    /usr/local/nginx/sbin/nginx
    sleep 3
    echo -n $"Starting $prog: "
    daemon keepalived ${KEEPALIVED_OPTIONS}
    RETVAL=$?
    echo
    [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0#注意网卡要与本机网卡名称一致
    virtual_router_id 51
    priority 99#优先权权重,值大的会被先启用
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.20.116#自己设置的VIP
    }
track_script {  
        chk_http_port  #启用脚本检测
    } 
}

4.实现步骤

4.1.步骤一：在192.168.20.114和192.168.20.115上安装tomcat

4.2步骤二：在192.168.20.112和192.168.20.112上安装nginx

4.3步骤三：分别在192.168.20.112和192.168.20.112上做nginx反向代理配置和负载均衡配置代理到两台tomcat服务器

4.4步骤四：在192.168.20.112和192.168.20.112上安装keepalived

4.5步骤五：修改192.168.20.112和192.168.20.112两台服务器的keepalived配置文件

4.6步骤六：启动192.168.20.112和192.168.20.112两个节点的keepalived服务

5.高可用原理

    当主节点出故障，keepalived会根据priority的值大小竞争来决定谁是真正的MASTER，脚本检测也是在失败的时候会把权重减去相应的值，比如原来master的priority=100，如果脚本检测到端口80无法连接，就会priority-2=98，权重98小于从节点的priority（99），此时从节点将竞争成为master，这样就实现了web应用的热备。

注：此处是做两个节点，如果是两个以上节点，那么节点权重最大的将成为主节点。

6.安装说明

整个安装过程很简单，安装keepalived只需执行：

yum install -y keepalived (centos redhat)
    或者
    apt-get install keepalived (debian ubuntu)

Nginx和Tomcat在此就不再赘述，可以参考我的其他文档。

谢谢！