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 keepalivedglobal_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nginxstart() {    /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 keepalivedglobal_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nginxstart() {    /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！