nginx+keepalived 高可用负载均衡

废话就不多说了，nginx安装与配置，还有负载均衡呢，可以看我写的另一篇文章《nginx负载均衡实战》，还有关于负载均衡呢，大家可以看一下我写的另外两篇文章，一个是《lvs+keepalived负载均衡》，另一个是《haproxy+keepalived负载均衡》,三种负载均衡的区别呢，可以看一下我转载的一篇文章《软件级负载均衡器(LVS/HAProxy/Nginx)的特点简介和对比》，下面直接进入配置步骤：

1.系统环境

系统版本：CentOS release 5.9 (Final) x86 32位    
nginx版本：   1.2.8  
keepalived版本：    1.2.4

主keepalived:192.168.207.130

从keepalived:192.168.207.131


VIP：192.168.207.140 
WEB_1:192.168.207.129 80端口 
WEB_2:192.168.207.130 8080端口 
WEB_3:192.168.207.131 8080端口

2.自定义nginx配置文件

在192.168.207.130和192.168.207.131上操作

useradd nginx
vi /usr/local/nginx/conf/nginx.conf

内容如下：

#运行用户    
user nginx nginx;    
#启动进程    
worker_processes 2;    
#全局错误日志及PID文件    
error_log logs/error.log notice;    
pid logs/nginx.pid;    
#工作模式及每个进程连接数上限    
events {    
    use epoll;    
    worker_connections 1024;     #所以nginx支持的总连接数就等于worker_processes * worker_connections  
}    
#设定http服务器,利用它的反向代理功能提供负载均衡支持    
http {    
    #设定mime类型    
    include mime.types;  #这个是说nginx支持哪些多媒体类型，可以到conf/mime.types查看支持哪些多媒体  
    default_type application/octet-stream;   #默认的数据类型   
    #设定日志格式    
  
    log_format main '$remote_addr - $remote_user [$time_local] '   
    '"$request" $status $bytes_sent '   
    '"$http_referer" "$http_user_agent" '   
    '"$gzip_ratio"';    
  
    log_format download '$remote_addr - $remote_user [$time_local] '   
    '"$request" $status $bytes_sent '   
    '"$http_referer" "$http_user_agent" '   
    '"$http_range" "$sent_http_content_range"';    
    #设定请求缓冲    
    client_header_buffer_size 1k;    
    large_client_header_buffers 4 4k;    
    #开启gzip模块    
    #gzip on;    
    #gzip_min_length 1100;    
    #gzip_buffers 4 8k;    
    #gzip_types text/plain;    
    #output_buffers 1 32k;    
    #postpone_output 1460;    
    #设定access log    
    access_log logs/access.log main;    
    client_header_timeout 3m;    
    client_body_timeout 3m;    
    send_timeout 3m;    
    sendfile on;    
    tcp_nopush on;    
    tcp_nodelay on;    
    keepalive_timeout 65;    
    #设定负载均衡的服务器列表    
  
    upstream mysvr {    
        #weigth参数表示权值,权值越高被分配到的几率越大   
        server 192.168.207.129:80 weight=5;    
        server 192.168.207.130:8080 weight=5;    
        server 192.168.207.131:8080 weight=5;  
    }    
    server { #这个是设置web服务的，监听8080端口  
        listen        8080;  
        server_name    192.168.207.131;          #这个根据系统ip变化
        index     index.html index.htm;  
        root        /var/www/html;  
        #error_page     500 502 503 504    /50x.html;  
        #location = /50x.html {  
        #    root     html;  
        #}  
        }   
    #设定虚拟主机    
    server {    
        listen 80;    
        server_name 192.168.207.140;                   #这里是VIP
        #charset gb2312;    
        #设定本虚拟主机的访问日志    
        access_log logs/three.web.access.log main;    
        #如果访问 /img/*, /js/*, /css/* 资源,则直接取本地文件,不通过squid    
        #如果这些文件较多,不推荐这种方式,因为通过squid的缓存效果更好    
        #location ~ ^/(img|js|css)/{    
        #   root /data3/Html;    
        #   expires 24h;  
        #}   
            #对 "/" 启用负载均衡    
        location / {    
            proxy_pass http://mysvr;  #以这种格式来使用后端的web服务器  
            proxy_redirect off;    
            proxy_set_header Host $host;    
            proxy_set_header X-Real-IP $remote_addr;    
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;    
            client_max_body_size 10m;    
            client_body_buffer_size 128k;    
            proxy_connect_timeout 90;    
            proxy_send_timeout 90;    
            proxy_read_timeout 90;    
            proxy_buffer_size 4k;    
            proxy_buffers 4 32k;    
            proxy_busy_buffers_size 64k;    
            proxy_temp_file_write_size 64k;  
        }    
        #设定查看Nginx状态的地址 ，在安装时要加上--with-http_stub_status_module参数  
        location /NginxStatus {    
            stub_status on;    
            access_log on;    
            auth_basic "NginxStatus";    
            auth_basic_user_file conf/htpasswd;     #设置访问密码，htpasswd -bc filename username password  
        }  
    }  
}   

3.自定义keepalived配置文件

vi /etc/keepalived/keepalived.conf

内容如下：

global_defs {
   notification_email {
        [email protected]
   }
   notification_email_from [email protected]
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

vrrp_script chk_http_port {
                script "/etc/keepalived/check_nginx.sh"         ###监控脚本
                interval 2                             ###监控时间
                weight 2                                ###目前搞不清楚
}
vrrp_instance VI_1 {
        state MASTER                            ### 设置为 主
        interface eth0                             ### 监控网卡
        virtual_router_id 51                    ### 这个两台服务器必须一样
        priority 101                                 ### 权重值 MASTRE 一定要高于 BAUCKUP
        authentication {
                     auth_type PASS
                     auth_pass 1111
        }
        track_script {
                chk_http_port                     ### 执行监控的服务
        }
        virtual_ipaddress {
             192.168.207.140                            ###    VIP 地址
        }
}

4.写自定义脚本

vi /etc/keepalived/check_nginx.sh

内容如下：

!/bin/bash
A=`ps -C nginx --no-header |wc -l`                ## 查看是否有 nginx进程 把值赋给变量A
if [ $A -eq 0 ];then                                         ## 如果没有进程值得为 零
        /usr/local/nginx/sbin/nginx
        sleep 3
        if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
                  /etc/init.d/keepalived stop                       ## 则结束 keepalived 进程
        fi
fi

这里是检查nginx是否启动好，如果没有启动，先启动 nginx，隔了3秒后还没有启动好，则将keepalived进程也关闭，这样从keepalived就能接手过去了，提供高可用性，在这里呢，keepalived服务是提供高可用性，而nginx是提供后端web服务器的负载均衡。

这里还要给脚本加上执行权限，如下

chmod +x /etc/keepalived/check_nginx.sh

5.启动服务，并测试

在这里先说一下啊，在WEB_1上，我是使用系统自带的apache昨晚web服务器的，比较省事，这样呢，我只要启动好主从keepalived就ok了，因为它会利用check_nginx.sh脚本来自动启动nginx。

都启动好了。

访问http://192.168.207.140就可以轮训访问后端的三台web服务器内容啦

这里我们把主keepalived服务给关掉，来测试高可用性

然后会在从keepalived服务器上的/var/log/messages看到这样的日志

Apr 19 17:42:44 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Apr 19 17:42:45 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Apr 19 17:42:45 localhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.
Apr 19 17:42:45 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.207.140
Apr 19 17:42:45 localhost Keepalived_vrrp: Netlink reflector reports IP 192.168.207.140 added
Apr 19 17:42:45 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.207.140 added
Apr 19 17:42:45 localhost avahi-daemon[4204]: Registering new address record for 192.168.207.140 on eth0.

继续访问http://192.168.207.140，依旧可以访问后端的三台web服务器

然后再把原主keepalived打开，可以观察到原从keepalived服务器的日志显示

Apr 19 17:42:50 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.207.140
Apr 19 17:44:06 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Received higher prio advert
Apr 19 17:44:06 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE
Apr 19 17:44:06 localhost Keepalived_vrrp: VRRP_Instance(VI_1) removing protocol VIPs.
Apr 19 17:44:06 localhost Keepalived_vrrp: Netlink reflector reports IP 192.168.207.140 removed
Apr 19 17:44:06 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.207.140 removed
Apr 19 17:44:06 localhost avahi-daemon[4204]: Withdrawing address record for 192.168.207.140 on eth0.

说明有恢复了原来的主从结果。

生产环境中，后端的机器也可能会挂掉，但是呢，这就不用你操心啦，nginx会自动把session分配到好的后端web服务器上的啦

ok，到这里全部结束了，实践亲测，祝君成功