配置方法一（可用）：

upstream  tomcatserver1  {
    server 192.168.70.170 weight=3;  
    server 192.168.70.172;
    server 192.168.70.173 down;
    server 192.168.70.174;
    server 192.168.70.175 backup;   
}   
  
 server {  
        listen       80;
        server_name  localhost;
        #charset koi8-r;  
        #access_log  logs
 
/host.access.log  main;  
        location / {  
            proxy_pass   http://tomcatserver1

;   index index.html index.htm; } }

通過以上配置，便可以實現，在訪問192.168.70.169這個網站時，由於配置了proxy_pass地址，所有請求都會先通過nginx反向代理服務器，在服務器將請求轉發給目的主機時，讀取upstream為 tomcatsever1的地址，讀取分發策略，配置tomcat1權重為3，所以nginx會將大部分請求發送給49服務器上的tomcat1，也就是192.168.70.170；較少部分給tomcat2來實現有條件的負載均衡，當然這個條件就是服務器1、2的硬件指數處理請求能力。

1）down：表示單前的server暫時不參與負載

2）Weight：默認為1.weight越大，負載的權重就越大。

3）max_fails：允許請求失敗的次數默認為1.當超過最大次數時，返回proxy_next_upstream 模塊定義的錯誤

4）fail_timeout：max_fails 次失敗後，暫停的時間。

5）Backup：其它所有的非backup機器down或者忙的時候，請求backup機器。所以這臺機器壓力會最輕。

配置方法二（可用）：

#user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs
 
/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}




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

    #log_format  main  ‘$remote_addr - $remote_user [$time_local] "$request" ‘
    #                  ‘$status $body_bytes_sent "$http_referer" ‘
    #                  ‘"$http_user_agent" "$http_x_forwarded_for"‘;

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;

　　// 位置1：upstream
    upstream  192.168.70.169  {
    　　server   192.168.70.170;
    　　server   192.168.70.172;
    　　#ip_hash;
    }

    server {
        listen       80;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {
        
            root   html;
            index  index.html index.htm index.php;
            
            
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ \.php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        location ~ \.php$ {
            root           html;
            #fastcgi_pass   127.0.0.1:9000;
            fastcgi_index  index.php;
       #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
            fastcgi_param  SCRIPT_FILENAME  /$document_root$fastcgi_script_name;
            
　　　　　　　//位置2：proxy_pass　
            proxy_pass        http://192.168.70.169;
            proxy_set_header   Host             $host;
            proxy_set_header   X-Real-IP        $remote_addr;
            proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
        

            include        fastcgi_params;
            
        }

        # deny access to .htaccess files, if Apache‘s document root
        # concurs with nginx‘s one
        #
        #location ~ /\.ht {
        #    deny  all;
        #}
    }


    # another virtual host using mix of IP-, name-, and port-based configuration
    #
    #server {
    #    listen       8000;
    #    listen       somename:8080;
    #    server_name  somename  alias  another.alias;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}


    # HTTPS server
    #
    #server {
    #    listen       443 ssl;
    #    server_name  localhost;

    #    ssl_certificate      cert.pem;
    #    ssl_certificate_key  cert.key;

    #    ssl_session_cache    shared:SSL:1m;
    #    ssl_session_timeout  5m;

    #    ssl_ciphers  HIGH:!aNULL:!MD5;
    #    ssl_prefer_server_ciphers  on;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}






}

nginx負載均衡二：配置