nginx tomcat请求分发的问题

配置好，启动后tomcat请求能够分发到不同端口的登录界面，但是填好账号和密码后，点击提交就请求不到了！
nginx.cof/劳烦大家给点帮助....thx

#user  nobody;
worker_processes  2;
error_log    logs/error.log;
#error_log    logs/error.log  notice;
#error_log    logs/error.log  info;
pid    logs/nginx.pid;
events {
    use epoll;
    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;
    upstream tomcat_server {
        server 192.168.0.185:8091 weight=5;
        server 192.168.0.185:8092 weight=5;
        server 192.168.0.185:8093 weight=5;
    }
    server {
        listen       81;
        server_name  localhost;
        charset utf-8;
        access_log  logs/host.access.log  main;
        location / {
            proxy_pass http://tomcat_server;
            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;

补充：负载均衡默认轮训