nginx post ONE request to one more upstream_addr

[MaLi]

hi, everyone,

 nginx version is 0.8.53,
configure (http definition)  is :
====================================
http{
    upstream my_loads {
        server 10.10.1.12;
        server 10.10.1.13;
    }

    log_format combined_addsvr '$remote_addr - $remote_user [$time_local]  '
                        '"$request" $status $body_bytes_sent '
                        '"$http_referer" "$http_user_agent" $upstream_addr
$upstream_cache_status ';
    access_log logs/access.log combined_addsvr;

    server {
        listen 80;
        server_name mytest.com;
        client_max_body_size 100m;
        proxy_buffering off;
        proxy_read_timeout 120;
        proxy_send_timeout 120;
        client_body_timeout 120;
        send_timeout  120;

        location / {
            proxy_pass http://my_loads/;
            proxy_set_header Host $host;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }
    }
===========================================

there is a strange line in log file: (sorry to use xxx replace of true url)
192.168.1.1 - - [14/Jun/2011:20:53:24 +0800]  "POST /1.php HTTP/1.1" 200
3729558 "http://mytest.com/xxx" "Mozilla/4.0 (compatible; MSIE 7.0;)"
10.10.1.12:80, 10.10.1.13:80 -

when nginx deals with 1.php, it sends  POST to  all upstream servers!

the next is normal log:
192.168.1.1 - - [14/Jun/2011:20:53:44 +0800]  "POST /1.php HTTP/1.1" 302 2 "
http://mytest.com/xxx" "Mozilla/4.0 (compatible; MSIE 7.0;)" 10.10.1.12:80 -

Could anyone tell me if it is  a bug or just any configure improperly?
thanks.
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