apache 的http代理出错 502 Proxy Error

不久刚部署好的网站，忽然访问报错提示错误

Http 502 Proxy Error
The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /.
Reason: Error reading from remote server

看了半天也没看出个所以然来， 刚刚还好好的呢！过了一会网站又能打开了....
查看了一下apache 的access_log。发现

.....Get / HTTP/1.0....

这是ie5.5以下的版本访问过。所以又找来台ie5.5(挺难整，这年头这玩意少了！！)访问了一下，然后出错。在用别的机器访问错误还有。在刷新了一会又好了!
就这个问题Google了一下发现是mod_proxy的事，又G了一下他的文档
http://httpd.apache .org/docs/2.3/mod/mod_proxy.html
找到了这一段话

For circumstances where mod_proxy is sending requests to an origin server that doesn't properly implement keepalives or HTTP/1.1, there are two environment variables that can force the request to use HTTP/1.0 with no keepalive. These are set via the SetEnv directive.
These are the force-proxy -request-1.0 and proxy -nokeepalive notes.

译了一下大概是这意思(不是我译的)

当mod_proxy向一个没有正确实现持久连接(KeepAlive)或HTTP/1.1的原始服务器发送请求的时候，可以通过设置两个环境变量来发送不带持久连接(KeepAlive)的HTTP/1.0请求。这两个变量是通过SetEnv指令设置的。
以下是force-proxy -request-1.0和proxy -nokeepalive的例子：

<Location /buggyappserver/>
  ProxyPass http://buggyappserver:7001/foo/

SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
</Location> 

最后在我的httpd.conf的VirtualHost里加上了上面的两行设置

<VirtualHost *:80> 
   JkMount /hr/servlet/* worker1 
   JkMount /hr/*.jsp worker1 
   JkMount /hr/*.do worker1 
   ServerAdmin [e-mail] 
   ServerName www.iteye.com 
   ServerAlias www.iteye.com.cn 
   RewriteEngine On 
   RewriteRule ^/$　/hr/　[R,P] 　　　　　 
   
SetEnv force-proxy-request-1.0.1 
SetEnv proxy-nokeepalive 1
 </VirtualHost> 

重启apache ，在拿ie5.5访问O了