Ask help for nginx and tomcat


Hi everybody,
I’m new to nginx. Recently I use comet in my project. I choose tomcat
for the java server. and enable the Http11NioProtocol connector.
client send a ajax request,and the server side suspend it, and set a
timeout(5 seconds),when timeout reach,the tomcat end the response
in tomat server.xml

when I test with tomcat directly, means http://localhost:8080/xxxxx,
it works as what I expect,
but when I use nginx to proxy, when the timeout reach,the tomcat
server end the response,but the request still there,
nginx wait for its own “request timeout”(I don’t what to call it).
in nginx.conf,I set the follow proxy-relative config
proxy_buffering off;
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For

is there something i missed ? Any suggestion will be appreciate…