nginx does not close the connection to backend pop3 server

[Joe Wong]

Hello Igor,

I am evaluating nginx pop3 proxy function and encounter 1 problem. Here 
is my setup:

OS: RedHat FC7 2.6.21-1.3194.fc7 #1 SMP Wed May 23 22:35:01 EDT 2007 
i686 i686 i386 GNU/Linux
GCC: gcc version 4.1.2 20070502 (Red Hat 4.1.2-12)
Nginx version: 0.5.26
Config option: --with-debug --with-mail --with-select_module

Nginx config:
daemon on;
user root;
worker_processes 10;

error_log logs/error.log debug;
pid       logs/nginx.pid;

#maximum total connections of each worker
events {
    worker_connections 100;
#    use select;
    debug_connection 127.0.0.1;
}

mail {
    auth_http   localhost:8088/auth.php;

    pop3_capabilities  "TOP"  "USER";
    pop3_auth          plain;
    imap_capabilities  "IMAP4rev1"  "UIDPLUS";

    #pop3 configuration
    server {
        listen     110;
        protocol   pop3;
        proxy      on;
    }
 }


Test case:
- A mailbox with message around 10M large
- Use telnet to port 110, issue the USER/PASS command to login
- Issue RETR 1 to download the 10M message
- Close the connection by pressing Ctrl-] then 'q' right after RETR 
command is issued

At this time,  Netstat shows that the connection from nginx to the 
backend POP3 server remains connected.

Now, I repeat the above test case with "use select" turns on in 
nginx.conf.  This time, I don't see the connection to backend pop3 
remains after my client connection to nginx is terminated in the middle. 
I suspect this is something to do with epoll call?

I only did the test on POP3 proxy, not sure if it has the same behaviour 
on HTTP.

Please let me know if you need more information.

Regards,

- Joe