Weblogic shutting down keep-alive socket improperly?

Question

We were sometimes experiencing strange IE behaviour when surfing on webapps on our Weblogic application servers. After investigation we found that IE has a bug in its resend behaviour, so when resending a POST request it sends the headers (including Content-Length) but forgets the form-data. This causes the server to time out waiting for the data. (Note: We are using Win2K and IE6 SP1 on the clients.)
The IE resend is triggered on a default installation when 31-59 seconds have passed since the last request.
This is because IE will try to reuse a socket that has been told to keep-alive until it has been idle for 60 seconds but WLS will by default close kept-alive sockets when they have been idle for 30 seconds. So in the range 31-59 seconds IE will consider the socket alive but WLS has closed it.
The resend bug is really an IE bug and doesn't concern WLS, but then I saw that IE would function correctly with an Apache server with a default keep-alive timeout of 15 seconds.
Using Ethereal I could get the information depicted in the tables below:
Weblogic with keep-alive timeout 30 secs
old socket
Time 00 : User navigates : IE POST request -> WLS, WLS HTML -> IE
Time 30 : Socket times out : (no network traffic)
Time 45 : User navigates : IE POST request -> WLS, WLS TCP_FIN -> IE
new socket
Time 45 : : IE resends POST request without form-data
Apache with keep-alive timeout 15 secs
old socket
Time 00 : User navigates : IE POST request -> Apache, Apache HTML -> IE
Time 15 : Socket times out : Apache TCP_FIN -> WLS
new socket
Time 45 : User navigates : IE POST request -> Apache, Apache HTML -> IE
To summarize, IE handles Apache well as Apache sends a TCP FIN telegram (to close the connection) as soon as the kept-alive socket times out.
Therefore IE never tries to reuse the socket but instead starts on a fresh one on the next navigation and a resend is never necessary.
Weblogic, on the other hand, doesn't send the TCP FIN (connection close) telegram until IE actually tries to use the connection even though it timed out 15 seconds earlier. In this case IE needs to resend the POST request and this is when the form-data is forgotten.
So, my question now is if WLS behaviour could be caused by not shutting down kept-alive sockets properly at keep-alive timeout? Or why are there no TCP FIN telegrams sent at timeout?
Mike Wilson

Answer 1

After doing some more investigation I have found that the "silent" shutdown of keep-alive sockets is only seen on the Linux version. The Windows version of Weblogic 8 behaves correctly, like Apache on Linux, but Weblogic on Linux does not...
Anyone can confirm if this is to be considered a bug?