[hobbit] performance tuning

[Henrik Stoerner]

On Tue, Apr 04, 2006 at 06:11:57PM -0500, Jeff Newman wrote:
> 
> I'm running Hobbit 4.1.2p1 on a Redhat AS 4 server.
> 
> I currently have a number of server side scripts that post-process
> incoming test results.
> 
> My concern is a high number of "1984" sockets in TIME_WAIT condition
> (upwords of 60 on the client at times) The clients are AIX boxes.

I dont really understand why you see so many TIME_WAIT connections on
the *client*. I could understand if they were on the Hobbit server, but
not on the client...

If there is a firewall between the clients and the server, it could be
that the firewall terminates the connection tracking state before the
final exchange of FIN/ACK packets has completed between the two sides.
But then I'd expect it to be in FIN_WAIT_[1,2] ...

What's TIME_WAIT anyway ... from
http://www.ssfnet.org/Exchange/tcp/tcpTutorialNotes.html:

  "The main thing to recognize about connection teardown is that a
   connection in the TIME_WAIT state cannot move to the CLOSED state until
   it has waited for two times the maximum amount of time an IP datagram
   might live in the Inter net. The reason for this is that while the local
   side of the connection has sent an ACK in response to the other side's
   FIN segment, it does not know that the ACK was successfully delivered.
   As a consequence this other side might re transmit its FIN segment, and
   this second FIN segment might be delayed in the network. If the
   connection were allowed to move directly to the CLOSED state, then
   another pair of application processes might come along and open the same
   connection, and the delayed FIN segment from the earlier incarnation of
   the connection would immediately initiate the termination of the later
   incarnation of that connection."

So TIME_WAIT states should only stay around for a few minutes - I
believe a common "2 x max lifetime" is 2 minutes, but this is somewhat
OS dependant. Since the Hobbit client only runs once every 5 minutes,
I don't understand why you have many of these on the clients.


Henrik