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Date: Thu, 14 Jul 2005 12:10:32 -0700 (PDT)
From: Alex Burmester <adb@plushpix.com>
Reply-To: <adb@pobox.com>
To: Vinod Panicker <vinod.p@gmail.com>
Cc: <adb@pobox.com>,
	Apache Directory Developers List <dev@directory.apache.org>
Subject: Re: losing packets when load testing my mina app
In-Reply-To: <a8f18ca30507132325618d4db3@mail.gmail.com>
Message-ID: <Pine.LNX.4.33.0507140948050.2666-100000@www.plushpix.com>
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I think I have isolated the problem to a firewall 
between the two machines I am using.  If I look at traffic dumps from both 
the client and the server, I see the resets as originating from the client
when I look at the server's dump but when I look at the client dump I see 
no resets, I just see no acknowledgement of the packet so the client does 
a few tcp retransmissions of the packet which the server then ignores 
because of the reset.

This was confirmed by running the load test client on another machine on 
the same subnet and no resets were triggered.

Thanks for helpful pointers all.

Alex.


On Thu, 14 Jul 2005, Vinod Panicker wrote:

> On 7/14/05, Alex Burmester <adb@plushpix.com> wrote:
> > I just noticed in my ethereal traffic that it is the load testing client
> > that is initiating the tcp reset packets so this may be unrelated to mina
> > as the client currently doesn't use mina.
> 
> IIRC, the RST would be generated if the client got an unexpected
> response/timeout from the server.
> 
> > The server is runing mina 0.7.3 using jdk1.5.0_04 and the os/kernel is
> > redhat 2.4.21-20.ELsmp
> 
> Linux kernels 2.6.x are known to have an improved tcp implementation -
> maybe that would help.
> 
> > The client is fedora 2.6.10-1.741_FC3smp
> > 
> > What is strange is that I don't see any tcp errors on either machine
> > using netstat -i eth0 -t -c 10
> > 
> > Both jvms have ample memory allocated.
> 
> Could you tell me the command line args that you are using for the
> jvm?  And did you notice the memory/cpu utilization of both apps
> during the test?
> 
> > After running the load test for about 10 seconds I start to see occasional
> > read timeouts on the client.  First I thought the mina server was not
> > responding but then I found that the client is actually issuing a tcp
> > reset before actually trying to send it's payload to the mina server.
> > As a result the mina server never actually accepts the packet and the
> > client after doing a tcp retransmission a few times eventually times out.
> > 
> > Any suggestions?
> 
> You could post the source and I could try it out on my machines and
> see if the problem can be reproduced.
> 
> --snip--
> 
> Regards,
> Vinod.
>