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From Pid <...@pidster.com>
Subject Re: Wrong Response returned for a Request
Date Thu, 28 Jul 2011 08:37:48 GMT
On 28/07/2011 09:26, Robert Elliot wrote:
> ----- Original Message -----
>> From: "Pid" <pid@pidster.com>
>> To: "Tomcat Users List" <users@tomcat.apache.org>
>> Sent: Thursday, 28 July, 2011 9:07:13 AM
>> Subject: Re: Wrong Response returned for a Request
>>
>>>>> On 27/07/2011 17:23, Robert Elliot wrote:
>>>>>> We are using Tomcat 6.0.29, and occasionally experiencing
>>>>>> concurrency issues
>>>>>> which look very much like the wrong response is being returned
>>>>>> for a request.
>>>>>> While we cannot reproduce it reliably, it seems to happen when
>>>>>> Keep-Alive is turned on.
>>
>> In most cases this symptom turns out to be a result of the session,
>> request or response object being retained (perhaps as an instance
>> field
>> in a Servlet) where they should not be.
>>
>> Can you double check your code to see if this is possible?
>>
> 
> Unfortunately it's a third party application we're running.  

Ah.

> However as a gut feeling I'd expect a straightforward bug like that to be easier to reproduce;
we've spent a day chucking between 100 and 1200 concurrent clients at it and we only see the
problem very occasionally.  

Try reducing the number of connector threads, try 10 and work down from
there.

> Oddly once it has happened it keeps happening for a period - and then
stops.

Maybe not.  Speculation: once the JVM is hot, JIT optimisation might
reduce the window size further.

> I think we need to think harder about how to diagnose it - at the moment we can't pin
it to a specific layer, it could be the application (most likely), Tomcat, mod_proxy or Apache
HTTPD (we're running 2.2.3). I only asked here as the bug sounded so like what we were seeing.

Fair enough.


p


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