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From Rob Davies <rajdav...@gmail.com>
Subject Re: Race Condition?
Date Sat, 06 May 2006 07:04:10 GMT
I think wayne is saying this is a network race condition - where the  
broker can send the wireformat info before the client starts reading.  
However, as the client doesn't start reading from the socket until  
after initializeStreams is called - I'm not sure how the socket will  
miss the wireformat info from the broker?

On 6 May 2006, at 07:34, James Strachan wrote:

> On 4/28/06, Wayne1285 <WayneSIrwin@hotmail.com> wrote:
>>
>> I am using ActiveMq-4.0-RC3.  I have been having intermittent  
>> problems
>> getting sessions created and closed.  I have downloaded the code  
>> and traced
>> through it and I think I have found the problem.
>>
>> There is a race conditon in the TcpTransport class, in the doStart 
>> () method.
>> As near as I can tell, as soon as the socket is created, the  
>> Broker responds
>> with its WireFormatInfo.  This information is usually stored as the
>> remoteWireFormatInfo in the InactivityMonitor.  The race condition  
>> occurs in
>> the doStart() method as it appears the broker can sometimes send the
>> wireFormatInfo before the initializeStreams() method can be  
>> called.  This
>> results in the information not being capture in the dataIn input  
>> buffer.
>
> I just refreshed my memory of the code for TcpTransport and took a
> peek at InactivityMonitor. I'm not sure I grok yet the race condition.
> TcpTransport only allows itself to be started once and uses a
> semaphore around the doStart(); so that all looks good. Also
> TcpTransport doesn't allow messages to be sent until the transport is
> started (it throws an exception if an attempt is made to send to the
> transport before its started).
>
> So I don't quite follow the sequence of events causing the race
> condition; is some thread trying to use the TcpTransport before its
> been started? If so I don't understand why the checkStarted() method
> is not throwing an exception?
>
> --
>
> James
> -------
> http://radio.weblogs.com/0112098/

Rob Davies
http://rajdavies.blogspot.com/




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