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Date: Tue, 4 Sep 2007 08:09:33 -0700 (PDT)
From: corcorda <dave.corcoran@gmail.com>
To: users@activemq.apache.org
Subject: Re: Blocking transactions
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 <ec6e67fd0709040754i1187f06em2cbd7f3d628c5643@mail.gmail.com>


It's not the default prefetch values because I can recreate the problem with
just 2 consumers and a few jobs. I think the problem must be with the way
I'm using sessions. I haven't used JMS before so I'm following the samples
and maybe they're too simple.

The code is very simple. Create a connection using the
ActiveMQConnectionFactory, call createSession with true and -1 as params.
Then using this session create a producer that writes jobs and commits.

On each consumer I do the exact same thing, except I create a consumer and
call commit after the processing. They run in different VMs.

What do you mean "Each consumer should be in its own session"? This sounds
like where I'm going wrong ;)


James.Strachan wrote:
> 
> On 9/4/07, corcorda <dave.corcoran@gmail.com> wrote:
>>
>> I'm having some trouble with transactions. The problem is multiple
>> consumers
>> block each other if they spend a long time in a transaction.
> 
> Each consumer should be in its own session to avoid them blocking each
> other right?
> 
> 
>> What I'm looking to do is send several hundred jobs into a queue. Each
>> job
>> takes somewhere between a few seconds and 30 minutes to run. Each
>> consumer
>> reads a job from the queue, processes it, writes the result back to the
>> queue then commits the transactions. If any problems happen in between it
>> should rollback and someone else should try the job. Each consumer runs
>> in
>> it's own VM. It doesn't matter what order the jobs are processed in.
>>
>> The problem is if one consumer receives a message and starts to process
>> it
>> all the other consumer block on the receive call until the first one has
>> done a commit or rollback. This happens even though there are plenty of
>> messages in the queue. Is there a way around this?
> 
> Am thinking you're just hitting the default prefetch values...
> http://activemq.apache.org/what-is-the-prefetch-limit-for.html
> 
> -- 
> James
> -------
> http://macstrac.blogspot.com/
> 
> 

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