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From "Vadim Pesochinskiy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (AMQ-855) Add support for prefetchSize = 0
Date Wed, 09 Aug 2006 22:40:23 GMT
    [ https://issues.apache.org/activemq/browse/AMQ-855?page=comments#action_36736 ] 
            
Vadim Pesochinskiy commented on AMQ-855:
----------------------------------------

> e.g. if we did implement prefetch of zero - which means don't deliver a message to a
consumer at all - 
> unless they perform a consumer.receive() - even then, the consumer could then hang/deadlock
and never
> actually acknowledge or process the message.

If consumer hangs and message is not processed is a different problem. Even if messages are
lost in such case, nobody would blame AMQ. If you kill consumer and re-despatch, it would
be brilliant. But if my consumers do not hang, crash or burn, can I just get my messages?

James, could you please re-open this issue? I spend 1 month working on this project and now
I will have to throw it all away and do explaining with my manager. I cannot apply my own
fix, you will not fix it. What am I supposed to do now?

> Add support for prefetchSize = 0
> --------------------------------
>
>                 Key: AMQ-855
>                 URL: https://issues.apache.org/activemq/browse/AMQ-855
>             Project: ActiveMQ
>          Issue Type: New Feature
>          Components: Broker
>    Affects Versions: 4.0, 4.0.1, 4.0.2
>         Environment: any
>            Reporter: Vadim Pesochinskiy
>            Priority: Critical
>             Fix For: 4.2
>
>
> This feature would enable to support following test case:
> 2 servers are processing 3 submitted jobs with following processing times 10 min, 1 min,
1 min. This sequence should finish in 10 minutes as one service will pick up the 10 minutes
job, meanwhile the other one should manage the two 1 minute jobs. Since I cannot set prefetchSize=0,
one of the 1 minute jobs is sitting in prefetch buffer and the jobs are processed in 11 minutes
instead of 10.
> This is simplification of the real scenario where I have about 30 consumers submitting
jobs to 20 consumers through AMQ 4.0.1. I have following problems:
> • Messages are sitting in prefetch buffer are not available to processors, which results
in a lot of idle time.
> • Order of processing is random. For some reason Job # 20 is processed after Job # 1500.
Since senders are synchronously blocked this can result in time-outs.
> • Some requests are real-time, i.e. there is a user waiting, so the system cannot wait,
so AMQ-850 does not fix this issue.

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