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From "Maxim Fateev (JIRA)" <j...@apache.org>
Subject [jira] Commented: (AMQ-855) Add support for prefetchSize = 0
Date Wed, 09 Aug 2006 23:40:23 GMT
    [ https://issues.apache.org/activemq/browse/AMQ-855?page=comments#action_36739 ] 
            
Maxim Fateev commented on AMQ-855:
----------------------------------

#1. I wasn't presize. Yes it holds references. But it doesn't really matter as these references
are locked to the particular subsription and are not reassigned while this subscription is
alive.
#2. I think prefetch buffers are used to boost peformance. Pull model doesn't preclude their
use. The question is if messages are assigned to subscriptions up front or only when space
is available in prefetch buffers.

I've already voted for it.

> 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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