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From "Gary Tully (JIRA)" <>
Subject [jira] Resolved: (AMQ-2020) Messages are arriving out of sequence with large message volumes
Date Wed, 03 Dec 2008 18:05:05 GMT


Gary Tully resolved AMQ-2020.

    Resolution: Fixed

two problems, the test case with the commit shows both.
there was an inadvertent audit rollback on every ack which meant the audit did not suppress
all duplicates.
Under high load, way too many duplicates were being produced by the reference store. A queue
caches its received messages up to a point and dispatches from this cache. However once the
cache is exhausts, all remaining messages in the store are re dispatched. The resolution is
to set the batch start point once the cache is full such that resuming after the cache is
exhausted begins with the first non cached message rather than with the current start of the
The additional setBatch method that is present in the KahaStore probably needs to be pulled
up into the MessageStore interface. currently there is a cast down in the cursor. If this
solution proves generally applicable we can do this.

> Messages are arriving out of sequence with large message volumes
> ----------------------------------------------------------------
>                 Key: AMQ-2020
>                 URL:
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.2.0
>         Environment: all
>            Reporter: Gary Tully
>            Assignee: Gary Tully
>             Fix For: 5.3.0
> With large volumes of messages, some messages can arrive out of order on occasion. Scenario
is hard to reproduce but a single producer and single consumer can cause the problem if the
volume is sufficiently high. The Producer needs to exceed the memory limit such that the cache
is filled and when the broker moves over to the store from the cache, the consumer need to
ack a message that will be redelivered from the store but would normally be suppressed as
a duplicate. 
> One way to avoid the problem is to disable the cache for a Queue:
> {code}
> <amq:policyEntry queue=">" useCache="false" >
> {code}

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