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https://issues.apache.org/activemq/browse/AMQ-2016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=48814#action_48814
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Gary Tully commented on AMQ-2016:
---------------------------------
prefetch=1 should help here. Part of the problem is that the dispatch logic can
only deal with the consumers that it has and on the first dispatch iteration it
finds only one consumer and figures that that consumer has to deal with all of
the groups. With prefetch of one, after the first dispatch iteration there may
be another consumer (at least it allow the internal dispatch lock to be
released so that another consumer can be added between dispatch attempts)
Currently there is an issue that evaluates message group selection before
determining if a consumer is full, but if this is resolved, prefetch=1 should
make group selection evenly distributed among subscriptions that arrive at the
same time and before the group assignment has been determined.
> Message grouping not honored when consumers started with existing messages
> --------------------------------------------------------------------------
>
> Key: AMQ-2016
> URL: https://issues.apache.org/activemq/browse/AMQ-2016
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 5.1.0, 5.2.0
> Environment: JBOSS 4.2.2, AMQ 5.2.0 RA, JDK 1.5, Windows
> Reporter: Hari Iyer
> Priority: Blocker
> Attachments: MessageGroupDelayedTest.java,
> MessageGroupNewConsumerTest.java, MessageGroupTest.java
>
>
> Messages are processed FIFO when messages with different groups are sent to a
> queue and then the consumers are started.
> If the messages are sent after the consumers are started, then message
> grouping works as expected.
> Two JUnit tests are attached.
> 1. MessageGroupTest.java starts up 3 consumers and then sends 30 messages
> evenly distributed across 3 groups A, B, and C.
> Each consumer then gets assigned a group and the ordering is as expected
> based on the different sleep intervals defined as seen in the log below
> {quote}
> 2008-11-26 15:06:09,841 INFO [main] [com.test.MessageGroupTest] 30 messages
> sent to group A/B/C
> 2008-11-26 15:06:09,841 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 9
> 2008-11-26 15:06:09,841 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 9
> 2008-11-26 15:06:09,841 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 9
> 2008-11-26 15:06:09,934 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 8
> 2008-11-26 15:06:10,044 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 7
> 2008-11-26 15:06:10,137 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 6
> 2008-11-26 15:06:10,247 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 5
> 2008-11-26 15:06:10,340 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 4
> 2008-11-26 15:06:10,450 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 3
> 2008-11-26 15:06:10,544 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 2
> 2008-11-26 15:06:10,653 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 1
> 2008-11-26 15:06:10,747 INFO [Thread-4] [com.test.MessageGroupTest] worker3
> received msg C remaining 0
> 2008-11-26 15:06:10,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 8
> 2008-11-26 15:06:11,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 7
> 2008-11-26 15:06:12,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 6
> 2008-11-26 15:06:13,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 5
> 2008-11-26 15:06:14,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 8
> 2008-11-26 15:06:14,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 4
> 2008-11-26 15:06:15,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 3
> 2008-11-26 15:06:16,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 2
> 2008-11-26 15:06:17,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 1
> 2008-11-26 15:06:18,840 INFO [Thread-2] [com.test.MessageGroupTest] worker1
> received msg B remaining 0
> 2008-11-26 15:06:19,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 7
> 2008-11-26 15:06:24,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 6
> 2008-11-26 15:06:29,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 5
> 2008-11-26 15:06:34,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 4
> 2008-11-26 15:06:39,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 3
> 2008-11-26 15:06:44,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 2
> 2008-11-26 15:06:49,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 1
> 2008-11-26 15:06:54,840 INFO [Thread-3] [com.test.MessageGroupTest] worker2
> received msg A remaining 0
> {quote}
> 2. MessageGroupDelayedTest.java sends 30 messages evenly distributed across 3
> groups A, B, and C and then starts up 3 consumers.
> All 30 messages are delivered in FIFO order to a single consumer as seen in
> the log below
> {quote}
> 2008-11-26 15:25:50,021 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 9
> 2008-11-26 15:25:55,021 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 9
> 2008-11-26 15:25:56,021 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 9
> 2008-11-26 15:25:56,130 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 8
> 2008-11-26 15:26:01,130 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 8
> 2008-11-26 15:26:02,130 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 8
> 2008-11-26 15:26:02,224 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 7
> 2008-11-26 15:26:07,224 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 7
> 2008-11-26 15:26:08,224 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 7
> 2008-11-26 15:26:08,333 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 6
> 2008-11-26 15:26:13,333 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 6
> 2008-11-26 15:26:14,333 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 6
> 2008-11-26 15:26:14,427 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 5
> 2008-11-26 15:26:19,427 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 5
> 2008-11-26 15:26:20,427 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 5
> 2008-11-26 15:26:20,536 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 4
> 2008-11-26 15:26:25,536 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 4
> 2008-11-26 15:26:26,536 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 4
> 2008-11-26 15:26:26,630 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 3
> 2008-11-26 15:26:31,630 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 3
> 2008-11-26 15:26:32,630 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 3
> 2008-11-26 15:26:32,739 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 2
> 2008-11-26 15:26:37,739 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 2
> 2008-11-26 15:26:38,739 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 2
> 2008-11-26 15:26:38,833 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 1
> 2008-11-26 15:26:43,832 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 1
> 2008-11-26 15:26:44,832 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 1
> 2008-11-26 15:26:44,926 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg A remaining 0
> 2008-11-26 15:26:49,926 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg B remaining 0
> 2008-11-26 15:26:50,926 INFO [Thread-4] [com.test.MessageGroupDelayedTest]
> worker3 received msg C remaining 0
> {quote}
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