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https://issues.apache.org/jira/browse/ROCKETMQ-175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15968833#comment-15968833
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ASF GitHub Bot commented on ROCKETMQ-175:
-----------------------------------------
Github user Jaskey commented on the issue:
https://github.com/apache/incubator-rocketmq/pull/92
Actually missing message can not be avoided when the diffrerent tags are
subscribed in the same consumer groups.
Say for two queues q1 q2, two consumers c1 c2.
c1->TAG1
c2->TAGB
when allocating, c1->q1, c2->q2 100 messages are sent to this topic with
TAG1.
C2 will recive nothing and c1 will recieve 50 messages. but the consumer
offset of q2 is till moving on. Then 50 messages are missing.
> Consumer may miss messages because of inconsistent subscription
> ---------------------------------------------------------------
>
> Key: ROCKETMQ-175
> URL: https://issues.apache.org/jira/browse/ROCKETMQ-175
> Project: Apache RocketMQ
> Issue Type: Bug
> Components: rocketmq-broker
> Affects Versions: 4.0.0-incubating
> Reporter: Eric Liu
> Assignee: yukon
> Fix For: 4.1.0-incubating
>
>
> When consumers in one group have different subscriptions(with tag), broker
> will select the one has latest client version. Although when this consumer
> shutdown, broker would not update the subscription until someone in group
> restart, so other consumers will miss messages by the dead consumer's tag.
> Broker should refresh the group's subscriptions when someone was off-line.
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