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https://issues.apache.org/jira/browse/AMQ-5542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14296330#comment-14296330
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Arthur Naseef commented on AMQ-5542:
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DLQs are a common cause of this problem. My recommendation when using DLQs is
*always* have a plan for handling them and consume them in a timely manner.
Again, if the messages need to be stored for a period of time (like 2 days),
the best approach is to get them out of ActiveMQ and put them in some type of
message store. Another consideration of this use-case: keeping the messages
for this period means some manual action is expected. ActiveMQ is not designed
to give "random access" to messages, which would typically be needed for manual
intervention, but instead to produce and consume as a queue. This use-case
would be better served with a database in which individual messages could be
referenced.
Regardless, this is how ActiveMQ currently functions. Until something better
is implemented, these data files must not be deleted until they are no longer
used.
> KahaDB data files containing acknowledgements are deleted during cleanup
> ------------------------------------------------------------------------
>
> Key: AMQ-5542
> URL: https://issues.apache.org/jira/browse/AMQ-5542
> Project: ActiveMQ
> Issue Type: Bug
> Components: Message Store
> Affects Versions: 5.10.0, 5.10.1
> Reporter: Sergiy Barlabanov
> Attachments: AMQ-5542.patch, AdjustedAMQ2832Test.patch
>
>
> AMQ-2832 was not fixed cleanly.
> The commit dd68c61e65f24b7dc498b36e34960a4bc46ded4b by Gary from 8.10.2010
> introduced a problem by deleting too many files.
> Scenarios we are facing currently in production:
> Data file #1 contains unconsumed messages sitting in a DLQ. So this file is
> not a cleanup candidate.
> The next file #2 contains acks of some messages from file #1. This file is
> not a cleanup candidate (because of ackMessageFileMap logic).
> The next file #3 contains acks of some messages from file #2. And this file
> is deleted during the cleanup procedure. So on Broker restart all messages
> from #2, whose acks were from the deleted file #3, are replayed!
> The reason is gcCandidates variable, which is a copy of gcCandidateSet (see
> MessageDatabase#checkpointUpdate at the end of the method -
> org/apache/activemq/store/kahadb/MessageDatabase.java:1659 on 5.10.0 tag). So
> when a candidate is deleted from gcCandidateSet
> (org/apache/activemq/store/kahadb/MessageDatabase.java:1668 on 5.10.0 tag),
> gcCandidates still contains that candidate and the comparison on
> org/apache/activemq/store/kahadb/MessageDatabase.java:1666 works wrong!
> I will try to adjust AMQ2832Test.
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