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https://issues.apache.org/jira/browse/AMQ-5542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14294463#comment-14294463
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Sergiy Barlabanov commented on AMQ-5542:
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I think, you are right. Otherwise KahaDB will loose acks and replay messages.
If this is true, than the current cleanup mechanism have to be reconsidered. It
will not work well for scenarios, where messages may stay unconsumed for some
time. Some sort of compaction has to be done.
In the current project we have nearly always some messages in DLQs sitting
there for maximum 2 days. This means that we would always have nearly all data
files for the last two days.
Currently it is ok, we have enough of place on the SAN. But what if that would
be 2 weeks instead of 2 days?
I think in this case we would use JDBC storage.
Another possibility would be to use mKahaDB and put DLQs to a separate storage.
That storage would not grow fast since there would not be much traffic.
> 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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