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https://issues.apache.org/jira/browse/AMQ-6572?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Christopher L. Shannon reassigned AMQ-6572:
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Assignee: Christopher L. Shannon
> KahaDB journal may not handle max file length changes correctly
> ---------------------------------------------------------------
>
> Key: AMQ-6572
> URL: https://issues.apache.org/jira/browse/AMQ-6572
> Project: ActiveMQ
> Issue Type: Bug
> Components: KahaDB
> Affects Versions: 5.14.3
> Reporter: james
> Assignee: Christopher L. Shannon
> Priority: Minor
>
> I was exploring the idea of changing the kahadb journal file length on an
> activemq instance which already has existing data (during a system restart).
> Initial response from activemq insiders was that this was a supported action,
> but while examining the Journal source, i stumbled on code which would seem
> to indicate that it isn't handled correctly
> Source thread:
> http://activemq.2283324.n4.nabble.com/Can-you-change-the-kahadb-journal-file-size-between-broker-starts-td4721155.html#a4721252
> Potential problem areas (from forum post):
> https://fisheye.apache.org/browse/activemq-6/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/journal/Journal.java?hb=true#to310
> This is the startup code. it attempts to adjust the total length by shaving
> off an unused portion of the final data file. if you have made the
> maxFileLength smaller since the last run, and you have actual data in the
> last journal file which is _after_ the new maxFileLength, then this
> computation will incorrectly return a negative value. my suspicion is that
> the length of the last data file should be used here instead of maxFileLength.
> https://fisheye.apache.org/browse/activemq-6/activemq-kahadb-store/src/main/java/org/apache/activemq/store/kahadb/disk/journal/Journal.java?hb=true#to867
> likewise, this code attempts to handle adjustments to maxFileLength since the
> journal file was created, but i think it again fails. if the maxFileLength
> has been increased since the data file was created, this would seem to be
> setting an offset which is past the length of the current data file. again,
> it seems like the length of the data file should be used directly.
> in general, in order for this to work correctly, the maxFileLength should
> only be used for code which is creating new files. all the other code should
> be solely relying on the size of the existing file, right?
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