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https://issues.apache.org/jira/browse/KAFKA-1008?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13739105#comment-13739105
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Elizabeth Wei commented on KAFKA-1008:
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Thanks for the feedback!
1 - Currently tryUnmap does a type checking. If the super class of "m" is
changed in the future, the type check will be false, and there will be no
casting errors like ClassNotFoundException at runtime.
2 - I removed the flush(). I probably used an older copy a couple of weeks ago.
3 - Reading through the bug report, I'm not sure if the cases matter in terms
of Kafka - I think all the threads in a Kafka process should be trusted and the
race condition between the unmap/remap shouldn't happen if coded properly. I
noticed that in the most recent version, the resize method is synchronized,
which should prevent multiple threads trying to resize/unmap the files.
> Unmap before resizing
> ---------------------
>
> Key: KAFKA-1008
> URL: https://issues.apache.org/jira/browse/KAFKA-1008
> Project: Kafka
> Issue Type: Bug
> Components: core, log
> Affects Versions: 0.8
> Environment: Windows, Linux, Mac OS
> Reporter: Elizabeth Wei
> Assignee: Jay Kreps
> Labels: patch
> Fix For: 0.8
>
> Attachments: unmap-v2.patch
>
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> While I was studying how MappedByteBuffer works, I saw a sharing runtime
> exception on Windows. I applied what I learned to generate a patch which uses
> an internal open JDK API to solve this problem.
> Following Jay's advice, I made a helper method called tryUnmap().
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