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https://issues.apache.org/jira/browse/HADOOP-3554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12605315#action_12605315
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Aaron Greenhouse commented on HADOOP-3554:
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Okay. After reevaluating in the SVN Trunk (rather than based on the 0.17.0
source code), the field maxLineLength also needs to be made final.
So, in summary
* If objects of the class LineRecordReader really are used by multiple threads,
then the class needs to be updated:
- Make the fields start, end, and maxLineLength final.
- Make the method getProgress() synchronized.
* Otherwise, remove the existing synchronization from methods next(), getPos(),
and close() and update the class documentation to indicate that instances are
not thread safe.
> LineRecordReader needs more synchronization
> -------------------------------------------
>
> Key: HADOOP-3554
> URL: https://issues.apache.org/jira/browse/HADOOP-3554
> Project: Hadoop Core
> Issue Type: Bug
> Affects Versions: 0.17.0
> Environment: All java platforms
> Reporter: Aaron Greenhouse
> Attachments: LineRecordReader.patch
>
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> LineRecordReader has three index fields start, end, and pos. All of these
> fields are long, which means that, in general, access to them is not atomic.
> This can cause problems if the fields are accessed without appropriate
> synchronization.
> I propose the following changes to the class:
> - Make the fields start and end final. This requires some minor changes to
> the constructor LineRecordReader(Configuration, FileSplit).
> - Make the method getProgress() synchronized.
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