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https://issues.apache.org/jira/browse/HDFS-7698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14296318#comment-14296318
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Colin Patrick McCabe edited comment on HDFS-7698 at 1/29/15 3:11 AM:
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* It is not necessary (or useful) to synchronize
{{HdfsDataInputStream#getReadStatistics}} on the {{HdfsDataInputStream}} lock.
getReadStatistics is synchronized inside {{DFSInputStream}} already, and the
methods modifying the statistics are not synchronized on
{{HdfsDataInputStream}}.
* Add a {{ReadStatistics#clear}} method which clears the stats.
* Add {{libhdfs}} support for clearing the read statistics.
* The {{ReadStatistics}} need to be synchronized on {{infoLock}}, not on the
positional lock. {{pread}} modifies these statistics, and it shouldn't have to
take the positional lock to do that. This could have resulted in lost updates
or incorrect read statistics being read when doing {{preads}} (but not when
doing regular reads under the positional lock).
was (Author: cmccabe):
* It is not necessary (or useful) to synchronized
{{HdfsDataInputStream#getReadStatistics}}. getReadStatistics is synchronized
inside {{DFSInputStream}} already, and the methods modifying the statistics are
not synchronized on {{HdfsDataInputStream}}.
* Add a {{ReadStatistics#clear}} method which clears the stats.
* Add {{libhdfs}} support for clearing the read statistics.
* The {{ReadStatistics}} need to be synchronized on {{infoLock}}, not on the
positional lock. {{pread}} modifies these statistics, and it shouldn't have to
take the positional lock to do that. This could have resulted in lost updates
or incorrect read statistics being read when doing {{preads}} (but not when
doing regular reads under the positional lock).
> Fix locking on HDFS read statistics and add a method for clearing them.
> -----------------------------------------------------------------------
>
> Key: HDFS-7698
> URL: https://issues.apache.org/jira/browse/HDFS-7698
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.7.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-7698.001.patch
>
>
> Fix locking on HDFS read statistics and add a method for clearing them.
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