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https://issues.apache.org/jira/browse/HDFS-12964?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16317619#comment-16317619
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Yang Yun commented on HDFS-12964:
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Yes, the pollnewData() has same function, with it user can make the external
blocking read.
One more thing, the pollnewData() calls getFileInfo and readBlockLength every
time. That will increase the burden to a busy HDFS system. Do we need to add
the cache for RPC to Namenode and connection to Datanode? In our productive
environments, many readers may read small messages only from one block for a
long time with high speed.
> Read a opened file timely and effectively when it's being written by other
> --------------------------------------------------------------------------
>
> Key: HDFS-12964
> URL: https://issues.apache.org/jira/browse/HDFS-12964
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Reporter: Yang Yun
> Priority: Minor
> Attachments: HADOOP-12964.001.patch
>
>
> One thread opens a HDFS file and keeps writing. Another thread opens same
> file and keeps reading it at the same time, also want to get the newest
> content of file. that happens in many environments, for example, in some
> message transmission applications. And it also requires the new content can
> be read timely and effectively, for there maybe many tasks are working in
> same time.
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