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https://issues.apache.org/jira/browse/HDFS-8136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14497482#comment-14497482
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Kai Sasaki commented on HDFS-8136:
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I have a question about how to obtain schema information from NN.
{{DFSClient}} is assumed to use {{DFSStripedInputStream}} after opening file.
Which is better to pass {{ECSchema}} from {{DFSClient}} or to restore
{{ECSchema}} inside {{DFSStripedInputStream}} itself? The reason why I have
this question is that {{DFSStripedInputStream}} has not reference to
{{ClientProtocol}} now. I think these requests to NN should be delegated to
{{DFSClient}} because it is already responsible to handle {{ClientProtocol}}.
Thank you.
> Client gets and uses EC schema when reads and writes a stripping file
> ---------------------------------------------------------------------
>
> Key: HDFS-8136
> URL: https://issues.apache.org/jira/browse/HDFS-8136
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: HDFS-7285
> Reporter: Kai Zheng
> Assignee: Kai Sasaki
>
> Discussed with [~umamaheswararao] and [~vinayrpet], in client when reading
> and writing a stripping file, it can invoke a separate call to NameNode to
> request the EC schema associated with the EC zone where the file is in. Then
> the schema can be used to guide the reading and writing. Currently it uses
> hard-coded values.
> Optionally, as an optimization consideration, client may cache schema info
> per file or per zone or per schema name. We could add schema name in
> {{HdfsFileStatus}} for that.
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