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https://issues.apache.org/jira/browse/HDFS-5182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13841882#comment-13841882
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Colin Patrick McCabe commented on HDFS-5182:
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The data xceiver protocol would stay the same as it is now. It's just that
after the SCR request, we would hang on to the socket and use a different
protocol, which I call the SCR notification protocol. The data xceiver
threads, protocols, etc. are not involved at that point, just the same as now.
> BlockReaderLocal must allow zero-copy reads only when the DN believes it's
> valid
> ---------------------------------------------------------------------------------
>
> Key: HDFS-5182
> URL: https://issues.apache.org/jira/browse/HDFS-5182
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Affects Versions: 3.0.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
>
> BlockReaderLocal must allow zero-copy reads only when the DN believes it's
> valid. This implies adding a new field to the response to
> REQUEST_SHORT_CIRCUIT_FDS. We also need some kind of heartbeat from the
> client to the DN, so that the DN can inform the client when the mapped region
> is no longer locked into memory.
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