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https://issues.apache.org/jira/browse/HDFS-5182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13891547#comment-13891547
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Colin Patrick McCabe commented on HDFS-5182:
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bq. Okay now it looks more clear to me now. Thanks for the explanation.
Glad to be helpful.
bq. My bad. I mixed Linux with SunOS. You can do it using sendmsg() / recvmsg()
as you mentioned in the previous comments.
I didn't realize that ioctl was the way to do this under SunOS. Interesting.
Sending fds via {{sendmsg}} seems to work on all the modern UNIX variants, so I
think that we're good there. On Windows, we'll need to use {{DuplicateHandle}}.
> 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: Improvement
> 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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